Cyclic Response of Woodframe Shearwalls: Loading Protocol and Rate of Loading Effects

Transcription

1 CUREE Publication No. W-13 Cyclic Response of Woodframe Shearwalls: Loading Protocol and Rate of Loading Effects Kip Gatto Chia-Ming Uang Department of Structural Engineering University of California, San Diego 22

2 Disclaimer The information in this publication is presented as a public service by California Institute of Technology and the Consortium of Universities for Research in Earthquake Engineering. No liability for the accuracy or adequacy of this information is assumed by them, nor by the Federal Emergency Management Agency and the California Governor s Office of Emergency Services, which provide funding for this project. the CUREE-Caltech Woodframe Project The CUREE-Caltech Woodframe Project is funded by the Federal Emergency Management Agency (FEMA) through a Hazard Mitigation Grant Program award administered by the California Governor s Office of Emergency Services (OES) and is supported by non-federal sources from industry, academia, and state and local government. California Institute of Technology (Caltech) is the prime contractor to OES. The Consortium of Universities for Research in Earthquake Engineering (CUREE) organizes and carries out under subcontract to Caltech the tasks involving other universities, practicing engineers, and industry. CUREE

3 CUREE Publication No. W-13 Cyclic Response of Woodframe Shearwalls: Loading Protocol and Rate of Loading Effects Kip Gatto Chia-Ming Uang Department of Structural Engineering University of California, San Diego 22 CUREE Consortium of Universities for Research in Earthquake Engineering 131 S. 46th Street - Building 42 Richmond, CA Tel.: Fax curee@curee.org website:

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5 Acknowledgements Funding for the research detailed in this report was provided by the Consortium of Universities for Research in Earthquake Engineering (CUREE) as part of the CUREE- Caltech Woodframe Project ( Earthquake Hazard Mitigation of Woodframe Construction ), under a grant administered by the California Office of Emergency Services and funded by the Federal Emergency Management Agency. Acknowledgement is gratefully given to the American Plywood Association (APA), International Staples, Nails and Tools Association (ISANTA), and Expo Builders Supply for their material donations. Professor John Hall was the Project Manager and Mr. Robert Reitherman was the Project Director. The guidance and advice of Professors André Filiatrault and Bryan Folz has been very valuable and is much appreciated. Gratitude is also given to the supporting staff at the Powell Structural Systems Research Laboratory and specifically, Bob Conway, Ryan Evans, Carmen Diaz, and Emily Fung for their help in materials testing and preparing the test specimens. i

6 Table of Contents Acknowledgements... i Table of Contents... ii List of Tables... iv List of Figures... v Chapter 1 Introduction Background Task of the CUREE-Caltech Woodframe Project... 2 Chapter 2 Overview of Protocols ASTM E 72 (1995) ASTM E 564 (1995) SPD Protocol (1987) FCC Protocol (1993) CEN Short Protocols (1995) SAC Protocols (1997) ISO Protocol (1998) CUREE-Caltech Protocols (2) Protocol Characteristics... 6 Chapter 3 Literature Review Wilcoski (1999) Dinehart and Shenton (1998) Karacabeyli and Ceccotti (1998) Yamaguchi and Minowa (1998) He, Lam, and Prion (1998) Ficcadenti, Steiner, Pardoen, and Kazanjy (1998)... 2 Chapter 4 Testing Program Test Specimens Materials Testing Test Matrix Test Setup Instrumentation Data Reduction Chapter 5 Test Results General Observations Specific Observations ii

7 Chapter 6 Comparison of Results Nailing Effect Loading Protocol Effects Near-fault Effects Gypsum Wallboard Effect Dynamic Loading Effect Stucco Effect Summary of Response Parameters Code Deflection Recommendations Chapter 7 Conclusions Loading Protocol Effects Near-fault Protocol Effects Nailing Effects Gypsum Wallboard Effect Dynamic Loading Effect Stucco Effect Code Implications Recommendations for Future Studies References 21 Appendix: Connection Test Plots iii

8 List of Tables Table 4.1 Test Matrix for Connection Test Specimens Table 4.2 Average Stucco Compressive Strength Table 4.3 Test Matrix (Two Specimens per Test)... 4 Table 4.4 Reference Displacements in inches Used for Test Protocols Table 4.5 Calculation of Period Based on Secant Stiffness Table 4.6 Instrumentation Table 4.7 Instrumentation Details Table 4.8 Instruments Available for East Wall Specimens Table 4.9 Instruments Available for West Wall Specimens Table 6.1 Peak Strength in kips and Percent Change from Monotonic Test Table 6.2 Absorbed Energy in kip-in and Percent Change from Monotonic Test Table 6.3 Deformation Capacity in inches and Percent Change from Monotonic Test Table 6.4 Initial Stiffness in kips/in and Percent Change from Monotonic Test using ASTM E 564 Method Table 6.5 Initial Stiffness in kips/in and Percent Change from Monotonic Test using FEMA-273 Method Table 6.6 Variable Values Used in Deflection Equation Table 6.7 Percent Change in Response parameters iv

9 List of Figures Figure 2.1 SPD Protocol Displacement History... 7 Figure 2.2 FCC Protocol Displacement History... 7 Figure 2.3 CEN Protocol Displacement Histories... 8 Figure 2.4 SAC Protocol Displacement Histories... 9 Figure 2.5 ISO Protocol Displacement History... 1 Figure 2.6 Calculation of and m... 1 Figure 2.7 CUREE-Caltech Protocol Displacement Histories Figure 3.1 Response Curves from Dinehart and Shenton (reversed loading not shown) Figure 3.2 Response Curves from Karacabeyli and Ceccotti Figure 3.3 Response Curves from He, Lam, and Prion Figure 4.1 Details of Test Specimens Figure 4.2 Stucco Application Figure 4.3 Cured Brown Coat Figure 4.4 Parallel-to-Grain Connection Test Specimen Details (Illustration Courtesy of Fischer) Figure 4.5 Test Setup for Parallel to-grain Connection Tests Figure 4.6 Perpendicular-to-Grain Connection Test Specimen Details (Illustration Courtesy of Fischer)... 5 Figure 4.7 Test Setup for Perpendicular to-grain Connection Tests... 5 Figure 4.8 Moisture Content Figure 4.9 Loading History for CUREE Dynamic Protocol Figure 4.1 Secant Stiffness Calculation (Test 2 West) Figure 4.11 Test Frame with Two Shearwall Specimens Figure 4.12 Test Frame Figure 4.13 Load Cell Placement Figure 4.14 Profile of Test Frame (Shearwalls not Shown) Figure 4.15 Loading Column with Pinned Column Base v

10 Figure 4.16 Specimen Boundary Configurations Figure 4.17 East Wall Instrumentation Figure 4.18 West Wall Instrumentation Figure 4.19 GWB Instrumentation for Test Figure 4.2 Calculation of Chord Bending Deflection... 6 Figure 4.21 Free-Body Diagram of Shearwall and Load Beam... 6 Figure 5.1 Failure Modes for Test 1: OSB with Monotonic Loading Figure 5.2 Damage Photographs for Test 1: OSB with Monotonic Loading Figure 5.3 Global Response for Test 1: OSB with Monotonic Loading Figure 5.4 Comparison of Wall Load and Holdown Force for Test 1: OSB with Monotonic Loading Figure 5.5 Failure Modes for Test 2: OSB with CUREE Protocol... 8 Figure 5.6 Damage Photographs for Test 2: OSB with CUREE Protocol Figure 5.7 Global Response for Test 2: OSB with CUREE Protocol Figure 5.8 Sill Plate Slip for Test 2: OSB with CUREE Protocol Figure 5.9 Sheathing Rotations for Test 2: OSB with CUREE Protocol Figure 5.1 Holdown Stud Uplift Displacement for Test 2: OSB with CUREE Protocol Figure 5.11 Anchorage Force Distribution at Peak Positive Load for Test 2: OSB with CUREE Protocol Figure 5.12 Sheathing Translations of West Wall (North Panel) for Test Figure 5.13 Failure Modes for Test 3: OSB with ISO Protocol Figure 5.14 Damage Photographs for Test 3: OSB with ISO Protocol Figure 5.15 Global Response for Test 3: OSB with ISO Protocol... 9 Figure 5.16 Sill Plate Uplift Profile at Peak Positive Load for Test 3: OSB with ISO Protocol Figure 5.17 Comparison of Interior and Exterior Holdown Stud Strains for Test 3 (East Wall): OSB with ISO Protocol Figure 5.18 Failure Modes for Test 4: OSB with SPD Protocol Figure 5.19 Damage Photographs for Test 4: OSB with SPD Protocol Figure 5.2 Global Response for Test 4: OSB with SPD Protocol vi

11 Figure 5.21 Comparison of Deflection Components for Test 4: OSB with SPD Protocol Figure 5.22 Failure Modes for Test 5: OSB with SPD Protocol Figure 5.23 Damage Photographs for Test 5: PWD with Monotonic Loading Figure 5.24 Global Response for Test 5: PWD with Monotonic Loading Figure 5.25 Anchorage Force Distribution for Test 5: PWD with Monotonic Loading... 1 Figure 5.26 Failure Modes for Test 6: PWD with CUREE Protocol Figure 5.27 Damage Photographs for Test 6: PWD with CUREE Protocol Figure 5.28 Global Response for Test 6: PWD with CUREE Protocol Figure 5.29 Failure Modes for Test 7: PWD with ISO Protocol Figure 5.3 Damage Photographs for Test 7: PWD with ISO Protocol Figure 5.31 Global Response for Test 7: PWD with ISO Protocol Figure 5.32 Failure Modes for Test 8: PWD with SPD Protocol Figure 5.33 Damage Photographs for Test 8: PWD with SPD Protocol Figure 5.34 Global Response for Test 8: PWD with SPD Protocol Figure 5.35 Failure Modes for Test 9: OSB with Near-fault Protocol Figure 5.36 Global Response for Test 9: OSB with Near-fault Protocol Figure 5.37 Damage Photographs for Test 9: OSB with Near-fault Protocol Figure 5.38 Holdown Stud Strain Distribution at Peak Load for Test 9: OSB with Near-fault Protocol Figure 5.39 Failure Modes for Test 1: PWD with Near-fault Protocol Figure 5.4 Damage Photographs for Test 1: PWD with Near-fault Protocol Figure 5.41 Global Response for Test 1: PWD with Near-fault Protocol Figure 5.42 Failure Modes for Test 11: OSB with Monotonic Loading and 4 in. Effective Nailing at all Edges Figure 5.43 Damage Photographs for Test 11: OSB with Monotonic Loading and 4 in. Effective Nailing at All Edges Figure 5.44 Global Response for Test 11: OSB with Monotonic Loading and 4 in. Effective Nailing at all Edges Figure 5.45 Failure Modes for Test 12: GWB with Monotonic Loading vii

12 Figure 5.46 Damage Photographs for Test 12: GWB with Monotonic Loading Figure 5.47 Global Response for Test 12: GWB with Monotonic Loading Figure 5.48 Failure Modes for Test 13: OSB + GWB with CUREE Protocol Figure 5.49 Damage Photographs for Test 13: OSB + GWB with CUREE Protocol Figure 5.5 Global Response for Test 13: OSB + GWB with CUREE Protocol Figure 5.51 Deformation Components for Test 13: OSB + GWB with CUREE Protocol Figure 5.52 Failure Modes for Test 14: PWD + GWB with CUREE Protocol Figure 5.53 Damage Photographs for Test 14: PWD + GWB with CUREE Protocol Figure 5.54 Global Response for Test 14: PWD + GWB with CUREE Protocol Figure 5.55 Sheathing Shear Strains for Test 14: PWD + OSB with CUREE Protocol Figure 5.56 Failure Modes for Test 15: OSB + GWB with CUREE Dynamic Protocol Figure 5.57 Damage Photographs for Test 15: OSB + GWB with CUREE Dynamic Protocol [Figures (b) and (c) with GWB Removed] Figure 5.58 Global Response for Test 15: OSB + GWB with CUREE Dynamic Protocol Figure 5.59 Failure Modes for Test 16: PWD + GWB with CUREE Dynamic Protocol Figure 5.6 Damage Photographs for Test 16: PWD + GWB with CUREE Dynamic Protocol [Figures (a), (b), and (c) with GWB Removed] Figure 5.61 Global Response for Test 16: PWD + GWB with CUREE Dynamic Protocol Figure 5.62 Sheathing Shear Strains for Test 16: PWD + GWB with CUREE Dynamic Protocol Figure 5.63 Failure Modes for Test 17: OSB + Stucco with CUREE Dynamic Protocol viii

13 Figure 5.64 Damage Photographs for Test 17: OSB + Stucco with CUREE Dynamic Protocol Figure 5.65 Global Response for Test 17: OSB + Stucco with CUREE Dynamic Protocol Figure 5.66 Failure Modes for Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 5.67 Damage Photographs for Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 5.68 Global Response for Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 5.69 Sill Plate Slip for Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 5.7 Holdown Stud Uplift Displacements for Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 6.1 Comparison of Monotonic Tests: Nailing Effects Figure 6.2 Comparison of Peak Strength: Nailing Effects Figure 6.3 Comparison of Absorbed Energy: Nailing Effects Figure 6.4 Examples of Deformation Capacity Calculation Figure 6.5 Comparison of Deformation Capacity: Nailing Effects Figure 6.6 Examples of Initial Stiffness Calculation using ASTM E Figure 6.7 Examples of Initial Stiffness Calculation using FEMA Figure 6.8 Comparison of Initial Stiffness: Nailing Effects Figure 6.9 Comparison of Backbone Curves (OSB Specimens): Loading Protocol Effect Figure 6.1 Comparison of Backbone Curves (PWD Specimens): Loading Protocol Effect Figure 6.11 Comparison of Peak Strength: Loading Protocol Effects Figure 6.12 Comparison of Absorbed Energy: Loading Protocol Effects Figure 6.13 Comparison of Deformation Capacity: Loading Protocol Effects Figure 6.14 Comparison of Initial Stiffness: Loading Protocol Effects ix

14 Figure 6.15 Comparison of Deflection Components at Yield with FEMA-273 for Test 1: OSB with Monotonic Loading Figure 6.16 Comparison of Deflection Components at Yield with FEMA-273 for Test 2 (West Wall): OSB with CUREE Protocol Figure 6.17 Comparison of Deflection Components at Yield with FEMA-273 for Test 3 (West Wall): OSB with ISO Protocol Figure 6.18 Comparison of Deflection Components at Yield with FEMA-273 for Test 4 (West Wall): OSB with SPD Protocol Figure 6.19 Comparison of Deflection Components at Yield with FEMA-273 for Test 5 (West Wall): PWD with Monotonic Loading Figure 6.2 Comparison of Backbone Curves (OSB Specimens): Near-fault Effects Figure 6.21 Comparison of Backbone Curves (PWD Specimens): Near-fault Effects Figure 6.22 Comparison of Peak Strength: Near-fault Effects Figure 6.23 Comparison of Absorbed Energy: Near-fault Effects Figure 6.24 Comparison of Deformation Capacity: Near-fault Effects Figure 6.25 Comparison of Initial Stiffness: Near-fault Effects Figure 6.26 Comparison of Deflection Components at Yield with FEMA-273 for Test 9: OSB with Near-fault Protocol Figure 6.27 Comparison of Deflection Components at Yield with FEMA-273 for Test 1: PWD with Near-fault Protocol Figure 6.28 Comparison of Backbone Curves (OSB Specimens): GWB Effects Figure 6.29 Comparison of Backbone Curves (PWD Specimens): GWB Effects Figure 6.3 Comparison of Peak Strength: GWB Effects Figure 6.31 Comparison of Absorbed Energy: GWB Effects Figure 6.32 Comparison of Deformation Capacity: GWB Effects Figure 6.33 Comparison of Initial Stiffness: GWB Effects Figure 6.34 Comparison of Deflection Components at Yield with FEMA-273 for Test 13: OSB + GWB with CUREE Protocol x

15 Figure 6.35 Comparison of Backbone Curves (OSB + GWB Specimens) : Loading Rate Effects Figure 6.36 Comparison of Backbone Curves (PWD + GWB Specimens): Loading Rate Effects Figure 6.37 Comparison of Peak Strength: Loading Rate Effects Figure 6.38 Comparison of Absorbed Energy: Loading Rate Effects Figure 6.39 Comparison of Deformation Capacity: Loading Rate Effects Figure 6.4 Comparison of Initial Stiffness: Loading Rate Effects Figure 6.41 Comparison of Deflection Components at Yield with FEMA-273 for Test 16: PWD + GWB with CUREE Dynamic Protocol Figure 6.42 Comparison of Backbone Curves (OSB Specimens): Stucco Effects Figure 6.43 Comparison of Backbone Curves (PWD Specimens): Stucco Effects Figure 6.44 Comparison of Peak Strength: Stucco Effects Figure 6.45 Comparison of Absorbed Energy: Stucco Effects Figure 6.46 Comparison of Deformation Capacity: Stucco Effects Figure 6.47 Comparison of Initial Stiffness: Stucco Effects Figure 6.48 Comparison of Deflection Components at Yield with FEMA-273 for Test 17: OSB + Stucco with CUREE Dynamic Protocol Figure 6.49 Comparison of Deflection Components at Yield with FEMA-273 for Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 6.5 Ratios of Experimentally Determined Nail Slip and FEMA-273 Nail Slip Component... 2 Figure 6.51 Ratios of Experimentally Determined Anchorage Uplift and FEMA- 273 Anchorage Uplift Component Figure 6.52 Comparisons Between Current Code and Modified Code Yield Displacements for Specimens without Finish Materials Figure 6.53 Comparisons Between Current Code and Modified Code Yield Displacements for Specimens with Finish Materials Figure A.1 OSB Monotonic: Parallel-to-Grain Figure A.2 PWD Monotonic: Parallel-to-Grain xi

16 Figure A.3 OSB Monotonic: Perpendicular-to-Grain Figure A.4 PWD Monotonic: Perpendicular-to-Grain Figure A.5 OSB Cyclic: Parallel-to-Grain Figure A.6 PWD Cyclic: Parallel-to-Grain Figure A.7 OSB Cyclic: Perpendicular-to-Grain Figure A.8 PWD Cyclic: Perpendicular-to-Grain xii

17 Chapter 1 Introduction 1.1 Background The lateral force demand imposed on woodframe structures by seismic events is typically resisted by a shearwall system composed of wood studs overlaid by a structural sheathing. Woodframe shearwall allowable unit load capacity is tabulated in the Uniform Building Code (ICBO 1997) and is based on the type of sheathing and the type and quantity of nails. The code values are empirical, derived from tests performed by the American Plywood Association (APA) under quasi-static, monotonic loading using the ASTM E-72 (ASTM 1995) or the ASTM E-564 (ASTM 1995) test procedures (Dolan 1999). Recently there has been concern among engineers that the monotonic testing that forms the basis for current design values is not representative of the actual demand imposed by a seismic event and can lead to unconservative designs. This concern is largely a result of the considerable damage that occurred to woodframe structures during the 1994 Northridge Earthquake (EERI 1995). As a result, recent shearwall tests have been performed using cyclic loading protocols with fully reversed loading cycles in an effort to reproduce the demands imposed by a seismic event. Additionally, some researchers have also increased the loading rate to what can be considered dynamic, which generally means on the order of magnitude of an actual structural response to an earthquake ground motion. Although it is believed that cyclic testing better characterizes the seismic capacity of woodframe shearwalls, the lack of a standardized protocol that defines the test procedure presents a problem. Some common protocols that have been used in lieu of a recognized standard are the Sequential Phased Displacement (SPD) protocol, the Forintek Canada Corporation (FCC) protocol, and the International Standards Organization (ISO) protocol, as well as several others (see Chapter 2). The SPD and the FCC protocols involve a large number of cycles with the amplitude of each cycle based on the yield displacement of the test specimen. The ISO protocol has a smaller number of cycles with the cyclic amplitude based on the displacement at ultimate load. Most of the protocols have been used under both quasi-static as well as dynamic loading rates. With researchers 1

18 from different institutions using different displacement histories, loading rates, and other parameters, it becomes difficult, if not impossible, to justifiably compare the results and come to a consensus on the cyclic performance of wood shearwalls. Furthermore, the protocol used should result in a failure mode that represents observed woodframe structural damage that has occurred during major earthquakes. The need for a welldefined, standardized protocol that outlines the test procedure is clear. 1.2 Task of the CUREE-Caltech Woodframe Project In an effort to improve the state of the art in woodframe construction, the Federal Emergency Management Agency (FEMA) has funded the CUREE-Caltech Woodframe Project through the California Office of Emergency Services (OES). Prompted by woodframe damage that occurred as a result of the Northridge Earthquake, the project is a collaboration of efforts from a number of institutions with the prime contractor being the California Institute of Technology (Caltech). The project is broken up into five separate elements: Element 1: Testing and Analysis Element 2: Field Investigations Element 3: Building Codes and Standards Element 4: Economic Applications Element 5: Education and Outreach As part of Element 1, Task Loading Protocol and Loading Rate Effects deals with the issue of evaluating the effect of loading protocol and loading rate on shearwall performance and is the focus of this report. 2

19 Chapter 2 Overview of Protocols Several different loading protocols exist for the cyclic testing of woodframe shearwalls. The following gives brief descriptions of some of the more common protocols used to test shearwall specimens. 2.1 ASTM E 72 (1995) ASTM provides a standard procedure for the evaluation of sheathing panels used in woodframe shearwalls. According to this standard, the specimen is loaded at a constant rate to 3., 7., and 1.5 kn with complete unloading between each load increment. After the 1.5 kn load is applied, the specimen is unloaded and then reloaded monotonically until failure. Note that this procedure is not intended to test a shear wall assembly due to the overturning forces being resisted by the steel rod at the end of the wall. 2.2 ASTM E 564 (1995) A standard for testing an entire woodframe shearwall as opposed to just the sheathing is given in ASTM E 564. The standard provides two loading sequences: a static test (only positive excursions) and an optional cyclic test. In the static test the specimen is preloaded to 1% of the expected ultimate load to seat the connections and then unloaded. After seating the connections, three load increments are applied starting with one-third the expected ultimate load followed by increases of one-third the ultimate load until the ultimate load is reached in the third increment. At each increment the specimen is unloaded before application of the next higher load increment. In the optional cyclic sequence the 1% static preload is applied and removed. A load increment of one-third the expected ultimate load is then applied and removed, followed by an equal magnitude load in the reverse direction. The reversed load is then released to form a complete cycle. Five cycles are completed at each one-third load increment specified in the static test until failure of the specimen. ASTM states that The duration of load application at each increment shall be sufficient to permit load and deflection readings to be recorded. This statement implies that the optional cyclic procedure is a quasi-static test. 3

20 2.3 SPD Protocol (1987) Originally developed by the Technical Coordinating Committee on Masonry Research (Porter 1987), the Sequential Phased Displacement (SPD) protocol has been modified and adopted by the Structural Engineers Association of Southern California (SEAOSC) for woodframe shearwall testing. The protocol is based on the so-called First Major Event (FME), which can generally be considered as the displacement corresponding to the yield state of the specimen. Prior monotonic testing must be performed to determine the FME for this cyclic protocol. The displacement history is composed of groups of stabilization and degradation cycles that are repeated at higher amplitudes as shown in Figure FCC Protocol (1993) The FCC protocol, developed by the Forintek Canada Corporation(Karacabeyli 1995), consists of sinusoidal cycle groups of three equal magnitude cycles. Cycle group amplitude is determined from the nominal yield slip ( yield ), defined as half the ultimate load displacement and found from prior monotonic testing. The first cycle group amplitude is equal to 5% of yield followed by 1% of yield and then 5% again for the third cycle group. A similar pattern is repeated in subsequent cycle groups, as shown in Figure 2.2, until specimen failure is reached. 2.5 CEN Short Protocols (1995) The Comité Europeen de Normalisation (CEN) has two protocols specified for cyclic testing; a short protocol and a long protocol (CEN 1995). The short protocol consists of three equal amplitude cycles followed by a constant ramp load until failure. The amplitude of the three initial cycles is found by multiplying the yield slip ( yield ) by an assumed ductility (D). An initial monotonic test must be performed to determine the yield slip. An example of a typical displacement history for D=3 is given in Figure 2.3(a). The CEN long protocol consists of three cycle groups with three equal magnitude cycles per group. The third cycle group is followed by a constant ramp load until failure. The amplitude of the first cycle group is equal to 35% of the ultimate load displacement followed by 5% and 8% for the second and third cycle groups respectively. The 4

21 displacement at maximum load must be found from previous monotonic testing. A plot of a typical displacement history is given in Figure 2.3(b). 2.6 SAC Protocols (1997) Krawinkler (SAC 1997) developed for SAC two loading protocols for the cyclic testing of steel moment connections, a standard loading protocol and a near-fault loading protocol (Figure 2.4). These loading protocols are based on the interstory drift angle, which is defined as the interstory drift divided by the story height. A major advantage of the SAC protocol is that no prior testing is required to obtain parameters (δ y, FME, etc.) necessary for characterization of the protocol. 2.7 ISO Protocol (1998) Working Group 7 of the ISO Technical Committee on Timber Structures developed the ISO protocol (ISO 1998). Originally developed for joint testing, the procedure is considered appropriate for the testing of woodframe shearwalls. The load history is based on the displacement at ultimate load (v u ), where the amplitude of each cycle is a percentage of v u. A schedule of the displacement history is given in Figure CUREE-Caltech Protocols (2) As part of Element 1 of the CUREE-Caltech Woodframe Project, Task was assigned with the development of new protocols intended for the testing of woodframe components (Krawinkler 2). Using nonlinear dynamic modeling of hysteretic singledegree-of-freedom systems representative of wood structures under both ordinary and near-fault ground motions, two protocols were developed; a standard protocol and a nearfault protocol. The standard protocol, based on a reference displacement, begins with a sequence of small amplitude cycles intended to address cumulative damage from small tremors that are then followed by large amplitude cycles as shown in Figure 2.7(a). The Near-fault protocol, based on reference displacement m, consists of small amplitude cycles followed by very large amplitude pulses intended to simulate the effect of being near the source of the ground motion [see Figure 2.7(b)]. Reference displacement m is the displacement at 8% of the ultimate load on the degradation portion of the monotonic 5

22 curve and reference displacement is defined as 6% of m. Figure 2.6 provides an illustration of the calculation of and m. (For shearwall testing, story drift is used as the displacement.) 2.9 Protocol Characteristics Protocols used for testing of woodframe components have been presented. Descriptions of research that has been performed using some of the protocols will be given in the next chapter. This section briefly explores some of the characteristics of the different protocols and compares their similarities and differences Reference Displacements With the exception of the SAC and the ASTM E-72 protocols, a reference displacement determined from either prior monotonic testing or a prior estimate of the specimen response is required. The lack of a requirement for prior knowledge of the specimen behavior provides not only the advantage of convenience, but helps to provide consistency between different tests. The reference displacements for two of the protocols are based on the yield displacement (SPD and FCC) as opposed to the displacement at ultimate load. Using the smaller yield displacement tends to result in a large number cycles, as can be observed in Figure 2.1 and Figure Trailing Cycles The SPD and the CUREE protocols are the only two protocols that have trailing cycles (cycles that have amplitudes smaller than previous cycles). These trailing cycles may be more indicative of the behavior of actual seismic events and also allow for observation of the specimen response to these trailing cycles Symmetry The Near-fault protocols defined by CUREE and SAC are the only protocols that are nonsymmetrical. Although earthquakes are never perfectly symmetric, they are often very close (except for near-fault earthquakes), hence, the protocols have been defined as symmetric. The symmetry also allows for observation of how the specimen responds to negative excursions of the same amplitude as the positive excursions. 6

23 Cycle No. Figure 2.1 SPD Protocol Displacement History Cycle No. Figure 2.2 FCC Protocol Displacement History 7

24 Cycle No. (a) CEN Short 2 15 % max Cycle No. (b) CEN Long 1 Figure 2.3 CEN Protocol Displacement Histories 8

25 Cycle No. (a) SAC Standard Cycle No. (b) SAC Near-fault Figure 2.4 SAC Protocol Displacement Histories 9

26 Cycle No. Figure 2.5 ISO Protocol Displacement History F u.8 F u Load =.6 m Displacement m Figure 2.6 Calculation of and m 1

27 Cycle No. (a) CUREE Standard Cycle No. (b) CUREE Near-fault Figure 2.7 CUREE-Caltech Protocol Displacement Histories 11

28 Chapter 3 Literature Review A total of six publications were reviewed for the effect of loading protocols and loading rate on the cyclic response of woodframe shearwalls. The following sections provides brief descriptions of the research performed and the conclusions drawn. 3.1 Wilcoski (1999) Research performed by the Army Corps of Engineers at the Construction Engineering Research Laboratory compared PWD sheathed shearwalls with a proprietary integrated wood truss design proposed by the Building Science Corporation. A monotonic and two cyclic loading protocols (SPD and Modified SAC) were used for testing the wall configurations. The review here is focused on the results from testing of the PWD sheathed walls. All of the wall specimens were approximately 8 ft by 8 ft square with a single 4 ft by 8 ft sheet of 1/2 in. STR I PWD fastened near the center of the wall to provide lateral resistance. Each wall was anchored by fastening the bottom plate with 7/8 in. A325 bolts and 1/2 in. steel plates. The test setup consisted of a steel box test frame oriented symmetrically around the specimen and bolted to a strong floor. Stub columns with teflon sliders attached to the frame prevented out of plane motion of the specimen. Vertical actuators attached to the frame provided vertical load and ensured the top plate remained horizontal. A 4 in. stroke actuator bolted to a nearby strong wall at specimen height provided the lateral load through a steel load distribution beam. Monotonic testing was performed by loading the specimen at a rate of 1/2 in. per second until complete wall failure or until 8 in of displacement was reached. The cyclic tests were performed using an FME displacement amplitude of.4 in. A loading frequency of.1 Hertz was used in the SPD tests, and the SAC tests used a constant loading rate of.2 in per second. Initial monotonic testing indicated that the presence of vertical load increased shearwall capacity due to the resistance of overturning moment. Consequently, in subsequent monotonic tests, the vertical load was removed to create the most critical condition. No vertical loads were applied to the specimens tested with the 12

29 SPD protocol. A vertical load of 8 lb was applied to specimens tested under the SAC protocol. The authors noted that a common failure mechanism in the tests without vertical load or holdown anchors was nails tearing through the sheathing at the top and bottom plate edges. This was observed in both the monotonic and cyclic testing protocols and is likely due to the lack of overturning resistance, causing the nail loads to be concentrated at the top and bottom plates. Another contributing factor was the small edge distances of the nails due to the 2 top and bottom plates and edge studs. In the monotonic and SAC tests in the walls with holdowns, the nails tended to fail in bending and then pull through the PWD while remaining embedded in the framing. In the SPD tests, unlike the other protocols, the nails tended to fail in shear. This may be a result of the large number of cycles imposed after the specimen has reached its yield state. The difference in failure mechanisms between the wall configurations can be attributed to the use of holdowns in in addition to larger members at the sheathing edges providing for larger edge nail distances. Since the primary objective of the research was a comparison of standard shear wall systems with a newly designed truss system, a comparison of the different sheathing configurations and loading protocols was not emphasized. However, there were some useful conclusions made by the author worth noting: Cyclic loading reduces wall ductility. The SPD protocol produced consistently lower wall capacities than the SAC protocol. The SPD protocol produced consistently lower ductility than the SAC protocol. 3.2 Dinehart and Shenton (1998) Research performed by Dinehart and Shenton investigated the resistance of woodframe shearwalls subjected to static and dynamic racking loads. Their study compared the response of identical shearwalls to the loading procedures using the same test facility. Of interest was the dynamic response of a standard shearwall, and a comparison of the differences in stiffness, ductility, ultimate load, and failure mechanism that occurred between the loading procedures. 13

30 A total of twelve walls were tested, four static tests and eight dynamic tests. Half of the specimens were sheathed with 15/32 in. thick plywood (PWD) and the other half with 1/2 in. thick oriented strand board (OSB). Two 4 ft 8 ft sheathing panels were used per wall oriented vertically and fastened with 8d nails. Edge nails were placed at 4 in. on center with field nails placed at 12 in. on center. All wall components and construction other than sheathing were consistent among the walls. Standard 2 4 studs made from No. 2 Spruce-Pine-Fir were used for the framing. The studs were spaced at 16 in. on center with double end studs, double top plates, and a single sill plate. The test apparatus consisted of a self-reacting steel frame made from channels, angles, and wide flange sections welded or bolted together. Roller bearing guides were used at the top of the wall in order to prevent lateral movement of the specimen during testing. The wall was anchored by placing a 1 in. 3 in. 1/2 in. steel plate on top of the sill plate and fastening it to the test frame with 3/4 in. bolts. This shear anchorage was designed to prevent any movement of the base during testing. In addition, commercially available holdowns were fastened to the ends of the wall and bolted to the test frame. The actuator used to load the wall was bolted to the test apparatus at wall height and load was applied to the specimen via a steel member fastened to the top plate. The protocol prescribed in ASTM E 564 was used for the static testing with the exception that higher test loads were used. The higher loads were used to ensure that the ultimate load was reached in the third stage, which is consistent with the practice used by the American Plywood Association. Two walls were tested with PWD and two with OSB. The dynamic testing was performed using the SPD protocol at a frequency of 1 Hertz, except for the final seven cycles, which were performed at.5 Hertz due to equipment limitations. The FME chosen corresponded to wall drift of.75% and it was noted that this FME utilized the full ±3 in. stroke of the actuator at the end of the test sequence. Three of the dynamic tests were conducted with PWD and three with OSB. Different failure mechanisms were observed between the static and dynamic tests. In the static tests the sheathing pulled away from the framing along the edges, pulling the nails with it. Sill plate splitting parallel to the grain occurred at the uplift corner of the wall. Some interior studs were observed to twist along their length and split. In the 14

31 dynamic tests most of the damage occurred in the sheathing fasteners. The nails either fatigued and broke off or pulled out from the framing and sheathing. The load-deformation responses of the PWD and OSB sheathed specimens were similar in the static tests. The response of the PWD was similar to that of the OSB in the dynamic tests, although the average ultimate load of the PWD walls was slightly higher than that in the OSB walls. Plots containing positive values of the load histories are given in Figure 3.1. Ultimate loads produced in the static and dynamic tests were similar, with the static results slightly higher. In the dynamic tests, however, the displacements at which ultimate loads occurred were significantly lower. Assuming the same yield displacement of.25 in., a conclusion was made by the authors that the static specimens had a higher ductility. The ductility was calculated to be 34% larger in the PWD walls and 42% higher in the OSB walls. The authors did note, however, that it was not clear whether this difference was due to the effects of cyclic loading or the effects of the dynamic loading rate. 3.3 Karacabeyli and Ceccotti (1998) Research by Karacabeyli and Ceccotti investigated the effects of different loading protocols on the performance of PWD shearwalls. They subjected shearwalls of the same construction to various loading schedules and compared the respective responses. Some quantities under consideration were the ultimate load capacity, the displacement at ultimate load, and the dissipated energy. Shearwalls used in the testing were 16 ft wide by 8 ft high and used 2 4 Spruce- Pine-Fir dimension lumber for all of the framing members. Wall studs were positioned at 16 in. on center and blocking was placed at mid-height. Double top plates and single bottom plates were used and anchored with 1/2 in. bolts at both the top and bottom. An actuator applied the racking load through a distribution beam attached to the top plate and a weight of 7264 lb was used to apply a constant vertical load. The following protocols and loading rates were used to specify the actuator displacement history. 15

32 Monotonic loading with a displacement rate of.5 in/sec SPD using a constant frequency of.5 Hertz CEN Long Cyclic Procedure using a constant velocity of.17 in/sec CEN Short Cyclic Procedure using a constant velocity of.17 in/sec FCC Cyclic Procedure using a constant frequency of.5 Hertz ISO Cyclic Procedure using a constant velocity of.8 in/sec Pseudo-dynamic tests using a peak displacement velocity of.8 in/sec Different failure mechanisms were observed depending on the loading protocol used. Four failure modes were prevalent. 1. Shear fatigue failure of the nails. 2. Nails pulling through the sheathing. 3. Nail withdrawal. 4. Nails tearing out of the edges of the sheathing. The only tests where nail fatigue failure was observed were under the SPD and FCC protocols. This was attributed to much higher energy demand occurring under these protocols as compared with the others. The other protocols produced a mix of the other three failure modes. Figure 3.2 contains plots of typical responses obtained from the testing superimposed on the monotonic test curve. The SPD protocol is denoted as ASTM in the test results because SPD was being considered for adoption by ASTM. All of the test protocols produced roughly the same maximum load capacity (within ±1%). Tests performed under the SPD protocol produced ultimate load displacements that were smaller than those produced with the other protocols (about 4% less than the monotonic displacement). Energy demands in the SPD tests were significantly higher than in the other tests, which is a likely cause of the reduced displacement at ultimate load. Pseudo-dynamic testing produced ultimate loads and displacements that were consistently higher than those produced under various protocols including the monotonic. The authors provided this as evidence that monotonic testing can be conservatively used to determine the maximum design capacity. They also pointed out that the first envelope of the hysteresis loops as opposed to the commonly used third envelope could be conservatively used to obtain the design capacity. 16

33 3.4 Yamaguchi and Minowa (1998) Research by Yamaguchi and Minowa involved dynamic testing of woodframe shearwalls by means of a shake table. The testing, motivated by the 1995 Kobe Earthquake, was carried out in order to determine the dynamic performance of wood shearwalls and to compare the shake table test results with previously performed quasistatic tests. In addition, a mathematical model was developed to predict collapse of the shearwalls under dynamic loading, which was compared with results from the dynamic testing. The discussion here involves only the test results. Each shearwall specimen consisted of essentially two PWD sheathed shearwalls separated by an 6 ft opening and connected by the top and bottom plates. PWD sheathing fastened flush with the edge of the wall had dimensions of 3 ft 9 ft and was 3/8 in. thick. N5 nails (.11 in. diameter) spaced at 6 in. were placed at the sheathing edges. Accelerometers were placed at the base and top of the specimens and laser displacement meters were used to measure the relative displacement between the top and bottom of the specimens. A steel braced frame with wooden cross walls placed perpendicular to the direction of shaking was used as the test apparatus. The cross walls were pinned to allow rotation in the direction of shaking and were used to support mass required to simulate inertial loads. Although the cross wall supported all of the vertical loads, the shearwall specimens were fastened to the cross walls such that they provided the lateral load resistance. The apparatus was placed on a shake table capable of simulating Kobe Earthquake ground motions. Tests were performed relating the wall load to the tilting angle (interstory drift angle) of the wall for specimens with shear coefficients of.3,.4, and.5. The shear coefficient was defined as the allowable lateral wall load divided by the inertial weight (C o = P allow / W) and was adjusted by changing the inertial weight. The allowable lateral load is defined as the wall strength when the tilting angle is 1/12 rad. Common failure mechanisms observed were the nails pulling out of the framing and, in some cases, nails punching through the sheathing. In either case the sheathing tended to pull away from the framing at large deformations. 17

34 A comparison of the quasi-static and dynamic testing showed a trend of higher ultimate strength and lower ductility for specimens under dynamic loading. For the specimen with a shear coefficient of.3, the ultimate strength in the dynamic test was found to be 114% of that in the quasi-static test. The displacement at ultimate load in the dynamic test was found to be 5% of that in the quasi-static test. It was speculated that the slow rate of loading in the quasi-static test allowed the wall to creep, which would account for the higher displacement. It was also noted that although a reasonably well defined yield point existed for both the quasi-static and dynamic tests, the points did not coincide. The dynamic yield point occurred at a higher load. 3.5 He, Lam, and Prion (1998) Researchers at the University of British Columbia investigated the effects of three commonly used protocols on the performance of woodframe shearwalls. The authors were interested in how test results are affected by the use of different loading protocols, and which protocols produce results that best reflect those observed in shake table testing and in actual earthquakes. They were also interested in the effects of different panel sizes and nailing configurations on shearwall performance. Five walls were tested using three different loading protocols. The protocols used were FCC, CEN Short, and CEN Long. Three walls of the same construction were used to evaluate the three different protocols. Two additional walls were constructed using different panel sizes and nail configurations and tested under the FCC protocol to evaluate the effects of these parameter changes. The discussion here looks only at the three walls tested under the three different protocols. Test walls were 24 ft long by 8 ft high and used standard North American framing with blocking at mid-height. Standard 2 4 studs were placed at placed 16 in. on center. Double end studs and top plates were used with single bottom plates. The framing was connected with air-driven 3 in. common nails. Each wall used a single oversized 3/8 in. OSB sheet that completely covered the framing. The sheathing was fastened using 2 in. spiral nails placed at 3 in. on center at the edges, and 12 in. on center at the interior studs. An actuator bolted to a steel reaction frame at wall height was used to load the specimen. The load was applied through a steel distribution beam bolted to the test wall. 18

35 Steel rods attached to hydraulic jacks were spaced at 8 ft on center and applied a vertical load to the load distribution beam. This setup created a constant vertical load of 625 lb/ft and was used to simulate vertical dead loads. Displacement values were measured with reference to the foundation in order to eliminate any effects of flexibility in the reaction frame Previous monotonic tests performed by Lam et al. (1997) on walls of the same construction as the walls in the study were used to obtain parameters (ultimate load, yield displacement, etc.) necessary to characterize the protocols. An initial cyclic frequency of.25 Hertz was used in the FCC protocol until the later stages of testing where the frequency was changed to.125 Hertz. A constant velocity of.4 mm/s was used in both the CEN Short and Long protocols. The wall tested under the FCC protocol was subjected to 22 cycle groups. The results showed that smaller ultimate loads and displacements occuring in the FCC protocol are likely a result of nail fatigue that occurred when testing under this protocol. No nail fatigue was observed in the CEN protocols where failure was a result of nails pulling out of the framing and nails pulling through the sheathing. The ultimate load in the CEN Short protocol occurred in the first cycle of testing and was never reached again. This prompted the authors to conclude that permanent damage had occurred in the first cycle and to question whether subsequent cycles produced meaningful results. The ultimate load in the CEN Long protocol occurred during the monotonic stage. Response curves shown in Figure 3.3 allowed for the calculation of strength degradation and energy dissipation for each specimen. Results from prior monotonic tests are plotted with the curves for comparison purposes. Energy dissipation was highest using the FCC protocol, which was a result of the large number of high amplitude cycles. Although energy dissipation was lower in the CEN protocols, it was still well above that observed in shake table testing of specimens under simulated earthquake loads. A comparison of the three different protocols indicates the CEN Long protocol produces results that best represent the behavior of an actual structure under earthquake loading. The FCC protocol produced a failure mechanism inconsistent with that observed in actual earthquake loading. Furthermore, the large number of cycles produced unrealistic energy dissipation damand. Permanent damaged that occurred in the first cycle 19

36 of the CEN Short test created a lack of confidence in results obtained from subsequent cycles. The CEN Long test produced a realistic failure mechanism and had the highest ultimate load. However, the energy dissipation was still high when compared with actual earthquake loading. The authors concluded that although the CEN Long protocol produced the most realistic results, improvements are still required to emulate an actual earthquake response. 3.6 Ficcadenti, Steiner, Pardoen, and Kazanjy (1998) Researchers at the University of California, Irvine performed shearwall testing on standard shearwalls using three variations of the SPD protocol. The study was prompted by the lack of a standard procedure for the cyclic testing of woodframe shearwalls. Researchers were interested in identifying the effects of different loading sequences on the performance of woodframe shearwalls. Twenty-four standard 8 ft 8 ft shearwalls were constructed using Douglas fir dimension lumber. Standard 2 4 framing members were used with a single bottom plate and double top plates. Double studs were used at panel edges and 4 in. 4 in. posts were used at the wall ends. Sheathing was 3/8 thick PWD and oriented vertically with 1/8 in. spacing between panel edges. Bolted steel holdowns were used at the end studs and four 5/8 in. bolts with steel plate washers were used to anchor the bottom plates. Four different nail types were used to fasten the sheathing to the framing for a total of six walls with each nail type. The nail types were: 8d hand driven common nails, 8d hand driven galvanized box nails, 8d pneumatically driven common nails, and 8d pneumatically driven box nails. The test apparatus conformed to standards outlined by ASTM E 564. A steel base plate thin enough to allow full rotation of the sheathing was bolted to the strong floor and used to secure the specimens. Racking load was applied through a steel distribution beam lag bolted to the top plate. The load distribution beam was attached to a vertical steel column pin connected to the strong floor to allow rotation in the direction of loading. A ±76 mm actuator bolted to a strong wall and placed at mid-height of the vertical beam was used to apply the load. Because the top of the vertical beam was attached to the 2

37 horizontal loading beam, this setup allowed the limited stroke of the actuator to be amplified. Two walls of each nail type were tested with one of three variations of the SPD protocol. The first sequence used the loading protocol defined by the SPD standard (Figure 2.1). The second sequence followed the SPD standard except that the tests began at a displacement of 2% of the FME and continued as specified from there. This was intended to simulate the large excursions that are indicative of near-field events. The third sequence followed the SPD standard except that the three equal magnitude cycles following the decay cycles were removed. These cycles were removed in an attempt to minimize nail fatigue failure. The testing was performed at a cyclic frequency ranging from.25 to.5 Hertz until a displacement of 4 mm was reached, at which point the frequency was reduced to obtain a constant maximum velocity. Typical failure mechanisms observed were nail fracture, nails pulling through the sheathing, and nail withdrawal from the framing. It was noted that common nails were more prone to pulling through the PWD, while box nails tended to fracture more frequently. No mention was given to whether a failure mode appeared more frequently in one loading sequence than another. Some key observations made by the authors are given below. Specimens subjected to a larger number of prior inelastic cycles produced lower strength levels. Nail type did not significantly affect shearwall performance but loading sequence did, with sequence 2 producing the highest loads followed by sequence 3. There was no significant influence of loading sequence on the displacement capacity of the specimens 21

38 (a) PWD Walls (b) OSB Walls Figure 3.1 Response Curves from Dinehart and Shenton (reversed loading not shown) (a) SPD Test (b) ISO Test Figure 3.2 Response Curves from Karacabeyli and Ceccotti (a) FCC Protocol (b) CEN Long Protocol Figure 3.3 Response Curves from He, Lam, and Prion 22

39 Chapter 4 Testing Program Testing for Task of the CUREE-Caltech Woodframe Project was carried out in the Structural Components laboratory at the University of California, San Diego. A total of 36 specimens were tested using different sheathing configurations, loading protocols, and loading rates. 4.1 Test Specimens Structural Components Standard 8 ft square woodframe shearwalls intended to model modern construction practice were used as the test specimens. Studs were placed at 16 in. on center with double top plates and a single sill plate. Double studs anchored by Simpson HTT22 holdowns were used at the holdown boundaries. The holdowns were fastened to the end studs using thirty 16d green vinyl sinkers and were anchored to the test frame using a single 5/8 in. A325 high strength bolt at each holdown. A 5/8 in. A325 bolt using a Simpson BP 5/8-2 plate washer was fastened through the sill plate to form the shear anchorage. Two shear anchors were installed, each in the second bay on both ends of the specimen. The framing was nailed together using 16d gun nails according to the specifications outlined in UBC Table 23-II-B-1 (ICBO 1997). Two vertically oriented 4 ft 8 ft Structural I Rated sheets of either 15/32 in. plywood (PWD) or 3/8 in. oriented strand board (OSB) were fastened to the framing using 8d box gun nails to form the lateral-force-resisting system. Edge nails were placed at 4 in. on center and field nails were placed at 12 in. on center. A 1/8 in. gap was placed between the two sheathing panels at the interior interface. The nailing scheme resulted in ¾ in. edge distance at the outer and bottom edges and 3/8 in. edge distance at the inner and top edges of the sheathing panels. An illustration outlining the elements of the wall system is given in Figure Gypsum Wallboard On ten specimens, 1/2 in. gypsum wallboard (GWB) was applied to the interior side, opposite of the structural sheathing in order to evaluate the effects of interior 23

40 nonstructural finish materials. Two 4 ft 8 ft sheets were oriented horizontally and fastened with 1-1/4 in. screws placed at 16 in. on center in both the vertical and horizontal directions. The joint between the two sheets was finished with paper joint tape overlaid by all-purpose joint compound Stucco For the purpose of determining the influence of exterior stucco finish, residential grade stucco was applied to the outside of the sheathing on four specimens. The stucco boundaries were confined by a 7/8 in. Gr. 1 stucco stop. The stucco stop was installed because no return details were provided. The following components were used in the stucco application: 2-ply Jumbo Tex paper 17 gage self furred wire 1-1/4 wide crown staples (6 in. on center along framing members) Expo base #4 stucco (scratch coat, brown coat) Riverside plastic cement (finish coat) 1/2 chop strand fibers (mixed with stucco) Figure 4.2 shows the application of the brown coat over the scratch coat and Figure 4.3 shows the brown coat after it had cured. 4.2 Materials Testing Nail Connection Tests Connection tests of nailed sheathing to framing assemblies were performed using the test procedure followed by Fischer et al. (2) to determine the hysteretic properties of connections typical of those that exist in this shearwall study. Four types of connection tests were performed using two different test configurations with sheathing and framing materials from the test specimens. In two of the connection test configurations, the specimens were loaded to produce nail deformations parallel to the grain of the framing lumber. For the other two connection test configurations, the specimens were loaded to produce nail deformations perpendicular to the grain of the framing lumber. The specimens used the same 3/8 in. thick OSB, 15/32 in. thick PWD, and 8db gun nails used 24

41 in the shearwall study. Displacement-controlled monotonic tests were performed for all connection test configurations. In addition, displacement-controlled cyclic tests were also performed using the CUREE protocol The parallel-to-grain specimens were constructed using two 1 in. 2 4 pieces of framing lumber joined together with a 5 in. 1 in. piece of sheathing on each side as shown in Figure 4.4. The top half of each piece of sheathing was nailed to the top piece of lumber with two gun nails. The bottom half of each piece of sheathing was fastened to the bottom piece of lumber with two gun nails and one screw along with epoxy to produce a fixed condition. With this fixed condition at the bottom piece of lumber, only the top four nails (two each side) underwent deformation. The specimens were installed in a 11 kip MTS 81 Material Test System machine using custom steel brackets with two steel pins through each piece of framing lumber as shown in Figure 4.5. The machine applied an axial load to each specimen producing parallel-to-grain deformation in the framing members. The perpendicular-to-grain specimens were constructed using one 1 in. 2 4 piece of framing lumber with a 5 in. 1 in. piece of sheathing edge nailed on each side as shown in Figure 4.6. Each piece of sheathing was nailed at the edge to the 2 4 piece of lumber with three gun nails (6 total). The perpendicular-to-grain loading specimens were installed in a 11-kip MTS 81 Material Test System machine using custom steel brackets at the top with two steel pins through each piece of sheathing as shown in Figure 4.7. A flat bar placed across the surface of the 2 4 framing lumber was bolted to another bracket in the MTS machine creating a distributed load on the lumber when loaded. The machine applied an axial load to the brackets producing perpendicular-to-grain deformation in the framing-to-sheathing connections. The connection test specimens were instrumented with a linear potentiometer to measure the displacement of the sheathing relative to the framing lumber. For the parallel-to-grain loading test specimens, a linear potentiometer was installed to measure the displacement between the two pieces of framing lumber. A linear potentiometer was installed on the perpendicular-to-grain loading test specimens to measure the displacement of the sheathing relative to the MTS 81 Material Test System machine (or equivalently to the framing lumber since it was held fixed in place). 25

42 In total, thirteen connection tests were performed. Table 4.1 contains a test matrix showing how many specimens were tested under each configuration. Plots of the loaddisplacement history for each connection specimen can be found in the Appendix. Because the information is most useful in a single connector format, the forces for the parallel-to-grain specimens have been divided by four and the forces for the perpendicular-to-grain specimens have been divided by six so that only a single connector is considered Moisture Content At various points in the testing program the moisture content of the wood structural members was determined using the procedure outlined in ASTM D 4442 (ASTM 1992). Shown in Figure 4.8 is a plot of the moisture content progression over time. Apparent from the plot is a convergence of the moisture content from the asdelivered values to what is likely the equilibrium state (about 12%) for wood in the coastal area of San Diego. The moisture content of all components was less then 19% during each test, implying that each test was carried out under dry conditions to eliminate the moisture content effect Stucco Strength The stucco was applied by a commercial plastering company. At each stage of the stucco application a sample was taken that allowed for compressive testing to establish the strength of the stucco concrete. Three specimens from each application were placed in 2 in. cylinders and tested on Dec. 11, 2, near the date of the stucco shearwall tests. Given in Table 4.2 are the results from the compressive testing. 4.3 Test Matrix In addition to varying the loading protocol and loading rate, a variety of different sheathing, fastening, and finishing configurations were used to evaluate the influence of these parameters. Six different groups of specimens were used to determine the effects of the different test variables. A matrix outlining the organization of the testing is given in 26

43 Table 4.3. Note that two nominally identical specimens were tested simultaneously in each test Loading Protocol Effect Three different loading protocols in addition to the monotonic loading were used to determine the loading protocol effect. 1. CUREE-Caltech Standard Protocol (CUREE) 2. International Standards Organization Protocol (ISO) 3. Sequential Phased Displacement Protocol (SPD) For convenience, the CUREE-Caltech Standard protocol will be referred to as the CUREE protocol and the CUREE-Caltech Near-fault protocol will be referred to as the Near-fault protocol. Two different sheathing configurations were used to evaluate the loading protocol effects; four tests were performed with OSB sheathing and four tests were performed with PWD sheathing. All of the cyclic protocols used in the study required a reference displacement to characterize the displacement history. For the CUREE protocols (Figure 2.6) and the ISO protocol, the monotonic tests were used to determine the reference displacements. The reference displacement for the SPD protocol was chosen based on recommendations given in the SPD procedure in addition to reference displacements used in previous research (Dinehart and Shenton 1998). Table 4.4 contains values for the reference displacements used in this study Near-fault Effect The Near-fault protocol, characterized by a large pulse in the displacement history, is intended to model a building response to ground motions near the source of a seismic event. A point of interest is how the preliminary cycles and the large excursion affect the response. It is also of interest to compare the Near-fault response with that produced by monotonic testing, since the monotonic test is effectively an exaggerated one sided pulse. Two near-fault tests were performed, one with OSB sheathing and one with PWD sheathing. 27

44 4.3.3 Edge Nailing Effect It was shown in Figure 4.1 that double edge nailing at the top and exterior vertical edges of the sheathing panels was used in this study. The double nailing at these boundary regions effectively changes the nail spacing to 2 in. on center. The basis for the choice of this nail schedule was that this was the nail schedule used on the full-scale house tested under Task of the CUREE-Caltech Woodframe Project (Fischer et al. 2). This house was designed by an engineering firm and constructed by a general contractor. It was therefore decided to use the same nail schedule as the house, which would allow for easier correlation with the findings under that task. It was realized that the double edge nailing may not be indicative of what is commonly used in industry. In order to quantify the effect of the double edge nailing, a monotonic test was performed with OSB sheathing and nails at an effective 4 in. on center at the top and exterior vertical edges. This was accomplished by double nailing at 8 in. on center at these locations (double nailing was still required to provide shear transfer between the double holdown studs and the double top plates) Gypsum Wallboard Effect The effect of interior nonstructural finish materials has traditionally been considered negligible and, therefore, is usually not considered in design. As a result, the majority of research performed on woodframe shearwalls has not included the presence of nonstructural finish materials. In an effort to evaluate what effects, if any, the presence of GWB has on shearwall performance, GWB was installed on ten specimens. One monotonic test was performed with GWB only so that the effect of GWB could be isolated from the structural shearwalls. Two static tests were performed using the CUREE protocol and two dynamic tests were performed using the CUREE-Dynamic protocol (see next section) Dynamic Loading Rate Effect It has been well established that the performance of structural steel is dependent on strain rate. Since the fasteners used in woodframe construction are fabricated from steel, and the fasteners play a major role in the performance of woodframe shearwalls, it is reasonable to assume that strain rate plays an important role in woodframe shearwall 28

45 performance. Four specimens, each with both structural sheathing and GWB, were tested under a dynamic loading rate to explore what influence rapid loading has on shearwall performance. In order to investigate the influence of loading rate on shearwall performance, the CUREE protocol was modified so that a dynamic time history that simulates a seismic event could be imposed on the specimens. A sinusoidal curve was fitted to each distinct displacement amplitude with a fifth-order polynomial curve fit between changes in amplitude. The result was a smooth curve with no kinks or discontinuities in the velocity or acceleration time histories. By differentiating the displacement time history, the velocity could be obtained as shown in Figure 4.9. A reduction in specimen stiffness as it is loaded inelastically was modeled by an increase in period in the imposed input motion. Three different periods (T =.3,.5,.7 sec) corresponding to three different zones in the displacement history were used as shown in Figure 4.9. The decision of what periods to use were based on the following four criteria. 1. The initial natural period of the structure is estimated as T =.3 sec, which is considered the higher end for woodframe structures (Fischer et al. 2, Beck and Camelo et al. 21). The associated stiffness is defined as k i. 2. The period in zone i elongates based on secant stiffness degradation in zone i (see Figure 4.1), determined from monotonic testing, according to Ti k1 T 1 = (4.1) k i 3. Actuator limitations. 4. Engineering judgment. Figure 4.1 provides an example of the secant stiffness determination in each zone for an OSB specimen. Table 4.5 compares the value of (T i /T 1 ) based on the secant stiffness with the value used for the testing, which is designated as the period ratio. The secant stiffness is determined by finding the slope of a line connecting the origin with the point corresponding to the average displacement in zone i, designated as i. As Table 4.5 indicates, the (T i /T 1 ) values are in good agreement with the period ratio. 29

46 4.3.6 Stucco Effect Like GWB, exterior stucco finish is not usually, at least from a design perspective, considered to contribute to the structural performance of woodframe shearwalls. Testing under Task showed that the stucco contribution was significant and should be accounted for in some form (Fischer et al. 2). In order to help quantify what effects the stucco finish has, stucco was applied to four test specimens. For both of the stucco tests the CUREE-Dynamic Protocol was used. However, due to concerns about the testing system, the loading rate for Test 18 (PWD + stucco) was much slower than what can be considered dynamic; it can be considered as a static test using the dynamic protocol. 4.4 Test Setup A self reacting steel frame capable of testing two specimens in parallel was used as the test setup (Figure 4.11 and Figure 4.12). It was designed such that out-of-plane motion at the specimen boundaries (top and bottom) was prevented and the two specimens would undergo approximately the same displacements. A 165 kip, ±6 in. stroke dynamic actuator was used to load the specimens. It was placed at one-third height of a loading column pinned at the base, which allowed for amplification of the actuator displacement and velocity by a theoretical value of three. The loading column transferred load through a load cell attached to a WT1 41 load beam connected to the top plate (Figure 4.13). Examples of the pinned loading column are given in Figure 4.14 and Figure The load beam was guided such that it prevented out-of-plane displacement but allowed for uplift of the specimen as shown in Figure 4.16(a). An extra 2 4 member was placed between the load beam and top plate to allow space for rotation of the sheathing panels and provide a better simulation of the wood interface that normally would be at the top of the shearwall. Space was also provided for sheathing rotation at the bottom of the specimen by placing the specimen on a TS3 2 5/16 square tubing as shown in Figure 4.16(b). As mentioned, two walls were tested in parallel in each test. Due to torsion in the system caused by one wall inevitably being stiffer than the other, especially after failure of one specimen, there was some difficulty in constraining the specimens to equal 3

47 displacements. This resulted in the displacement history of the west wall to diverge from the desired input displacement. The displacement control of the actuator was controlled according to the displacement of the east wall, so the east wall displacement history always reflected the desired input motion. The net result of this difficulty was that for some tests the west wall displacement history did not exactly reflect the desired input displacement. However, the displacement protocol was satisfactorily followed by the west wall up to the ultimate load in all of the tests, and throughout the full displacement history in most of the tests. 4.5 Instrumentation An extensive instrumentation plan was used to capture localized effects in addition to the global response of the test specimens. A variety of different instruments were used to this end, which are outlined in Table 4.6. Since two walls were tested in parallel in each test, the instrument designations listed in Table 4.6 are appended with "E" for the East Wall and "W" for the West Wall. Figures 4.17 and 4.18 show the instrument layout for the East and West Walls, respectively. With each instrument designation is an arrow indicating a positive reading for that instrument. Most of the instruments used require some supplementary information for the data to be analyzed properly. For example, the width and height of a pair of diagonally placed displacement transducers is necessary to determine the shear deformation. Table 4.7 provides additional information not provided in Table 4.6. Furthermore, all of the instruments designated in Table 4.6 were not installed on every test specimen. Table 4.8 and Table 4.9 show which instruments were utilized during each test for the east and west walls, respectively. Instead of using structural sheathing on the exterior of the specimens in Test 12, GWB was used. Because the GWB was placed horizontally, some of the instrument locations needed to be altered. Figure 4.19 shows which instruments were used to evaluate the sheathing behavior and their respective locations. In subsequent tests where GWB was used, no instruments were installed on the GWB because either they were needed for the structural sheathing or the deformation was so small that it approached the resolution of the instrument. 31

48 4.6 Data Reduction Calculation of Global Shear Strain Potentiometers designated WSD and SSD were used to measure the global shear deformation of the shearwall and the sheathing panels, respectively. Information given in Table 4.7 provides the width and height of the X-pattern formed by the instruments, which allows for calculation of the shear strain using the following equation. where γ γ g δ 1 δ 2 a b δ 2ab δ 1 2 g = (4.2) 2 2 a + b = global shear strain = deformation of instrument 1 (WSD or SSD) = deformation of instrument 2 (WSD or SSD) = width of X-pattern = height of X-pattern Once the shear strain is calculated it can be multiplied by the height to obtain the component of drift due to shear deformation Calculation of Local Shear Strain Strain gages designated S1A, S1B, S2A, and S2B were used to measure local shear strain of the sheathing panels at a location near the center of the panel. The shear strain from these 9 strain rosettes is given by the following equation (Dally and Riley 1978) γ l = ε ε (4.3) a b where γ l ε a ε b = local shear strain = strain in gage a = strain in gage b Calculation of Deflection Components For seismic rehabilitation design, FEMA-273 (FEMA 1997) provides an equation (8-2) that allows for the calculation of woodframe shearwall deflection at yield. The 32

49 equation contains four terms that are used to characterize the deflection (Breyer et al. 1999): 1. bending of the chords ( b ), 2. shear in the sheathing ( v ), 3. slip of the nails ( n ), and 4. elongation of the holdown anchorage ( a ). Using each of the four terms, the shearwall deflection equation is given by where y v y h b E y 3 8v yh v yh = he EAb Gt n + = deflection at yield (in) h b = unit shear force applied at top of wall at yield (lb/ft) = height of shearwall (ft) = width of shearwall (ft) = elastic modulus of chord members (psi) A = area of chord members (in 2 ) G t d a e n = shear modulus of sheathing (psi) = effective thickness of sheathing (in) = deflection of holdown anchorage at end of wall (in) = nail deformation (in) d a (4.4) FEMA-273 defines yield as the force level that corresponds to 8% of the wall ultimate strength Chord Bending The first term accounts for bending deflection of the shearwall assuming the holdown studs act as the flanges or chords of a deep beam, connected by the sheathing, which acts as the web. Figure 4.2 can be used to help in the derivation of the first term. Assuming the wall rocks about the toe and the applied load (P) is the product of the unit shear force in kips per ft at yield (v y ) and the wall width (b), the reaction forces (R) can be calculated using simple statics giving 33

50 R = Ph b v ybh = = v yh b Assuming elastic behavior, the maximum strain at the base of the end stud is given by R v yh ε o = = (4.5) EA EA Shortening of one end stud and lengthening of the other produces a curvature at the base of 2ε 2v yh φ o o = = (4.6) b EAb Assuming the curvature varies from φ o at the base of the wall to zero at the top as shown in Figure 4.2, the curvature-area method can be used to calculate the deflection due to chord bending as b 2 1 2h φoh = φoh = (4.7) Substituting Equation 4.6 into Equation 4.7 and multiplying by 12 to convert to inches gives φ h 2v yh h v yh o 8 b = = ( 12) = 3 EAb 3 (4.8) EAb which is the first term in Equation 4.4. With slight modification, Equations 4.6 and 4.7 can be used to experimentally determine the deflection due to bending of the shearwall. For most of the tests, strain gages (HSS) were placed at approximately mid-height of the holdown studs (chords). Assuming a linear distribution of strain comparable to what is done in the code equation (see Section for experimental verification of this assumption), the measured strains will be half of the strain at the base. The theoretical difference in strain at the base (2ε o ) can be replaced with twice the difference of the measured strains [2(ε 2 -ε 1 )] in Equation 4.6, which gives ( ε ε ) φ o = (4.9) b where ε 1 and ε 2 are the measure strains at mid-height of each holdown stud. Substituting Equation 4.9 into Equation 4.7 gives 34

51 b ( ε ε ) 2 2 φoh h = = (4.1) 3 3b Equation 4.1 was used to experimentally determine the deflection due to the bending effect of the shearwall Sheathing Shear Deformation The second term in the Equation 4.4 accounts for deflection due to shear in the sheathing panels. If the shear force (P=vb) at the top of the wall is known, the shear strain can be found using the following equation γ = vb = Gtb v Gt where G is the shear modulus of the sheathing. The shear deflection can then be determined by multiplying the shear strain (γ) by the wall height (h). vh v = γh = (4.11) Gt which is the second term in Equation 4.4. Note that shear deflection of the sheathing panel may not translate directly into the global deformation of the shearwall (measured at the top plate) since there is relative movement between the framing and the sheathing. However the approximation is still reasonable, especially considering that the contribution of panel shear deformation is small, as will be shown later. Strain gages placed on the sheathing allow for the experimental determination of the sheathing shear deflection. Assuming the local shear strain is relatively uniform over the sheathing panel, the panel shear strain can be determined from Equation 4.3. Each panel has an independent set of strain gages so the average strain from the two panels was used to find the sheathing shear strain. The sheathing shear strain was then multiplied by the wall height to experimentally determine the deflection due to sheathing shear as shown in Equation v ( γ + γ ) l l 2 = (4.12) 2 1 h where γ l1 and γ l2 are the local shear strains from panels 1 and 2, respectively. 35

52 Anchorage Component The fourth term in Equation 4.4 accounts for deformation in the holdown anchorage. If the uplift of the wall corner due to deformation of the anchorage is defined as d a, then the aspect ratio (h/b) can be used to transform this vertical deformation into horizontal displacement by the following equation: h a = d a (4.13) b which is the last term in Equation 4.4 A similar approach is used to experimentally determine the displacement due to anchorage deformation except that, in addition to uplift, compression in the holdown region at the wall corner is also accounted for by the following equation: a h = ( da2 da 1) b ) (4.14) where d a1 and d a2 is the compressive and tensile deformation on opposite ends of the shearwall, respectively. These values are measured using instruments designated HSU Nail Slip Component The third term in Equation 4.4 accounts for slip in the nails as the wall is loaded. It is a semi-empirical term based on experimentally determined nail slip values and the sum of nail slip components at different locations on the sheathing giving n =.75he n (4.15) Based on the FEMA-273 document, the 8db nails used in the study correspond to an e n value of.6. Although no instrumentation was used that allowed for direct calculation of the nail slip component, it could be indirectly determined by subtracting the other measured components from the global displacement. n T ( b + v + a s = + (4.16) where T is the total lateral displacement taken at the top plate and measured from instruments designated WD. Note also the addition of an additional term ( s ). This term is needed to account for sill plate slip that is not included in Equation 4.4, which is directly measured using instruments designated SS. 36

53 4.6.4 Inertial Components of Dynamic Load Due to the high rate of loading that was used in the dynamic testing, inertial effects needed to be accounted for. An illustration of the free-body diagrams for the load beam and the shearwall are given in Figure The diagrams show all of the forces and accelerations acting on the load beam and shearwall with the following definitions for each of the variables shown: F = measured force acting on the load beam (see Figure 4.13 for the measuring device) R = resisting force of shearwall on load beam V = base shear on shearwall a b = measured acceleration of load beam a w (y) = assumed acceleration distribution in shearwall m b m w h b = mass of load beam = mass of shearwall = height of shearwall = width of shearwall Applying Newton's second Law to the load beam gives R = F m b a b (4.17) So the resisting force at the top of the wall is equal to the measured wall force minus the inertial component of the load beam. In actuality, for positive displacements the acceleration is typically negative so the resisting force turns out to be greater than the measured wall force. Assuming the acceleration follows a linear distribution from zero at the base to a b at the top of the shearwall and assuming a uniform distribution of mass, Newton's second Law can be applied to the shearwall giving: R V h m = h w a w ( y) dy (4.18) where a w is given by a ab ( y) y (4.19) h w = 37

54 Substituting Equation 4.19 into Equation 4.18 gives 2 2 dy 2 2 b w b w h b w a m h h a m y h a h m V R = = = 2 2 b w b b b w a m m a F a m R V = = + = 2 w b b m m a F (4.2) This base shear force was used in reporting the test results. Clearly some liberties were taken in the assumptions used to derive the inertial components of the shearwall force. Specifically, the acceleration distribution is not necessarily linear and the mass of the sheathing was included in the shearwall mass, which does not undergo the same accelerations as the framing. Nevertheless, the assumptions made should provide a reasonable estimate of the inertial force effect Filtering for Dynamic Test Data Consistent with what is typically done in dynamic testing, high frequency noise was filtered from the test data. A Fourier transform was performed to determine a reasonable frequency at which to filter the data. Based on the frequency spectrum obtained from the Fourier transform, the dynamic test data was passed through a lowpass filter with a cut-off frequency of 1 Hertz and a roll-off frequency of 11 Hertz. 38

55 Table 4.1 Test Matrix for Connection Test Specimens Loading Configuration Sheathing Monotonic Parallel Perpendicular No. Specimens OSB 2 PWD 2 OSB 1 PWD 2 Cyclic Parallel Perpendicular OSB 1 PWD 1 OSB 2 PWD 2 Table 4.2 Average Stucco Compressive Strength Coat Strength (psi) Age (days) Scratch 11 3 Base 8 27 Finish

56 Table 4.3 Test Matrix (Two Specimens per Test) Group Test No. Protocol Sheathing Notes Loading Protocol Effect 1 Monotonic OSB 2 CUREE OSB 3 ISO OSB 4 SPD OSB 5 Monotonic PWD 6 CUREE PWD 7 ISO PWD 8 SPD PWD Near-fault 9 Near-fault OSB Effect 1 Near-fault PWD Nailing Effect GWB Effect Dynamic Effect Stucco Effect 11 Monotonic OSB 12 Monotonic GWB 13 CUREE OSB + GWB 14 CUREE PWD + GWB 15 CUREE OSB + GWB 16 CUREE PWD + GWB 17 CUREE OSB + Stucco 18 CUREE PWD + Stucco CUREE Dynamic Loading with GWB CUREE Dynamic Loading with GWB CUREE Dynamic Loading CUREE Dynamic Loading at Static Rate 4

57 Table 4.4 Reference Displacements in inches Used for Test Protocols Sheathing CUREE ( ) ISO (ν u ) Protocol SPD (FME) Near-fault ( m ) OSB PWD Values of, m, and v u are determined from Figure 5.3 and Figure 5.24 for OSB and PWD, respectively. Table 4.5 Calculation of Period Based on Secant Stiffness Zone i (in) ki (kips/in) T i k 1 T 1 = k i Period Ratio

58 Table 4.6 Instrumentation Instrument Name Type Function sill uplift SU1 potentiometer sill uplift at wall end sill uplift SU2 potentiometer sill uplift at shear anchor sill uplift SU3 potentiometer sill uplift at center of wall sill uplift SU4 potentiometer sill uplift at shear anchor sill uplift SU5 potentiometer sill uplift at wall end sill slip SS1 potentiometer sill slip at first interior stud sill slip SS2 potentiometer sill slip at first interior stud holdown stud uplift HSU1 potentiometer holdown uplift at wall end holdown stud uplift HSU2 potentiometer holdown uplift at wall end wall shear displacement WSD1 string pot. deformation between wall corners wall shear displacement WSD2 string pot. deformation between wall corners sheathing shear displ. SSD1 string pot. deformation between sheathing corners sheathing shear displ. SSD2 string pot. deformation between sheathing corners sheathing shear displ. SSD3 string pot. deformation between sheathing corners sheathing shear displ. SSD4 string pot. deformation between sheathing corners wall displacement WD string pot. global wall displacement (control displ.) horiz. sheathing displ. HSD string pot. horizontal displ. at center of sheathing vert. sheathing displ. VSD string pot. vertical displ. at center of sheathing holdown stud elongation HS1 string pot. elongation of holdown stud holdown stud elongation HS2 string pot. elongation of holdown stud wall force WF 5 kip load cell global wall force anchorage force AF1 load cell force at holdown stud anchorage force AF2 load cell force at shear anchor anchorage force AF3 load cell force at shear anchor anchorage force AF4 load cell force at holdown stud sheathing rotation SR1 inclinometer rotation of sheathing sheathing rotation SR2 inclinometer rotation of sheathing sheathing shear strain S1A strain gage leg of 9 strain rosette on sheathing sheathing shear strain S1B strain gage leg of 9 strain rosette on sheathing sheathing shear strain S2A strain gage leg of 9 strain rosette on sheathing sheathing shear strain S2B strain gage leg of 9 strain rosette on sheathing holdown stud strain HSS1 strain gage strain at exterior center of holdown stud holdown stud strain HSS2 strain gage strain at exterior center of holdown stud holdown stud strain HSS3 strain gage strain at interior center of holdown stud holdown stud strain HSS4 strain gage strain at interior center of holdown stud holdown stud strain HSS5 strain gage strain at interior top of holdown stud holdown stud strain HSS6 strain gage strain at interior bottom of holdown stud acceleration A1 accelerometer acceleration at top of wall acceleration A2 accelerometer acceleration at top of wall 42

59 Table 4.7 Instrumentation Details Instrument Information WSD1, WSD2 a = 93", b = 94.5" SSD1, SSD2 a = 93", b = 94.5" SSD1, SSD2 a = 39", b = 78" SSD3, SSD4 a = 39", b = 78" SSD1, SSD2 For Test 12: a = 78", b = 39" HSD only on north sheathing of west wall VSD only on north sheathing of west wall HS1-2 initial length = 86" S1A, S1B placed in X pattern near center of sheathing S2A, S2B placed in X pattern near center of sheathing b a 43

60 Instrument Table 4.8 Instruments Available for East Wall Specimens Test Number SU1-E SU2-E SU3-E SU4-E SU5-E SS1-E SS2-E HSU1-E HSU2-E WSD1-E WSD2-E SSD1-E SSD2-E SSD3-E SSD4-E WD-E HS1-E HS2-E WF-E AF1-E AF2-E AF3-E AF4-E SR1-E SR2-E S1A-E S1B-E S2A-E S2B-E HSS1-E HSS2-E HSS3-E HSS4-E A1-E A2-E 44

61 Table 4.9 Instruments Available for West Wall Specimens Instrument Test Number SU1-W SU2-W SU3-W SU4-W SU5-W SS1-W SS2-W HSU1-W HSU2-W WSD1-W WSD2-W SSD1-W SSD2-W SSD3-W SSD4-W WD-W HS1-W HS2-W HSD-W VSD-W HS1-W HS2-W WF-W AF1-W AF2-W AF3-W AF4-W SR1-W SR2-W S1A-W S1B-W S2A-W S2B-W HSS1-W HSS2-W HSS3-W HSS4-W HSS5-W HSS6-W A1-W A2-W 45

62 8db FIELD 12" O.C. 8db GUN NAILS 2 4" O.C. 2x4 STUD GRADE DOUGLAS FIR 16" (TYP) 15/32" PWD OR 3/8" OSB STRUC 1 SHEATHING 8db GUN NAILS 1 4" O.C. SHEAR ANCHOR 5/8" BOLT WITH 2" PLATE WASHER " 2x4 PRESSURE TREATED SILL PLATE HTT22 SIMPSON HOLDOWN 24" 96" Figure 4.1 Details of Test Specimens 46

63 Figure 4.2 Stucco Application Figure 4.3 Cured Brown Coat 47

64 Figure 4.4 Parallel-to-Grain Connection Test Specimen Details (Illustration Courtesy of Fischer) 48

65 Figure 4.5 Test Setup for Parallel to-grain Connection Tests 49

66 Figure 4.6 Perpendicular-to-Grain Connection Test Specimen Details (Illustration Courtesy of Fischer) Figure 4.7 Test Setup for Perpendicular to-grain Connection Tests 5

67 OSB PWD STUD TOP PL. SILL PL May 23-Jun 12-Aug 1-Oct 2-Nov 9-Jan Date Figure 4.8 Moisture Content Displ. (in) 6 4 T =.3 sec T =.5 sec T =.7 sec Time (sec) Vel. (in/sec) Time (sec) Figure 4.9 Loading History for CUREE Dynamic Protocol 51

68 1 8 6 k 3 4 k 2 2 k Drift (in) Figure 4.1 Secant Stiffness Calculation (Test 2 West) East Figure 4.11 Test Frame with Two Shearwall Specimens 52

69 (a) Test Frame with Shearwalls Removed (b) Test Frame with Two Shearwalls Figure 4.12 Test Frame 53

70 Figure 4.13 Load Cell Placement GUIDE LOADING COLUMN ACTUATOR Figure 4.14 Profile of Test Frame (Shearwalls not Shown) 54

71 Figure 4.15 Loading Column with Pinned Column Base 55

72 GUIDE CHANNELS (MC6X16.3) LOAD BEAM (WT7X41) TEFLON SLIDER EXTRA 2x4 MEMBER 2x4 TOP PLATES (a) Top of Specimen FRAMING SHEATHING TUBING (TS3X2X5/16) BASE (W1X68) (b) Base of Specimen Figure 4.16 Specimen Boundary Configurations 56

73 WF N WD WSD1 WSD2 HS1 HS2 HSS1 HSS3 HSS4 HSS2 HSU1 HSU2 SU1 AF1 SS1 AF2 SU2 SU3 AF3 SU4 AF4 SS2 SU5 (a) Framing Side A1 N A2 SSD1 SSD2 SSD3 SSD4 SR1 SR2 S1A, S1B S2A, S2B (b) Sheathing Side Figure 4.17 East Wall Instrumentation 57

74 N WD WF HSS5 WSD1 WSD2 HS1 HS2 HSD HSS1 HSS3 HSS4 HSS2 HSS6 HSU1 VSD HSU2 SU1 SS1 AF1 AF2 SU2 SU3 AF3 SU4 AF4 SS2 SU5 (a) Framing Side N A1 A2 SSD1 SSD2 SSD3 SSD4 SR1 SR2 S1A, S1B S2A, S2B (b) Sheathing Side Figure 4.18 West Wall Instrumentation 58

75 N SR1 SR2 (a) East Wall N SSD1 SSD2 SR1 SR2 (b) West Wall Figure 4.19 GWB Instrumentation for Test 12 59

76 P b h ε1 ε2 φο, εο R R Figure 4.2 Calculation of Chord Bending Deflection a b LOAD BEAM m b R F SHEARWALL R a w (y) h L m w y L b V Figure 4.21 Free-Body Diagram of Shearwall and Load Beam 6

77 Chapter 5 Test Results Some aspects of the shearwall behavior were consistent for many or all of the test specimens regardless of the loading protocol or sheathing configuration used. An overview of characteristics general to all the specimens is presented in Section 5.1. Observations specific to each specimen are presented in subsequent sections. 5.1 General Observations As has been observed in previous shearwall testing, the sheathing panels rotated and the fasteners deformed as the displacement demand was increased [Figure 5.27(c)]. The rotation in each panel was essentially equal until a line of fasteners failed in one panel, at which point that panel pulled away from the framing and the rotation was relaxed [Figure 5.6(a)]. The top and bottom plates remained relatively horizontal with some double curvature bending occurring in the top plates. Slanting of the interior studs such that they act pinned top and bottom contributed more to the shearwall deformation than did stud bending. Eccentricity was imposed on the framing due to the structural sheathing being applied only to one side of the framing. A common result of this was twisting of the studs, especially in the holdown region [Figure 5.19(b)]. Fastener (nail) failure can be characterized by four different failure modes, all of which were observed at some point in the testing. 1. nails pulling out of the framing [pullout, Figure 5.19(d) and Figure 5.4(a)], 2. nails pulling through the sheathing material [pullthrough, Figure 5.43(d)], 3. nails tearing through the edge of the sheathing material [tearout, Figure 5.19(a)], 4. fracture of the nails [fracture, Figure 5.19(c)]. Although all of these modes were observed, all of them were not necessarily present in each test. Nail tearout was typically concentrated at the inner corners of the sheathing panels and at the top row of nails at the top edge. The number of nail fractures in a specimen appeared to be related to the number of cycles imposed on the specimen, especially when there are groups of equal amplitude cycles. Nail fracture was also related to the performance of the specimens, where more nail fractures tended to result in poorer 61

78 performance. It also appears that a large number of nail fractures resulted in less demand on the other structural elements, such as the framing members. Framing damage was more apparent in monotonic tests where very few or no nail fractures occurred. Due to the double nailing provided at the vertical exterior edges of the sheathing, it is not surprising that there was little fastener damage at these locations. Damage was concentrated at the top and bottom portions of the vertical edges. For the two specimens with 4 in. effective nailing at all of the sheathing boundaries (Test 11), fastener damage at the vertical edges was more pronounced in the East Wall. However, it still did not contribute as much to specimen failure as fastener damage at the other edges. Although also double nailed, fasteners at the top edge of the sheathing experienced more damage than the left and right edges. This is likely a result of the smaller edge distance for the outer row and the close proximity of the outer row to the interface between the two top plates. Considerable bending was observed in the studs, especially in the holdown studs [Figure 5.23(b)] when the load approached the ultimate load. Bending of the studs generally occurred in the bottom portion of the wall when significant damage in the fasteners occurred, causing the shear to be resisted by the studs, not sheathing. The bending (and sometimes fracture) in the holdown studs was most pronounced right above the holdown strap. This is due to the holdown studs being much stronger and stiffer in the holdown strap region where a total of thirty 16d strap nails along with the sheathing edge nailing bonded the strap and studs together. Above the holdown strap were only a few nominal fabrication nails in addition to the sheathing edge nailing, creating an abrupt transition in member properties above the strap. Splitting of the sill plate with the grain was a common occurrence, especially at the holdown area [Figure 5.3(a)]. The 8db sheathing nails in addition to the four 16d nails used to fasten the holdown studs to the sill plate created small cracks in the sill plate that proliferated as the deformation demand on the specimen was increased. The sill plate cracks, however, did not appear to have a significant influence on the performance of the specimens. 62

79 5.2 Specific Observations Plots showing the global response and schematics illustrating the failure patterns are provided for each specimen. The schematics outline the fastener failures depicted by dashed lines that show where fastener damage occurred. The dashed lines do not necessarily imply that all of the fasteners were damaged in that region, only that some fastener damage existed there. Where available, a rough estimate of the relative percentage of the occurrence of each nail failure mode in each line of fasteners is provided. Nail locations where there are no dashed lines imply that no fastener damage occurred there. The schematics also display the framing side and any damage that occurred to the framing members Loading Protocol Effect Test 1: OSB with Monotonic Loading Figure 5.1(a) contains an illustration of the failure pattern of the East Wall. The north sheathing panel separated out of plane as shown in Figure 5.2(b), causing the specimen strength to quickly degrade. Holdown uplift with the holdown stud separating from the sill plate contributed to wall drift as shown in Figure 5.2(d). A plot of the global response is given in Figure 5.3(a). Figure 5.1(b) contains an illustration of the failure pattern for the West Wall. Significant nail tearout occurred near the center of the specimen as shown in Figure 5.2(a). Top plate separation [Figure 5.2(c)] occurred at both ends of the specimen, forming a double bending pattern. A plot of the global response is given in Figure 5.3(b). Often of interest to engineers is the holdown force that results from a given horizontal load at the top of the specimen. Shown in Figure 5.4 are plots showing the tensile holdown force as a function of the applied load. If statics is used for this calculation assuming the shearwall rocks about the leading edge of the specimen, then the tensile force should increase on a one-to-one basis with the applied load. Although the plots show this is not a perfect assumption, the results are approximately correct. 63

80 Test 2: OSB with CUREE Protocol An illustration of the failure pattern for the East Wall is given in Figure 5.5(a). Figure 5.6(a) shows a sheathing panel partially separating from the framing, and Figure 5.6(b) shows the sill plate framing nails pulling away from a stud allowing the stud to separate from the sill. Eccentricity caused by placing the sheathing on one side caused holdown twisting as shown in Figure 5.6(c). A plot of the global response is given in Figure 5.7(a). For comparison purposes, the response from the monotonic test (Test 1) is also presented. Figure 5.5(b) contains an illustration of the failure pattern for the West Wall. Nail pullout occurred at the bottom of the holdown studs allowing the sheathing to separate as shown in Figure 5.6(d). A plot of the global response is given in Figure 5.7(b). Note that the West Wall displacement was less than that of the East Wall due to causes described in Section 4.4 (corrective action was taken after this test to help minimize this effect). The FEMA-273 document introduced in Section contains an equation (Equation 4.4) for calculation of the lateral displacement of a woodframe shearwall. Missing from the Equation is a term for sill plate slip. Figure 5.8 contains plots of sill slip versus applied load (slip along the length of the sill plate was relatively uniform). Although both plots show the stick-slip phenomenon indicative of friction effects, the West Wall plot is one sided. Apparently there is some mechanism preventing negative slip in the West Wall. Examples of which could be binding of the toe against an imperfection in the base or tolerances in the anchor bolt holes being biased to one side. The plots do show that the sill slip component of shearwall deflection is not trivial. As mentioned earlier, the sheathing panels rotate as the shearwall deflects. Figure 5.9 shows the measured rotation of the sheathing panels as the wall is loaded. The plots show that the two adjacent sheathing panels on each specimen undergo similar rotations. Furthermore, the rotation of each panel is approximately the same as that of the vertical framing members, as implied by the global drift ratio of the specimen. This is to be expected given that the double edge nailing at the holdown studs essentially constrains the rigid sheathing panels to the same rotations as the holdown studs. Instruments were placed at the ends of the specimens to measure uplift of the holdown studs. The measurements were taken using the base of the specimen as a 64

81 reference so the values produced include uplift of the holdown stud and the sill plate taken together. Plots provided in Figure 5.1 show the uplift of the holdown studs. A small correction was made so that the plots represent the holdown uplift at the centroid of the holdown stud as opposed to the edge where the measurement was taken. The peak uplift of over.5 in. verifies the significant amount of deformation that was observed in the holdown straps. Because the specimens were square, uplift of the holdown studs translated directly into lateral drift of the specimen. Another interesting observation that can be obtained from the plots is the considerable negative holdown displacement. This was largely a result of the high compressive loads in the holdown studs compressing the relatively soft pressure treated sill plates. Figure 5.11 shows the anchorage force distribution measured at the four anchor bolt locations at peak positive load. Although the load cells were only capable of measuring compressive loads, their placement was such that they measure tension in the anchor bolts. Any compressive (negative) force reading can only reflect decompression of the load cells from their initial compressive state that resulted from tightening of the anchor bolts, so compressive forces higher than the initial anchor bolt tension will not be registered. However, the plots can verify that the only tensile force that existed at peak load was in the holdown stud opposite the load direction. For comparison purposes the peak applied load is shown on the plots. It provides an example of the accuracy that can be obtained by using statics and assuming the wall rotates about the toe of the wall. Although not a perfect relationship, it shows that a reasonable approximation can be obtained by using this simple model. At the centroid of the north panel on the West Wall, potentiometers were placed to measure the global translation of the sheathing panel. Plots comparing the horizontal and vertical component of the sheathing displacement to the global displacement are given in Figure Because the centroid of the panel is at half the wall height, the horizontal sheathing component is approximately half of the global displacement. This helps to substantiate the assumptions made is Section It can be observed from Figure 5.12(b), indicative of the rocking motion of the panel, that the vertical component of sheathing displacement is always positive and is negligible. 65

82 Test 3: OSB with ISO Protocol Figure 5.13(a) contains an illustration of the failure pattern for the East Wall. Although small in number, some nail fractures occurred in this test, which were not present in the monotonic or the CUREE tests. Towards the end of the test the center stud broke due to bending at a knot near the bottom of the wall [Figure 5.14(b)] and the north sheathing panel separated from the framing. A plot of the global response is given in Figure 5.15(a). Figure 5.13(b) contains an illustration of the failure pattern for the West Wall. A small number of nail fractures were observed in this specimen as well. A large longitudinal split in the sill plate was initiated near the peak load and grew larger towards the end of the test [Figure 5.14(a)]. Significant top plate separation occurred at both ends of the specimen, forming a double bending pattern as shown in Figures 5.14(c) and (d). A plot of the global response is given in Figure 5.15(b). Figure 5.16 contains a profile of the sill plate uplift at five locations along the specimen at peak positive load. All of the measurement locations are at anchor bolts except for the instrument at the center of the wall. Although the sill plate uplift at the leading edge of the specimen is to be expected, the significant compression at the opposing edge may be unexpected. Inspection of the plots show that the sill plate is in double bending at peak load. For this test strain gages were placed at mid-height on both the interior and exterior sides of the holdown studs in the East Wall. A plot of the strains from each side of the holdown studs is given in Figure The plot shows that the strain is of the same sign and approximately constant across the cross-section, indicating that axial components dominate any bending that occurred Test 4: OSB with SPD Protocol Figure 5.18(a) contains an illustration of the failure pattern for the East Wall. A longitudinal split formed in the north holdown stud where the outer row of sheathing nails penetrated the stud. The south sheathing panel separated from the framing, contributing to the softening of the specimen. Figure 5.19(b) provides an example of the holdown twisting that resulted from sheathing eccentricity, and nail tearout that occurred at the top-center of the specimen is shown in Figure 5.19(a). As indicated in Figure 66

83 5.18(a), a large number of nail fatigue fractures occurred in this test, considerably more than had occurred with the other protocols. As a result, the specimen exhibited a reduced strength and deformation capacity as shown by the global response in Figure 5.2(a). Figure 5.18(b) contains an illustration of the failure pattern for the West Wall. Similar to the East Wall, there were a large number of nail fractures that occurred in this specimen. Examples of nail fatigue fracture and nail pullout that occurred in this specimen are given in Figure 5.19(c) and Figure 5.19(d), respectively. Both sheathing panels separated from the center stud due to nail fracture causing the specimen to fail. A plot of the global response is given in Figure 5.2(a). As discussed in Section 4.6.3, the shearwall deflection Equation uses four components to characterize the shearwall deflection that are reproduced here. 1. shearwall bending, 2. shear in the sheathing, 3. slip of the nails, and 4. elongation of the holdown anchorage. Components 1, 2, and 3 can be lumped into racking shear of the wall assembly, component 4 can be viewed as uplift of the holdown stud, and as mentioned earlier, sill plate slip can be added to the equation. Plots comparing the overall measured displacement with the displacement determined from summing the components of wall assembly racking shear, holdown stud uplift, and sill plate slip are shown in Figure Assuming pure shear, the wall assembly racking shear was determined by using the procedure given in Section to calculate the global shear strain (γ g ) using instruments designated WSD and multiplying it by the wall height. The holdown stud uplift and sill plate slip was obtained from instruments HSU and SS directly. Ideally the plot should show a one-to-one relationship between the summed components and the measured deflection, which was reasonably close to the case, although as indicated by the plot, there was a slight underprediction Test 5: PWD with Monotonic Loading Figure 5.22(a) contains an illustration of the failure pattern for the East Wall. Failure of the specimen was primarily due to the north sheathing panel separating from the framing. Examples of nail pullout and nail tearout that contributed to sheathing 67

84 separation are given in Figures 5.23(a) and (c), respectively. A plot of the global response is given in Figure 5.24(a). Figure 5.22(b) contains an illustration of the failure pattern for the West Wall. Bending in the holdown stud leading to considerable curvature is shown in Figure 5.23(b). The south holdown stud split and broke longitudinally as shown in Figure 5.23(d). A plot of the global response is given in Figure 5.24(b). Figure 5.25 shows plots of the anchorage force like those created for Test 2. Similar to Test 2 (Figure 5.11); the only anchor location where tension was observed was at the holdown stud opposite the direction of applied load. The peak applied load added to the plots shows that the tensile force in the holdown can be reasonable estimated using a simple static analysis Test 6: PWD with CUREE Protocol Figure 5.26(a) contains an illustration of the failure pattern for the East Wall. Observable nail damage started at a displacement of 7% and progressed from there. At the last primary cycle, the two sheathing panels binded against each other and buckled out of plane as shown in Figures 5.27(a) and (b). Sheathing rotation and shearwall deformation that allowed the specimen to deform are shown in Figure 5.27(c) and (d). A plot of the global response is given in Figure 5.28(a). Figure 5.26(b) contains an illustration of the failure pattern for the West Wall. The south sheathing panel separated from the framing causing the stiffness to deteriorate. A plot of the global response is given in Figure 5.28(b) Test 7: PWD with ISO Protocol Figure 5.29(a) contains an illustration of the failure pattern for the East Wall. At a displacement of 1% ν u, splits were initiated in the holdown studs leading to deterioration of specimen strength [Figures 5.3(b) and (d)]. A plot of the global response is given in Figure 5.31(a). Figure 5.29(b) contains an illustration of the failure pattern for the West Wall. A cross-grain split in the north holdown stud occurred at a displacement of 1% ν u. The sill plate split at the south end of the specimen near the holdown region as shown in Figure 5.3(a) and a 45 rotation occurred in the center stud as shown in Figure 5.3(c). A plot of the global response is given in Figure 5.31(b). 68

85 Test 8: PWD with SPD Protocol Figure 5.32(a) contains an illustration of the failure pattern for the East Wall. Relative rotation of the sheathing panels was observed as shown in Figure 5.33(a). An example of the nail fracture common in the SPD tests and pulling away of the sheathing that can result is given in Figures 5.33(b) and (c). At 175% of the FME a sill plate crack formed at the north end of the specimen [Figure 5.33(d)]. At 25% of the FME nails started pulling away from the framing and at 4% of the FME nail fractures at the center stud were observed. As was the case with the OSB panels, a large number of nail fractures occurred under this protocol. A plot of the global response is given in Figure 5.34(a). Figure 5.32(b) contains an illustration of the failure pattern for the West Wall. Fastener failures followed a similar history as those on the East Wall. global response is given Figure 5.34(b) Near-fault Effect A plot of the Test 9: OSB with Near-fault Protocol Figure 5.35(a) contains an illustration of the failure pattern for the East Wall. Fastener damage leading to specimen failure was initiated in the first large cycle (6% m ) and the load reached in this cycle was never reached again. Significant stud damage occurred in this specimen, examples of which are given in Figures 5.37(a) and (d). This stud damage was more severe than any observed in the monotonic testing or with the CUREE protocol. However, damage patterns in the fasteners were comparable. A plot of the global response is given in Figure 5.36(a). Figure 5.35(b) contains an illustration of the failure pattern for the West Wall. Like the East Wall, the peak load was reached in the first large cycle (6% m ) and degraded in subsequent cycles. Severe separation of the top plates that lead to double bending in the top plate is shown in Figure 5.37(b). Studs lifting from the sill plate are shown in Figure 5.37(c). A plot of the global response is given in Figure 5.36(b). For this test, more detailed strain gage instrumentation was installed on the south holdown stud of the West Wall. Although strain gages were installed on the holdown studs in most tests, for this test three gages were installed so that a strain profile along the 69

86 holdown stud could be obtained. A bottom gage was placed right above the holdown strap, a middle gage was placed at the typical location near mid-height of the stud, and a top gage was placed near the top of the stud. Figure 5.38 shows a plot of the strain profile on the south holdown stud of the West Wall. The plot shows a varying strain distribution that attenuates from bottom to top with a near linear profile Test 1: PWD with Near-fault Protocol Figure 5.39(a) contains an illustration of the failure pattern for the East Wall. Similar to the OSB specimens, the peak load was reached in the first large cycle (6% m ) and degraded in subsequent cycles. An example of the nail pullout predominate in this specimen is provided in Figure 5.4(a). A plot of the global response is given in Figure 5.41(a). Figure 5.39(b) contains an illustration of the failure pattern for the West Wall. An example of the significant bending that is imposed on the holdown studs is given in Figure 5.4(b). Damage to the center stud is shown in Figure 5.4(c) and nail pullout at the south holdown stud is shown in Figure 5.4(d). A plot of the global response is given in Figure 5.41(b). The failure modes observed using the Near-fault protocol were similar to that of the monotonic testing and the testing using CUREE protocol Nailing Effect Test 11: OSB with Monotonic Loading (4 in. Effective Edge Nailing) Figure 5.42(a) contains an illustration of the failure pattern for the East Wall. Pullthrough of the nails occurred at the upper portion of the holdown studs, which was not observed in any of the other specimens with the 2 in. edge nailing. There was also a broken stud at the upper portion of the specimen as shown in Figure 5.43(b) (stud failures were limited to the bottom portion of the specimens in all of the other tests.) Another unique feature of this specimen was the slip of the two top plates relative to each other as shown in Figure 5.43(a). This was probably due to the reduced shear transfer capacity between the top plates (provided by the sheathing) resulting from reduced sheathing nailing there. A plot of the global response is given in Figure 5.44(a). Figure 5.42(b) contains an illustration of the failure pattern for the West Wall. Nailing at the holdown studs remained relatively intact in this specimen, as did the 7

87 relative displacements of the top plates. Failure of the fasteners at the sheathing boundaries occurred first, leading to degradation of the stiffness and capacity protection of the other elements. Examples of the nail pullthrough that was common in this specimen are given in Figures 5.43(c) and (d). A plot of the global response is given in Figure 5.44(b) GWB Effect Test 12: GWB with Monotonic Loading Figure 5.45(a) contains an illustration of the failure pattern for the East Wall. Because no structural sheathing was applied, the peak strength of this specimen was drastically reduced as indicated by the global response shown in Figure 5.47(a). The GWB panels and the mud and tape at the joint remained essentially intact as shown Figures 5.46(a) and (c). Most of the damage was isolated to pullthrough of the screws in the top panel [Figure 5.46(b)] and cracking of the GWB at the corners [Figure 5.46(d)]. Some of the interior screws also pulled through the sheathing and there were a couple of screws that fractured. Figure 5.45(b) contains an illustration of the failure pattern for the West Wall. The behavior was very similar to that of the East Wall, except that the damage was concentrated in the bottom panel as opposed to the top. A plot of the global response is given in Figure 5.47(b) Test 13: OSB + GWB with CUREE Protocol Figure 5.48(a) contains an illustration of the failure pattern for the East Wall. A severe split in the sill plate [Figure 5.49(b)] and a small crack in the holdown stud occurred at 15%. Nail tearout at the top of the panels near the center is shown in Figure 5.49(c). The GWB behaved similarly to that in the GWB only test (Test 12), eventually reaching the point where only a couple of screws were still fastening it to the framing. A plot of the global response is given in Figure 5.5(a). Figure 5.48(b) contains an illustration of the failure pattern for the West Wall. Significant top plate separation occurred at the south end of the specimen as shown in Figure 5.49(a). An example of sheathing separation that lead to specimen failure is given in Figure 5.49(d). Except for the screw locations, no cracking was observed in the GWB. 71

88 A plot of the global response is given Figure 5.5(b). The most significant impact of adding the GWB to the OSB specimens seemed to be a reduction in stud twisting caused by eccentricity. This is reasonable given that the presence of GWB on the opposite side of the wall from the OSB will help to reduce the eccentricity. The method of experimentally determining the components of woodframe shearwall drift discussed in Section was used to find the deflection components at several peak displacement cycles. Plots given in Figure 5.51 illustrate the relative contribution of each of the components. Observation of the plots shows that nail slip and anchorage deformation contribute the most to shearwall displacement, followed by sill slip and sheathing shear deformation. Moreover, the plots indicate that the contribution of chord bending is practically null when compared with the other components Test 14: PWD + GWB with CUREE Protocol Figure 5.52(a) contains an illustration of the failure pattern for the East Wall. There was little damage to the framing members during the test, with failure of the specimen occurring at the fastener level. A plot of the global response is given in Figure 5.54(a). Like the OSB specimens, the addition of GWB to the PWD specimens helped to prevent the eccentricity caused by placing sheathing on only one side of the specimen. Figure 5.52(b) contains an illustration of the failure pattern for the West Wall. Figure 5.53(a) shows the splitting of the top plate that occurred where it was penetrated by the sheathing nails. During the positive excursion of the final cycle, the sheathing panels binded against each other and buckled out of plane as shown in Figure 5.53(b). Figure 5.53(c) shows a horizontal split that developed in the sill plate and Figure 5.53(d) provides an example of the center stud separating from the sill during the negative excursion of the final cycle and popping out of plane. A plot of the global response is given in Figure 5.54(b). Shear strains near the center of the sheathing panels are plotted vs. applied load in Figure The linear nature of the strains coupled with the small strain values imply that the sheathing panels act essentially as rigid bodies. Moreover, strains on adjacent panels are approximately the same. 72

89 5.2.5 Dynamic Loading Rate Effect Test 15: OSB + GWB with CUREE Dynamic Protocol Figure 5.56(a) contains an illustration of the failure pattern for the East Wall. The center stud was damaged [Figure 5.57(b)] and pulled away from the sill allowing the bottom of the panel to pop out of plane. The north sheathing panel pulled away from the framing except at the holdown stud region. A plot of the global response is given in Figure 5.58(a). Note that the load given in the ordinate axis is the computed base shear, calculated using Equation 4.2, as is typical for all dynamic tests. Figure 5.56(b) contains an illustration of the failure pattern for the West Wall. Examples of sheathing separation and stud damage that occurred in this specimen are given in Figures 5.57(a) and (c), respectively. A longitudinal split formed in the north holdown stud [Figure 5.57(d)], leading to failure of the specimen. A plot of the global response is given in Figure 5.58(b). In general, the dynamic loading was observed to be more demanding on the framing members than was the static loading Test 16: PWD + GWB with CUREE Dynamic Protocol Figure 5.59(a) contains an illustration of the failure pattern for the East Wall. Two of the studs separated from the sill plate and a crack formed in the sill plate at the north end of the specimen [Figures 5.6(a) and (c)]. The GWB remained loosely fastened to the framing but only by a couple of screws. A plot of the global response is given in Figure 5.61(a). Figure 5.59(b) contains an illustration of the failure pattern for the West Wall. Considerable top plate separation occurred at the south end of the specimen and four of the studs came separated from the sill plate. An example of the sheathing separating from the framing is given in Figures 5.6(b) and (d). The GWB fell off of the framing as a unit with both sheets still connected together by the tape and mud. Nail fracture appeared to be a more common occurrence than it was in the static tests. A plot of the global response is given in Figure 5.61(b). Plots of the sheathing strain versus applied load are shown in Figure Like the Test 16 plots, the sheathing shows a relatively linear behavior that is clearly elastic. 73

90 5.2.6 Stucco Effect Test 17: OSB + Stucco with CUREE Dynamic Protocol Figure 5.63(a) contains an illustration of the failure pattern for the East Wall. The framing members suffered extensive damage that was concentrate to the bottom portion of the specimen. Three of the studs broke [Figure 5.64(c)], including one of the holdown studs. In addition to broken studs, four of the studs separated from the sill plate. The only observable damage to the stucco was minor separation between the stucco and the stucco stop. A plot of the global response is given in Figure 5.65(a). Figure 5.63(b) contains an illustration of the failure pattern for the West Wall. The framing members suffered extensive damage that was isolated to the bottom portion of the specimen as shown in Figure 5.64(a). Figure 5.64(b) provides an example of the stucco still bonded to the sheathing as it separated from the framing at the bottom portion of the specimen. Five of the studs separated from the sill plate, and example of which is shown in Figure 5.64(d). A plot of the global response is given in Figure 5.65(b) Test 18: PWD + Stucco with CUREE Dynamic Protocol Figure 5.66(a) contains an illustration of the failure pattern for the East Wall. The framing members suffered extensive damage that was isolated to the bottom portion of the specimen. Four of the studs broke including the two holdown studs, and five of the studs separated from the sill plate. Fastener damage was also concentrated to the bottom portion of the specimen with pullthrough being the predominant failure mode at the sill plate and pullout at the bottom portion of the holdown studs. The only observable damage to the stucco was minor separation between the stucco and the stucco stop [Figure 5.67(a)]. The stucco remained bonded to the sheathing while it pulled away from the framing as shown in Figure 5.67(b). A plot of the global response is given in Figure 5.68(a). Figure 5.66(b) contains an illustration of the failure pattern for the West Wall. Damage to studs and twisting of the holdowns [Figure 5.67(c)] was concentrated at the bottom portion of the specimen. As was typical with the stucco specimens, the sheathing and stucco pulled away from the framing near the bottom as shown in Figure 5.67(d). A plot of the global response is given in Figure 5.68(b). 74

91 A plot of the sill plate slip displacement like that provided for Test 2 (Figure 5.8) is given in Figure Similar to Test 2, the sill slip shows the stick-slip behavior that results from friction effects. The figures show that the slip in the East Wall was larger and more symmetric than that in the West Wall. Although the West Wall slip was one sided like that in Test 2, note that the slip is on the opposite side. Plots providing the holdown uplift given in Figure 5.7 show that considerable holdown uplift of up to 1. in. occurred. The plots also show that compression led to a significant negative holdown displacement of up to.5 in. 75

92 N N PULLOUT TOP PLATE SEPARATION 8% PULLTHROUGH 1% PULLOUT PULLOUT (MINOR) TEAROUT PULLOUT TEAROUT (a) East Wall N N PULLTHROUGH TEAROUT PULLTHROUGH TOP PLATE SEPARATION PULLTHROUGH PULLOUT PULLTHROUGH PULLOUT PULLTHROUGH (b) West Wall Figure 5.1 Failure Modes for Test 1: OSB with Monotonic Loading 76

93 (a) Nail Tearout (b) Sheathing Separation (c) Top Plate Separation (d) Holdown Uplift Figure 5.2 Damage Photographs for Test 1: OSB with Monotonic Loading 77

94 1 8 Load (kips) Drift (in) (a) East Wall 1 8 Load (kips) Drift (in) (b) West Wall Figure 5.3 Global Response for Test 1: OSB with Monotonic Loading 78

95 12 1 Wall Force (kips) Holdown Tensile Force (kips) (a) East Wall 12 1 Wall Force (kips) Holdown Tensile Force (kips) (b) West Wall Figure 5.4 Comparison of Wall Load and Holdown Force for Test 1: OSB with Monotonic Loading 79

96 N N 15% TEAROUT 2% PULLTHROUGH 1% TEAROUT TOP PLATE SEPARATION 9% PULLTHROUGH 9% PULLTHROUGH 1% PULLOUT 75% PULLOUT 25% PULLTHROUGH STUD SEPARATED FROM SILL (a) East Wall N N PULLOUT (MINOR) PULLOUT PULLTHROUGH PULLOUT PULLOUT PULLOUT PULLTHROUGH (b) West Wall Figure 5.5 Failure Modes for Test 2: OSB with CUREE Protocol 8

97 (a) Sheathing Separation (b) Stud Separation from Sill (c) Holdown Twisting (d) Sheathing Separation Figure 5.6 Damage Photographs for Test 2: OSB with CUREE Protocol 81

98 1 % Load (kips) Drift (in) (a) East Wall CUREE Monotonic 1 % Load (kips) Drift (in) (b) West Wall CUREE Monotonic Figure 5.7 Global Response for Test 2: OSB with CUREE Protocol 82

99 1 5 Load (kips) Sill Slip (in) (a) East Wall 1 5 Load (kips) Sill Slip (in) (b) West Wall Figure 5.8 Sill Plate Slip for Test 2: OSB with CUREE Protocol 83

100 Load (kips) Load (kips) Sheathing Rotation (rad) Sheathing Rotation (rad) (a) East Wall (North Panel) (b) East Wall (South Panel) Load (kips) Load (kips) Sheathing Rotation (rad) Sheathing Rotation (rad) (c) West Wall (North Panel) (d) West Wall (South Panel) Figure 5.9 Sheathing Rotations for Test 2: OSB with CUREE Protocol 84

101 Load (kips) Load (kips) Holdown Uplift (in) (a) East Wall (North End) Holdown Uplift (in) (b) East Wall (South End) Load (kips) Load (kips) Holdown Uplift (in) (c) West Wall (North End) Holdown Uplift (in) (d) West Wall (South End) Figure 5.1 Holdown Stud Uplift Displacement for Test 2: OSB with CUREE Protocol 85

102 1 Anchorage Force (kips) Applied Load -4-6 AF1 AF2 AF3 AF4 (a) East Wall 1 Anchorage Force (kips) AF4 Applied Load AF3 AF2 AF1-6 (b) West Wall Figure 5.11 Anchorage Force Distribution at Peak Positive Load for Test 2: OSB with CUREE Protocol 86

103 6 Global Displacement (in) Horizontal Sheathing Displacement (in) (a) Horizontal Component 6 Global Displacement (in) Vertical Sheathing Displacement (in) (b) Vertical Component Figure 5.12 Sheathing Translations of West Wall (North Panel) for Test 2 87

104 N N TEAROUT 3% PULLTHROUGH TOP PLATE SEPARATION 8% PULLTHROUGH 3 FRACTURES 8% PULLOUT (MINOR) BROKEN STUD (a) East Wall N N 2% TEAROUT 5% TEAROUT TOP PLATE SEPARATION PULLOUT (MINOR) 9% PULLTHROUGH 1 FRACTURE PULLOUT 9% PULLTHROUGH 1% TEAROUT 1 FRACTURE 2% PULLTHROUGH 25% PULLOUT 1% TEAROUT CRACKED SILL PLATE (b) West Wall Figure 5.13 Failure Modes for Test 3: OSB with ISO Protocol 88

105 (a) Split Sill Plate (b) Broken Center Stud (c) Top Plate Separation (d) Top Plate Separation Figure 5.14 Damage Photographs for Test 3: OSB with ISO Protocol 89

106 1 % ν u Load (kips) -5 ISO Monotonic Drift (in) (a) East Wall 1 % ν u Load (kips) -5 ISO Monotonic Drift (in) (b) West Wall Figure 5.15 Global Response for Test 3: OSB with ISO Protocol 9

107 Sill Uplift (in) SU1 SU2 SU3 SU4 SU5 (a) East Wall Sill Uplift (in) SU5 SU4 SU3 SU2 SU1 -.4 (b) West Wall Figure 5.16 Sill Plate Uplift Profile at Peak Positive Load for Test 3: OSB with ISO Protocol 91

108 Holdown Stud Strain North Stud South Stud. HSS1 HSS3 HSS2 HSS4 Figure 5.17 Comparison of Interior and Exterior Holdown Stud Strains for Test 3 (East Wall): OSB with ISO Protocol 92

109 N N 9% TEAROUT TOP PLATE SEPARATION 9% PULLOUT 6% PULLTHROUGH 4% FRACTURE PULLOUT 5% PULLTHROUGH 5% FRACTURE DAMAGED HOLDOWN STUD (a) East Wall 1% TEAROUT 15% PULLTHROUGH 2% FRACTURE N 25% TEAROUT 2% PULLOUT 2% FRACTURE N 8% FRACTURE PULLOUT PULLOUT 5% PULLTHROUGH 25% PULLTHROUGH 25% FRACTURE (b) West Wall Figure 5.18 Failure Modes for Test 4: OSB with SPD Protocol 93

110 (a) Nail Tearout (b) Holdown Twisting (c) Nail Fracture (d) Nail Pullout Figure 5.19 Damage Photographs for Test 4: OSB with SPD Protocol 94

111 % FME Load (kips) -5 SPD Monotonic Drift (in) (a) East Wall % FME Load (kips) -5 SPD Monotonic Drift (in) (b) West Wall Figure 5.2 Global Response for Test 4: OSB with SPD Protocol 95

112 Sum of Components (in) º Reference Line Measured Drift (in) (a) East Wall Sum of Components (in) º Reference Line Measured Drift (in) (b) West Wall Figure 5.21 Comparison of Deflection Components for Test 4: OSB with SPD Protocol 96

113 N N TEAROUT TEAROUT PULLOUT PULLOUT 4% PULLTHROUGH 6% PULLOUT PULLOUT (a) East Wall N N TOP PLATE SEPARATION 8% PULLOUT 2% PULLTHROUGH PULLOUT BROKEN HOLDOWN STUD (b) West Wall Figure 5.22 Failure Modes for Test 5: OSB with SPD Protocol 97

114 (a) Nail Pullout (b) Stud Bending (c) Nail Tearout (d) Split Holdown Figure 5.23 Damage Photographs for Test 5: PWD with Monotonic Loading 98

115 1 8 Load (kips) Drift (in) (a) East Wall 1 8 Load (kips) Drift (in) (b) West Wall Figure 5.24 Global Response for Test 5: PWD with Monotonic Loading 99

116 1 Anchorage Force (kips) AF1 Applied Load AF2 AF3 AF4-6 (a) East Wall 1 Anchorage Force (kips) AF4 Applied Load AF3 AF2 AF1-6 (b) West Wall Figure 5.25 Anchorage Force Distribution for Test 5: PWD with Monotonic Loading 1

117 N N 2% PULLOUT 1% TEAROUT TOP PLATE SEPARATION 5% PULLTHROUGH 4% PULLOUT 3 FRACTURES PULLOUT PULLOUT PULLOUT (a) East Wall N N 3% PULLOUT 7% TEAROUT 2% PULLOUT 9% PULLTHROUGH 1% PULLOUT 7% PULLOUT 3% PULLTHROUGH (b) West Wall Figure 5.26 Failure Modes for Test 6: PWD with CUREE Protocol 11

118 (a) Sheathing Buckling (b) Sheathing Buckling (c) Sheathing Rotation (d) Wall Deformation Figure 5.27 Damage Photographs for Test 6: PWD with CUREE Protocol 12

119 % Load (kips) 5-5 CUREE Monotonic Drift (in) (a) East Wall % Load (kips) -5 CUREE Monotonic Drift (in) (b) West Wall Figure 5.28 Global Response for Test 6: PWD with CUREE Protocol 13

120 N N PULLOUT PULLOUT PULLOUT BROKEN HOLDOWN STUD DAMAGED CENTER STUD BROKEN HOLDOWN STUD (a) East Wall N N PULLOUT 8% PULLOUT 2% FRACTURE PULLOUT CRACKED SILL PLATE CENTER STUD SEPARATED FROM SILL BROKEN HOLDOWN STUD (b) West Wall Figure 5.29 Failure Modes for Test 7: PWD with ISO Protocol 14

121 (a) Split Sill Plate (b) Split Holdown Stud (c) Center Stud Twisting (d) Broken Holdown Stud Figure 5.3 Damage Photographs for Test 7: PWD with ISO Protocol 15

122 % ν u Load (kips) 5-5 ISO Monotonic Drift (in) (a) East Wall % ν u Load (kips) -5 ISO Monotonic Drift (in) (b) West Wall Figure 5.31 Global Response for Test 7: PWD with ISO Protocol 16

123 N N 2% PULLOUT 1% TEAROUT TOP PLATE SEPARATION 9% FRACTURE PULLOUT PULLOUT 9% FRACTURE CRACKED SILL PLATE (a) East Wall N N 2% PULLOUT 2% FRACTURE 9% FRACTURE 2% PULLOUT 1% PULLTHROUGH 7% FRACTURE (b) West Wall Figure 5.32 Failure Modes for Test 8: PWD with SPD Protocol 17

124 (a) Sheathing Rotation (b) Nail Fracture (c) Sheathing Separation (d) Cracked Sill Plate Figure 5.33 Damage Photographs for Test 8: PWD with SPD Protocol 18

125 % FME Load (kips) 5-5 SPD Monotonic Drift (in) (a) East Wall % FME Load (kips) -5 SPD Monotonic Drift (in) (b) West Wall Figure 5.34 Global Response for Test 8: PWD with SPD Protocol 19

126 N N 9% PULLOUT 1% TEAROUT 5% PULLOUT 1% PULLTHROUGH 7% PULLTHROUGH 3% PULLOUT 8% PULLTHROUGH 2% PULLOUT 9% PULLTHROUGH 1% PULLOUT BROKEN STUDS (a) East Wall STUD SEPARATED FROM SILL N N 9% TEAROUT TOP PLATE SEPARATION TOP PLATE SEPARATION PULLOUT 9% PULLTHROUGH 5% PULLOUT 5% TEAROUT 5% PULLTHROUGH 5% PULLOUT STUD SEPARATED FROM SILL (b) West Wall Figure 5.35 Failure Modes for Test 9: OSB with Near-fault Protocol 11

127 1 % m Load (kips) -5 Near-fault Monotonic Drift (in) (a) East Wall 1 % m Load (kips) -5 Near-fault Monotonic Drift (in) (b) West Wall Figure 5.36 Global Response for Test 9: OSB with Near-fault Protocol 111

128 (a) Stud Damage (b) Top Plate Separation (c) Stud Separation (d) Broken Stud Figure 5.37 Damage Photographs for Test 9: OSB with Near-fault Protocol 112

129 Wall Height (in.) Strain (x.1) Figure 5.38 Holdown Stud Strain Distribution at Peak Load for Test 9: OSB with Nearfault Protocol 113

130 N N PULLOUT TEAROUT TOP PLATE SEPARATION 9% PULLOUT 1% PULLTHROUGH PULLOUT PULLOUT 9% PULLOUT 1% PULLTHROUGH CRACKED SILL PLATE (a) East Wall N N PULLOUT TEAROUT 9% PULLOUT 1% PULLTHROUGH PULLOUT PULLOUT 9% PULLOUT 1% PULLTHROUGH STUD SEPARATED FROM SILL DAMAGED STUD (b) West Wall Figure 5.39 Failure Modes for Test 1: PWD with Near-fault Protocol 114

131 (a) Nail Pullout (b) Holdown Stud Bending (c) Stud Damage (d) Nail Pullthrough Figure 5.4 Damage Photographs for Test 1: PWD with Near-fault Protocol 115

132 % m Load (kips) 5-5 Near-fault Monotonic Drift (in) (a) East Wall % m Load (kips) -5 Near-fault Monotonic Drift (in) (b) West Wall Figure 5.41 Global Response for Test 1: PWD with Near-fault Protocol 116

133 7% PULLTHROUGH 25% PULLOUT 5% TEAROUT N BROKEN STUD N TOP PLATES SLIPPED RELATIVE TO EACH OTHER PULLTHROUGH PULLTHROUGH 9% PULLTHROUGH 1% PULLOUT 8% PULLOUT (MINOR) 2% PULLTHROUGH (a) East Wall 5% PULLTHROUGH 5% PULLOUT 1 TEAROUT N N TOP PLATE SEPARATION 9% PULLTHROUGH 1% PULLOUT 8% PULLOUT (MINOR) 2% PULLTHROUGH (b) West Wall Figure 5.42 Failure Modes for Test 11: OSB with Monotonic Loading and 4 in. Effective Nailing at all Edges 117

134 (a) Slip Between Top Plates (b) Broken Stud (c) Nail Pullthrough (d) Nail Pullthrough Figure 5.43 Damage Photographs for Test 11: OSB with Monotonic Loading and 4 in. Effective Nailing at All Edges 118

135 1 8 Load (kips) Drift (in) (a) East Wall 1 8 Load (kips) Drift (in) (b) West Wall Figure 5.44 Global Response for Test 11: OSB with Monotonic Loading and 4 in. Effective Nailing at all Edges 119

136 N N PULLTHROUGH PULLTHROUGH PULLTHROUGH TEAROUT (a) East Wall N N PULLTHROUGH TEAROUT PULLTHROUGH TEAROUT PULLTHROUGH (b) West Wall Figure 5.45 Failure Modes for Test 12: GWB with Monotonic Loading 12

137 (a) Sheathing Joint (b) Screw Pullthrough (c) Sheathing Joint (d) Cracking at Corner Figure 5.46 Damage Photographs for Test 12: GWB with Monotonic Loading 121

138 Load (kips) Drift (in) (a) East Wall Load (kips) Drift (in) (b) West Wall Figure 5.47 Global Response for Test 12: GWB with Monotonic Loading 122

139 N N PULLOUT TEAROUT 9% PULLOUT 1% PULLTHROUGH PULLOUT PULLTHROUGH TEAROUT PULLOUT PULLTHROUGH TEAROUT PULLOUT PULLTHROUGH BROKEN STUD CRACKED SILL PLATE (a) East Wall N N PULLTHROUGH TEAROUT TEAROUT PULLOUT TOP PLATE SEPARATION PULLOUT PULLTHROUGH 5% PULLOUT 5% PULLTHROUGH (b) West Wall Figure 5.48 Failure Modes for Test 13: OSB + GWB with CUREE Protocol 123

140 (a) Top Plate Separation (b) Split Sill Plate (c) Nail Tearout (d) Sheathing Separation Figure 5.49 Damage Photographs for Test 13: OSB + GWB with CUREE Protocol 124

141 % Load (kips) Drift (in) (a) East Wall % Load (kips) Drift (in) (b) West Wall Figure 5.5 Global Response for Test 13: OSB + GWB with CUREE Protocol 125

142 Drift (in) Sill Slip Anchorage Nail Slip Sheathing Shear Chord % (a) East Wall Drift (in) Sill Slip Anchorage Nail Slip Sheathing Shear Chord % (b) West Wall Figure 5.51 Deformation Components for Test 13: OSB + GWB with CUREE Protocol 126

143 N N TEAROUT PULLOUT 5% PULLOUT 5% PULLTHROUGH PULLTHROUGH 5% PULLOUT 5% PULLTHROUGH (a) East Wall N N TEAROUT TOP PLATE SEPARATION SPLIT TOP PLATE PULLOUT PULLTHROUGH 8% PULLOUT 2% PULLTHROUGH 7% PULLTHROUGH 3% PULLOUT STUDS SEPARATED FROM SILL CRACKED SILL PLATE (b) West Wall Figure 5.52 Failure Modes for Test 14: PWD + GWB with CUREE Protocol 127

144 (a) Top Plate Damage (b) Sheathing Buckling (c) Horizontally Split Sill Plate (d) Out-of-Plane Damage Figure 5.53 Damage Photographs for Test 14: PWD + GWB with CUREE Protocol 128

145 % Load (kips) Drift (in) (a) East Wall % Load (kips) Drift (in) (b) West Wall Figure 5.54 Global Response for Test 14: PWD + GWB with CUREE Protocol 129

146 1 1 Load (kips) 5-5 Load (kips) Local Shear Strain (rad) (a) East Wall (North Panel) Local Shear Strain (rad) (b) East Wall (South Panel) 1 1 Load (kips) 5-5 Load (kips) Local Shear Strain (rad) (c) West Wall (North Panel) Local Shear Strain (rad) (d) West Wall (South Panel) Figure 5.55 Sheathing Shear Strains for Test 14: PWD + OSB with CUREE Protocol 13

147 N N TEAROUT PULLOUT 8% PULLOUT 2% PULLTHROUGH 8% PULLTHROUGH 2% PULLOUT 8% PULLTHROUGH 2% PULLOUT 1 FRACTURE 6% PULLOUT 4% PULLTHROUGH DAMAGED STUD STUDS SEPARATED FROM SILL (a) East Wall N N PULLOUT PULLOUT 5% PULLOUT 5% PULLTHROUGH BROKEN STUD DAMAGED HOLDOWN (b) West Wall Figure 5.56 Failure Modes for Test 15: OSB + GWB with CUREE Dynamic Protocol 131

148 (a) Sheathing Separation (b) Stud Damage (c) Stud Damage (d) Holdown Damage Figure 5.57 Damage Photographs for Test 15: OSB + GWB with CUREE Dynamic Protocol [Figures (b) and (c) with GWB Removed] 132

149 % Load (kips) Drift (in) (a) East Wall % Load (kips) Drift (in) (b) West Wall Figure 5.58 Global Response for Test 15: OSB + GWB with CUREE Dynamic Protocol 133

150 N N 6% PULLOUT 3% PULLTHROUGH 1% FRACTURE CRACKED SILL PLATE STUDS SEPARATED FROM SILL (a) East Wall N N TEAROUT PULLOUT TOP PLATE SEPARATION PULLOUT 5% PULLTHROUGH 3% PULLOUT 2% FRACTURE PULLOUT 9% PULLOUT 1% PULLTHROUGH STUDS SEPARATED FROM SILL (b) West Wall Figure 5.59 Failure Modes for Test 16: PWD + GWB with CUREE Dynamic Protocol 134

151 (a) Split Sill Plate (b) Sheathing Separation (c) Split Sill Plate (d) Sheathing Separation Figure 5.6 Damage Photographs for Test 16: PWD + GWB with CUREE Dynamic Protocol [Figures (a), (b), and (c) with GWB Removed] 135

152 % Load (kips) Drift (in) (a) East Wall % Load (kips) Drift (in) (b) West Wall Figure 5.61 Global Response for Test 16: PWD + GWB with CUREE Dynamic Protocol 136

153 1 1 Load (kips) 5-5 Load (kips) Local Shear Strain (rad) (a) East Wall (North Panel) Local Shear Strain (rad) (b) East Wall (South Panel) 1 1 Load (kips) 5-5 Load (kips) Local Shear Strain (rad) (c) West Wall (North Panel) Local Shear Strain (rad) (d) West Wall (South Panel) Figure 5.62 Sheathing Shear Strains for Test 16: PWD + GWB with CUREE Dynamic Protocol 137

154 N N BROKEN STUDS 65% PULLTHROUGH 35% PULLOUT 75% PULLTHROUGH STUDS SEPARATED 25% PULLOUT FROM SILL (a) East Wall N N TOP PLATE SEPARATION BROKEN STUDS PULLOUT 5% PULLOUT 5% PULLTHROUGH 1 FRACTURE STUDS SEPARATED FROM SILL (b) West Wall Figure 5.63 Failure Modes for Test 17: OSB + Stucco with CUREE Dynamic Protocol 138

155 (a) Stud Damage (b) Sheathing Separation (c) Stud Damage (d) Stud Separation from Sill Figure 5.64 Damage Photographs for Test 17: OSB + Stucco with CUREE Dynamic Protocol 139

156 % Load (kips) Drift (in) (a) East Wall % Load (kips) Drift (in) (b) West Wall Figure 5.65 Global Response for Test 17: OSB + Stucco with CUREE Dynamic Protocol 14

157 N N BROKEN STUDS PULLOUT PULLOUT 75% PULLTHROUGH 25% PULLOUT 1 FRACTURE STUDS SEPARATED FROM SILL (a) East Wall N N TOP PLATE SEPARATION BROKEN STUDS PULLOUT PULLOUT 9% PULLOUT 1% PULLTHROUGH STUDS SEPARATED FROM SILL CRACKED SILL PLATE (b) West Wall Figure 5.66 Failure Modes for Test 18: PWD + Stucco with CUREE Dynamic Protocol 141

158 (a) Stucco Damage (b) Sheathing Separation (c) Holdown Twisting (d) Sheathing Separation Figure 5.67 Damage Photographs for Test 18: PWD + Stucco with CUREE Dynamic Protocol 142