The Wood Products Council and AIA/CES www.fpinnovations.ca Midply Shearwall System: Concept, Performance and Code Implementation C. Ni, M. Popovski FPInnovations, Building Systems The Wood Products Council is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-aia members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation. Learning Objectives FPInnovations - Background At the end of this program, participants will be able to: Identify the advantages and disadvantages of mid-ply shear wall systems from the information provided in the presentation. Identify and explain what the various components (anatomy) of a mid-ply shear wall using the various pictures provided in the presentation. Calculate late and create details of the mid-ply shear from the various examples provided in the presentation. Verify the validity of using mid-ply pyshear walls with the information on the research and testing that has been done on the mid-ply wall system which will be provided. FPInnovations is a world leader that specializes in the creation of scientific solutions in support to the Canadian forest sector s global competiveness, and responds to the priority needs of its industrial and government members With over 55 employees across the country and an annual budget of $9 million it is the world s largest private, not-for-profit forest products research institute This unique forestry research centre is capable of providing complete value chain solutions from forest management and transportation to products, such as structural systems
Midply Walls Outline Concept of Midply walls Background and Research Information Design Approach Construction ti Details Application Examples Conclusions Why Midply Shearwall? Wood frame construction has evolved to include 3 or 4 storey multi-family residence Large openings, long span, concrete topping have become common practice New construction practices at times create additional demand on lateral load resistance Concept of Midply Shearwall Reasons for Improved Performance Standard shear wall 16 16 16 2x4 studs 38 89 mm lumber stud spaced at 46 mm o.c. 1.22 2.44 m wood-based panel Sheathing fastened to the narrow face of framing members Midply TM shear wall Sheathing 24 24 1.22 2.44 m wood-based panel at the center of the wall 38 89 mm lumber stud rotated 9 degree to those in standard shearwall Sheathing fastened to the wide face of framing members Sheathing Drywall/Sheathing Cladding/Sheathing Drywall/Sheathing Nails work in double shear thus increasing the lateral load capacity Stud or Plate Greater edge distance - panel chip out failure is reduced Nail head away from panel Grain surface - nail pull through failure is prevented Capable of accommodating additional sheathing direction 89 mm Nail in single shear Sheathing 38 mm 38 mm Stud or Plate Nail in double shear
Testing Program Publications Performed over 7 full-scale quasi-static and shaking table tests on Midply walls in several wall configurations Investigated effects of: stud size, stud spacing, nail spacing, vertical loads, construction details Evaluated several types of hold-down connections Details of the tests are published in ASCE Journal of Structural Engineering Midply Wood Shear Wall System: Concept and Performance in Static and Cyclic Testing, 132(9): 1417-1425 Midply Wood Shear Wall System: Performance in Dynamic Testing, 133(7): 135-142 Stud and Plate Details Considered Hold-Down Connections Used End Studs Type 1 Type 2 Intermediate Studs Type 1 Type 2 Regular hold-down Inverted-triangle holddown Double-shear hold-down Strip tie Steel rods Type 1 Type 2 Type 3 Type 4 Type 5
Quasi-Static Tests at FPInnovations (Forintek) Shake Table Tests at the University of BC Effects of stud size, stud spacing, nail spacing, and vertical loads were investigated Test Results - Monotonic & Cyclic Tests Test Results - Monotonic & Cyclic Tests ) Load (kn/m) 4 3 2 1-1 -2-3 Specimen m3-1 Specimen S39-4 -15-1 -5 5 1 15 Displacement (mm) Average test results of Midply shearwalls Wall No. Stud Vertical 1 Load P 2 3 spacing Load max u K E Protocol (kn/m) (mm) (kn/m/mm) (J/m) (mm) (kn/m) M4/M41-1 61 Monotonic 18.2 31.4 121 b 1.66 - M39 61 Monotonic None 3.2 12 b 1.32 - M28/M29/M3/M14 61 Cyclic a 18.2 28.7 95 165 1.65 13,655 M31 61 Cyclic a None 27.9 1 1.24 15,79 M32 46 Monotonic 18.2 36.3 13 c 1.57 - M46 d 46 Cyclic a None 27.6 83.44 8,75 Average test results of standard shearwalls Wall No. Load Vertical P max u K E Protocol Load (kn/m) (mm) (kn/m/mm)/ (J/m) S31/S51/S52 Monotonic 18.2 8.8 15.58 - S37/S38 Monotonic None 8.7 88.55 - S33 Cyclic a 18.2 9.6 78.76 3,82 S34/S39/S4 Cyclic a None 9 9. 77 68.68 321 3,21
Design Possibilities for Midply Shearwalls Code Proposal for 214 CSAO86 in Canada Canada NBCC Alternate Solution Method (based on peer-reviewed evidence). A proposal on Midply wall is being prepared for implementation in 214 CSAO86 USA Alternate Solution Method. Design values can be established by using ICC Evaluation Criteria AC 13 - Prefabricated Wood Shear Panels A proposal for AF&PA SDPWS will be prepared Lateral Load Resistance Midply shearwall = 2. standard shearwall Shear strength of a nailed joint in double shear is about twice that in 8 6 single shear 4 2 Lateral load capacity may be further -2 increased through the elimination of -4 failure modes observed in standard -6-8 shearwalls d (kn) Load Comparison of joint load-slip response under reversed cyclic test -3-2 -1 1 2 3 Displacement (mm) Joint in double shear Joint in single shear Code Proposal for 214 CSA O86 Study on Seismic Force Modification Factors Rd, Ro Deflection 3 2vH vh sw. 25He 3EAb Gt n H b The nail deformation e n should be calculated based on the formula for single shear and load per fastener shall be taken as half of the load applied on the midply wall d a Rd = 3., Ro = 1.7 same as for standard nailed shearwalls Factors were confirmed by numerical modelling of a four-storey wood-frame building 4-storey wood-frame structure Surrey, BC, PGA =.51g Rd = 3.; Ro = 1.7 Designed according to NBCC 25 22 earthquakes, scaled to.51g
Case Study Results CDF Function of Storey Drifts ICC-ES AC13 Evaluation Criteria in the US Frequency (% %) 1 8 6 4 Standard shear wall, R=3 Midply shear wall, R=3 2.5% inter-storey drift 2 Near collapse standard wall Near collapse Midply wall 4 8 12 16 2 Storey Drift (mm) Developing design values and assigning an R-factor for new wood shearwall assemblies (such as Midply py walls) in the US can be done by using the ICC-ES AC-13 evaluation criteria entitled Acceptance Criteria for Prefabricated Wood Shear Panels The AC-13 criteria is based on showing equivalency of the seismic performance of the new assemblies (Midply walls) with respect to lumber-based nailed shearwalls Midply Shearwalls in the US - AC13 Evaluation Midply Shearwall Envelope Curve for AC13 IBC allowable shear for Midply shearwalls (Seismic) The allowable shear shall be the lesser of the allowable shear based on a drift limit or strength limit obtained from first-cycle loaddisplacement backbone curve DiftLi Drift Limit it(51311) (5.1.3.1.1) a) Maximum inelastic response displacement, x = min (2.5%H, SLS ) b) Strength Design level response displacement, xe = x (I / C d ) c) Force corresponding to xe is P xe d) Allowable shear, P DL =.7 P xe e) Drift corresponding to P DL is DL Strength Limit (5.1.3.1.3) a) Allowable shear, P SL = P max / 2.5 b) Drift corresponding to P SL is SL Load (kn/m) L 4 3 2 1-1 -2-3 Specimen m3-11 -4-15 -1-5 5 1 15 Displacement (mm)
Evaluation of Midply Shearwall - AC13 Evaluation of Midply Shearwall - AC13 Drift Limit (Seismic) a) x =min( 2.5%H, SLS )=61mm b) xe = x (I / C d ) = 15.25 mm c) P xe = 17. kn/m d) P DL =.7 P xe = 11.9 KN/m e) DL = PDL = 7.5 mm Load (kn/m) Strength Limit (Seismic) 5 a) P SL = P max / 2.5 = 12.3 KN/m b) SL = PSL = 7.9 mm 4 35 P max 3.8P 25 max 2 P xe 15 P P SL DL 1 Specimen m3-1 SLδ DL xe 2.5%H SLS u 4 8 12 16 Displacement (mm) IBC allowable shear for Midply shearwall (Wind) The allowable shear shall be the lesser of the allowable shear based on a drift limit or strength limit obtained from first-cycle loaddisplacement backbone curve Drift Limit (5.1.3.1.2) a) Allowable shear, P DL = load corresponding to DL = H / 18 Strength Limit (5.1.3.1.3) a) Allowable shear, P SL = P max / 2. b) Drift corresponding to P SL is SL Evaluation of Midply Shearwall - AC13 Using Midply Shearwall in US - AC13 Evaluation Drift Limit (Wind) 4 a) DL = H / 18 = 13.6 mm b) P DL = P DL = 16.2 KN/m Strength Limit (Wind) Load (kn/m) a) P SL = P max / 2. = 15.4 KN/m b) SL = PSL = 12.1 mm 35 P max 3 ).8Pmax 25 2 P DL 15 P SL 1 5 Specimen m3-1 DL SL u 4 8 12 16 Displacement (mm) Light-framed walls sheathed with wood structural panels (ASCE-7) Response Modification Coefficient: R = 6.5 System Over-strength Factor: =3 Deflection Amplification Factor: C d =4 Compatibility with above Seismic-Force i Resisting System (AC 13) Ductility (5.2.2) : u / ASD 11 (test result = 14) Drift capacity (5.2.3): u.28 H (68 mm) (test result = 16 mm) Over-strength (5.2.4): 2.5 P max / P ASD 5. (test result = 2.6)
Design of Midply Shearwalls Design of Midply Shearwalls Design for gravity loads Check stud compression capacity Check plate bearing capacity Recommend to design pair studs as built-up columns in accordance with NDS Clause 15.3 Column stability factor, Cp, calculated in accordance with NDS Clause 15.3.2 Connection of the built-up studs Nails or screws: Connection details in accordance with NDS Clause 15.3.3 Bolts: Connection details in accordance with NDS Clause 15.3.4 Intermediate studs Studs at panels joints Design of Midply Shearwalls Design of Midply Shearwalls Design for lateral loads Shear capacity Chord (end-stud) member capacity Hold-down connection capacity Shear transfer connection capacity Design of shear capacity Midply shearwall capacity = 2. x standard shearwall (same nail spacing and diameter)
Design of Midply Shearwalls Design of Midply Shearwalls Design of the chord members Recommend to design end studs as built-up columns in accordance with NDS Clause 15.3 Recommend to use bolted built-up studs to prevent studs from separation. Design of the hold-downs Recommend to use continuous steel rods Shrinkage compensators should be used to control excessive deformation (for multi-storey buildings) Design of Midply Shearwalls Design of Midply Shearwalls Design of hold-downs (con t) Design for shear transfer Stud Steel rod Sill plate Floor sheathing Steel plate Bottom plate Sill plate Floor joist Stud Steel rod A A Concrete Top plate Steel plate Bottom plate Shear transfer at foundation Shear transfer at floor Section A - A
Construction Details for Midply Shearwalls Construction Details for Midply Shearwalls Two types of connections Nails around panel edges to provide lateral resistance of the wall Screws or bolts to form built-up columns (making sure they don t contribute to lateral resistance) 1/2 inch gap between panel edges and ends of top and bottom plates 1/8 inch gap between adjacent panels Min. nail penetration into the side member in accordance with NDS Clause 11.1.5.5 1/2 inch L p 6d Midply Wall Application Midply Wall Application Four-storey residential building in Vancouver Midply walls used in all corridor and party walls A non-structural t parallel l wall used for acoustic reasons Steel rods used to resist up-lift forces
Shaking Table Tests of 6-Storey NEESWood Building Details of Midply Walls in the NEESWood Building Nail spacing 3 in 1 3 stories 4 in 4th storey 6 in 5th storey Framing 2 x 4 lumber for top and bottom plates 2 x 6 lumber intermediate studs 2 x 8 lumber for end studs A total of fourteen 2 x 8 studs were used at the ends of the wall to meet the bearing capacity of plates Details of Midply Walls in the NEESWood Building Details of Midply Walls in the NEESWood Building
Shaking Table Test of 6-Storey NEESWood Building Insulation Detail Example Earthquake record Northridge ground motion recorded at the Canoga Park Earthquake intensity Maximum Credible Earthquake (MCE) for California 2x 4 Interior gypsum plyw ood sheathing rigid insulatinon, based on energy codes cladding sheathing membrane Detailed wall assembly for exterior walls should be checked with building envelope professionals Sheathing membrane can use sheets such as Tyvek or building paper It can also be liquid-applied selfadhered membrane Conclusions Thank You The Midply shearwall is a new wall system which provides much greater lateral load capacity than a standard shearwall with same length and same specifiacations The Midply shearwall can be used in residential or non-residential wood construction where demand for lateral load capacity is high Extensive technical evidence including a full-scale shaking table tests of a 6-storey building with Midply walls is available Procedures for design of Midply wall system are presented www.fpinnovations.ca TM 21 FPInnovations. All rights reserved. Copying and redistribution prohibited. TM Fpinnovations, its marks and logos are trademarks of FPInnovations.