Keri L. Ryan Associate Professor/ University of Nevada, Reno Visiting Scholar to University of Auckland,

Lessons Learned from 3D Shake Table Testing of a Full-Scale Seismically-Isolated Building Keri L. Ryan Associate Professor/ University of Nevada, Reno Visiting Scholar to University of Auckland, 216-17

Introduction to the Test Program on Innovative Isolation Systems Collaboration of NEES TIPS, NEES Nonstructural, NIED in Japan Testing at Japan s E-Defense facility in August 211 Project Wrap-Up Workshop in September 213 Dissertations/Theses resulting from this project Nhan D. Dao, UNR, August 212 Siavash Soroushian, UNR, May 213 Keisuke Sato, Hokkaido University, 213 Camila B. Coria, UNR, Dec. 215 Investigators: Ryan, Mahin, Maragakis, McMullin, Mosqueda, Okazaki, Sasaki, Sato Academic Collaborators: Kajiwara, Kasai, Morgan, Nakashima, Zaghi Industry Collaborators/Sponsors: Aseismic Design Company, CEMCO Steel, Dynamic Isolation Systems, Earthquake Protection Systems, Hilti Corporation, Takenaka Corporation, Tolco, USG Building Systems, Victaulic

History of Shake Table Testing on Isolated Buildings Kelly et al. 198a, 198b Kelly and Beucke 198 Kelly and Hodder 1981 Kelly and Chalhoub Mokha et al. 199, 1991; Al-Hussaini et al. 1994 Constantinou et al. 199, 1991 Roussis and Constantinou 26 Fenz and Constantinou 28; Morgan and Mahin 211 Kelly and Tsai 1985; Juhn et al. 1992; Wolff and Constantinou 24 Griffith et al. 1982, 1983 Griffith et al. 199; Nagarajaiah et al. 1992; Kasalanati and Constantinou Clark et al. 1997 Elastomeric bearings with steel dampers Friction fail-safe device Lead-rubber bearings Rubber bearings and sliders Friction pendulum (FP) bearings Teflon-discs and helical steel springs Tension capable FP bearings Multi-stage FP bearings Secondary system response (mounted cantilevers and floor spectra) Column uplift effects Uplift restraint approaches and mechanisms Ultimate behavior Conclusions: No damage to structure even in large motions

History of Shake Table Testing on Isolated Buildings Kelly et al. 198a, 198b Kelly and Beucke 198 Kelly and Hodder 1981 Kelly and Chalhoub Mokha et al. 199, 1991; Al-Hussaini et al. 1994 Constantinou et al. 199, 1991 Roussis and Constantinou 26 Fenz and Constantinou 28; Morgan and Mahin 211 Kelly and Tsai 1985; Juhn et al. 1992; Wolff and Constantinou 24 Griffith et al. 1982, 1983 Griffith et al. 199; Nagarajaiah et al. 1992; Kasalanati and Constantinou Clark et al. 1997 Elastomeric bearings with steel dampers Friction fail-safe device Lead-rubber bearings Rubber bearings and sliders Friction pendulum (FP) bearings Teflon-discs and helical steel springs Tension capable FP bearings Multi-stage FP bearings Secondary system response (mounted cantilevers and floor spectra) Column uplift effects Uplift restraint approaches and mechanisms Ultimate behavior What the vast majority of these tests share in common: Reduced scale structures Lacking realistic floor systems (use added mass for inertial properties) Lacking nonstructural components Table shaking is 1D or 2D (no vertical input)

Scope of Tests 3 Configurations Isolated with triple friction pendulum (TP) bearings Fixed at the base Isolated with hybrid configuration of lead-rubber and cross-linear bearings Period T =.7 sec First Yield Base Shear ~.67W

Specimen Tested Steel moment frame w/ box columns and wide flange beams 12x1 m in plan, 16 m tall W = 52 kn (12 kip) Period T =.7 sec (from testing) Strength from pushover anal. First plastic hinging ~ 35 kn (.67W) Not precise Full mechanism strength ~ 55 kn (1.5W) Specimen was tested extensively in March 29 Value Added Building Project

System Specific Test Objectives Triple Pendulum System Demonstrate seismic resiliency of the system in a very large event. Provide continued functionality and minimal disturbance to contents. Lead Rubber Bearings Evaluate performance of a leadrubber bearing isolation system designed for a nuclear power plant in extended design basis shaking Performance Evaluation of Bearings

Nonstructural Components Ceilings, partition walls and piping installed on 4 th and 5 th floors Nearly identical configuration over the two floors 4 th floor ceilings unbraced while 5 th floor ceilings used seismic bracing 4 th floor partitions used full connections while 5 th floor partitions used slip track connections

Nonstructural Components Ceilings and Partitions Fire Sprinkler Piping Enclosed contents rooms

Structural System Asymmetries Objective: Compare torsional response in each configuration. Unequal bay widths in long direction (7 m and 5 m) Added mass at each floor level for live load (2 to 3 kn per floor) Roof Plan Typical Floor Plan Added mass at roof = 535 kn to represent equipment (note strong asymmetric configuration)

Atypical Base Diaphragm Column bases with stiffeners Horizontal bracing in plane

Design of the Triple Pendulum Isolators System Force-Deformation Triple Pendulum System.275W.214W.8W.2W T 2 =5.57 s T 1 =1.84s T eff =4.55s Bearings were sized by EPS for 1999 Chichi at TCU68 1989 Tabas at Tabas Sta. Yield Force =.8W T 2 = 5.57 sec Disp. Capacity = 1.14 m (45 in)

Spectral Disp. S D (m) The TPB system was to be subjected to a wide variety of ground motions. 1.6 1.4 1.2 1.8.6.4.2 15% Damped Spectral Disp. for Table Motions Takatori Chi-Chi 1 2 3 4 5 6 Natural Period (sec) Sylmar Tabas Sannomaru Iwanumua Michoacan El Centro Typical broadband frequency motion El Centro Typical near-fault (2-3 sec pulse) Sylmar (Northridge) Takatori (Kobe) Very long period nearfault (4-5 sec pulse) Chichi, Tabas Long period, long duration subduction Sannomaru Iwanuma (Tohoku) Soft soil record Michoacan (Mexico City)

Configuration of Triple Pendulum Bearings beneath Building 9 isolators, one beneath each column 1.4 m (55 in).33 m (13 in)

Design of the Lead Rubber System The isolation system was sized for extended design basis motions at Vogtle, a hypothetical central and eastern U.S. soil site. Utilized a suite of site specific motions developed by Huang et al. System Force-Deformation Hybrid LRB System.37W.53W T 2 =2.78s T eff =2.55s Huang NY, Whittaker AS, Kennedy RP, Mayes RL (29) Assessment of Base-Isolated Nuclear Structures for Design and Beyond-Design Basis Earthquake Shaking, Tech. Report MCEER-9-8, University at Buffalo. Yield Force =.53W T2 = 2.78 sec Disp. Capacity =.6 m (24 in)

4 lead rubber bearings Stability was a concern Initial Isolator Configuration Preferred support under every column because vertical vibration was a concern

Solution: Add 5 Cross Linear Bearings Flat slider with.48% friction Tension resistance Carries weight at large displacements Isolator Configuration

Comparison of the Isolation Systems System Force-Deformation Triple Pendulum System.275W T 2 =5.57s System Force-Deformation Hybrid LRB System.37W T 2 =2.78s.214W.8W.2W.53W T eff =2.55s T 1 =1.84s T eff =4.55s Yield Force =.8W T 2 = 5.57 sec Disp. Capacity = 1.14 m (45 in) Yield Force =.53W T2 = 2.78 sec Disp. Capacity =.6 m (24 in)

Comparative Response of TPB, Hybrid LRB, and Fixed Base Configuration NEES September TIPS WORKSHOP 216 San NZSEE Diego, Travelling CA, Sept18, Lecture 213

Test Program and Input Ground Motions System Direct Comparisons Triple Pendulum Bearings (TPB) Westmorland 8% PGA =.18g Iwanuma 2D 1% PGA =.6g Lead Rubber Bearings (LRB/CLB) Westmorland 8% PGA =.2g Iwanuma 2D 1% PGA =.59g Fixed Base Building Westmorland 8% PGA =.23g Iwanuma 2D 7% PGA =.39g Rinaldi 2D 88% Rinaldi 2D 88% Rinaldi 2D 35% Rinaldi 3D 88% PGA = 1.26g PGA vert = 1.2g Rinaldi 3D 88% PGA = 1.2g PGA vert = 1.15g Rinaldi 3D (35% XY, 88% Z) PGA =.43g PGA vert = 1.5g

Tohoku Iwanuma Comparison (2D Excitation)

Level Tools for Isolation and Protective Systems Comparison of Story Accelerations Tohoku - Iwanuma Roof 5 4 Peak Acceleration Profile Normalized Acceleration Profile Roof 5 4 3 Fixed x Fixed y 2 TPB x TPB y Base LRB x LRB y Table.5 1 1.5 2 Peak Acc. (g) 3 2 Base Table 1 2 3 4 Peak Acc. / PGA

TPB Kobe Takatori 1% PGA =.92g PGA V =.28g Peak Isolator Disp = 56 cm Peak Story Drift =.25% Peak Floor Acc. =.66g Movement above the isolation system appears to be rigid body No damage to the structure Only light content disruption

TPB Tabas 1% PGA = 1.15g Peak Isolator Disp = 7 cm Peak Story Drift =.23% Peak Floor Acc. =.45g

Bearing Displacement X (cm) Displacement Trace Tabas 1% 1 Analysis Test Nominal isolator properties used in analysis 1 1 7 cm SE -1-1 1 69 cm -1-1 1 S 68 cm SW -1-1 1 1 1 1 7 cm E -1-1 1 69 cm C -1-1 1 68 cm W -1-1 1 1 1 1 X Y 7 cm 69 cm 68 cm NE N NW -1 Dao ND, Ryan KL, Sato E, Sasaki -1 T (213). Predicting the displacement -1 of triple pendulum bearings -1 in a full scale shake 1table experiment -1 using a three-dimensional 1-1 element, 1 Earthquake Engineering and Structural Dynamics, 42(11):1677-1695 Bearing Displacement Y (cm)

Hybrid LRB System 95% Diablo Canyon PGA = 1.9g Peak Isolator Disp = 55 cm Peak Story Drift =.28% Peak Floor Acc. =.43g

Bearing Displacement X (cm) Displacement Trace Diablo Canyon 95% Nominal Isolator Properties Used in Analysis 5 5 5 Analysis Test SE -5-5 5-5 -5 5 S SW -5-5 5 5 5 5 E -5-5 5 C -5-5 5 W -5-5 5 5 5 5 Y X -5-5 5 NE N NW -5-5 5 Bearing Displacement Y (cm) -5-5 5

Bearing Displacement X (cm) Displacement Trace Diablo Canyon 95% Nominal Isolator Properties Used in Analysis 5 59 cm 5 51 cm 5 46 cm SE -5-5 5-5 -5 5 S SW -5-5 5 5 55 cm 5 46 cm 5 41 cm E -5-5 5 C -5-5 5 W -5-5 5 5 51 cm 5 44 cm 5 39 cm Y X -5-5 5 NE N NW -5-5 5 Bearing Displacement Y (cm) -5-5 5

Rotation Angle at Base (rad) Peak Rotation Angle Observed in Each System LRB System Peak Rotation Angle =.19 rad.2.18973 TPB System Peak Rotation Angle =.5 rad.2.1.1 -.1 -.1.53953 -.2 1 2 3 Time (sec) -.2 1 2 3 4 Time (sec) Ryan KL, Coria CB, Dao ND (213). Large Scale Earthquake Simulation of a Hybrid Lead Rubber Isolation System Designed With Consideration of Nuclear Seismicity, CCEER Report No. 13-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno

Hybrid LRB System Vogtle 175% Observation of Torsion

Max Residual Disp. (cm) Max Residual Disp. (cm) Tools for Isolation and Protective Systems Summary of Residual Isolator Displacement 12 TPB Isolators 12 LRB Isolators 1 1 8 8 6 6 4 4 2 2 1 3 5 7 9 11 13 15 17 19 21 1 3 5 7 9 11 13 15 Trial No. Trial No. TPB System Peak Residual Disp = 1.8 cm Average Residual Disp = 5.4 cm LRB System Peak Residual Disp = 2.1 cm Average Residual Disp = 1.2 cm Ryan KL, Coria CB, Dao ND (213). Large Scale Earthquake Simulation of a Hybrid Lead Rubber Isolation System Designed With Consideration of Nuclear Seismicity, CCEER Report No. 13-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno

Residual Displacement LRB/CLB Permanent displacement due to plate slippage of nearly 1.1 cm

Influence of Vertical Excitation

Hybrid LRB System, Vogtle 175% Representative Influence of Vertical Input (Simulated: Peak Table Acc =1.2 g horizontal,.5 g vertical)

Test Program and Input Ground Motions System Direct Comparisons Triple Pendulum Bearings (TPB) Westmorland 8% PGA =.18g Iwanuma 2D 1% PGA =.6g Lead Rubber Bearings (LRB/CLB) Westmorland 8% PGA =.2g Iwanuma 2D 1% PGA =.59g Fixed Base Building Westmorland 8% PGA =.23g Iwanuma 2D 7% PGA =.39g Rinaldi 2D 88% Rinaldi 2D 88% Rinaldi 2D 35% Rinaldi 3D 88% PGA = 1.26g PGA vert = 1.2g Rinaldi 3D 88% PGA = 1.2g PGA vert = 1.15g Rinaldi 3D (35% XY, 88% Z) PGA =.43g PGA vert = 1.5g

Rinaldi 88% - 3 System Comparison 6 th floor column 6 th floor slab Shake table (ground)

Damage Observed During Extreme Vertical Excitation Northridge, Rinaldi Vertical PGA = 1.5 to 1.2g Peak Slab Acc = 7 to 8g Similar damage was observed in all three systems, induced by vertical excitations.

Vertical Acceleration (g) Tools for Isolation and Protective Systems Observed Damage Measures vs. Horizontal and Vertical Floor Acceleration 5 th Slab (4 th floor ceilings) Roof Slab (5 th floor ceilings) Horizontal Floor Acceleration (g)

Observations from the Damage Assessment The threshold for vertical vibration induced damage to ceiling and piping is about 2-3 g. Damage to ceiling and piping systems was more closely correlated to vertical acceleration than horizontal. Ryan KL, Soroushian S, Maragakis EM, Sato E, Sasaki T, Okazaki T (215). Seismic simulation of an integrated ceiling-partition wall-piping system at E-Defense, I: Three-dimensional structural response and base isolation, Journal of Structural Engineering, 142(2):4153.

Peak Vertical Acc. (g) Peak Normalized Acc. Tools for Isolation and Protective Systems Amplification of peak vertical acceleration from table to floor slabs Absolute Accelerations Normalized Accelerations Ground Motion Number Ground Motion Number On average, peak slab acceleration increased up the building height Average amplification factors = 3 (2 nd floor) to 6 (roof)

Summary of Observations Damage to the ceiling and piping systems correlated more closely to vertical slab acceleration than horizontal floor acceleration (Ryan et al., JSE 215). The threshold slab acceleration for vertical ceiling or piping damage was 2-3 g. EQUIPMENT Damage Measure Disruption of unanchored equipment (sliding, rolling, etc) Can function be quickly restored? (Resilience) Depends Mitigation Measures Anchor expensive equipment if possible CEILINGS Fallen ceiling panels Easily repaired Consider not using seismic bracing ** CEILINGS Damage to ceiling grid system Moderate to significant repairs CEILING/ PIPING Damage due to interaction of ceiling panels and sprinkler heads Easy to moderate repairs PIPING Rotation and loosening of pipes Potential for widespread water damage INTERIOR PARTITIONS INTERIOR PARTITION Large vertical cracks in gypsum board Buckling of studs, damage at stud and track boundaries Moderate repairs Moderate to significant repairs Adequate seat length at ceiling boundaries Use flex hose with sprinkler heads Flexible pipe couplings ** Soroushian S, Maragakis EM, Ryan KL, Sato E, Sasaki T, Okazaki T, Mosqueda G (215). Seismic simulation of an integrated ceiling-partition wall-piping system at E-Defense, II: Evaluation of nonstructural damage and fragilities, Journal of Structural Engineering, 142(2):41531.

Other Performance Issues (1) Load Transfer in Hybrid Systems

Bearing Displacement Histories for DC 95% 5 Bearing Displacement X (cm) -5 5 Bearing Displacement Y (cm) -5 8 6 Vector Sum Displacement (cm) S E W N 4 2 5 1 15 2 25 Time (sec)

Bearing Displacement Histories for DC 95% 8 6 4 2 Vector Sum Displacement (cm) S E W N 5 Bearing Axial Force (kn) -5-1 -15 1 Total Axial Force (kn) -1-2 -3 Time (sec)

Bearing Displacement Histories for DC 95% 8 6 4 2 Vector Sum Displacement (cm) S E W N 5-5 -1-15 1-1 -2-3 Bearing Axial Force (kn) Total Axial Force (kn) Time (sec) Even considering overturning, all bearings unload at large displacements.

Bearing Displacement Histories for DC 95% 8 6 4 2 Vector Sum Displacement (cm) S E W N 5 Bearing Axial Force (kn) -5-1 -15 1-1 -2-3 Total Axial Force (kn) Time (sec) There is a net load transfer from LRB to CLB (sliders) at large displacement excursions, sometimes resulting in net tension.

Bearing Displacement Histories for DC 95% 8 6 4 2 Vector Sum Displacement (cm) S E W N 5-5 -1-15 1-1 -2-3 Bearing Axial Force (kn) Total Axial Force (kn) Time (sec) Time instances of peak displacement correspond directly to unloading of lead rubber bearings.

Hybrid LR System - Load Transfer Effect P CLB P LRB CLB @ start of test P CLB +DP LRB @ start of test P LRB P LRB -DP Load transferred from LRBs to CLBs CLB deformed horizontally LRB deformed horizontally (unconstrained) LRB deformed horizontally (constrained) Ryan KL, Coria CB, Dao ND (213). Large Scale Earthquake Simulation of a Hybrid Lead Rubber Isolation System Designed With Consideration of Nuclear Seismicity, CCEER Report No. 13-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno

Significance of Load Transfer in a Hybrid System The hybrid configuration of bearings was effective to stabilize the isolation system allow a larger displacement to be targeted increase the isolation period provide resistance to overturning P CLB +DP P LRB -DP The rigidity of the CL bearings (sliders) and base diaphragm caused tension in some bearings. Load transfer was exaggerated due to the stiffness of the base diaphragm in the test configuration. -Ryan KL, Coria CB, Dao ND (213). Large Scale Earthquake Simulation of a Hybrid Lead Rubber Isolation System Designed With Consideration of Nuclear Seismicity, CCEER Report No. 13-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno CLB deformed horizontally LRB deformed horizontally (constrained) -Coria CB, Ryan KL, Dao ND (215). Response of Lead Rubber Bearings in a Hybrid Isolation System during a Large Scale Shaking Experiment of an Isolated Building, CCEER Report No. 15-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno

Other Performance Issues (2) Amplification of Horizontal Acceleration due to H/V Coupling

Roof Acceleration (g) Tools for Isolation and Protective Systems Sources of horizontal acceleration amplification due to horizontal/vertical coupling (1) Coupled modes of the structure, (2) Bearings Roof Acceleration in Each System Configuration (Northridge RRS: Peak Table Acc = 1.14 g horizontal, 1.2 g vertical) TPB System LRB/CLB System Fixed Base System 1.5 1.5 3D excitation 2D excitation 1.5 -.5 -.5 -.5-1 1 2-1 1 2 Time (sec) -1 1 2 Horizontal Input scaled to 4% on Fixed-Base System

Floor Acceleration Response in Hybrid LRB System, XY vs 3D Motion (Vert. PGA =.44g) Ryan KL, Coria CB, Dao ND (213). Large Scale Earthquake Simulation of a Hybrid Lead Rubber Isolation System Designed With Consideration of Nuclear Seismicity, CCEER Report No. 13-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno

Acceleration (g) Acceleration (g) What was the cause of the increase in horizontal floor acceleration? X-direction F1 F2 F3 F4 F5 F6 Y-direction Additional F1 F2 F3 peaks in y- direction for 3D input F4 F5 F6

Acceleration (g) Analysis of Floor Spectra, Hybrid LRB Mode 1 System and XY Input Floor Spectra for Diablo Canyon 95%, x-direction Floor 1 Floor 2 Floor 3 Isolation Mode T = 2.72 sec Mode 5 Floor 4 Floor 5 Floor 6 1 st Structural Mode T =.36 sec Period (sec)

Acceleration (g) Analysis of Floor Spectra, Hybrid LRB System and XY Input Floor Spectra for Diablo Canyon 95%, x-direction Floor 1 Floor 2 Floor 3 Mode 8 Floor 4 Floor 5 Floor 6 2 nd Structural Mode T =.17 sec Period (sec)

Acceleration (g) Analysis of Floor Spectra, Hybrid LRB System and 3D Input Floor Spectra for Diablo Canyon 8%, y-direction Floor 1 Floor 2 Floor 3 3rd Structural Mode Y-direction T =.1 sec Floor 4 Floor 5 Floor 6 3rd Structural Mode X-direction T =.1 sec Period (sec)

Floor Acceleration Response in TPB System, XY vs. 3D Motion Ryan KL, Dao ND (215). Influence of vertical ground shaking on horizontal response of seismically-isolated buildings with friction bearings, Journal of Structural Engineering (ASCE), 142(1):41531

Floor Acceleration Response in TPB System, 3D Takatori (Vert. PGA =.28g) Mode 8 The acceleration profile in X-dir follows the 2 nd structural mode. 2 nd Structural Mode T =.17 sec

Analysis of Floor Spectra, TPB System 3D Input Floor Spectra for Takatori 1%, x-direction Mode 8 2 nd Structural Mode T =.17 sec

Base Shear in TPB System, 3D Takatori (Vert. PGA =.28g) Oscillation at 7 Hz (.14 sec) due to vertical acceleration is transmitted to the base shear, and amplifies the second structural mode.

15 1 Total Reaction R x (kn) Force (kn) Base Shear in 2D vs 3D Shaking TPB System, Northridge Rinaldi Base Shear X 5-5 -1 5 6 7 8 9 1 11 12 13 14 15 1 Base Shear Y R y (kn) 5-5 R z (kn) -1-15 5 6 7 8 9 1 11 12 13 14 15 1.5 1.5 2 x 14 Total Axial Force Z 3D Input 2D input 3D 2D 5 6 7 8 9 1 11 12 13 14 15 Time (s) Time (sec)

System lateral response was very predictable Dao et al., EESD 213; Dao and Ryan, JSE 213; Giammona et al., EQ Spectra 215) Bearing Displacement Trace Horizontal Acceleration Profile Disp. Y, u Y (cm) 5 Test Analysis -5-75 -5-25 25 5 75 Disp. X, u X (cm) Bearing Force vs. Displacement 2 15 Force X, F X (kn) 1 5-5 -1-75 -5-25 25 5 75 Disp. X, u X (cm) Important assumptions Composite beam slab action Superstructure damping 2-3% per mode

Practical Implications for Structural Design Seismic isolation attenuates horizontal acceleration and protects the structure from damage, as expected. Increasingly, design of isolated buildings will be performance driven, and performance of many components is determined by acceleration requirements. Many of the effects seen in the test can be predicted by analysis, and should be considered if performance requirements are strict Acceleration amplification due to H-V coupling (3D input) Vertical slab vibration (3D input) Axial force variation in hybrid systems Torsional response Residual displacement??

For Seismic Isolation to Achieve Seismic Resiliency Things we can do now Include the effects of vertical acceleration explicitly in analysis to predict forces and accelerations Use validated best practices for nonstructural component detailing Things we might think about Refined methodology for nonstructural component design forces Mitigation of vertical slab vibration (understand motion that the building sees, influence of floor system properties, response control of slab vibration)

Thanks to the many sponsors! National Science Foundation NEES Program (Grant No. CMMI-1113275 and CMMI-721399) Nuclear Regulatory Commission Earthquake Protection Systems Dynamic Isolation Systems, Aseismic Devices Company, Sumiken Kansai, THK Takenaka Corporation USG Building Systems, CEMCO Steel, Victaulic, Tolco, Hilti Japan Society for the Promotion of Science (JSPS)

ASCE 7-16 Major Revisions to Chapter 17: Seismic Design Requirements for Seismically Isolated Structures

Background Information Requirements in ASCE 7-1 and prior believed by many to be overly conservative and burdensome. In early 2 s, some U.S. engineers advocated for relaxation of standards for SI aligned with consistent performance objectives Na Naaseh S, Morgan TA and Walters MT (22). A critical evaluation of current U.S. building code provisions and FEMA guidelines for the design of seismic isolated structures, Proc. ATC 17-2 Seminar on Seismic Isolation, Passive Energy Dissipation and Active Control, Applied Technology Council, Los Angeles.

Background Information Requirements in ASCE 7-1 and prior believed by many to be overly conservative and burdensome. In early 2 s, some U.S. engineers advocated for relaxation of standards for SI aligned with consistent performance objectives A paradigm shift? Old Paradigm I want to use base isolation to offer improved performance to my client at little to no increased cost, opening its potential to a much wider class of common structures. The excessive regulation of the code makes it impossible to do that. New Paradigm I accept that base-isolation carries significant additional first costs. If I am going to recommend it to my client, I want to be able to provide assurance that they will see the performance they are looking for.

New in ASCE 7-16 Commentary communicates explicit performance objectives In general, isolated structures designed in accordance with the standard are expected to: 1. resist minor and moderate levels of earthquake ground motion without damage to structural elements, nonstructural components, or building contents and 2. resist major levels of earthquake ground motion without failure of the isolation system, significant damage to structural elements, extensive damage to nonstructural components, or major disruption to facility function.

Why Move to All MCE Design? Simpler procedure Enhanced performance An early code changed justification wrote that MCE based design greatly improved the reliability of ELF design to meet MCE performance objectives. Removed other sources of conservatism in computing design forces.

Lower Bound Properties (largest displacement) F k Dmin Upper Bound Properties (largest force) F k Dmax D Dmin D D Dmax D ASCE 7-1 where (D D is the lower bound displacement)

Lower Bound Properties (largest displacement) F V b V b(max) Upper Bound Properties (largest force) F V b(max) k Dmax D D Dmin D Dmax D ASCE 7-1 where (D D is the lower bound displacement) This pairs the upper bound stiffness with the lower bound displacement (intentional conservatism). E D determined from prototype testing. Use the cycle that minimizes E D, but pair with k Dmax. Attempts to minimize effective damping.

Lower Bound Properties F kdmin V bmin Upper Bound Properties F V bmax k Dmax D D Mmin D Mmax D ASCE 7-16 Intent: All response quantities are evaluated using both upper and lower bound properties, and the larger of the two controls.

Code Change Suggestions (from 2 s) Complaint Excessive limits on application of ELF V s = V b Suggested Solution Code Change Relax limits Removed restriction S 1.6g Removed 4-story height restriction (if no tension in isolators) Extended T M limit from 3 sec to 5 sec (but added a limit of 3% damping) V s = (W s /W) V b Triangular distribution of story shear Uniform distribution of story shear

Vertical Distribution of Forces value of k determines shape ASCE 7-1 (reflects linear 1 st mode) ASCE 7-16 Based on York and Ryan (28) Proposed by SEAOC (reflects uniform 1 st mode) k = : uniform 1 st mode k = 1: linear 1 st mode k > 1: higher mode effects

Code Change Suggestions (from 2 s) Complaint Excessive limits on application of ELF V s = V b Suggested Solution Code Change Relax limits Removed restriction S 1.6g Removed 4-story height restriction (if no tension in isolators) Extended T M limit from 3 sec to 5 sec (but added a limit of 3% damping) V s = (W s /W) V b Triangular distribution of story shear Uniform distribution of story shear

Code Change Suggestions (from 2 s) Complaint Suggested Solution Code Change R i 1.6 to 2. Ductile design and detailing required Peer review is cumbersome Testing requirements are cumbersome Reconsider limits on R to achieve comparable performance Specify design and detailing consistent with R i Exempt certain classes of structures from peer review Simplify test requirements. Exception if pushover strength exceeds MCE base shear by 1% at max story drift. Allow steel OCBFs with R=1 up to 16 ft tall (additional requirements apply). Only one peer reviewer required. Reviewer is no longer required to attend prototype testing. Permitted to substitute test data from similar sized units from the same manufacturer for required tests. Introduced λ factors from AASHTO.

E-Defense Project and ASCE 7-16 Guidance was added to the commentary about how to properly consider the effect of vertical shaking Explanation of potential effects of vertical input, including acceleration amplification and axial load effects on isolators Several approaches for explicitly considering the effect of vertical shaking in the analysis, depending on the analysis method Modeling recommendations for reproducing the effect of vertical accelerations accurately Ground motion selection and scaling recommendations New provision: components that cross the isolation interface must accommodate any permanent displacement A procedure to estimate residual displacement is offered in the commentary.

Thank You for Attending Discussion I d be happy to share a pdf copy of the presentation slides. Email me at: klryan@unr.edu to request. References 1. Ryan KL, Coria CB, Dao ND (213). Large Scale Earthquake Simulation of a Hybrid Lead Rubber Isolation System Designed With Consideration of Nuclear Seismicity, CCEER Report No. 13-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno 2. Dao ND, Ryan KL (215). Seismic Response of a Full-Scale 5-Story Steel Frame Building Isolated by Triple Pendulum Bearings under 3D Excitations, CCEER Report No. 15-1, Center for Civil Engineering Earthquake Research, University of Nevada, Reno 3. Coria CB, Ryan KL, Dao ND (215). Response of Lead Rubber Bearings in a Hybrid Isolation System during a Large Scale Shaking Experiment of an Isolated Building, CCEER Report No. 15-9, Center for Civil Engineering Earthquake Research, University of Nevada, Reno 4. Ryan KL, Dao ND (215). Influence of vertical ground shaking on horizontal response of seismically-isolated buildings with friction bearings, Journal of Structural Engineering (ASCE), 142(1):41531

References 5. Ryan KL, Soroushian S, Maragakis EM, Sato E, Sasaki T, Okazaki T (215). Seismic simulation of an integrated ceiling-partition wall-piping system at E-Defense, I: Three-dimensional structural response and base isolation, Journal of Structural Engineering (ASCE), 142(2):4153. 6. Soroushian S, Maragakis EM, Ryan KL, Sato E, Sasaki T, Okazaki T, Mosqueda G (215). Seismic simulation of an integrated ceiling-partition wall-piping system at E-Defense, II: Evaluation of nonstructural damage and fragilities, Journal of Structural Engineering (ASCE), 142(2):41531. 7. Dao ND, Ryan KL, Sato E, Sasaki T (213). Predicting the displacement of triple pendulum bearings in a full scale shake table experiment using a three-dimensional element, Earthquake Engineering and Structural Dynamics, 42(11):1677-1695. 8. Dao ND, Ryan KL (214). Computational simulation of a full-scale fixed-base and isolated-base steel moment frame building tested at E-Defense, Journal of Structural Engineering (ASCE), 14:A4145. 9. Giammona AP, Ryan KL, Dao ND (215). Evaluation of assumptions used in engineering practice to model buildings isolated with triple pendulum isolators in SAP 2, Earthquake Spectra (EERI), 31(2):637-66. 1. Guzman J, Ryan KL (215). Data from a NEES/E-Defense collaborative test program on innovative isolation systems and nonstructural components, Earthquake Spectra (EERI), 31(2):1195-129. 11. York K, Ryan KL (28). Distribution of lateral forces in base-isolated buildings considering isolation system nonlinearity, Journal of Earthquake Engineering, 12(7):1185-124.