Patricia M. Clayton University of Washington

1. Resilient Steel Plate Shear Walls: Analysis of Performance Using OpenSees and TeraGrid Resources Patricia M. Clayton University of Washington Jeffrey Berman (PI) Laura Lowes (Co-PI)

2. NEES-SG: SPSW Research • Tasks: • Develop a resilient SPSW • Develop performance based design tools for SPSW • Develop a new model for SPSW web plates • Explore the behavior of coupled SPSWs and develop design recommendations Jeff Berman and Laura Lowes Michel Bruneau Larry Fahnestock K.C. Tsai Jeff Dragovich Rafael Sabelli Sponsored by NSF through the George E. Brown NEES Program

3. What is a Resilient Steel Wall? • Combines benefits of Steel Plate Shear Walls (SPSWs) with self-centering technologies • SPSW provides: • Ease of construction • High strength and initial stiffness • Ductility • Yielding over many stories • Replaceable energy dissipation elements (steel plates) • Post-Tensioned (PT) Connection provides: • Self-centering capabilities • Quick return to occupancy after earthquake

4. Conventional SPSW Behavior • Resists lateral load through development of Tension Field Action angle of lateral inclination load HBE a tensile stresses Web plate VBE HBE diagonal Courtesy of Berman and Bruneau folds

5. Conventional SPSW Behavior • Idealized hysteretic behavior of SPSW with simple HBE-to-VBE connections: VSPSW Unloading Plate yields D Low Stiffness 1st Cycle 2nd Cycle

6. PT Connection Behavior • Provides self-centering capabilities • Connection is allowed to rock about its flanges • PT remains elastic to provide recentering force • Requires some energy dissipation • Examples from previous research: • Yielding angles (Garlock, 2002) • Friction devices (Iyama et al., 2009; Kim and Christopoulos, 2008) Garlock (2002) Iyama et al. (2009)

7. PT Connection Behavior • Nonlinear elastic cyclic behavior of PT connection: VPT Connection Decompression D 1st Cycle qr 2nd Cycle

8. Combined System: Resilient SPSW VPT VSPSW D D Unloading VR-SPSW Plate yields Connection Decompression Plates Unloaded 1st Cycle 2nd Cycle D Connection Recompression

9. Performance-Based Design Collapse Prevention Repair of Plates Only V V2/50 V10/50 First occurrence of: • PT rupture • Excessive PT yielding • Excessive frame yielding • Excessive story drifts No Repair First occurrence of: • PT yielding • Frame yielding • Residual drift > 0.2% V50/50 Plate yielding Connection decompression Vwind D D50/50 D20/50 D10/50

10. Prototype Building Designs • Based on 3- and 9-story SAC buildings in LA • Vary number of R-SPSW bays in building • 2 design types: • Plates designed for V50/50 • Plates designed for V10/50/R

11. Analytical Model • Nonlinear model in OpenSees • SPSW modeled using strip method: • Tension-only strips with pinched hysteresis • Strips oriented in direction of tension field

12. Analytical Model (cont.) • PT connection model: Shear transfer Rocking about HBE flanges Compression-only springs at HBE flanges Diagonal springs HBE VBE PT tendons Truss elements with initial stress (Steel02) Rigid offsets Physical Model Analytical Model • Compression-only springs at HBE flanges • Diagonal springs to transfer shear

13. Dynamic Analyses • Each model subjected to 60 LA SAC ground motions representing 3 seismic hazard levels • 50% in 50 year • 10% in 50 year • 2% in 50 year • Used OpenSeesMP to run ground motions in parallel on TeraGrid machines Processor = 0 Processor = 1 R-SPSW model Processor = n-1

14. Using TeraGrid OpenSeesMP .tcl scripts Batch submission script Ground acceleration records #!/bin/bash #$ -V #$ -cwd #$ -N jobName #$ -o $JOB_NAME.o$JOB_ID #$ -e $JOB_NAME.err$JOB_ID #$ -pe 16way 64 #$ -q long #$ -l h_rt=48:00:00 #$ -M myemail@u.washington.edu #$ -m be set –x ibrun $HOME/OpenSeesMP $WORK/OSmodel.tcl Abe Ranger

15. Using TeraGrid Run all models and ground motions simultaneously using OpenSeesMP Processor = 0 Processor = 1 Abe R-SPSW model Processor = n-1 Ranger

16. Using TeraGrid All results in the time it takes to run one ground motion. OpenSees recorder & output files Abe Ranger

17. Response History Results • Example of Response during 2% in 50 year EQ • System Response • Connection Response

18. Response History Results • Statistical results from all 60 ground motions • Performance Objectives: • No plate repair (Story drift < 0.5%) in 50/50 (this example designed using V10/50/R; plates not explicitly designed to remain elastic) • Recentering (Residual Drift < 0.2%) in 10/50 • Story drift < 2.0% in 10/50 (represents DBE) • Limited PT, HBE, and VBE yielding in 2/50 All performance objectives met !!!

19. Comparing Designs R-SPSW designed using V50/50 R-SPSW designed using V10/50/R Plates designed using reduced “DBE” forces • Plates designed to remain elastic in 50% in 50 year EQ • Larger plate thicknesses & frame members • Improved response • Recentering at all hazard levels • Smaller peak drifts

20. Conclusions • Preliminary design procedure developed for R-SPSW • Dynamic analyses show R-SPSW can meet proposed performance objectives • including recentering in 10% in 50 year EQ • Highly nonlinear model  significant computational effort • Use of TeraGrid resources reduced computational time by more than 90% • Experimental studies on R-SPSW currently taking place

21. Thank You