NEESR-SG: Controlled Rocking of Steel-Framed Buildings with Replaceable Energy Dissipating Fuses Greg Deierlein, Paul Cordova, Eric Borchers, Xiang Ma, Alex Pena, Sarah Billington, & Helmut Krawinkler, Stanford University Jerome Hajjar, Kerry Hall, Matt Eatherton, University of Illinois Mitsumasa Midorikawa, Hokkaido University Toko Hitaka, Kyoto University David Mar, Tipping & Mar Associates and Greg Luth, GPLA 1

Controlled Rocking System Component 3 – Replaceable energy dissipating fuses take majority of damage Component 2 – Post-tensioning strands bring frame back down during rocking Component 1 – Stiff braced frame, designed to remain essentially elastic - not tied down to the foundation. Bumper or Trough

Rocked Configuration Corner of frame is allowed to uplift. Fuses absorb seismic energy Post-tensioning brings the structure back to center. Result is a building where the structural damage is concentrated in replaceable fuses with little or no residual drift

Controlled-Rocking System

Pretension/Brace System Fuse System Base Shear Drift a,f b c d e g PT Strength Frame Stiffness Fuse System Base Shear Drift a b c d e f g Fuse Strength Eff. Fuse Stiffness b c Origin-a – frame strain + small distortions in fuse a – frame lift off, elongation of PT b – fuse yield (+) c – load reversal (PT yields if continued) d – zero force in fuse e – fuse yield (-) f – frame contact f-g – frame relaxation g – strain energy left in frame and fuse, small residual displacement Base Shear 2x Fuse Strength d a PT Strength e f PT – Fuse Strength g Drift Combined System

Shear Fuse Testing - Stanford Attributes of Fuse high initial stiffness large strain capacity energy dissipation Candidate Fuse Designs ductile fiber cementitious composites steel panels with slits low-yield steel mixed sandwich panels damping devices Panel Size: 400 x 900 mm

Trial Steel Fuse Configurations thickness t h a L b B Rectangular Link Panel Butterfly Panel KEY PARAMETERS: Slit configuration b/t and L/t ratios Butterfly – b/a ratio Out of plane bracing

ABAQUS Modeling of Fuse Similar Deformation Mode 9

Prototype Structure

Parametric Study – Parameters Studied A/B ratio – geometry of frame Overturning Ratio (OT) – ratio of resisting moment to design overturning moment. OT=1.0 corresponds to R=8.0, OT=1.5 means R=5.3 Self-Centering Ratio (SC) – ratio of restoring moment to restoring resistance. Initial P/T stress Frame Stiffness Fuse type including degradation

Sample of Parametric Study Results: Mean Values of Peaks from Time Histories OT=1.0 SC=1.0 A/B=2.3 SC=1.0 A/B=2.3 OT=1.0

UIUC Half Scale Tests

UIUC Half Scale Tests

UIUC Half Scale Tests Typical Alternative Configuration: Six Fuses

Elevation of Post Tensioning UIUC Half Scale Tests Elevation of Post Tensioning Column Base

Test Matrix Test ID Dim “B” 1 A/B Ratio OT Ratio SC Ratio Num. of 0.5” P/T Strands Initial P/T Stress2 and Force Fuse Type and Fuse Strength Fuse Configuration Testing Protocol A1 2.06’ 2.5 1.0 (R=8) 0.8 8 0.287 Fu (94.8 kips) Steel Butterfly 1 (84.7 kips) Six – 1/4” thick fuses 3F-025-AB2.5-OT1.0 Quasi-Static A2 Steel Butterfly 2 Two – 5/8” thick Fuses 1F-0625-AB2.5-OT1.0 A3 1.5 0.430 Fu (142.3 kips) Steel Butterfly 3 1F-0625-AB2.5-OT1.5 Hybrid Simu-lation3 A4 (R= 5.3) (127.0 kips) Two – 1” thick Fuses 1F-1-AB2.5-OT1.5 B1 3.06’ 1.69 7 0.328 Fu Steel Butterfly 4 (75.4 kips) 3F-025-AB1.69-OT1.0 B2 Steel Butterfly 5 (75.4 kips) 1F-0625-AB1.69-OT1.0 B3 Steel Butterfly 4a B4 0.492 Fu Steel Butterfly 6 (113.2 kips) 1F-1-AB1.69-OT1.5

System Test at E-Defense (2009) Large (2/3 scale) frame assembly Validation of dynamic response and simulation Proof-of-Concept construction details re-centering behavior fuse replacement Collaboration & Payload Projects Special thanks to Profs. Takeuchi, Kasai, Nakashima and all those involved in the testbed development and E-Defense operations 18

Conclusion Seismic loads prescribed in current building codes assume considerable inelasticity in the structure during a severe earthquake. This can result in structural damage and residual drift that cannot be economically repaired. The controlled rocking system satisfies two key performance goals: Minimize residual drift. Concentrate bulk of structural damage in replaceable fuses. Experimental and analytical work has been carried out at Stanford to optimize fuses. A parametric study was conducted at UIUC to optimize A/B ratio, OT ratio, and SC ratio. Half-scale tests will be conducted at the UIUC MUST-SIM Facility to improve details and validate the performance of the controlled rocking system for implementation in practice. Tests will be carried out at E-Defense to further validate the system performance and demonstrate the self-centering and repairability of the controlled rocking system when subjected to a realistic ground motion.

Controlled Rocking Project