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NEESR-SG: Controlled Rocking of Steel-Framed Buildings with Replaceable Energy Dissipating Fuses . Greg Deierlein, Paul Cordova, Eric Borchers, Xiang Ma, Sarah Billington, & Helmut Krawinkler, Stanford University Jerome Hajjar & Kerry Hall, University of Illinois
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NEESR-SG: Controlled Rocking of Steel-Framed Buildings with Replaceable Energy Dissipating Fuses Greg Deierlein, Paul Cordova, Eric Borchers, Xiang Ma, Sarah Billington, & Helmut Krawinkler, Stanford University Jerome Hajjar & Kerry Hall, University of Illinois Mitsumasa Midorikawa, Hokkaido University David Mar, Tipping & Mar Associates
Shortcomings of Current Approaches Throw-away technology: Structure and Architecture absorbs energy through damage Large Inter-story Drifts: Result in architectural & structural damage High Accelerations: Result in content damage & loss of function Deformed Section – Eccentric Braced Frame
Objective Develop a new structural building system that employs self-centering rocking action and replaceable* fuses to provide safe and cost effective earthquake resistance. *Key Concept – design for repair
Leveraging previous research … • Self-Centering Concepts • rocking frame/wall systems • post-tensioned frames • Energy Dissipating Shear Panels • ductile fiber cementitous composites • slit steel shear walls • Performance-Based Engineering (PEER/ATC) • damage & collapse limit states • economic losses & life-cycle assessment • simulation tools
Scope • System Design Development - parametric design studies - shear panel fuse design and testing - building simulation studies • Subassembly Frame/Fuse Tests - quasi-static cyclic loading - PT rocking frame details & response - panel/frame interaction - model calibration • Shake Table System Tests - proof-of-concept - validation of simulation models Stanford NEES - Illinois E-Defense
Replaceable Fuse Pivoting Fuse Braced Frames D H A B A Shear Strains = D/H x A/B
Combined Pivoting Fuse Base Shear MRF Drift Pivoting Fuse System with Backup MRF • Elastic restoring force • Reduce damage in fuse • Reduce residual deformations • Provides redundancy Moment Resisting Frames
“Rocking” Braced Frames No Permanent Displacement Force Gravity load overturning resistance Displacement Midorikawa, M., Azuhata, T., Ishihara, T. and Wada, A. (2003)
Rocking Braced Frame w/Post Tensioning Orinda City Offices Architect:Siegel and Strain Architects
Controlled Rocking Braced Frame with Fuses Yielding of Structural Fuse Structural Fuse Post-tensioning (PT) Tendons PT Cables & Braces remain elastic Steel Braced Frame Could potentially employ additional fuse at base of column A B A
Pretension/Brace System Fuse System c b c d e b Base Shear a,f Base Shear Fuse Strength Eff. Fuse Stiffness a d PT Strength g Drift Frame Stiffness g f e Drift b c Origin-a – frame strain + small distortions in fuse a – frame lift off, elongation of PT b – fuse yield (+) c – load reversal 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
Energy Dissipating Fuse Options • Attributes of Fuse • high initial stiffness • large strain capacity • hysteretic energy dissipation • Candidate Fuse Materials & Designs • ductile fiber cementitious composites** • steel panels with slits** • low-yield steel • mixed sandwich panels
Ductile Fiber Reinforced Cemetitious Panels • Tapered Flexural/Shear Links • Designed for distributed plasticity • Similar in concept to a “butterfly” link beam HPFRCC Flexural Panel Tests by Kesner & Billington 2005
Steel Shear Wall with Slits Hitaka et al., 2004
OpenSees Simulation Model Nonlinear Truss Members Elastic Truss Members EPP Post-Tensioning Tendons Uplift Spring
PT Yielding RDR = 3% Global Behavior A A B Cyclic Response 4% shear strain cap PD Fuse Behavior DESIGN with R = 8.0 Vd = 0.125W PT = 1055kN, Vp,fuse = 1687kN br = 1.0 Pinching 50% residual
Bilinear vs. Pinching Fuse Not Restoring Restoring PT Strength = Fuse Strength (2PT*A) / (Vp,fuse (A+B)) = 1.0
Maximum Interstory Drift vs. Sa(T1) 2.7% 2/50 Level • Inelastic Time History Analyses: • 20 EQ record pairs, scaled to increasing intensities • Primary EDP: interstory drift • structural limit states • - column lift-off (rocking) • fuse yielding/damage • PT yielding 1.6% 10/50 Level PT Yielding Unscaled records The yellow squares represent the median, 16th and 84th percentile response.
Subassembly Frame Tests (NEES-Illinois) • Test Configuration • 2/3 scale planar rocking frame with realistic details • quasi-static • System Response • structural details & PT • various fuse types • indeterminate shear-fuse/frame interaction • Simulation model validation NEES - Illinois
Shake Table Validation Test (E-Defense) • Large-scale frame assembly • Validation of dynamic response and simulation • Proof-of-Concept • construction details • re-centering behavior • fuse replacement • Collaboration & Payload Projects
shaking direction E-Defense Testbed Structure Section Plan View E-Defense
Collaboration Opportunities • Alternative Fuse Designs • Alternative Rocking Systems • rocking column base details • hydraulically actuated self-centering • Industrial Collaboration • Steel manufacturers/fabricators • Design practitioners • Related Japanese “Steel Project” • Related US Initiatives • PEER Building Benchmarking • ATC 58 & 63
Seismic & Green Design Rocking Frame Design Decision Matrix