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 Subassembly Frame/Fuse Tests - 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

Pivoting Fuse Braced Frames H Replaceable Fuse A B A Shear Strains = D/H x A/B

Pivoting Fuse System with Backup MRF Elastic restoring force Reduce damage in fuse Reduce residual deformations Provides redundancy Base Shear Drift MRF Pivoting Fuse Combined 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

PT Cables & Braces remain elastic Controlled Rocking Braced Frame with Fuses Yielding of Structural Fuse Structural Fuse Post-tensioning (PT) Tendons PT Cables & Braces remain elastic Steel Braced Frame A B A Could potentially employ additional fuse at base of column

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 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

Cyclic Response DESIGN with R = 8.0 A B PT Yielding RDR = 3% Global Behavior PT Yielding RDR = 3% A B 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

E-Defense Testbed Structure Section shaking direction 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

Design Decision Matrix Seismic & Green Design Rocking Frame Design Decision Matrix

Life-cycle Financial Assessment