Team UCDSESM Yihai Bao, YeongAe Heo, Zhiyu Zong University of California, Davis April 4 th, 2008 Prediction for Progressive Collapse Resistance of a 2D RC frame

Outline Background Methodology –the alternate path method by General Services Administration (GSA, revised June 2003) –nonlinear static, nonlinear dynamic Models –Macroscopic modeling approach –Beam column modeling: beam-column fiber model –Joint modeling: macro joint model Results –Dynamic response after removing first floor center column –Response from static pushdown Summary

Background Glass Column Testing frame at Northeastern University

Methodology: GSA Criterion GSA criterion utilizes the alternate path method to ensure that progressive collapse does not occur  Scenario: instantaneous removal of a column in the first story  Structural analysis for prescribed set of load combinations and material strength factors  Linear/Nonlinear Static  Nonlinear Dynamic  Evaluating the potential for progressive collapse  Strength requirements (DCR, Demand Capacity Ratio)  Reinforcement detailing and ductility requirements

Methodology: Two Step Test First step –Dynamic loading: breaking the glass column with sudden impact Second step –Static loading: displacement controlled pull down if frame dose not collapse during first step Testing frame with dynamic loading Northeastern University Testing frame under pull down loading Northeastern University

Models: Macroscopic Modeling Macroscopic modeling approach –Using simplified models to predict a specific overall behavior Advantages: computational efficiency; compatibility with traditional structural analysis models. Disadvantages: complexities involved in development of an objective and transparent calibration procedures. Finite element model Beam fiber model Macro joint model

Models: Materials Panel Shear Spring Property Reference: Vecchio & Collins (1986) Interface Shear Spring Property Reference: Walraven (1981) Concrete Property Reference: Mander et al (1988) Bond-Slip Property Reference: Lowes & Altoontash (2003)

Bond-Slip For With, Table: Average bond strengths as a function of steel stress state and Bond and bar stress distribution for a reinforcing bar anchored in a joint From Lowes, L.N. & Altoontash, A. (2003) PEER Report

Interface shear Walraven J.C. (1981)

Results Observed position of first bar fracture Predicted position, “top bar”, of first bar fracture

Summary Both simulation results and test results show the frame dose not collapse and no wire fractures after removal of first floor center column. Simulation results and test results indicate the same location of first wire fracture which is close to steel cutting region in second floor middle bay beams. No shear failure (joint shear failure or beam shear failure) is observed. Simulation responses give a good prediction for the tested frame although minor disparity exists.

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