More attentions have been paid on the Non-Ductile Concentrically Braced Frames (ND-CBFs) in low and moderate seismicity regions recently due... Show moreMore attentions have been paid on the Non-Ductile Concentrically Braced Frames (ND-CBFs) in low and moderate seismicity regions recently due to their low ductility detailing requirements for design and construction. In this work, seismic collapse performances of two ND-CBFs are studied. One 3-story and one 9-story ND-CBF using small response modification coefficients (R=3) are designed firstly. Nonlinear finite element technologies are used to study the behaviors of local components. Practical analytical models for brace/gusset-plate assemblies and steel gravity frames are developed based on finite element simulations and engineering judgment. Three 2D structural models having increased local modeling complexity are developed for each braced frame. Nonlinear static pushover analyses on 3-story frames are conducted to get basic understandings of the damage evolution patterns and the interactions between main brittle braced frames and the steel gravity frames. Nonlinear dynamic analyses references the concepts of Incremental Dynamic Analysis are followed to investigate the seismic collapse responses of studied frames. The seismic assessments referenced the evaluation methods in FEMA P695 for ductile seismic load resisting frames through incremental dynamic analysis are carried out. Studied results show that Non-Ductile Concentrically Braced Frames would have little chance to prevent building collapse under severe ground motions. However, it seems that such buildings at least with low-to-moderate heights would have high probability of collapse prevention for up to moderate ground motions with conventional gravity framing systems used in modern steel buildings. PH.D in Civil Engineering, December 2012 Show less
