Effect of Bracing Type and Topology on Progressive Collapse Resistance of Eccentrically Braced Frames

This paper presents a comparative study on the progressive collapse behavior of eccentrically braced frames with different types and topology. Progressive collapse analysis was conducted on a set of diagonal, Inverted-V and combined braced frames in a five story building with different braced bays under gravity and earthquake loads, simultaneously. Nonlinear dynamic analysis and alternate path method were performed to assess the progressive collapse-resisting capacity of these braced frames and determine the most critical locations of element loss as well as element removal impact factor. Different scenarios of sudden columns and their adjacent braces removal were utilized to calculate the removal impact factor. The results show that the Inverted-V eccentrically braced frames with two braced bays have more robustness for mitigating progressive collapse due to fewer impacts. Moreover, the comparison of the impact factors of different types of bracings indicates that the combined V and Inverted-V eccentrically braced frame (using V and Inverted-V braces in the consecutive stories alternately) is less vulnerable to progressive collapse respectively.