Reducing Cost on Progressive Collapse

In recent years progressive collapse analysis has materialized into explicit requirements for redundancy in building codes all over the world. Although progressive collapse is a nonlinear dynamic procedure, progressive collapse codes permit the use of linear static analysis combined with some load factors.

In many cases a simplistic procedure is used, which models only linear beam and column elements. This neglects the contribution of walls and slabs, leading to uneconomic and/or unconservative results. Walls and slabs may be considered secondary members in other types of analysis but in progressive collapse analysis, walls and slabs often behave as primary members with slabs carrying load though membrane action and walls providing alternate load paths in case of loss of columns.

In a comparison study, ASI found that analysis using simplified finite element linear and nonlinear analysis suggested a significant increase in the weight of the steel frame is required to satisfy the UFC progressive collapse code requirements. Using more advanced analysis, like Extreme Loading^® for Structures (ELS) software shows that the original design required little to no increase in weight required.