ABSTRACT
In this study, the effect of span length on progressive collapse resistance capacity of Welded Unreinforced Flange-Bolted web (WUF-B) connections was investigated by using the alternate path method as per Unified Facilities Criteria (UFC). Towards this aim, several nonlinear analyses were performed for three generic moment resisting frames with WUF-B connections considering various span lengths. In order to reduce the simulation time, a macro-element, or component-based model is introduced and verified against the NIST test results. The analysis results revealed that for a certain frame length, by decreasing the span length (increasing the number of spans) as an indirect approach, it is possible to enhance the alternate path capacity of WUF-B connections and decrease the risk of progressive collapse occurrence. For example, for the cases studied here, it was shown that by decreasing the span length to half the failure overload factor of the frame increases more than twice.
