Seismic performance of retrofitted WFP connections joined to box column using ribs

In this paper, design methodology and retrofitting detail of welded flange plate (WFP) moment resisting connections have been proposed. Existence of defected complete joint penetration (CJP) groove weld at the only top flange of the connection and presence of the box column with different ductility were the main construction challenge of the mentioned connections, which are less investigated in the technical literature. Reference experiment was carried out based on the proposed design methodology. Experimentally validated analytical study was performed to evaluate the applicability of the mentioned design approach of retrofitting connection by rib plates. Ductility of the column and the number of utilized rib plates were considered as the main criteria to be focused. Potential of fracture in welds of connection, seismic performance of connection and failure mechanism were investigated in cyclically loaded specimens. The experimental and analytical results proved the applicability of the proposed design method. Also, highly ductile box columns guaranteed the acceptable performance of retrofitted connection based on AISC special moment resisting frame requirements. Finally, the acceptable limits of rib plate's design methodology were developed.