Effect of Converting Connections to Moment-Resisting on the Seismic Retrofit of Existing Steel Structures

Converting beam-to-column connections to moment-resisting connections can be considered as a retrofit strategy for various steel structural systems, including moment frames, braced frames, and mixed (dual) systems. Welded Flange Plate (WFP) connections are rigid beam-to-column connections in which steel plates are welded to the beam and column flanges to provide flexural strength and stiffness. In this study, an existing five-story steel building was evaluated under a vertical expansion scenario (adding stories up to nine). First, the structure was modeled in ETABS as an intermediate moment-resisting frame (IMRF) in the X direction combined with a special concentric braced frame (SCBF) in the Y direction. Next, an alternative model with the same geometry and member sizes was developed, in which the connections in the moment-frame direction were replaced with WFP rigid connections, resulting in a dual system. Member checks and acceptance evaluations were performed using the Iranian guideline for seismic retrofit of existing steel buildings (Publication ۱-۳۶۳). The results indicate that, for the ۷-, ۸-, and ۹-story configurations, stiffening the connections increases the number of braces that satisfy the acceptance criteria; approximately ۵۰% of the braces that did not meet the acceptance criteria in the simple-frame system satisfy the criteria after connection stiffening in the dual system.

کلیدواژه ها:

seismic retrofit ، Steel structures ، WFP connections ، adding stories ، existing structures