Comparison of steel frames with RWS and WFP beam-to-column connections through seismic fragility analysis

Abstract

Reduced web section (RWS) connections and welded flange plate (WFP) connections can both effectively improve the seismic performance of a structure by moving plastic hinges to a predetermined location away from the column face. In this paper, two kinds of steel frames—with RWS connections and WFP connections—as well as different frames with welded unreinforced flange connections were studied through seismic fragility analysis. The numerical simulation was conducted by using multiscale FE modelling. Based on the incremental dynamic analysis and pushover analysis methods, probabilistic seismic demand analysis and seismic capability analysis were carried out, respectively. Finally, combined with the above analysis results, probabilistic seismic fragility analysis was conducted on the frame models. The results showed that the RWS connection and WFP connection (without double plates) have little influence on reducing the maximum inter-storey drift ratio under earthquake action. RWS connections slightly reduce the seismic capability in non-collapse stages and improve the seismic collapse resistance of a structure, which exhibits good structural ductility. WFP connections can comprehensively improve the seismic capability of a structure, but the seismic collapse resistance is worse than that of RWS connections when the structure has a large number of storeys. The frame with WFP connections has a lower failure probability at every seismic limit state, while the frame with RWS connections sacrifices some of its structural safety in non-collapse stages to reduce the collapse probability.

Investigation of Behavior of Interior Steel Connections With Openings in Beam Web and Flange Under Monotonic Loading

“…Also, the capability of RWS models to reach higher story drifts (six percent) was evaluated by [82][83] both in experimental and numerical ways. The behavior of RWS connections via numerical or experimental studies in the recent years are assessed by many researchers among which [107] developed a novel RWS connection with vertical slits; [108] investigated the RWS connection with an elliptic opening in the web; [109] evaluated the cyclic performance of an eight-story welded moment frame with elliptical-shaped RWS and compared it to the conventional RBS connections; Yu and Li [110] evaluated the steel frames with RWS connections and WFP connections using the probabilistic seismic demand analysis and seismic capability analysis; Lin et al [111] investigated the behavior of RWS in progressive collapse under critical column removal scenario, the results demonstrated the capability of the mentioned connections in terms of rotational capacity; Erfani et al [112] studied the lateral load carrying behavior of steel moment resisting frames with reduced web beam sections and propounded an algorithm to select appropriate opening size; Bi et al [113] scrutinized the castellated beam-to-column connections with four regular hexagonal web openings under cyclic loading with and without floor slab, the results indicated the importance of the space between web openings, and depth-to-thickness ratio of the web. Moreover, due to the limitations imposed on beam span-to-depth ratio in different codes which result in the impossibility of the use of short beams in some of the prequalified rigid connections, Hoseinzadeh Asl and Jahanian [114] investigated using web opening located at the mid-span of the deep steel beams in rigid connections in order to lead the plastic hinge away from the column face.…”

Volume 17 Number 4

“…Also, the capability of RWS models to reach higher story drifts (six percent) was evaluated by [82][83] both in experimental and numerical ways. The behavior of RWS connections via numerical or experimental studies in the recent years are assessed by many researchers among which [107] developed a novel RWS connection with vertical slits; [108] investigated the RWS connection with an elliptic opening in the web; [109] evaluated the cyclic performance of an eight-story welded moment frame with elliptical-shaped RWS and compared it to the conventional RBS connections; Yu and Li [110] evaluated the steel frames with RWS connections and WFP connections using the probabilistic seismic demand analysis and seismic capability analysis; Lin et al [111] investigated the behavior of RWS in progressive collapse under critical column removal scenario, the results demonstrated the capability of the mentioned connections in terms of rotational capacity; Erfani et al [112] studied the lateral load carrying behavior of steel moment resisting frames with reduced web beam sections and propounded an algorithm to select appropriate opening size; Bi et al [113] scrutinized the castellated beam-to-column connections with four regular hexagonal web openings under cyclic loading with and without floor slab, the results indicated the importance of the space between web openings, and depth-to-thickness ratio of the web. Moreover, due to the limitations imposed on beam span-to-depth ratio in different codes which result in the impossibility of the use of short beams in some of the prequalified rigid connections, Hoseinzadeh Asl and Jahanian [114] investigated using web opening located at the mid-span of the deep steel beams in rigid connections in order to lead the plastic hinge away from the column face.…”