Analytical prediction on static collapse resistance of steel frames in multi-interior-column-removal scenarios

Author(s):  
JingZhou Zhang ◽  
Michael C. H. Yam ◽  
Ran Feng
2016 ◽  
Vol 7 (4) ◽  
pp. 518-546
Author(s):  
Milan Bandyopadhyay ◽  
Atul Krishna Banik

Progressive collapse studies of both unbraced and braced semi-rigid jointed steel frames have been carried out to evaluate the contribution of bracings in improving progressive collapse resistance potential. Numerical models of 10-story frames with different types of semi-rigid connections have been developed using SAP2000. Progressive collapse potential of semi-rigid frames is first investigated without bracings. Bracings are then included in a systematic manner, and response of the braced frame is compared with that of unbraced frame to evaluate the contribution of bracings. Two different arrangements of bracings, that is, bay-wise and floor-wise arrangements, are considered to find out a preferred arrangement of bracings. Parametric studies include eight column removal conditions at center and corner locations of different floors. Development of catenary action has also been considered as it gives additional resistance, especially to braced frame. Apart from nonlinear static analysis, effects of bracings are evaluated also through nonlinear dynamic analysis and the responses of the frames in nonlinear dynamic analysis are compared with those of nonlinear static analysis. From the study, it is found that provision of bracings significantly improves the progressive collapse resistance potential of the semi-rigid frames under different column removal conditions. Floor-wise arrangement of bracings is much effective as compared to bay-wise arrangement.


2020 ◽  
pp. 136943322097728
Author(s):  
Haoran Yu ◽  
Weibin Li

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.


2020 ◽  
Vol 14 (1) ◽  
pp. 174-184
Author(s):  
Antonella B. Francavilla ◽  
Massimo Latour ◽  
Gianvittorio Rizzano

Background: Forthe reliable prediction of the non-linear response of structures, severe seismic events have proven to be a challenging task. Although much non-linear analysis software exists, the accuracy of the results depends on the assumptions made in the characterization of the members. Typically, the analytical models are calibrated using experimental observations. With this scope, experimental research remains the most reliable mean for the assessment of the seismic performance of structures, and it is crucial to target the development of new analytical models and design methods. Objective: Quasi-static tests can provide information on the non-linear behaviour of subassemblies, but it is often difficult to relate the imposed force or displacement histories to those that might occur during an earthquake. The pseudo-dynamic method combines an on-line computer simulation with experimental information about the tested structure, providing the application of realistic dynamic response histories. In this paper, the preliminary analysis and the design of a pseudo-dynamic testing facility for the experimental study of a real scale two storeys-two bays steel MRF, with classical and innovative joint details, are shown. Methods: Pushover and Incremental Dynamic Analyses carried out with Seismostruct software estimate the forces and displacements expected at each storey for the selected ground motions. These analyses have been performed by varying the structural detail of the beam-to-column connections. Results / Conclusion: In this paper, the analytical prediction of the performance of two bays-two storeys steel frames equipped with different solutions of beam-to-column joints is focused. Based on the performed analyses, it has been recognized that steel frames with partial strength joints can provide satisfactory performance under severe seismic actions provided that the joints are adequately designed.


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