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Seismic behavior and damage assessment of mid-rise cold-formed steel-framed buildings with normal and reinforced beam-column joints

Jiang Liqiang, Zhang Xingshuo, Ye Jihong, Jiang Lizhong, Zhou Lingyu

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 3

675--690

This paper investigated the effects of normal and reinforced beam–column joints on seismic behavior and damages of mid-rise cold-formed steel (CFS) framed buildings, where the reinforced beam–column joint is strengthened by a pair of steel blocks and a gusset plate. Shaking table tests were conducted on a 5-story CFS frame building with normal beam-column joint (CFSM-NJ) and a 5-story CFS frame building with same configurations but with reinforced beam–column joint (CFSM-RJ). Formulae fitted from four damage models were used to assess the seismic damage indexes of these test buildings, and the assessed results were validated by the damage indexes observed from tests. The results show the following: (1) the CFSM-NJ failed due to plastic hinges formed at the column bases and large separate deformation at the beam-column joints; however, the weaken-story failure mode was appeared on the CFSM-RJ; (2) the peak inter-story displacement of the building was reduced about 10–30% due to the reinforced beam-column joints; (3) the Park-Ang model is more appropriate for seismic damage assessment of column bases, but all the damage models overestimates the seismic damages of CFS beams. Finally, the authors comment on the difference between the assessed seismic damage indexes and the observed results, and the maximum damage indexes obtained from the simplified formulae are recommended as the preliminary assessed damages for mid-rise CFS buildings.

Probabilistic seismic performance evaluation of composite frames with concrete-filled steel tube columns and buckling-restrained braces

Li Beibei, Wang Jingfeng, Yang Jian, Wang Yuanqing

Archives of Civil and Mechanical Engineering

2021

Vol. 21, no. 2

541--562

The concrete-filled steel tube (CFT) composite frames using blind bolts and buckling-restrained braces (BRBs) have been studied with the development of building industrialization and energy dissipation technology. However, there has been no research so far on the probabilistic seismic fragility analysis for the blind-bolted end-plate CFT composite frames with BRBs (BRB-BECFT). Therefore, a total of 6-, 9-, 12- and 20-story BRB-BECFT prototype structures were designed based on the performance-based plastic design method. The results obtained from nonlinear static and dynamic analyses indicated that the four structures achieved predefined performance objectives in terms of story drift, joint rotation, and BRB ductility demand. Subsequently, fragility curves including non-collapse and collapse states were established to evaluate the behavior of the structure for a given intensity measure using the incremental dynamic analysis approach. Meanwhile, the geometric mean of spectral acceleration over a period range (Sa,avg) was selected as the intensity measure to assess the structural collapse capacity. Results showed that the adoption of Sa,avg can result in 32–42% lower data dispersion for the determination of collapse point, and simplification of the process of calculation of the collapse margin ratio of a structure. Furthermore, based on the combination of Sa,avg, residual story drift and BRB core plate strain, a framework of probabilistic seismic damage analysis of structures for combined damage evaluation at three levels of the system, subsystem, and component was summarized and conducted by the 6- and 12-story case study. This is practically useful to assess structural damage state after an earthquake because it could present more information on the probability distribution of various damage scenarios.

Seismic damage behaviour of aeolian sand reinforced concrete columns with I-shaped structural steel

Wang Y. H., Wang H. Y., Wang Y. P., Zhao M., Qi J., Huo G. Z., Liu P. Q.

Archives of Civil Engineering

2020

Vol. 66, nr 4

633--650

To promote the application of aeolian sand resources for steel-concrete composite structures, an aeolian sand reinforced concrete column with I-shaped structural steel is proposed in this study. Four specimens are designed and manufactured with different replacement rates of aeolian sand. The seismic behaviour and damage evolution process of the specimens are studied by low-cycle repeated loading tests. Based on the test results, the mechanical characteristics, failure modes, hysteresis curves, skeleton curves, energy dissipation capacity, displacement ductility, and stiffness degradation of the specimens with different replacement rates of aeolian sand are analysed. In addition, the effects of the design parameters on the seismic behaviour of the specimens are also studied. The results show that the indexes of the seismic behaviour can be significantly improved by adding steel. Moreover, a revised damage model is proposed, to better reflect the evolution law of seismic damage of aeolian sand reinforced concrete columns with steel. The proposed model can provide an important reference for seismic damage assessment of the columns.