Fiber Model Considering the Local Instability Effect and Its Application to the Seismic Analysis of Eccentrically Compressed Steel Piers  
[PERSON]  
1 College of Civil Engineering and Architecture, Zhejiang University of Science &Technology,  
Hangzhou 310023, China; [EMAIL_ADDRESS] (H.Z. ); [EMAIL_ADDRESS] (F.S.) [PERSON]  
2 Center for Balance Architecture, Zhejiang University, Hangzhou 31  
On the other hand, the high computational cost of the shell-element model makes it challenging to be used in engineering applications, whereas the traditional single-degree-of-freedom-system model or fiber model cannot reflect the local instability deformation; thus, the calculation accuracy is low. Therefore, reasonable calculation methods for the elastoplastic seismic response of steel piers need to be urgently developed. For this reason, some scholars have successively proposed seismic response analysis models based on beam structures that can consider the local instability effect of steel plates to meet the requirements of actual engineering seismic response analysis for centrally compressed steel piers. For example, [PERSON] et al. [14], [PERSON] et al. [15], and [PERSON] et al. [12] proposed load-displacement hysteretic models for single-degree-of-freedom systems. [PERSON] et al. [16], [PERSON] et al. [17], and [PERSON] et al. [18; 19] respectively proposed improved fiber-element calculation models that can be used for horizontal bidirectional seismic response calculations. The above studies show that the seismic capacity of single-column centrally loaded steel piers under rarely met earthquakes has been relatively clear, and the structural seismic response calculation model has also been gradually improved. Recently, due to the functional or landscape requirements of newly built urban viaducts, steel piers with eccentric compression have emerged worldwide, which have also been referred to as inverted L-shaped steel piers. Under the action of a transverse earthquake, this form of bridge piers is subjected to an additional bending moment in the plane. When subjected to an earthquake action along the longitudinal direction, the piers are simultaneously subjected to additional torsional and bending moments. Thus, the cross-section internal force distribution of this kind of structure significantly differs from that of the centrally compressed bridge piers, and its seismic design method needs further investigation. In terms of in-plane seismic design, [PERSON] et al. [20] conducted an in-plane pseudo-static test study of eccentrically compressed steel columns. Furthermore, [PERSON] et al. studied the seismic performance of steel piers with embedded energy-dissipating shell plates under eccentric pressure through experiments and a finite element (FE) analysis, and analyzed the influence of various structural parameters [21]. On this basis, the influence of multi-directional seismic input was studied [22]. [PERSON] et al. [23] conducted a pseudo-static test and shell-element numerical simulation analysis, proposing that the bearing capacity and ductility performance indexes of eccentrically compressed circular- or rectangular-section steel piers in the in-plane direction can be directly obtained based on the results of centrally loaded steel piers. [PERSON] et al. [24] established a single-degree-of-freedom system hysteretic model for in-plane seismic response analysis and compared the calculation results with the experimental results. In terms of out-of-plane seismic performance, [PERSON] et al. [25] conducted a FE analysis on a continuous beam bridge under transverse eccentric compression. It was observed that the torsional deformation of the bridge piers should be restrained when performing out-of-plane seismic response analysis. [PERSON] et al. [26] conducted out-of-plane pseudo-static loading tests for eccentric steel piers with rectangular stiffened cross-sections. Based on the results of [PERSON]'s experiment [26] and numerical simulation, [PERSON] et al.