## 1 Introduction  
A concrete-filled steel tubular (CFST) frame is composed of CFST columns and steel or reinforced concrete beams [1, 2]. Nowadays, this CFST frame structure has been widely used in practical construction projects, due to remarkable features, such as high bearing capacity [3, 4, 5, 6], large stiffness [7, 8, 9], and superior anti-seismic performance [10, 11, 12, 13, 14]. Additionally, some special shaped concrete-filled steel tubular components, such as L-shaped columns, can be utilized to enhance the internal space and thus beneficial for the placement of furniture by avoiding undesired configuration of the edges and corners in structures [15, 16, 17, 18, 19, 20, 21]. Currently, some scholars have proposed a new model that is suitable for the single specimen of concrete-filled steel tube by considering the material constitutive model. [PERSON] et al. [22, 23, 24] developed a new numerical model to predict the cyclic characteristics of CFST columns, which was under cyclic loading or eccentric loading. Some theoretical and experimental investigations on the seismic behavior of steel beam connected to CFST column plane frames have been explored and reported in the literatures. [PERSON] et al. [25] used the finite element analysis program, named as DRAIN-2 DX, to establish a full-scale model of a four-story and five-bay frame made of wide flange H-shaped beams connecting to square CFST columns. [PERSON] et al. [26] carried out the test for a three-story and three-bay planar frame with CFST column connecting to steel beam. [PERSON] and [PERSON] [27] conducted a test to demonstrate that the yield load, ultimate load-carrying capacity, and ductility of the frame that was filled with masonry wall were greatly improved, as compared to those in the pure frame structure. [PERSON] [28] built a finite element analysis (FEA) to study the behavior of the composite frame, and the results obtained from the FEA model were validated against the test results. [PERSON] et al. [29] investigated the seismic performance of CFST frame structure under the constant axial load and cyclic horizontal load. [PERSON] et al. [30] analyzed the mechanism of composite frames with steel beams connecting to concrete-filled square steel tubular columns by using FEA modeling and proposed the simplified hysteretic lateral load-displacement models. [PERSON] et al. [31] established the nonlinear finite element model of squared CFST frame to study the influence of the slenderness ratio. [PERSON] et al. [32] and [PERSON] et al. [33] developed a design methodology for moment resisting frame structures with tubular CFST columns and conducted a nonlinear pushover analysis on the numerical frame models. [PERSON] [34; 35] conducted an experimental study and nonlinear finite element analysis to study the seismic behavior of concrete-filled square steel tubular frames. [PERSON] et al. [36] experimentally investigated the behavior of SCFST frames that were subjected to constant axial load and cyclic lateral load. [PERSON] [37] and [PERSON] [38] carried out experimental and theoretical studies on the seismic performance of three-story and two-story CFST structures that are based on damage assessment. In addition, structural damage detection [39; 40; 41] and health monitoring methods [42; 43; 44; 45; 46; 47; 48; 49] have been developed to monitor the damage status and health of structures in real time. On the other hand, experimental and numerical studies have also been performed to predict the structural behavior and failure mode subjected to unexpected loads like impacts, explosions, and other high dynamic loads [50; 51; 52]. Since the slips existed along the interface between the steel and concrete, some scholars conducted experimental investigations on concrete structure under cyclic loading and studied the bond-slip and debonding behavior between the steel and the concrete while using piezoelectric technologies [53; 54; 55; 56; 57; 58].