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Experimental and numerical investigation on non-welding CFDST joint for seismic evaluation of moment resisting frame

Guo Lei, Wang Jingfeng, Wang Wanqian, Liu Yong

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

128--145

EN

This paper aims to evaluate the seismic performance of concrete filled double-skin steel tubular (CFDST) frame structures. An experimental investigation on internal joints to CFDST columns was conducted to assess their seismic behavior, in which non-welding connection method was employed to avoid possible premature welding fracture. Experimental results declared that this type of joint behaved in a semi-rigid manner. Numerical models were then established to simulate the seismic performance of the joints. The moment–rotation relationship and shear behavior of panel zone were both accounted according to the component method and strut model, respectively. Subsequently, a CFDST moment resisting frame with non-welding connections (NWF) was numerically analyzed to detect its seismic response under design-based and maximum considered earthquakes. The numerical results confirmed that the NWF could lower the seismic response in terms of base shear force and joint moment compared with namely rigid frame (NRF). It also verified that the maximum story drift ratios of the NWF were higher than those of the NWF. Increment dynamic analyses (IDA) were also performed to evaluate the collapse behavior. Furthermore, a detailed discussion was conducted to analyze the influence of joint stiffness on global behavior of the NWF. The analytical results verified that this type of NWF had satisfied seismic behavior and excellent anti-collapse performance. More importantly, the NWF could conveniently adjust the stiffness of each story by varying the stiffness of the non-welding connection to decrease the story drift and to achieve a uniform story drift distribution.

2

Theoretical model and structural performance of assembled joint between circular CFDST column and composite beam

Guo Lei, Wang Jingfeng, Wang Wanqian

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 3

167--189

EN

Circular concrete filled double skin steel tubular (CFDST) has broader application aspects in engineering practice due to its superior confinement and elegant architectural appearance compared with square CFDST. However, there is still lack of an effective and reliable assembled method to connect the circular CFDST column to the beam. This paper focused on the theoretical and structural behavior on the assembled joint between circular CFDST column and composite beam. A sophisticated theoretical model was proposed to evaluate the initial rotational stiffness and moment capacity of the assembled joint. This theoretical model firstly accounted for the curved end plate in bending considering the clamping forces of blind bolts. Furthermore, a simplified arch model was developed to assess the circular steel tube in compression and the stiffness coefficients related to the circular CFDST column determined by the load transfer mechanism were also involved in the theoretical model. Subsequently, an experimental investigation on such kind of joint was conducted as a basis to verify the developed numerical model, indicating the numerical model could well replicate the typical failure modes and hysteresis curves. Parametric analyses based on the validated numerical model were performed to identify the effects of various parameters on the typical assembled joint. The theoretical model was verified to be capable of predicting the initial stiffness and moment capacity of assembled composite joint to circular CFDST column by comparing with the numerically observed results. The theoretical and analytical results performed in this paper would be beneficial for the application of the assembled beam to column joint in CFDST structures.

3

Seismic response investigation and analytical model of light polymer material-filled CFS shear walls

Wang Wanqian, Wang Jingfeng, Guo Lei, Shen Qihan

Archives of Civil and Mechanical Engineering

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2020

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Vol. 20, no. 2

423--436

EN

The light polymer material (LPM), prepared with suitable mix proportion and physical method, is a type of low-carbon and environmental-friendly material. Recently, the LPM is developed as structural material for cold-formed steel (CFS) structures to cover the shortages of traditional CFS shear wall. In this paper, material properties of gypsum-based and cement-based LPM including compressive strength, elastic modulus and thermal property were explored by tests. Experimental results demonstrate that LPM exhibits excellent thermal insulation, and the thermal insulation and compressive strength of LPM satisfy the demand of bearing capacity and thermal insulation property of shear walls. To explore the effect of LPM on seismic response and failure modes of CFS shear walls, three specimens are manufactured and tested under cyclic loading. The existence of LPM in CFS shear wall would restrain the failure of wall studs to some extent. Due to the restriction effect of LPM on wall studs and self-drilling screws and the bond-slip performance between LPM and studs, the shear walls exhibit better seismic behavior than traditional CFS shear walls. At last, a modified equivalent bracing model is employed to predict the lateral stiffness of LPM-filled CFS shear walls considering the effect of filling materials, rib lath, and sheathing. The lateral stiffness obtained by the proposed method is compared to the experimental results in this paper and other researches, and the proposed model is proved to supply a conservative result which is safe to be adopted in the design and application of the LPM-filled CFS shear wall.