As a new type of floor structure, steel vierendeel sandwich plates are widely applied in large-span buildings with multiple storeys. Shear connectors are important stressed members of such plates. To evaluate the seismic performance of the shear connectors, a full-scale test piece in two different connection forms, namely, A and B, is designed and tested under alternating load. Test analysis of the two connection specimens covers the failure modes, hysteresis curves, and main parameters (e.g., bearing capacity, ductility, stiffness degradation, and energy dissipation coefficient). The following results concerning type A connection are obtained: First, it exhibits good ductility and long yielding platform; second, elastoplasticity of steel is fully exerted with it; third, it absorbs and dissipates energy well with strong energy consumption; and fourth, when failure occurs, cracks usually happen in the heat-affected zone of the weld in the core zone. The following conclusions about type B are drawn: first, it has large bearing capacity with high stiffness; also, when failure occurs, the ribbed stiffeners crack and flexion deformity happen.

A reinforced concrete vierendeel beam (RCVB) is an open-web structure formed by connecting the top and bottom chords through block-shaped shear keys. In this study, the static load test was applied to understand the failure state and reinforcement ratios relationship with bending capacity of RCVBs. The results reveal that numbers of horizontal cracks appeared in the chord-key node area of the bendingshear section. The deflection development of specimens experienced elastic, elasticplastic, and plastic stages. The failure of the beam was controlled by the deflection and the ultimate load increased with the reinforcement ratio. A combined model for calculating the bending capacity of the top chords under eccentric compression and the bottom chords under axial tension is proposed. With the measured strains the loading coefficient of the beams are 1.15-1.20. According to the Chinese code, the continuous loading after the longitudinal reinforcement of the bottom chord yielding can make the top chord concrete reach the ultimate compressive strain, and the loading coefficient of the beams are 1.1-1.2. Therefore, the proposed model and formulas can effectively calculate the flexural bearing capacity of RCVBs. The finite element analysis results further indicate that the proposed calculation model and algorithm are appropriate. K E Y W O R D S finite element analysis, flexural bearing capacity, loading coefficient, reinforced concrete vierendeel beam (RCVB), reinforcement ratio, static load test | INTRODUCTIONMultistory large span buildings require a suitable floor system, and reinforced concrete (RC) beams and slabs are commonly used in floor structures. With a large span, the height of the beam section and the required building floor height must be large, which leads to a large self-weight and an obvious seismic response. In the Chinese code, the theory for calculating the flexural bearing capacity of RC beams is based on the calculation model shown in Figure 1. After the concrete in the tension zone cracks, the bending moment M is finally balanced by the resultant force F in the compression zone on the beam section and the tensile force T of the tension steel bars. The concrete in the tension zone of the beam can be removed, but the beam structure must be changed. In 1993, Ma et al. proposed a RCVB comprising a top chord, bottom chord, and shear key (Figure 2) with the structure of a RC open-web sandwich plate (RCOSP) (Figure 3) [1,2] to achieve the following improvements:1. Removing the concrete close to the neutral axis of the beam can reduce the self-weight to reduce the structural response and earthquake impact.

The shear key in the reinforced concrete open-web sandwich plate (RCOSP) is a block joint that connects with the top chord and the bottom chord. In order to understand the failure mode of the shear key and verify the accuracy of the current algorithm, a total of 9 test pieces are prepared and classified 3 groups were assigned longitudinal reinforcement (LR) ratios of 0.49%, 0.82%, and 1.24%, respectively. The horizontal concentrated static loading under simple support condition is carried out. The test results show that the shear key is horizontally cut and the concrete is pulled apart or crushed along the direction of chord width at the shear key-chords area; the strain level of the concrete and stirrup of the shear key is lower averagely; the development of the horizontal displacement and the strain of the longitudinal bars of the test pieces goes through elastic, elastoplastic, and plastic stages; the ultimate load of the test pieces has almost no relationship with the reinforcement ratio of shear key but is controlled by the degree of crack development in the area where shear key connects with the chords. To avoid the current algorithm overestimating the shear capacity of shear key, the restricted condition of shear section is proposed. The finite element analysis (FEA) further verifies that the restricted condition of shear section proposed in this paper is reasonable and necessary.