## 1 Introduction
[15] conducted fire tests on three continuous slabs: one has fire exerted at the side span only, one has fire exerted at both the side and the mid spans, and the other has fire exerted at all three spans. The furnace temperatures of each span, the temperature of concrete and steel, the slab deflection, the restraint forces at slab corners, and the failure modes were obtained. At present, many scholars have deduced some calculation methods according to their proposed film effect generation mechanism, but there are some problems such as complex calculation process and too many assumptions [4; 5; 6; 7; 16; 17]. The author's research group has also conducted in-depth research in this regard: [PERSON] [18; 19] solved the tensile membrane effect of concrete slab by using the deformation and decomposition principle and gave the calculation formula of the ultimate bearing capacity of rectangular and square two-way slabs without horizontal constraints. On this basis, [PERSON] [20], [PERSON] [21; 22], and [PERSON] [23; 24] proposed formulas for calculating the ultimate bearing capacity of reinforced concrete two-way slabs under fire, considering the tensile membrane effect with simply supported on four sides, fixedly supported on four sides, simply supported on adjacent sides and fixed supported on adjacent edges, and formulas for calculating the limit load-carrying capacity of two-way slab floors with beams only on columns and one-way slabs with flat beamless floors. In the numerical simulation of structural fire resistance analysis, the commonly used finite element software includes: ABAQUS [25; 26], FEAST [27], SAFIR [28], ADAPTIVE [29], Vulcan [30; 31], etc. At present, the work of Vulcan used to analyze the slab is mainly proposed by [PERSON] [30; 31]. The reinforced concrete slab is divided into several layers along the thickness direction, and the reinforcement is dispersed into separate reinforcement layers. The element used is a 4-node shell element. The formula used is based on the overall Lagrangian coordinates, and the Newton Raphson iterative method is used to solve the equation. Among the above software, FEAST and SAFIR cannot be used to simulate the tensile film effect, and only Vulcan can describe the tensile membrane film effect best. However, due to the Green strain tensor, when the deflection is large, the rotation of the plate along the thickness direction is very obvious, which cannot be described by the overall Lagrangian coordinate and Green strain tensor. Therefore, in the case of large deflection, there will be slow convergence or even non-convergence. In this paper, experiments were conducted on two full-scale two-way reinforced concrete slabs with three simply supported edges and one clamped edge, which are boundary conditions that have not been tested before. The purpose of the test is to research the temperature field distribution, deflection change at different positions, in-plane displacement change, crack occurrence, and development and failure mechanism of concrete slab under different support conditions. The influence of boundary conditions on the fire resistance of two-way slab is studied to fill the gap of previous research. The research generated valuable test data that can be used to validate the numerical models developed by fellow researchers in the field of structural fire engineering. Based on the original work of the research group, this paper further studies the calculation of the limit load-carrying capacity of reinforced concrete two-way slabs with three simply supported edges and one clamped edge.