Flexural performance of steel tube roof slab and parameter optimization

This study introduces a steel tube slab (STS), a novel pipe-roof structure used in underground engineering, whose structural system affects the bending loading conditions during construction. However, previous study used the transverse force of the STS structure to evaluate the overall structure, which results in an unreasonable structural force and material waste. The purpose of this investigation is to analyze the longitudinal flexural performance of the STS structure through a combination of experimental and numerical investigation, and to optimize the key parameters. Firstly, by conducting three flexural experiments, the failure model, load versus displacement curves, deformation characteristics, load versus strain curves and flexural capacity are investi-gated. The results of laboratory tests show that there are three stages to the loading of the STS structure, including the elastic stage, the elastic-plastic stage, and the fully plastic stage, and the structure exhibits progressive ductile failure. Furthermore, the finite element software (ABAQUS) is used to establish a series of finite element models, which are verified through laboratory tests, and the parametric coupling analysis is conducted. The results show that the flange thickness, steel tube diameter and spacing between the steel tubes have significant effect on the longitudinal ultimate capacity of the STS structure, however, the bolt diameter and steel tube thickness has a limited impact. Finally, different combination parameters are analyzed using the Fuzzy mathe-matical theory. Subsequently, the optimum ratio of key parameters is proposed.