Experimental and numerical studies on the mechanical performance of a wall‑beam‑strut joint with mechanical couplers for prefabricated underground construction

This paper investigates the nonlinear behavior of wall-beam-strut joints with mechanical couplers, which are proposed for prefabricated underground constructions, under monotonic and cyclic loading conditions using full-scale experimental tests and three-dimensional finite element modelings. The nonlinear behavior of the joint is discussed in terms of the load–displacement curves, concrete cracking distributions, and strains in the reinforcements obtained from both the experimental tests and the numerical modeling. The comparison indicates that the trends of both load–displacement curves are similar, although the cracking, yield and ultimate loads of the joints determined by the numerical modeling are 2.5% lower, 2.6% higher and 3.8% higher, respectively, than those determined by the experimental tests. The numerical simulation can capture the concrete cracking process in the joint in the early loading stage but cannot accurately model the crack distribution in later stages. Moreover, the reinforcement strains and the skeleton curve from the numerical modeling show the same tendency as those from the experimental test, but it is difficult to compare their exact values, especially after yielding. The differences are believed due to the fact that the numerical modeling idealizes the materials and fails to model the slippage between the reinforcements and concrete after the concrete cracking. On the basis of the experimental and numerical investigations, it is concluded that the proposed wall-beam-strut joint has not only an ultimate bearing capacity that is at least 3 times higher than the design load but also a good ductility. Therefore, the design of the wall-beam-strut joint satisfies the requirements for the prefabricated underground construction.