Experimental and numerical research on fabricated joint for CFST set in underground construction

Abstract

The quantitative design of fabricated joint is a key issue to realize the effective mechanized assembly of tunnel steel set. However, there is no reported research on the failure mechanism and quantitative design method of fabricated joint for underground support structures. Taking a type of fabricated joint used for concrete-filled steel tubular (CFST) set as research object, the refined finite element model is constructed in this paper considering the complex nonlinear characteristics of joints. The simulation scheme is verified and validated based on four-point flexural and eccentric compression experiments. Failure modes and bearing mechanism of fabricated joint are obtained through above methods. Research results prove that there are two primary failure modes: the destruction of joint components and the tearing fracture at joint-CFST junction, the latter of which might lead to overall brittle failure of tunnel support structures. Parametric studies of joint specimen are carried out accordingly to establish an analytical model for fabricated joint design. The research results could provide basis for the design and application of mechanized assembly construction in tunnel excavation.