Experimental and numerical investigation on behaviors of Mold-bag Concrete Clamped Joints (MCCJ).

The terminal joints of the steel support system play a critical role in controlling the deformation and stability of the foundation pit. However, accidents caused by issues with these terminal joints have been frequently observed. This paper introduces the Mold-bag Concrete Clamped Joint (MCCJ) as an innovative joint for enhancing the performance of terminal joints in the steel support system of subway station foundation pit projects. Design principles of MCCJ in the steel support system of the subway station foundation pit project are presented. It provides a detailed explanation of its structural characteristics and working principle, as well as elucidates its stress situation and force transmission mechanism. Three MCCJ specimens were designed and processed for indoor compression load tests, further their load-displacement curves, load-strain curves, and failure modes were obtained and analyzed to explore the load-bearing performance and mechanical characteristics in a more professional and academic manner. The test results demonstrate a designed bearing capacity of over 4000kN, exceeding the axial design bearing capacity of Φ609/630 steel support and meeting strong joint design requirements. Meanwhile, a refined numerical model of MCCJ was established using Abaqus, validated by comparing numerical and experimental results. Parameter analysis reveals the significant influence of steel tube wall thickness and connecting flange thickness on load-bearing performance, while the mold-bag concrete strength grade enhances MCCJ load-bearing capacity within a certain range. Furthermore, to fulfill the compatibility between MCCJ and existing steel supports, and achieve joint strength and high performance, the parameter optimization directions for MCCJ were proposed. • A novel joint, namely Mold-bag Concrete Clamped Joint (MCCJ) was proposed. • Three MCCJ specimens were designed and processed for indoor compression load tests to study bearing performance. • Load-displacement/strain curves and failure modes were analyzed to explore the load-bearing performance. • A numerical model of the MCCJ was established, and the parameter analysis was conducted by nonlinear numerical simulations. • Parameter optimization directions for MCCJ are proposed. [ABSTRACT FROM AUTHOR]