Mechanical Behaviors of a Symmetrical Bolt Fasten Wedge Active Joint for Braced Excavations

Abstract

Joint-failure of steel tube bracing structures usually causes an excavation accident. A symmetrical bolt fasten wedge (BFW) active joint has been innovatively developed in this paper, which overcomes the shortcomings of the traditional steel wedge (SW) active joint. Three full-scale BFW active joint specimens were manufactured for field operation tests. The test results show that the proposed active joint had a good construction feasibility and a wide applicability. After the field operation tests, axial compression experiments were implemented. Meanwhile, a series of numerical simulations were performed. The numerical results agreed with that of the experiments. Both showed that the working principle and mechanical principle of the BFW active joint was reasonable and ingenious; it had outstanding mechanical properties. Overall, the BFW active joint had the advantages of structure and mechanical properties, and it is suitable for popularization and application.

Influence of Symmetry of Tightened Parts on the Force in a Bolted Joint

“…An example of a symmetrical component, which in reality may not behave completely symmetrically, can be found e.g., in [23]. Their component was stressed more on one side during the experiment, which also caused the earlier occurrence of a critically stressed bolted joint.…”

“…Since bolted connections have a wide range of applications, it was easy to get into areas that are far from the topic of the article at first view. As an example, in reference [23], they dealt with the problem of a bolt fasten wedge active joint for braced excavations. However, it is in this paper that one can see the asymmetric behavior of loads with relation to bolts for apparently symmetric components.…”

“…As has been shown, e.g., in [10], sometimes even the experiment itself may not be conclusive due to the fact that additional operating bolt load is not only tensional but a combination of tension and bending and it is not possible to place strain gauges in the ideal position. For that reason, it is also not always advisable to put only one strain gauge per bolt (especially if it is on the outside of the shell of the bolt shank), as for example in [23] (p. 10.).…”

Unsymmetrically Distributed Bolt Axial Forces between Symmetrically Spaced Bolts of Clamping Sleeve

“…FEM simulation involves converting a real problem into a 3D model and setting boundary conditions. It is the setting of the boundary conditions that is the biggest problem, which is why the verification of the FEM model is usually achieved using measurements, such as in these articles [25][26][27]. The FEM model was setup considering information from the following sources [28][29][30].…”

Study on the Influence of the Performance Weakening of the Disconnectable Coupling (DC) Joint of Steel Support on the Retaining Structure of a Foundation Pit

“…Zhang [16] highlighted the weakened link within the support system and the eccentric force at the DC joints as contributing factors to the accident. Zhou [17] underscored the delayed However, studies have indicated that the bearing capacity and initial compression stiffness of DC joints are generally lower than those of the steel supports they connect, identifying them as a potential weak link within the support system [7][8][9]. This deficiency poses a significant risk to the structural integrity of the entire support system.…”