Experimental Research on Bending Bearing Capability of Grouted Double Mortise-Tenon Joint for Prefabricated Metro Station Structure

Abstract

The grouted mortise-tenon joint, invented as the connection between the large prefabricated elements, is the most important component in the prefabricated underground structures. This paper conducts analysis of load-carrying capacity performance and failure mode with 1 : 1 prototype test in key working direction of different double mortise-tenon joint types for the prefabricated metro station. The resistance moment is developed and used to analyze the bending bearing characteristic curve, and the corresponding test results of each stage of the characteristic curve are described in detail. In addition, the bending bearing performance of different types of double-tenon joints under different load conditions is compared. The test results clarify the ultimate failure mode of double-tenon joint and the variable bearing capacity characteristics of the joint with the increase in axial load and explain the bearing performance of each stage. It is also found the auxiliary pretightening device is helpful to delay the appearance of cracks and improve the bearing capacity, especially when it is set on the tension side. The research results have important application value for the joint design of prefabricated metro station structures.

Analysis of the Law of Joint Deformation for Grouted Mortise-Tenon Joint

“…It can be seen from the summary of experimental values of the joint deformation curve and calculated values of finite elements in different cases that the joint deformation curve mainly experiences the following four stages: linear variation stage ⟶ quasi-linear variation stage ⟶ nonlinear variation stage ⟶ stage of sharp increase in deformation until structural damage, which is exactly consistent with the four stages of the bearing characteristics curve of the grouted mortise-tenon joints [5,15,23]. By taking as an example the test in which the modified epoxy resin is poured within the grouting range b under the axial force of 1600 kN, various stages of the joint deformation of grouted long single-tenon joints are analyzed (see Figure 21).…”

“…e finite element software (ABAQUS) is used to create a grouted long single-tenon joint model having the same size, structure, material parameters, and boundary conditions as the test (Figure 18), and the model is poured with the modified epoxy resin grout and is designed as per grouting range (b), and then the simulation analysis of the loading test are conducted under the axial forces of 500 kN and 1,600 kN. And, the concrete damaged plasticity model is selected for C50 concrete, and HRB400 parameters are adopted for rebars and auxiliary pretightening device; it can be seen from the joint experiment failure modes [14][15][16] that the there is no crack at the epoxy resin bonding of the joint surface. erefore, the epoxy resin on the joint grouting section is defined as an elastic deformation body which is separately bound to the left and right faces contacting tenon and mortise.…”

“…is research monitors the joint deformation throughout the overall construction process of the Changchun prefabricated metro station (West Ring Road Station) from segmental ring erection, backfilling of topsoil upon completion of the station, and water-level recovery, and maintains statistics of BC joint deformation in the overall construction process (including deformation on both the tension side and the compression side), as shown in Figure 20. Obviously, the joint deformation is very small during the whole construction process, and there is sufficient safety margin from the design check line [23].…”

“…With regard to the structure of the prefabricated metro station using grouted mortise-tenon joints, the relevant rotational deformation of the joint between two precast components will result in the redistribution of internal force of the structure system and also be the important factor having a direct impact on the joint loadbearing capacity [13,14]. As the load effect varies, the change law of relevant rotational deformation of joints plays an important role in, and is of great significance to, the judgment of the bearing capacity and bending strength of joints [15,16].…”

A measuring method for layered compactness of loess subgrade based on hydraulic compaction

“…With the decrease of porosity and the discharge of pore water, the compression modulus of soil is also increasing. It can be seen that with the increase of compactness, the elastic modulus E is also increasing, along with the density, stiffness, spring coefficient and damping coefficient of soil [50][51][52]. Therefore, the displacement of the hammer decreases.…”