| Urban underground utility tunnel,abbreviated as utility tunnel,has the advantages of unified planning,management and maintenance of urban public pipelines,which greatly avoids the traditional pipeline network layout methods such as direct buried pipelines and attachments.The pollution caused by the environment and noise,thereby improving the utilization rate of urban land resources and economic benefits,has become a symbol of modern urban modernization.Utility tunnel have irreplaceable advantages and are developing rapidly in the process of urbanization in my country.Although a lot of research work has been carried out on the utility tunnel,there are still few studies on the mechanical properties of the corner joints.Taking the actual integrated pipe gallery project as the research background,this paper takes the corner joint s as the research object,calculates the working conditions of the overall four-compartment pipe gallery frame model,and obtains the internal force values of the corner connection nodes under various working conditions.The corner joints of the pipe gallery were designed,and pseudo-static loading tests were carried out in both directions of opening and closing.The internal force distribution,crack development,and failure modes of the two types of joints between the top plate connection node and the bottom plate connection under different stress conditions were studied.,And proposed a prefabricated end plate connection pipe gallery corner joint based on the end plate connection.The method of numerical simulation was used to compare and analyze the cast-in-place and prefabricated nodes,and then the connection parts of the prefabricated nodes were concretely analyzed.Parametric analysis of components.The main conclusions are as follows:(1)The opening and closing directions of the top plate corner connection node and the bottom plate corner connection node of the cast-in-situ integrated pipe gallery were loaded.The test results show that when the joint specimen is loaded in the opening direction to the elastic stage,the strain development form is more symmetrical,The amount of deformation is small.When loaded in the closed direction to the failure of the specimens,they all present a ductile bending failure mode.Compared with the bottom joint specimens,because the top plate joints are arranged at the axillary angle,the specimens are all the shorter axillary angles.The concrete compression failure occurs on the side,and the mechanical properties of the top plate joints are also better than those of the bottom plate joints,which indicates that the setting of the haunch angle can improve the overall bearing capacity and ductility of the joints to a certain extent.(2)Split the corner connection node of the cast-in-situ integrated pipe gallery floor into two plates,and use the end plate connection form to make a fully assembled dry connection,and propose an equal-strength assembled end plate connection pipe gallery corner joint design The process,which mainly includes the design of high-strength bolts,end plates,and steel structure connectors,and simplified calculation of the bending moment-angle curve of the assembled node connection part.(3)The finite element analysis software Abaqus/CAE 2019 was used to carry out corresponding numerical simulations on the corner joint tests of the cast-in-situ composite pipe gallery.The simulation results are in good agreement with the characteristic values of the load,which shows the numerical simulation.Accuracy,and using the calculated bending moment-angle curve to verify the reliability of the design of the assembled node connection part,and provide a reasonable modeling method.By comparing the load-displacement curve and the force state,it can be considered that the designed fabricated joint has semi-rigid characteristics.When the bearing capacity is similar to that of the cast-in-situ joint,it has better deformation performance,which also shows that the fabricated angle The rationality of the design of the connection node.(4)The numerical model parametric analysis of the connector part of the fabricated corner joint is carried out.The research results show that the position of the plastic hinge can be transferred by changing the thickness of the connector.Considering the excellent ductility of steel,the thickness is recommended in the design.The value can be appropriately reduced.The rigid end plate connection form has good overall working performance and can share the force of the flange of the connector.The end plate stiffener should be arranged reasonably during the design.When the bolt pre-tightening force value meets the design requirements,increasing the pre-tightening force value has little contribution to the mechanical performance of the joint.It is recommended that M24 bolts are generally used for component splicing. |
