| Municipal tunnels are generally multicellar.In accordance with the engineering habits,most cast-in municipal tunnels are equipped with haunches but assembled ones aren’t.And in order to facilitate the construction,roof and floor of municipal tunnels are generally thick plates without shear reinforcement.In order to study the crack propagation,failure mechanism,bearing capacity and deformability of the municipal tunnel,based on practical engineering,a full-scale multicell municipal tunnel section model was tested.And to study the effects of haunches and shear reinforcement on mechanical properties of municipal tunnels,the numerical simulation is carried out by nonlinear finite element analysis software ATENA.The main purpose of this paper is to evaluate the bearing capacity of the municipal tunnels designed according to Chinese current standard and the safety of the design scheme such as none haunches and none shear reinforcement,optimize the reinforcement scheme and provide a reference for the rational design of municipal tunnel structures.The test results show that the specimen experiences three stages of cracking,stiffness degeneration and ultimate failure;the failure mode of specimen is diagonal tension failure;when the load on the specimen reaches the quasi-permanent load,the crack width and deflection have no super limited value,which can meet the requirement of the serviceability limit state.The ultimate bearing capacity of the specimen reaches 2.37 times of the design load value,and it can meet the requirement of bearing capacity limit state.The ATENA finite element model of the test specimen is established,and it is found that ATENA can simulate the distribution,damage and ultimate bearing capacity of municipal tunnels.It’s proved that ATENA can be used to simulate the mechanical performance of municipal tunnels in scientific research and engineering.By comparing the results of ATENA model with concentrated load loading and uniform load loading,it is found that the two have the same damage process and failure mode.The rationality of the method of converting the concentrated load in the experiment into the distributed load in the actual project is verified by the same damage process and by comparing the ultimate bearing capacity of the two.Compared with the performance of haunched and non-haunched ATENA model under the same load,found that the presence of haunch can increase the stiffness and bearing capacity of components.With the data of the test,evaluated the formulas for calculating shear bearing capacity,and found that it is not safe to calculate the shear capacity of the roof of the specimen with GB50010-2010.Study the influences to failure mode and other mechanical properties of configuring the shear reinforcement or reducing the longitudinal reinforcement on the municipal tunnel model by ATEN A.It was found that the shear reinforcement had no effect on the early stiffness of the structure.But even the configuration of a small amount of shear reinforcement also have a greater capacity to enhance the shear bearing capacity in oblique section.With increase of the amount shear reinforcement,the contribution of shear reinforcement to increase the bearing capacity in oblique section is reduced.When the amount shear reinforcement exceed a certain degree,configure more shear reinforcement on the structural the bearing capacity has no ascension.With the shear reinforcement,cross-section failure occurs before the shear at the bearing.The failure mode of the model of only reducing the cross-longitudinal reinforcement in the bottom of mid-span is the same with model with shear reinforcement.The failure model of reducing the longitudinal reinforcement both in the bottom of mid-pan and the upper part of the bearing is that both the section of mid-span and the bearing will break.The model may still meet the requirement of the serviceability limit state and the ultimate bearing capacity after reducing the longitudinal reinforcement in the mid-span and the upper part of the bearing. |
PDF Full Text Request