Research On Bending Resistance Performance Of Tubular Roof Prefabricated Structure

Tubular roof prefabricated structure is a kind of underground structure constructed by tubular roof prefabricated method.Tubular roof prefabricated structure has unique advantages in some ultra-shallow buried underground projects which require strict settlement control.The steel pipe curtain in the tubular roof prefabricated structure not only plays a supporting role in the construction process,but also is an integral part of the underground structure after the completion of the construction,and forms the main structure together with the internal reinforced concrete.In current engineering,there are some problems that the mechanical properties of tubular roof prefabricated structure are not clear and the steel pipe curtain can not be fully utilized.This thesis is based on the underground excavation project of Yingze Street Underpass Railway Station in Taiyuan City,the failure mode and mechanical performance of tubular roof prefabricated structure are studied from the structure and member aspects by the method of laboratory experiment and numerical simulation.The main research work and achievements are as follows:The finite element software is used to establish the numerical calculation model of the structure,and the influence of structural section form on structural internal force is studied.The stress mode of the structure is analyzed based on the crack form of the quasi-rectangular tubular roof prefabricated structure.The results show that:the quasi-rectangular tubular roof prefabricated structure mainly bears the action of bending moment.Under the action of external load,the cracks of the structure are mainly distributed in the vault,inverted arch and side wall,and the form of crack is tensile crack caused by bending moment.The bending moment of the vault and the inverted arch of the structure is larger,and the bending cracks develop rapidly and the height is larger,the structure finally failed in bending.Through the two-point loading experiment,the failure form and stress mechanism about the bending members of the tubular roof prefabricated structure were studied,and the influence of the configuration of connectors and longitudinal bars on the flexural performance of the members were explored.The results show that: the damage of bending members of tubular roof prefabricated structure generally occurs at the intersection of steel pipe and flat steel plate.Because the steel tube curtain has a tendency to be flattened at the concave angle of the intersection of curved steel pipe and the flat steel plate.The damage form starts from the yielding of tensile reinforcement and column,and finally the yielding of steel plate after the steel pipe curtain is completely separated from concrete.The setting of stretch bar connectors can greatly improve the bending performance of the tubular roof prefabricated structural members,while the setting of stud connectors has little effect on the bending performance of the tubular roof prefabricated structure.The configuration of longitudinal reinforcement can slow down the deformation of the members and improve the stress performance of members.The finite element software is used to establish the numerical calculation model of the tubular roof prefabricated structure.The correctness of the model is verified by comparing with the experimental results,and the parameters of the bending member of the tubular roof prefabricated structure are analyzed.The results show that: The thickness of the steel plate has a great influence on the ultimate bearing capacity of the members.The diameter of the tension bar connector has little effect on the ultimate bearing capacity of the members.The strength of concrete and the strength of the tension bar connector have little effect on the ultimate bearing capacity of the members.The setting position of the tension bar connector has a great influence on the ultimate bearing capacity of the new tubular roof prefabricated structural members.the ultimate bearing capacity of the member is the largest when the tension bar connector is set at the junction of the steel pipe and the flat steel plate.The current specification predicts the ultimate bearing capacity of the flexural members of the tubular roof prefabricated structure to be too large.