Study On Mechanical Behavior Of Strut-waling-diaphragm Wall Joint In Prefabricated Metro Station

With the advantages of high quality,materials,low energy consumption,high efficiency and small noise pollution,the development of prefabricated construction is imperative when facing the problems such as disappearance of demographic dividend,increasingly severe environmental policy,etc.At present,the prefabricated underground structure is mainly used in shield tunnel,while the prefabricated metro station is rarely used.This paper studies a kind of prefabricated metro station that can be used to form an enclosure structure consisting of strut and waling,and serve as a permanent structure.The static and low-cycle repeated loading experiment of strut-waling-diaphragm wall are conducted.The mechanical properties of joints,such as static load bearing,ductility and energy dissipation are compared between the waling and diaphragm wall by steel plate connection and mechanical couplers connection.Further,a three-dimensional finite element model is established,and some suggestions are given to the strut-waling-diaphragm wall joint through the combination of full-scale test and finite element modeling simulation.The main research contents and achievements are as follows:(1)Select the appropriate full-scale component size according to the affected area of strut-waling-diaphragm wall joints,construct specimens,and carry out static and low-cycle repeated loading experiment.(2)The static loading experiment results of steel plate connection and mechanical couplers connection joints were analyzed by comparing to each other.The failure of both started from the yielding of the longitudinal bars at the top of the strut,and then the bottom concrete reached the biaxial strength under the action of normal stress and shear stress,and the specimen was destroyed finally.Compared with the mechanical couplers joint,the horizontal steel plate of the steel plate connection joint can better distribute the stress of steel bars at different positions.Comparing the bearing capacity,ductility and steel bar strain of steel plate and mechanical couplers connection joints under static load,it is concluded that the steel plate connection is better than mechanical couplers connection.(3)Compared with the low-cycle repeated loading experiment of the connection joint between the steel plate connection and the mechanical couplers connection,the strength degradation of the steel plate connection is less than that of the mechanical couplers connection,and the stiffness is greater than that of the mechanical couplers connection.The forward bearing capacity of the steel plate connection joint is less than that of the mechanical couplers connection joint,but the forward ductility is better than the latter.The negative bearing capacity and ductility of the steel plate joint are slightly better than those of mechanical couplers joint.The bearing capacity,ductility,strength and stiffness of steel plate connection joint are better than those of mechanical couplers connection joint.(4)A three-dimensional finite element model of steel plate connection was established.And the model is verified by comparing the results to the experiment.What's more further discussions about the factors that can affect the bearing capacity of joint,such as the vertical plate offset error,embedded anchor bar and horizontal steel-plate-bar,were carried out.According to the simulation results,within the allowable scope of design and construction,the vertical steel plate is supposed to move up appropriately.In addition,the embedded anchor bar and horizontal steel-plate-bar diameter and spacing can be furtherly optimized.