Mechanical Properties Of Key Joints Of Shenzhen Gangxia-north Integrated Transportation Hub Project

The steel-concrete composite structure makes full use of the characteristics of steel and concrete,and has the advantages of high bearing capacity,fast construction speed,and good seismic performance.Therefore,it has been promoted in high-rise and super high-rise buildings,large-span spaces,and underground building structures.With the development of urban rail transit projects,a large number of subways have been constructed in large and super large cities,and subway transfer stations often need to build large underground space structures to meet the transfer needs of passengers.However,large-scale underground space structures have the characteristics of difficult construction,complex loads,and huge component sizes.The connection methods of joints in the structure often exceed the existing specifications,and the nodes are important forcetransmitting components in the structural system,and the performance greatly affects the safety of the whole structure,so it is necessary to conduct special research on the complex nodes in some large-scale structures to meet the safety requirements of the structure,and at the same time provide reference and reference for the design of such node structures.The Gangsha North of Shenzhen large-scale subway hub project is an interchange station for 4 subway lines.In the design,there are no columns in the large-span area of the atrium within 48m*51.2m.At the same time,in order to meet the needs of building lighting functions,the large-span area is opened with a diameter of 24 m.In addition,there is a viaduct on the top of the subway transfer station.The piers of the viaduct are set on the transfer beams of the underground structure.The key nodes in the structure bear heavy loads and the forces are complex,and the design of some nodes exceeds the specification limit.Therefore,it is necessary to conduct related experiments and theoretical analysis on the nodes.Based on the actual project,this paper conducts experimental research on key nodes such as beam-column nodes,bridge pier conversion nodes,and column-foot nodes in the structural system.At the same time,a finite element model is established for supplementary verification.(1)Carry out the design,processing and production of the scale specimens of the key beam-column space nodes in the structural system,determine the corresponding test loading plan and loading steps,monitor the strain and displacement of the key parts of the nodes,and combine them according to the deformation development process of the specimens.The strain level of key parts analyzes the mechanical performance of the joint;at the same time,the mechanical performance of the test joint is simulated by finite element.The test and analysis results show that the joint strengthens the ring plate first to yield,and the joint meets the relevant design requirements and has a certain safety reserve.(2)The processing and production of scale specimens of complex joints for bridge pier conversion,combined with the actual joint force performance in the structure system,formulated a detailed loading plan,so that the joint force can truly reflect its force in the structure status.The test focused on monitoring the stress level,the development process of deformation and the torsional deformation during the stress process of the steelconcrete conversion beam;combined with the development process of strain,displacement and cracks,detailed analysis of the force mechanism of the complex joints of the bridge pier conversion was established;The finite element analysis model of the node;research shows that the node has a certain safety reserve,this kind of conversion node has higher bending stiffness,torsion stiffness,reliable connection and reasonable design.(3)The processing and production of the scaled specimens of the embedded column foot joints,the formulation of the loading plan of the column foot joints,and the study of the mechanical properties of the column foot joints under the state of compression and bending.The internal strain gauges are used to explore the flexural performance of the concrete-filled steel tube column,the punching resistance performance of the bottom of the cap,and the shear performance of the internal steel bars.At the same time,the finite element analysis model of the column foot joint is established.The research results show that the dangerous part of the column foot joint is the connection between the upper concrete-filled steel tube column and the cap.The cap is basically in an elastic state,and the joint is safe and reliable under the load combination of this project.