Research On Compression And Seismic Behavior Of Giant Steel Concrete Inclined Column In Underground Space Structure

With the rapid development of our country’s economy and the rapid urbanization,the city population densification has led to the increasing tension of the core area of the city so as to cause serious traffic jam.One of the methods to solve this problem is to establish three-dimensional underground integrated transportation hub.The "V" shaped inclined column(giant steel concrete inclined column)structure system is innovated in Shenzhen Huangmugang underground large-scale comprehensive transportation hub project.The displacement construction of the "V" shaped inclined column and the temporary support system as well as the bearing performance of the giant inclined column in the structure system have an important impact on the safety of the hub project.Based on the hub project,this paper adopts the method of field monitoring and finite element simulation to study the stress state and safety of the inclined column in the displacement process of the temporary support system of the giant steel concrete inclined column in the hub,and then carries out a simulation analysis on the compression mechanical properties of the full inclined column with different angles under vertical monotonic load and repeated load.Finally,The seismic performance of full scale inclined column with different inclination angles under low cycle reciprocating load is simulated and analyzed.The main research contents are as follows:(1)The construction scheme of force replacement of giant section steel concrete inclined column and temporary support system was investigated,and the inclined column replacement monitoring platform was built and used to conduct real-time monitoring of inclined column axial force,inner steel strain and reinforcement stress during the replacement of 12 and 13 axis inclined column system.The stress variation and distribution of steel and reinforcement in a giant steel concrete inclined column under actual displacement load are simulated and analyzed by finite element software ABAQUS.Results show that the displacement in the process of construction,in the inclined column sections are smaller,strain and stress changes in steel strain variable is not more than 26.99 με,reinforcement stress variable is greater than4.75 MPa;By comparing the simulated values and the monitored values,the results can provide an important theoretical reference for the stress displacement construction in similar projects.(2)Based on the structural parameters of giant steel concrete inclined columns in hub engineering,three-dimensional finite element models of full-size inclined columns with different inclinations(0°,3°,6°,9°,12°,15° and 18°)under vertical monotone load and repeated compression load are established to reveal the working mechanism of such inclined columns.The failure forms,stress states and peak loads of full-size inclined columns with different inclination angles were studied,and the influences of different factors such as concrete strength,steel content ratio of section steel,reinforcement ratio of longitudinal reinforcement,steel yield strength and hoop diameter on the compression bearing capacity and deformation properties of full-size inclined columns of giant section steel concrete were further analyzed.The results show that the full-foot inclined column with different inclination angles shows bending failure,and the instability along the inclination direction will occur with the increase of the inclination Angle.When the inclination Angle is the same,due to the phenomenon of unloading stiffness degradation of specimens under repeated loads,the peak load and post-peak bearing capacity of specimens are reduced compared with that under monotone loads.(3)The seismic performance of the giant steel concrete full size inclined column with different inclinations(0°,3°,6°,9°,12° and 15°)was simulated and analyzed,and the failure forms,hysteretic curves and skeleton curves of the full size inclined column with different inclinations were investigated.The effects of loading direction,axial compression ratio,concrete strength,reinforcement ratio of longitudinal bars,steel content ratio of section steel,yield strength of section steel and other factors on seismic performance of full-size inclined column of giant section steel concrete are further analyzed.The results show that the bending failure occurs in the full size inclined column with different angles,the concrete at the root of the specimen collapses in a large area,and the steel and steel at the bottom reach yield.The hysteretic curves of full-size inclined columns with different inclination angles are similar in shape,showing full fusiform and good seismic performance.However,with the increase of inclination Angle,the ability of specimens to resist load along the inclination direction is weakened.