Study On The Axial Compression Behavior Of Srpe Pipe-concrete-steel Tube Compound Double-tube Structure

In recent years,with the gradual advancement of my country’s "Western Development" strategy and the "One Belt,One Road" initiative,the scale of infrastructure construction in the western region has continued to expand.Therefore,it is necessary to build a large number of railway bridges and road bridges.There are a lot of strong corrosive salt media in the soil and groundwater of saline soil area in Western China.As the main load-bearing and lateral force resisting components,the lower part of bridge pier directly contacts with saline soil,and its durability is directly related to the safety and service life of bridge structure.The corrosion of traditional reinforced concrete structure is very serious under the combined action of corrosive salts and bad weather.Moreover,most of the saline soil areas in the West belong to seismic fortification areas.Therefore,the anti-corrosion of pier has become one of the key issues in the design and construction of bridges in saline soil area.In considering the above facts,this paper proposes a new composite "SRPE pipe-concrete-round steel pipe compound double-tube column" that combines anti-corrosion and seismic functions.Steel reinforced polyethylene plastic pipes（SRPE）completely block the contact between the bridge column and various corrosive ions,and at the same time confine the core concrete together with the steel pipe,so that the new composite structure has good bearing capacity and seismic performance.In this paper,10 SRPE pipe-concrete-circular steel tube compound double-tube structure short columns with 2 different combined column forms are compared with axial compression tests of specimens,the influence of SRPE pipe pressure grade,section hollow rate,inner steel pipe diameter-thickness ratio,diameter of steel pipe and whether the steel pipe is filled with concrete on the failure mode,the ultimate bearing capacity of the specimens,and the Load-Strain relationship curve are studied,and use the finite element simulation software ABAQUS to compare and analyze the test results,and the accuracy of the model has been verified.The main research results and conclusions are as follows:（1）The failure mode of hollow sandwich concrete short column under axial compression is shear failure or buckling failure of middle and lower parts,and the inner steel tube is buckled inward;The overall axial compression failure mode of the solid double-tube concrete short column is shear failure,with a larger shear failure surface,and the inner steel tube bulges outward.（2）When other control parameters are the same,the ultimate bearing capacity of hollow sandwich concrete short columns decreases with the increase of hollow ratio and diameter thickness ratio of steel tube,and increases with the increase of SRPE pipe pressure grade.For solid double-tube concrete short columns,the larger the diameter of the SRPE pipe and the inner steel tube,the higher the ultimate bearing capacity of the specimens.In addition,concrete filled steel tube can greatly improve the ultimate bearing capacity and ductility of hollow sandwich concrete short columns.（3）On the basis of verifying the reliability of the finite element model,the expanded parameter analysis of the hollow sandwich concrete specimen is carried out.The results of the finite element analysis show that the strength grade of the concrete,the strength of the inner steel pipe,the wall thickness of the SRPE pipe,the wall thickness of the inner steel pipe and the diameter of the inner steel pipe are improved,The ultimate bearing capacity of hollow sandwich concrete composite short columns under axial compression is improved;Changing the steel strength and diameter of the inner steel tube has little effect on the ductility of the specimen,while changing the concrete strength grade,SRPE pipe wall thickness and inner steel pipe wall thickness has a certain effect on the ductility of the specimen.（4）Based on the restraint mechanism of SRPE pipe confined solid concrete column,the ultimate bearing capacity formula of SRPE pipe concrete circular steel pipe hollow sandwich concrete short column under axial compression is proposed.