Mechanical Properties Of Cross-shaped PEC Columns Under Axial Compression Load

Axial compression tests and numerical calculation by software ABAQUS were performed on four cross-shaped PEC columns,one of which was filled with plain concrete and the other three were filled with concrete after transverse tie rods,shear members,and U-shaped hooks were installed on the steel plates,respectively.The basic mechanical properties such as the failure mechanism,ductility and ultimate bearing capacity of the cross-shaped PEC columns were researched according to the test results and finite element analysis results.The parameters such as the arrangement method of transverse tie rods,the tie rod spacing,the tie rod diameter,the width-to-thickness ratio of the main steel flange,the limb-length-to-thickness ratio and the concrete strength grade were discussed on the performance of cross-shaped PEC column under axial pressure.Finally,the calculation formula of the ultimate bearing capacity of the cross-shaped PEC column was proposed.The research found that: the steel and concrete in the four cross-shaped PEC columns could work well together;the failure mode was that the concrete in the middle and upper part of the column was crushed;setting transverse tie rods limited the development of concrete cracks,made the column more ductile,and prevented the steel plate from separating from the concrete;when setting transverse tie rods,the lateral tie rods in the x and y directions couldn’t be staggered,but should be overlapped with each other to form a closed loop to better limit the development of oblique cracks;the diameter of the transverse tie had little effect on the mechanical properties of the column;the smaller the spacing of the transverse tie rods,the higher the ultimate bearing capacity and the better the ductility of the column;the installation of transverse tie rods could ensure the local stability of the main steel flange,therefore,the limit value of the ratio could refer to the relevant requirements for the width-to-thickness ratio of thin and flexible flanges in the Canadian code,and the maximum width-to-thickness ratio could be set to 32;the cross-shaped PEC column’s steel content should not be less than 7%,and the ratio of the length of the limb to the thickness of the limb should not be greater than 2.5;the strength grade of concrete was not the higher the better,to maximize the synergy between the section steel and the concrete,the strength grades of the section steel and the concrete have to be matched,if the concrete strength grade was too high,the column’s strength would rapidly deteriorate once it reached its ultimate bearing capacity,exhibiting brittle failure characteristics.