Performance Of High Strength Steel-Concrete Composite Bridge Tower Under The Axial Load

Steel-concrete composite bridge tower,which consists of surrounded steel plates,longitudinal PBL shear connectors and core concrete column and whose cross section is usually divided into several cells by diaphragms,performs complexly under axial load.This research relied on National Key R&D Program of China(2016YFC0701202)and the science and technology R&D project of China Communications Construction Co.,Ltd.(2014-ZJKJ-PTJC03).In this study,finite element models were established through ABAQUS software for single-,double-and triple(L or I shape)-cell columns with the same cell dimensions,with the aim to analyze the principle of ultimate axial compression bearing capacity and restraint effect of the columns.The main contents are as follows:(1)Finite element models were established through ABAQUS software to analyze axial compression specimens concrete-filled square steel tube columns filled with PBL shear connectors(PBL-CFSST).The validity of finite element method was verified by comparing simulation results of Ultimate axial compression bearing capacity and load-strain curve with existing experimental results.After the whole process analysis,assumption for the PBL stiffeners setting was made at the most unfavorable lateral deformation of the columns.(2)Finite element models taking into consideration the material nonlinearity and the effect of PBL stiffeners were established through ABAQUS software for single-,double-and triple-cell columns(L or I shapes)with the same cell dimensions,with the aim to analyze the effect of number of cells,width-to-thickness ratio and restraint conditions on the ultimate axial compression bearing capacity and the restraint effect of the columns.By analyzing numerical results of load-displacement curves,load-strain curves and failure modes,it was found that when the cell dimensions are the same,increasing the number of cells would weaken the restraint effect between steel and concrete.Moreover,compared with specimens of I shape,specimens of L shape have a higher concrete strength-increasing coefficient.Meanwhile,higher ratio of width-to-thickness may result in stiffness increase but weaker restraint effect between steel and concrete.The bearing capacity of multi-cell specimen can not multiply increase because points on Diaphragms can only be deformed in the same direction,but still be higher than superposition results of steel and concrete.(3)A multi-cell high strength steel-concrete composite bridge tower taken as an example,Finite element models were established through ABAQUS software to perform numerical calculations.The results show that the composite tower has a higher axial load capacity which increased by 25% and core concrete bearing capacity improvement factor is 1.94.(4)numerical results of axial compression bearing capacity of steel-concrete composite bridge tower were compared with relevant codes.The results show that the ASI/AISC341-10 and the EC4(2004)are the most conservative,while GB50936-2014 is relatively conservative.But the calculation method is in agreement with the finite element results.However,due to safety considerations,corresponding safety factor should be multiplied.Innovation points:(1)The multi-cell steel-concrete composite bridge tower is divided into multiple small cells for axial compression performance analysis.(2)After the whole process analysis of PBL-CFSST under axial load,an approach of the PBL stiffeners setting was proposed at the most unfavorable lateral deformation of the columns.(3)Finite element models taking into consideration the material nonlinearity and the effect of PBL stiffeners were established through ABAQUS software for single-,double-and triple-cell columns(L or I shapes)with the same cell dimensions,with the aim to analyze the effect of number of cells,width-to-thickness ratio and restraint conditions on the ultimate axial compression bearing capacity and the restraint effect of the columns.(4)Discussed the reasonable calculation methods that can be applied to the design of axial compression bearing capacity of multi-cell steel-concrete composite bridge towers in practical engineering.