Study On The Axial Compressive Bearing Capacity Of Hollow Steel Tube Short Columns With Externally Bonded Transvers CFRP Sheets

Compared with the ordinary carbon steel,stainless steel has the advantages of good mechanical properties,excellent surface decoration and excellent durability,which makes it have a broad application prospect in the field of construction engineering.However,the constitutive relationship of stainless steel is different from that of ordinary carbon steel,which makes relevant scholars question whether the research results of strengthening ordinary carbon steel with CFRP sheet can be applied to stainless steel structure.At the same time,there are relatively few researches on strengthening stainless steel structure with CFRP.Based on this,this paper intends to study the strengthening of short columns of axially compressed hollow steel tubes(stainless steel and ordinary carbon steel)with externally bonded CFRP sheets through the finite element numerical simulation and theoretical analysis,analyze the influence of width thickness ratio(diameter thickness ratio)and the number of layers of externally bonded CFRP sheets on the strengthening effect,and then put forward the calculation method of ultimate bearing capacity of such composite members.The research contents of this paper are as follows:(1)The refined finite element models of the hollow square tube(stainless steel and ordinary carbon steel)short column and the hollow circular tube(stainless steel)short column strengthened by CFRP sheet are established by using the ANSYS finite element software according to the existing literature test.The validity of the model is verified by comparing the finite element model with the existing literature test results,which provide basis for further research.(2)With the help of the effective finite element model,the parameter analysis of the hollow steel tube short column strengthened with CFRP sheet is carried out,and the influence of the width thickness ratio(diameter thickness ratio)and the number of CFRP layers on the axial compression ultimate bearing capacity of the austenitic stainless steel tube short column is discussed.The results show that the ultimate bearing capacity of the specimens strengthened with circumferential CFRP sheet is significantly improved.For the specimens with the same width thickness ratio(diameter thickness ratio),the strengthening effect increases with the increase of the number of CFRP layers.With the increase of width thickness ratio(diameter thickness ratio),the percentage of bearing capacity of the member increases,which shows that the CFRP sheet is more sensitive to the strengthened thin-walled section.(3)When the thin-walled section is compressed,it will buckle locally,so it can't bear the whole section.In this paper,based on the concept of the effective section,it is assumed that the hoop constraint of CFRP only acts on the effective section,so as to determine the bearing capacity of the short column of hollow square steel tube(SHS)strengthened by CFRP under the axial pressure.(4)According to the code for the design of steel structures strengthened with externallybonded fiber reinforced materials compiled by CIRIA,The modified calculation coefficient ?t of the stable bearing capacity of the short stainless steel columns strengthened with carbonfiber sheet is given.And the ?t is estimated by reference to the experiment and the finiteelement analysis ?t=1.15.