| The Aluminum alloy has the advantages of high strength,light weight,high machinability,economy and beauty.In the structural form like long-span grid frame,aluminum alloy shows great advantages,and the box-type castellated beam can compensate for the poor stability of the aluminum alloy.The welded aluminum alloy box-type castellated beam can adopt different expansion ratio according to engineering needs to Improve the mechanical properties of the section.At present,there is no corresponding design code for aluminum alloy castellated beam in China.Therefore,this paper studies the 6061-t6 aluminum alloy box-type castellated beam by combining laboratory test and numerical simulation.The specific research content and results are as follows:（1）Through the test of six groups of plate-type aluminum alloy 6061-t6 material tensile specimens,the data were compiled and the main parameters of the constitutive relation were calculated,including elastic modulus E,elongation after fracture At,proof strength at non-proportional f0.2,the strain-hardening parameter n,poisson ratio v and other parameters.and constitutive relation equation is established according to Ramberg-Osgood[1].The results show that the ductility of aluminum alloy is poor and the tensile fracture is about 10%.（2）Bending tests and low-cycle reciprocating tests were conducted based on the constitutive relation,and four specimens with expansion ratios of 1.3 and 1.5 were designed by using the orthogonal test of L4.The initial imperfection and weld quality of the specimens were measured before the test.The influence of parameters such as expansion ratio,different welding methods and whether or not to grind the weld on ultimate flexural capacity was studied.The results show that the deformation in the corner of web perforation is the largest,and the deflection of the specimen is larger than the predictivity,and the deformation of the first opening at the fixed end is the largest.Through the orthogonal method,it is found that the expansion ratio has the largest influence on the bending strength,the choice of welding method is not the main parameter affecting the bearing capacity,and the improvement of the bearing capacity by grinding the weld is less than 10%.（3）The data of the tensile test were nonlinearly modeled by finite element analysis software,and the correctness of the finite element model was verified by comparison with the bending data.It is found that the strengthening extreme value is generated between 1.5 and 1.7,when the expansion ratio reaches 1.7,the flexural capacity of components will decrease.When the rations of height to the thickness of the web is below 75,the influence on the component performance is small.The mechanical properties of the component are better when the width to the thickness of the flange is around 22.The finite element simulation of the local stability of Perforated Web was carried out.（4）The deflection calculation formula and bending strength calculation formula of box-type castellated beam are derived based on the existing calculation formulas of H-type castellated beam and box girder.The mechanical response of the welded aluminum alloy box-type castellated beam under low frequency cyclic load is simulated on the basis of verification of low cyclic loading data by finite element software.It is found that the hysteretic curve of aluminum alloy specimens are plump and the narrow hysteretic characteristic is not obvious,indicating that the welded aluminum alloy box-type castellated beam has good seismic performance.The welded aluminum alloy box-type castellated beam exhibits excellent mechanical properties.The bearing capacity of the welded aluminum alloy box-type castellated beam is mainly affected by the expansion ratio,the depth-thickness ratio of the web,and the width-thickness ratio of the flange.Among them,the expansion ratio has the greatest influence,and the width-thickness ratio of the flange has effect on the shear force hysteresis of the web. |
