Study On Residual Stress And Overall Buckling Behavior Of Q420 Large-section Hot-rolled And Galvanized Steel Equal Leg Angles

At present,the practical engineering application of high strength steel has been increased rapidly in the world.690MPa and above high strength steel has already been applied in construction industry,besides 420MPa and above high strength steel has already been applied in transmission line industry.Previous studies have shown that High-strength Large-section Steel Angle(HLSA)members can completely replace the traditional combined steel angles members and circular steel tube members.And the High-strength Large-section Steel Angle tower has the advantage of unambiguous force transfer and can be uniformly stressed while reducing the manual error and project cost.However,there is still a lack of systematic study on the properties of this kind of angle and the research basis of the design methods of HLSA subjected to axial compression is as well.Aiming to investigate the performance of this new angle systematacially,the research object of this dissertation is selected as Q420 high strength L300 × 30 large section hot-rolled and galvanized steel equal leg angles.The research progress reported in existing literatures for residual stress is introduced in this dissertation.And then an experiment is conducted to quantify the residual stress within 6 angle steel specimens,allowing for two different lengths of the specimen and two types of surface treatments by the sectioning strain-gage method.And the longitudinal residual stress distributions over the section for all specimens are obtained to compare with the domestic and international distribution curves collected.Based on the experimental results,the welding residual stress distribution models and design formulas are developed.Then another experiment is conducted by the hole-drilling strain-gage method to quantify the residual stress within two HLSA welding end-plate specimens,allowing for two different types of surface treatments.So the welding residual stress distributions for all specimens are obtained and the models of welding residual stress distribution over the leg of the angle and design formulas are developed.In addition,a finite element model of axial compression angle allowing for the effects of initial geometric imperfections and residual stresses is developed in this dissertation by using the general-purpose finite element software,ABAQUS.This model is validated by comparison to domestic and international test results.Furthermore,a parameter analysis was performed and the column curves of hot rolled and galvanized angle steel specimens under axial compression are developed by calculation,which are compared with the design curves from current design codes in the world.Finally,appropriate selection of existing design curves-are suggested,and appropriate column curves,calculation formulas and design methods are respectively proposed for large section hot-rolled and galvanized steel equal leg angle specimens.