Study On Performance Of Steel Plate Near The Weld Toe In The STC-Steel Lightweight Composite Deck

In order to solve the problem of fatigue cracking and pavement damage of the traditional orthotropic steel bridge deck,Hunan University proposes a new steel-STC lightweight composite bridge structure.Through systematic theoretical analysis and experimental research,combined with engineering practice,it has been verified that the new structure can significantly reduce the stress amplitude of typical fatigue details of steel structure,and can effectively reduce the fatigue cracking risk.The steel-STC lightweight composite bridge structure connects the STC layer with the OSD as a whole by welding short studs on the steel panel.Because the thickness of the STC layer is very thin and the stud's size is smaller,in order to get a good combination,it is necessary to weld a large number of studs on the steel panel,and a large number of welding work will introduce the initial defect,residual stress and so on,so that the steel panel of stud welding toe becomes the new fatigue detail.There is little research on this detail,and the following work is carried out on the static performance and fatigue performance of this detail:(1)In order to study the static performance of steel panel at the toe of stud welding,the static test of the lightweight composite structure with slab rib was designed by taking the Wuyi bridge as the engineering background.The results show that reducing the stud spacing can improve the sliding load and ultimate bearing capacity of lightweight composite structure,wherein the influence of stud spacing on the sliding load is greater,the stud spacing decreases from 200mm to 150mm,the sliding load increases 36.6%,and the ultimate bearing capacity increases 8.9%.For the stress distribution of the steel panel near the stud welding toe,the stress in the pure bending section is uniformly distributed,however the steel plate near the stud welding toe in the bending shear section has obvious stress concentration phenomenon,the stress level is far greater than the non-weld area.The finite element simulation of the experiment is carried out based on ABAQUS,and the analysis results corresponded well with the experimental results.The analysis results show that:for the lightweight composite structure steel panel,there is a noticeable stress concentration phenomenon in the area of bolt welding toe in the bent-shear zone,the stress level is far greater than the non-weld toe area,the stress concentration degree of different cross-section is different,as the beding moment increases,the stress concentration becomes smaller.Parameter studies were carried out to explore the influence of the stud spacing and the thickness of the steel plate on the stress level and stress concentration of the steel plate.(2)The fatigue evaluation of Wuyi Bridge is carried out based on the multiscale finite element analysis method.The results show that the steel panel stresses are mainly influenced by the wheel local loads,the longitudinal and transverse stress levels are roughly the same.The longitudinal high stress area is located in the wheel load position and the diaphragm position,and the transverse high stress area is located in the wheel load position.For the detail of the steel plate of stud welding toe,the longitudinal stress in the negative bending moment area is greater than the transversal stress,while for the detail near the mid-span region,the longitudinal and transversal stresses are close to each other.In comparison,the positive moment region is more disadvantageous.The maximum stress amplitude of the negative bending moment in the steel plate of stud bolt welding toe is 34.25MPa,its anti-fatigue performance meets the design requirements,the maximum stress amplitude of the positive bending moment is 32.88MPa,it's anti-fatigue performance meets the design requirement,but the stress amplitude level is high and the potential fatigue cracking risk still exists.(3)To verify the steel plate in the Wuyi Bridge with plate ribs lightweight composite structure can whether meet the engineering requirements under the action of the positive bending moment,the positive bending moment fatigue test is designed,and the stress amplitude of the steel plate at the stud welding toe is 142.7MPa under fatigue load.After 500,000 fatigue cycles,the longitudinal rib of the lightweight composite structure is destroyed before the STC layer and the steel panel.According to the stress equivalent conversion,this fatigue detail is not destroyed by the cyclic loading of 2.58 million times under the design stress amplitude,satisfying the engineering requirements.