| Because of its advantages of light weight,high strength and large span,orthotropic plates are widely used in modern large-span bridge construction.However,due to the large number of structural welds,complex structure and large welding residual stress,fatigue problems are easy to occur under the long-term vehicle load,which seriously hinders the popularization and application of orthotropic plates.In order to improve the fatigue performance of orthotropic plates and improve the fatigue life of structures,based on the analysis and summary of the improvement methods for the fatigue performance of orthotropic steel deck by domestic and foreign scholars,the concept of wave plate-UHPC composite bridge deck structure with full curvilinear section is proposed,and its design parameters are optimized.Finally,compared with the traditional orthotropic plate,the fatigue performance of the weld joint of composite deck is studied.This paper mainly carried out the following research work:(1)This paper reviews the development history of fatigue problems of orthotropic plates,probes into the causes of fatigue problems based on the analysis of structural structure and stress characteristics,analyzes and summarizes the Countermeasures of improving the fatigue problems of orthotropic plates by scholars at home and abroad,puts forward a new type of composite deck structure-wave plate-UHPC composite bridge deck structure with full curvilinear section.At the same time,with reference to the traditional orthotropic plate,wave plate-UHPC composite bridge deck structure with full curvilinear section is designed,and the parameter value is determined preliminarily.(2)The finite element model of composite bridge deck is established by using AN SYS software,and the influence of the change of design parameters on the mechanical properties of the structure is analyzed.The results show that:the transverse projection length,longitudinal projection length and curve degree are all important structural design parameters that affect the mechanical properties of the structure,among which the longitudinal projection length has a greater impact,while the transverse projection length and curve degree have a relatively small impact,so it is necessary to take a reasonable value.(3)The response surface method and design expert data analysis software were used to optimize the three structural design parameters.It was found that the interaction of the three design parameters on the stress at the weld was not significant.the influence degree of the three factors on the stress at the weld is:longitudinal projection length>curve degree>transverse projection length.The error between the experimental value and the predicted value of the response surface method is 0.236%,and the optimized design parameters are ideal.The reasonable values of the optimized design parameters are:the transverse projection length is 135mm,the longitudinal projection length is 65mm,and the curve degree is 4.(4)Based on the analysis of various fatigue life design methods,the hot spot stress method based on S-N curve is selected to evaluate the fatigue performance of the weld joint of composite deck.Compared with the standard fatigue vehicles of various countries,the European Eurocode 3 fatigue vehicle model Ⅲ is selected for structural loading,and then the stress amplitude and the number of actions are obtained by using the water release method.Finally,the FAT90 S-N Curve and Miner’s linear cumulative damage theory are used to calculate the fatigue life of the structure,and compare the fatigue life between the traditional orthogonal plate and the composite deck,the results show that:the fatigue performance of the weld joint of the optimized composite deck structure is significantly improved,the fatigue life at the weld toe of the roof plate is increased by 4.9 times,and the fatigue life at the weld toe of the diaphragm plate is nearly infinite,which fully meets the requirements of the design specifications.Compared with the traditional orthogonal plate,the composite deck has obvious advantages. |
