Study On The Mechanical Properties Of PC Composite Box Girder Bridges With Corrugated Steel Webs Using Asynchronous Construction Method

As a new type of bridge structure,the PC composite box girder bridge with corrugated steel webs has obvious advantages compared with traditional PC box girder bridge,and has been developed rapidly in China in recent ten years.With the increase of bridge span,the cantilever construction method is often used in engineering.However,the traditional cantilever construction method has some disadvantages,such as overlapping construction platform,heavy weight of hanging basket and poor stability.Therefore,a new asynchronous construction method for this kind of bridge is proposed,which has the advantages of short construction period,good economy,high safety and strong constructability.Considering that the structural type of the PC composite box girder bridges with corrugated steel webs is special in the asynchronous construction process and its application is rare,it is necessary to conduct a systematic study on the mechanical properties of the structure during construction.Based on the existing research results and practical engineering,the structural mechanical performance of the long-span PC composite box girder bridge with corrugated steel webs in the asynchronous construction process is studied systematically by using the methods of experimental research and finite element analysis.The main research work are as follows:(1)The whole construction process entity finite element model is established,and the mechanical performance of the PC composite box girder bridge with corrugated steel webs under asynchronous construction method and traditional cantilever construction method is compared and analyzed.The results show that in the asynchronous construction process,the normal stress distribution of concrete is more uniform,the shear stress level of corrugated steel web is lower,and the deflection of the structure is smaller.After the completion of the bridge,the stress distribution of the structure under the two construction methods is basically the same.(2)The static loading test of asynchronous construction model beam with corrugated steel webs is carried out and the load-displacement curve,the key part,the failure mode and the stress distribution law of the test beam are obtained.The mechanical characteristics of the composite box beam with corrugated steel webs in the asynchronous construction process are preliminarily revealed.The results show that the key part of the test beam under the action of external force is the steel-concrete joint area of the connection between the N-1 section roof concrete and the N section web.The mechanical response of the test beam during the loading process can be roughly divided into four stages.(3)The parametric analysis of the bearing capacity of asynchronous construction beam is carried out by using finite element method.The results show that within limits,the bearing capacity of the structure increases with the increase of the compressive strength of concrete,the strength of corrugated steel webs,the thickness of corrugated steel webs,the width of flange plates,the thickness of flange plates,the reinforcement ratio of longitudinal ordinary steel bars,the decrease of the ratio of section width to height and the length of construction segments,but the influence degree of each parameter is different.(4)The influence of the structure form,layout position and section steel type of temporary transverse brace on the structural stability of PC composite box girder bridges with corrugated steel webs in the asynchronous construction process is studied by using finite element method.The results show that the temporary transverse brace can effectively limit the transverse displacement of corrugated steel webs under the temporary construction load,significantly improve the instability bearing capacity of the structure and the effect is relatively best when the structure form of temporary transverse brace is two-truss.In order to better limit the transverse deformation,the upper transverse brace should be set as close as possible to the upper flange of corrugated steel web.