Research On Crack Resistance Method In Negative Moment Area Of Steel-Concrete Composite Continuous Bridge Based On Fold Effect Of Corrugated Steel Plate

In the negative bending moment area of the steel-concrete composite continuous beam bridge,cracking of the concrete deck is an inevitable design problem.A large number of tests and studies have shown that the application of prestress in the negative bending moment area can effectively alleviate the problem of concrete cracking,and it is most widely used in engineering practice.However,due to the characteristics of the composite beam section,a considerable part of the prestress will be transmitted to the steel box girder web through the shear connection.On the one hand,it causes low efficiency of concrete prestress application in the negative bending moment area,the improvement of crack resistance is limited,on the other hand,the steel box girder slab may be buckled due to the excessive compressive stress.In order to solve the above problems,this paper proposes a steel-concrete composite continuous structure with variable steel webs in which the plain steel webs in the negative bending moment area are replaced with corrugated steel webs.This paper takes the No.2 bridge of the Xiao Qing River Extra Large Bridge in the Gao Guang section of the Chang Shen Expressway as the research background,replaces the plain steel webs in the negative bending moment area of the bridge with a corrugated steel webs,contrast and analyze the influence of web form changes on crack resistance and other mechanical properties in the negative bending moment area of the structure.Due to the folding effect of the corrugated steel web,it is easy to compress in the longitudinal direction,and it hardly bears the axial force and bending moment,and hardly bears the prestress.The steelconcrete composite structure of the variable steel web is based on the above characteristics of the corrugated steel web.It is hoped that more prestress will be borne by the concrete deck to improve the prestress application efficiency and the crack resistance of the concrete.The main work content and results of this article are as follows:(1)The solid finite element software Midas FEA is used to establish a solid finite element model of the steel-concrete composite continuous bridge with plain webs of the Xiao Qing River No.2 Bridge.On the basis of this model,the steel-concrete composite continuous beam model with variable steel webs established in the negative moment area and steel-concrete composite continuous beam model with corrugated steel webs established in the whole bridge are established.The study of the stress situation in the negative bending moment area of each model proves the effectiveness of improving the concrete deck crack resistance by changing the plain steel web to the corrugated steel web in the negative bending moment area,and obtains the law of internal force distribution of the section due to the change of the web form;(2)In this paper,a simple calculation method of prestress application efficiency is given through the proportion of preload,which quantitatively proves the effectiveness of the corrugated steel web to increase the prestress application efficiency of steel-concrete composite continuous beams.(3)In this paper,a two-span steel-concrete composite beam model with variable steel web is established.Considering the impact of the construction,it analyzes the sensitivity of the parameters such as the thickness of the corrugated steel web,the height of the steel web,the folding angle of the corrugated steel web,the length of the straight section of the corrugated steel web and the presence of the flange plate on the steel box girder.It found that the mechanical properties of the steel-concrete composite structure with variable steel webs are most sensitive to the parameters of the thickness of the corrugated steel web and the height of the steel web.Removing the flange plate on the steel box girder can effectively improve the crack resistance of concrete in the negative bending moment area;(4)Based on the simple plastic theory and the mechanical properties of corrugated steel webs,the calculation formula of the ultimate bearing capacity of the section of the negative bending moment area of the steel-concrete composite continuous beams with variable steel webs is derived.Based on the specification,without considering the influence of corrugated steel webs,the calculation formula for the cracking moment of the steel-concrete composite structure with variable steel webs is derived.The comparison between the existing theoretical formula and the derivation formula proves the rationality of the deduced formula.