Study On Mechanical Properties For Continuous Deck Structure Of Simply Supported Steel-concrete Composite Beam Bridge

With the popularization of steel structure bridge in China,the simply supported steel-concrete composite beam bridge will be widely used in the construction of medium and small span bridge in the future by virtue of their simple structure,clear force,quick construction and low cost.The continuous deck is used in the multi-simple-span steel-concrete composite beam bridge,which can not only solve the problem of vulnerability of expansion joints,but also improve the ride comfort.Because the continuous deck structure will participate in the work of the main beam,the simply supported beam bridge with continuous deck not only has the mechanical properties of the simply supported beam,but also presents the partial mechanical characteristics of the continuous beam.However,in the design of this kind of bridge,the influence of continuous deck structure on the main beam is usually ignored.At the same time,there is usually no special analysis and calculation for the design of continuous deck structures,and there is no generally accepted analysis and calculation method at present.Moreover,most of the research on continuous deck is based on single-piece simply supported slab beam,"T" beam and other concrete beams,and few researches on the continuous deck of simply supported steel-concrete composite bridge are found.Therefore,it is very necessary to study the mechanical characteristics of the continuous deck of simply supported steel-concrete composite beam bridge and to put forward effective improvement measures for the continuous deck structure.On the research of the continuous deck of simple supported steel-concrete composite beam bridge,the main work of this paper is as follows:1.The situation for operation of expansion joints of Xisha Yellow River Bridge and Qilihe Yellow River Bridge in Lanzhou were observed at different temperatures.The observation found that,for the multi-simple-span beam bridge,to a certain extent,the application of continuous deck(greatly reduce the number of expansion joint)reduces the adverse effect on structural maintenance and ride comfort,which is due to the excessive installation of expansion joints in traditional simply supported beam bridges.In addition,it was found that,along the cross-bridge direction,the width of the expansion joint is different at the same temperature.2.Some theoretical calculation methods of continuous deck are introduced,which are known at present.It is found that,through an example analysis,there is a large relative error in the calculation for angle of rotation at main beam ends by different methods.However,the angle of rotation at main beam ends is the key to accurately calculate the stress of continuous deck structure.3.Based on an engineering example,1 / 2 finite element solid model(rigid-type continuous deck structure)is established.Through calculation and analysis,when the temperature of the whole bridge rises or decreases,different bearing arrangements result in large differences in concrete stress of the continuous deck section.The combination of moving load,secondary load,temperature of the whole bridge rises and negative temperature gradient is determined to be the most unfavorable load combination of continuous deck structure.Under the action of the most unfavorable load combination,there is a serious stress concentration phenomenon along the cross-bridge direction in the rigid-type continuous deck structure,and the tensile stress of the upper surface of the continuous deck structure exceeds the limit.4.Based on the analysis and calculation,some improvement measures of the rigid-type continuous deck structure are proposed.Firstly,the geometric construction of the continuous deck structure is improved.Then,on the basis of geometric structure improvement,special performance materials(GFRP and ECC)are applied to further improve.Research shows that,the geometric construction improvement scheme in this paper has a good improvement effect.On the basis of geometric structure improvement,ECC is applied to continuous deck,which can effectively prevent the cracking at continuous deck upper surface.5.In this paper,the finite element model of composite beams with different shear connections is established to analyze the influence of slip effect of steel-concrete interface on the stress of continuous deck.Because of the relative slip of the steel-concrete interface,the shear studs will deform and absorb a part of energy,which is beneficial to the continuous deck.However,the slip effect will increase the deflection of composite beam,the angle of rotation and displacement of steel beam end,which is disadvantageous to the continuous deck.The advantages and disadvantages factors of the above-mentioned play a role at the same time,and finally reach a balance.