Experimental And Theoretical Study On Prefabricated Steel-concrete Composite Open-web Sandwich Bridg

The bridge is the throat of transportation and plays a very important role in the social and economic development.However,the tightening of resource and environmental constraints,the increasing density and load carrying capacity of highway traffic,and the increasing labor costs caused by the aging of the social population have led to the development of bridge structures in the direction of enriching bridge types,lightweight structures,resource conservation,and industrialization of construction.Therefore,this study introduces a new type of bridge structure—the fabricated steel-concrete composite open-web sandwich plate bridge(COSPB),which is composed of a concrete slab,steel Vierendeel beams(with top chords,bottom chords and shear keys),and studs(used for connecting steel Vierendeel beams and concrete slab).Under the same conditions,this kind of bridge structure has higher cross-sectional efficiency and construction convenience than traditional composite beam bridges,and has higher use value and economic value.However,the research and application of this kind of bridge structure at home and abroad are still in the initial stage,and the theoretical system is not yet perfect.In this paper,the ultimate flexural capacity,stiffness,lateral load distribution characteristics and vehicle dynamic response of COSPB are studied by means of full-scale specimen test,theoretical analysis and numerical simulation.The specific research contents are as follows:(1)A full-scale COSPB test specimen was designed and manufactured,and a full-scale static load test was carried out,the strain,deflection distribution and development law of the specimen were measured during the loading process.At the same time,the crack development,failure mode,and the local buckling of stiffened plate were observed during the loading.Finally,based on experimental study,the calculation method of ultimate flexural capacity of composite open web beams is put forward.(2)Taking the full-scale COSPB test specimen as the object,the finite element analysis model is established by shell-solid element,and the entire loading process of the test specimen is simulated by nonlinear numerical method.The results of the finite element model analysis are compared with the experimental results in terms of overall deformation,failure mode,load-deflection curves,and stress distribution of components,to verify the effectiveness of the nonlinear finite element model,so as to clarify the element types and constraints for subsequent analysis.Further,by changing the parameters such as the thickness of the concrete bridge deck,the thickness of the lower flange steel plate of the lower rib,the strength of concrete,and the strength of the section steel,the ultimate flexural capacity and stiffness performance of the COSPB are analyzed.(3)A modal parameter method for calculating the lateral distribution coefficient of load is proposed,and the principle of calculating the lateral distribution coefficient of bridge load by the modal parameter method is deduced theoretically.For two kinds of COSPBs with a width-span ratio of 0.4 and 0.6,the lateral distribution influence line and lateral distribution coefficient are calculated by the eccentric pressure method,the modal parameter method and the finite element static method respectively,and the calculation results of the three methods are compared and analyzed to verify the accuracy and applicability of the modal parameter method.Furthermore,the influence of girder spacing,grid size of vierendeel beam,and concrete deck thickness on the lateral distribution characteristics of COSPB is analyzed.(4)Through static analysis of composite vierendeel beam,the mechanical characteristics of concrete slab,upper rib,shear key and lower rib are studied,and the distribution of axial force,shear force and bending moment of each component is understood.Based on the mechanical characteristics of composite vierendeel beams,the concepts of converted section stiffness and equivalent bending stiffness of composite vierendeel beams are introduced,and the theoretical calculation formulas for converted deflection and equivalent deflection of composite vierendeel beams are deduced,and the correctness of the theoretical formulas is verified by static load tests.Parametric analysis of the deflection of composite vierendeel beams is carried out by changing the parameters such as the ratio of span to height,the ratio of width to span,the thickness of concrete slab,the ratio of vierendeel,the mesh size and the width of shear key,and the width of stiffened plate.On the one hand,the influence of different geometric parameters on the deflection of simply supported composite vierendeel beams can be explored,and on the other hand,the correctness and applicability of the theoretical formula can be further verified.Finally,the deflection correction factor is introduced based on the converted deflection ξ to consider the reduction of the cross-section stiffness of composite vierendeel beam caused by the vierendeel.Based on the results of parameter analysis,a deflection correction factor which is convenient for engineering application is put forward,and the practical deflection calculation method is verified by the experimental results.(5)Based on the simplified vehicle model,moving force model and moving mass model,the vibration equations of a COSPB under moving loads are derived in two cases,and the solution process of the system vibration equations is introduced in detail.On the basis of theoretical research,aiming at the full-scale specimen of a COSPB in the second chapter,a real vehicle test was conducted by passing a car on the bridge deck.The dynamic response parameters of the new bridge structure,such as vertical acceleration,dynamic deflection,and dynamic strain,were studied using different vehicle speeds,different vehicle weights,and different driving lanes as parameters.The Newmark-β Method is used to solve the vibration equation of an open web beam under the action of a moving mass,and the solving program is compiled based on MATLAB.By comparing and analyzing the results with the experimental results,the correctness of the theoretical solution program is verified.The effects of vehicle load,vehicle speed,and bridge deck irregularities on the vibration response of the bridge were further studied.(6)Relying on the practical engineering,the comparative analysis of composite box girder bridges and COSPB is conducted.Through finite element method,analytical models of the two types of bridge structures are established.Based on quantitative description and qualitative description,the mechanical properties of the two types of bridge structures under frequent load combination,basic load combination,and vehicle loads are studied,and the economic and technical properties of the two bridge structures are analyzed.