Study On The Static And Dynamic Performance Of A New Type Of Composite Beam Bridge With Pipe Flange Under Multiple Working Conditions

In recent years,with the rapid development of economy and the needs of people's life,new bridge structures emerge as requires.The new type of composite beam with pipe flange is a new type of composite structure which replaces the top flange of I-steel plate with concrete filled steel tube in the traditional steel-concrete composite beam.At present,most of the domestic scholars study the mechanical properties of single beam,and there is a gap in the research of the mechanical properties of the complete bridge.The new type of pipe flange composite girder bridge of G109 line in Gansu Province is the largest span of pipe flange composite girder bridge in China at present.The study of the mechanical characteristics of this kind of bridge under various working conditions can provide a reference for the design of this kind of bridge in the future.Based on the urban new viaduct project of G109 line in Gansu Province,this paper analyzes the static and dynamic analysis of K9+895~K10+058 section of new composite beam bridge with pipe flange under various working conditions by using the finite element software ABAQUS.The main work is as follows:(1)According to the existing project data,a refined full bridge model is established,in which the shell element is used to simulate the steel structure.The solid element is used to simulate the concrete,and the spring element is used to simulate the support.The grid is divided into fine mesh,and the mechanical behavior of different components is fully considered to determine the coupling between different components.(2)It is found that the stress and deformation of the pipe flange composite beam in four lifting sequences meet the requirements of the code.In view of the different static loads applied to the continuous skew pipe flange composite beam bridge,the section-stress characteristics of the composite beam are analyzed.Through the comparative analysis of the two kinds of bridges with the same span,it is found that the stress characteristics of the two kinds of bridges are different.Because of the skew angle,the stress of the bearing part of the skew bridge is larger.Because the calculated span of the orthogonal bridge is larger,the stress of some main beams is larger than that of the skew bridge.(3)The method of "equivalent bending rigidity" is used to establish the traditional steel-concrete composite girder bridge with the same span.The cross-section characteristics of the two structures are compared and analyzed.The stress and deformation of the pipe flange composite girder bridge and the traditional steel-concrete composite girder bridge under the same load condition are analyzed.The comprehensive comparison shows that the pipe flange composite girder bridge issuperior to the traditional steel-concrete composite girder bridge in stress characteristics and economic effects Composite girder bridge.(4)The strength grade of concrete and the steel ratio of the upper flange are selected as parameters for parameter analysis.Under different load conditions,the influence of the two parameters on the vertical displacement of the composite beam bridge with pipe flange is studied.The calculation results show that the concrete has little effect on the vertical displacement of the structure,while the steel ratio of the upper flange has little effect on the vertical displacement.(5)Based on the refined finite element model,the natural frequencies and vibration modes of the structure are calculated.Time history analysis method is used to analyze the structural dynamic response of skew pipe flange composite girder bridge under longitudinal,transverse and bidirectional earthquakes.The results show that bidirectional seismic action has greater influence on the structure.At the same time,the influence of vertical seismic action on the structure is analyzed.It is found that the vertical seismic action has little influence on the longitudinal and transverse displacement of the structure,and has a great influence on the stress of the capping beam and the main beam,which cannot be ignored in design.(6)The results show that: under the action of frequent and rare earthquake,the main beam and pier remain elastic,and the displacement of the main beam and pier is small.Under the action of rare earthquake,the change trend of acceleration and displacement of bridge pier is the same as that of frequent earthquake,the amplitude changes,the displacement and stress of bridge pier and main beam are large,and the seismic design of structure meets the requirements.(7)The impact resistance of steel piers with double thin-walled box section is analyzed,and the dynamic response of piers under different impact object diameter,impact velocity and impact location is analyzed.Through the above analysis and research,it is clearly recognized that the static stress characteristics of the new type of pipe flange composite girder bridge,the seismic response of the whole bridge under the action of earthquake and the dynamic response of piers under the impact of rockfall,and the conclusions obtained provide reference for the design and promotion of the new type of pipe flange composite girder bridge.