Study On The Feasibility Of "Optimization" Steel Truss-Concrete Composite Continuous Rigid Frame Bridge

Supported by the Ministry of transport construction technology projects(2013319 814 040)"the basic theory research of constructing the extra-large-span steel truss-concrete composite continuous rigid frame bridge" leaded by the tutor,aiming at the group’s conception of " optimization steel truss concrete composite continuous rigid frame bridge",the preliminary research on the new bridge type is carried out about the overall layout,conceptual design,construction method,key structure and static and dynamic characteristics analysis.The main research contents are as follows:①Based on the existing research results of the research group,the structural design scheme of the "optimization" steel-concrete-concrete composite continuous rigid frame bridge is improved,and assembled construction process that is compatible with structural features is proposed:the pier and the 0#concrete truss construction 一 the same period precasting steel truss section and concrete bridge section—Cantilever mounting steel truss segments to close together to form an integral steel truss beam 一Installing the prefabricated section of the bridge deck and forming a steel truss-concrete composite continuous rigid frame bridge by cast-in-place concrete—completing the construction of ancillary facilities such as bridge deck pavements and railings.Conducts economic and technical comparison with conventional prestressed concrete continuous rigid frame bridge.②For the structural characteristics of each segment of the"optimization" steel truss-concrete composite continuous rigid frame bridge,the theoretical analysis model for forming the main beam is established,and the method for dimensioning the main section is proposed.The truss beam and pier with variable stiffness are derived.The mechanical model of the main truss girder of the steel truss-concrete composite continuous rigid frame bridge considering the influence of the stiffness of the truss girder and the pier stiffness is derived.The bending moment equation of the main girders is proposed when calculating the thrust stiffness of the pier and not considering the thrust stiffness.The formula for calculating the proportional coefficient of the positive moment of the truss beam is derived.Targeting the reasonable force of the mid-span and the pier control section,the reasonable proportion of the mid-span is 0.56~0.66.The structural design of the optimal steel-concrete composite continuous rigid frame bridge is discussed.③Taking the continuous rigid frame bridge with a main span of 200 meters as an engineering example,the structural design of a 200m span "optimization" steel truss-concrete composite continuous rigid frame bridge was carried out,and the stress of the whole process of bridge construction was analyzed.The bridge stability and dynamic characteristics analysis of the bridge during construction and use are carried out,and compared with the same span prestressed concrete continuous rigid frame bridge,verifying the feasibility of the bridge type and the rationality of the force.④For the complexity of the stress state of the positive and negative bending moment transition sections of the "optimization" steel truss-concrete composite continuous rigid frame bridge,partially refined solid-shell element finite element model of the combination of steel truss and bridge deck with overlapping upper and lower chords is established.The finite element model of the solid-shell element is used to analyze the stress distribution characteristics under the combination of self-weight and unfavorable vehicle load.The influence of various node shape structure parameters on the local stress is analyzed and compared,and the improved joint structure is proposed.It effectively alleviates the stress concentration at the end of the web at the node.