Construction Mechanics Analysis And Monitoring Of Long-span And Wide-width Steel Truss Bridge

Steel truss bridge has the characteristics of strong bearing capacity,large span capacity,fast construction speed and good structural durability.It has been widely used in the construction of all kinds of bridges abroad and railway bridges in China.In recent years,in order to improve the quality and durability of highway bridges and reduce the cost of life cycle,steel truss bridges have been widely used in highway bridges in order to promote the construction of steel structure bridges in highway bridges.In this paper,the structure mechanics analysis,construction scheme comparison,construction mechanics analysis and construction monitoring of large-span and wide-width steel truss bridge are carried out based on the engineering background of the third contract section of Qinglan high-speed Taidong section.The main research contents are as follows:(1)The structural stress analysis of wide-width steel truss bridge(three lanes)is carried out in operation stage.The main truss deformation causes uneven stress of longitudinal beam,the axial force of side-longitudinal beam is the largest,and gradually decreases from side-longitudinal beam to middle-longitudinal beam.The external bending moment of steel transverse beam increases,which leads to the unbalanced force of the longitudinal beam of bridge deck system participating in the main truss.(2)In view of the construction methods commonly used in steel truss bridge,such as full-hall support assembly,push-up construction,towing erection and cantilever assembly,the construction schemes are compared and selected from the aspects of safety,cost,time limit and traffic influence on the bridge location,etc.To determine the use of support with cantilever assembly construction method.(3)In view of the construction method of support and cantilever assembly,the stability checking calculation of temporary support structure is carried out,and the technical measures to ensure the stability of support are put forward.The constructionmechanics analysis of the main truss cantilever is carried out,and the most unfavorable stress state of each construction condition is obtained,which provides the theoretical basis for the construction monitoring,and the construction mechanics analysis of the installation sequence of the bridge deck is carried out to determine the reasonable installation order of the bridge deck.(4)According to the construction mechanics analysis,the construction monitoring work of the steel truss beam bridge is completed,the middle supporting point is selected,three typical stress sections of the two spans of the two sides are selected,the stress monitoring at different installation stages is carried out on the upper chord rod,the lower chord rod and the abdominal rod respectively;and the left and the middle sections are arranged between each section of the main bow frame,The three linear monitoring points on the right shall be subjected to stress monitoring at different installation stages.According to the monitoring result,the problem of stress deviation is effectively solved by adopting the secondary jacking of the main frame,and the linear deviation problem is effectively solved by adjusting the assembling process.