Construction Monitoring And Load Test Of Steel Truss Double Cable Plane Suspension Bridge

Liujiaxia Yellow River Bridge is designed to cross the branch ditch of Liujiaxia reservoir.The west side is the direction of Linxia bridge,and the east side is the direction of Lanzhou Dachuan.The bridge is a double hinged simply supported steel truss girder and double cable plane suspension bridge with a single span of 536m.The west side cable span is 148m,and the east side cable span is 113m.Based on the design and construction characteristics of Liujiaxia Yellow River Bridge,this paper studies the construction monitoring of Liujiaxia Yellow River Bridge.The main tasks are as follows:(1)The construction phase of the Liujiaxia Yellow River Bridge was analyzed using the professional nonlinear analysis program for suspension bridges.Midas civil 2019 and SAP2000 were used to establish the corresponding finite element model for comparative analysis.Considering the actual characteristics of construction site materials,construction error of components,construction temperature and other factors,the finite element model was modified to simulate the actual stress state of bridge construction stage to the greatest extent,which provided a theoretical basis for bridge construction.(2)According to the design and construction characteristics of Liujiaxia Yellow River Bridge,a construction monitoring scheme of Liujiaxia Yellow River Bridge was formulated.Monitored the whole construction process of the main tower of Liujiaxia Yellow River Bridge,and studied the influence of temperature changes on the construction process of the main tower,including the influence on the elevation of the main tower,the deviation of the main tower and the pre-deviation of the main cable saddle.The strain and displacement measuring points were arranged on the key section of the main tower,and the displacement and elevation of the main tower were monitored during the construction process.The actual measurement results were compared and analyzed with the design value to verify the quality of the construction and ensure the safety of the construction process.(3)This paper introduces the analysis theory of the main cable of suspension bridge.The unstressed length of the main cable and the pre-deviation of the saddle were calculated through the professional nonlinear analysis program of the suspension bridge.The influences of construction process,temperature,working procedure,elastic elongation of main cable and span on the force of main cable and the cutting length of sling were considered.During the construction,the cable force of the main cable and the coordinates of the key sections were monitored,and compared with the design value to guide the construction.(4)Based on the analysis results of the SAP2000 finite element model,a hoisting scheme for the stiffening girder of Liujiaxia Yellow River Bridge was formulated,the influence of the hoisting scheme on the structure was analyzed.The displacement and stress of the main cable,bridge tower and other key positions were monitored during the construction process to verify the applicability of the hoisting scheme.At the same time,Midas Civi2019 was used to establish a finite element model for the closure section of the stiffening girder.The influence of temperature change on the displacement and stress of the closure section was analyzed,and the hoisting scheme of the stiffening girder was optimized.(5)The load test scheme of Liujiaxia Yellow River Bridge after completion was formulated and the load test was carried out.The displacement and strain of the structure under the most unfavorable condition were tested.The first five modes and impact coefficients of the bridge were tested by dynamic load test,and the measured results were compared with the design values to verify the quality of bridge design and construction.