| Modern suspension bridge is a kind of flexible suspension system composed of main cable and stiffening beam,which has the advantages of large span capacity and light shape.Therefore,we often choose suspension bridge in the construction of long-span bridges.In the process of bridge construction,it is necessary to monitor the stress and deformation of the structure,so that the bridge structure in the construction can reach the ideal state,and ensure the stability of the construction process and the alignment of the completed bridge meet the requirements of the specification.The existing steel truss suspension bridges are basically constructed in small sections with a length of about 10-15 m.If large sections with a length of 30 m are used for erection,it has the advantages of fast construction progress and good integrity.However,compared with the erection of small sections,the construction control of large sections is more difficult.In view of this,based on the Baiyang Yangtze River Highway Bridge construction project,this paper analyzes the key problems in the construction control of large section steel truss girder erection,and the main research work includes:(1)The theoretical basis of construction control for the integral erection of large section steel truss girder has been expounded.By referring to the literature and data,the structural form and stress characteristics of the steel truss suspension bridge have been summarized,the setting and calculation method of the pre deviation of the main cable saddle have been summarized,and the erection method and connection method of the large section steel truss girder have been summarized.(2)The finite element model of construction control for the integral erection of large section steel truss girder has been established.On the basis of the general layout of Baiyang Yangtze River Highway Bridge and the design of steel truss beam,the paper simulates the components of the bridge,including the main beam,suspender,main cable,bridge tower and cable saddle,describes the whole modeling process in detail,and finally establishes the finite element model of the steel truss suspension bridge with a main span of 1000 m through the finite element software Midas/Civil.The finite element model of Baiyang bridge consists of 4094 nodes and 5884 elements.(3)The deviation control of the main cable saddle for the integral erection of large section steel truss girder has been studied.Based on the analysis of the control mode of the main cable saddle deviation,the main cable saddle deviation in each construction stage is calculated according to the model.The deviation of main cable saddle gradually increases with the erection of steel truss beam and the pavement of bridge deck system,and its maximum value can reach 1521mm(Baiyang side)and 1482mm(Yidu side).Taking the maximum allowable deviation of 0.7 times of the main tower top as the control limit,the jacking amount and timing of the main cable saddle are determined,and the deviation between the measured value and the proposed value of the main cable saddle deviation in each jacking stage is compared and analyzed,which proves that the proposed jacking process is reasonable.(4)The linear control of the integral erection of large section steel truss girder has been studied.During the whole erection process of the large section steel truss,the linear and internal force state of the steel truss are monitored in real time,and the change of the main girder linear during the erection process is analyzed.Through the model analysis and calculation,the rigid connection time machine of the steel truss after the main girder section is closed is determined.The results show that the measured value is consistent with the calculated value,and the linear control effect of steel truss is ideal. |
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