| In recent years,China’s infrastructure construction has been developed rapidly,and cablestayed bridges play a very important role in transportation due to their excellent spanning ability and good force performance.In the design calculation of cable-stayed bridges,the longitudinal drift of the main girders also has a great influence on the force performance of cable-stayed bridges,in addition to the structural system,side to middle span ratio,main girder tower stiffness,and auxiliary pier location and quantity.This thesis takes Shaozhou Bridge,Shishou Yangtze River Highway Bridge and Chishi Special Bridge as engineering background,establishes finite element calculation model and studies the influence law of longitudinal drift on the overall mechanical properties of different types of cable-stayed bridges,the main research contents of this thesis are as follows.(1)The development and research status of cable-stayed bridges at home and abroad are introduced,and the relevant calculation theories of cable-stayed bridges,such as static calculation theory,nonlinear calculation theory,concrete shrinkage creep theory and finite element calculation theory,are summarized,laying the theoretical foundation for the subsequent research on the mechanical properties of cable-stayed bridges.(2)Based on the finite element theory,the full bridge model was established by using the finite element software BDCMS with the Shaozhou Bridge as the engineering background,and the longitudinal drift of the main girders of asymmetric single-tower hybrid girder cable-stayed bridges with or without support friction was analyzed under the conditions of system conversion,paved deck system and main span arrangement of vehicle load.The calculation results show that for the single-tower cable-stayed bridge,the longitudinal drift of the main beam is greatly reduced after considering the support friction,and the longitudinal drift has a strong correlation with the tower deflection,and the influence on the other mechanical properties is not so prominent compared with the tower deflection.(3)The longitudinal drift performance of the asymmetric twin-tower hybrid girder cablestayed bridge was investigated by using the finite element software BDCMS to build a fullbridge model of the Shishou Yangtze River Highway Bridge.The calculation results show that for the twin-tower cable-stayed bridge,after the longitudinal drift of the main girder,the main tower may still have a large unbalanced horizontal force,and the main tower of the twin-tower cable-stayed bridge can set the pre-deflection by the cable force,while the single-tower cablestayed bridge needs horizontal restraint to set the pre-deflection by the cable force.For twintower cable-stayed bridges,the influence law of longitudinal drift on structural mechanical properties is somewhat different from that of single-tower cable-stayed bridges.(4)To address the problem that the main towers of prestressed hybrid girder multi-tower cable-stayed bridges will have a large deflection toward the mid-span due to the effect of shrinkage creep after the bridge is completed.The method of adjusting the tower deflection by using the longitudinal drift of the main beam is proposed by the conclusion that the correlation between the longitudinal drift of the main beam and the deflection of the top of the main tower is high,and the influence on the elevation and cable force is relatively small.The feasibility of this method was analyzed and studied by taking Chishi Special Bridge as an example.The results show that it is feasible to use the longitudinal drift to adjust the tower deflection of the main tower. |
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