The Spatial Mechanics Behavior Analysis Of Single Pylon Earth-anchored PC Cable-stayed Bridge Based On Shear-flexible Grillage Method

For the single pylon earth-anchored PC cable-stayed bridge,there is a certain lag in the study of its spatial mechanical behavior and the problem of eccentric load effect in simplified analysis is also to be studied.In this paper,the spatial mechanical behavior was studied based on the shear-flexible grillage method by a real engineering under construction:1.Based on the principle of equivalent flexible box girder with shear flexible grillage theory,the key issues of the modeling method of grillage method were summarized from three aspects: the division of grillage,the calculation of cross-section characteristics of grillage,and the expression of internal force and stress of grillage.The values of cell width,crossbeam width and crossbeam shear area in the grillage method were analyzed.2.It shows that the calculation results of single beam and grillage model are very close and accurate,and the single beam model is recommended in the analysis of construction stage of the single pylon earth-anchored PC cable-stayed bridge according to the analysis of structural displacement,cable force,and dynamic performance in completion by the construction phase calculation of background engineering which calculated by single beam and grillage model.3.It shows that the calculation results of grillage model are safe and reliable,and the centering dividing grillage model is recommended in the analysis of operation stage according to the coMParison of structural displacement,stress,and cable force under live load by the operation phase calculation of background engineering which calculated by grillage model and plate element model.4.The parametric analysis was carried out on the eccentric load effect of background engineering.It shows that the eccentric load effect of deflection is influenced by the stiffness of the girder and the cable,the eccentric load effect of the stress is mainly influenced by the stiffness of the cable,and the eccentric load effect of cable force is mainly affected by the stiffness of the girder.The larger the vertical stiffness of the structure is,the greater the coefficient of eccentric load.The change of the stiffness of the crossbeam has a negligible effect on the eccentric load coefficient.5.The analysis of different position of longitudinal bridge was carried out on the eccentric load effect of background engineering.The results of the study show that it is not safe to take 1.15 and the actual eccentric load coefficient may reach 1.65.For the single pylon earth-anchored PC cable-stayed bridge,it is not safe to take value according to the empirical coefficient method,the grillage model can be established to consider the eccentric load effect.6.The structural system analysis of the eccentric loading effect of background engineering was carried out and the calculation results show that,for the single pylon earth-anchored PC cable-stayed bridge,the lateral stability of the fully floating system is generally the best,followed by the support system and the worst for the rigid frame system.And when it’s adjusting cable force,more attention should be paid to the non-uniformity of the lateral cable force,which causes uneven changes in the cable force of the main span near the abutment.For the rigid frame system,it is necessary to pay attention to the main span near the side of the tower.