| The main span of the cable-stayed composite bridge adopts steel girders,while the side spans adopt concrete girders.The steel beam and the concrete beam are connected as a whole through a steel-concrete joint section.It has the characteristics of large spanning ability and good mechanical performance,and is widely used in bridge engineering at home and abroad.The Weier Bridge is a 162 m cable-stayed bridge.It combines pylon-pillar-girder consolidation,mixed girders,and mixed towers with special shape.The structural characteristics of V-piers,spacial curve bridge towers,few-back cable system,ultra-wide bridge decks,and large-angle oblique crossing are very different from the mechanical characteristics of traditional bridge structures.It is necessary to evaluate the structural system performance of the Weier bridge and carry out a comprehensive study on the force safety,the rationality of the structure to ensure that the structure is safe and reasonable.This article takes Zhangjiakou Weier Bridge as the engineering background for studying construction control and mechanical performance of the composite section.The principal research activities are:First,the main points of the construction monitoring of Weier Bridge are described.For stay cables,it discusses the cable force control method of external force and unstressed cable length,and finally obtains a good cable force control result.The angle correction theory of cable tube is discussed,and the parabola can be used to obtain a sufficiently accurate cable pipe angle correction result under the conditions of large stress and short cable.The string theory of frequency method for measuring cable force and the influence of bending stiffness,sag and boundary conditions on this method are discussed.The calculation accuracy of low-order antisymmetric vibration frequency is better.The calculation method of the pre-camber in the forward and transverse directions of the wide beam bridge is given.For the skew abutment,the deformation of the beam has obvious asymmetry.This should be considered when setting the deflection.The main points of the linear control of the space curved tower are given.The stress of the tower is affected by the bending moments in the transverse plane and along the bridge direction at the same time,and the deformation is obviously different from that of the straight tower.Secondly,solid modeling calculations are carried out on the force-transmitting members in the transition section of the hybrid beam: PBL and welding nails.On the basis of the reliability of the finite element model confirmed by the experiments,a multi-layer shear key model was established,and the changes in the shear resistance of the members were analyzed with the change in the number of arrangements in the load direction.The article analyzes and narrates the stress distribution,contact surface state,bearing capacity,stiffness and load redistribution process.The calculation results show that the load slip curves of PBL and welding nails are obviously different.In addition,there is an obvious load redistribution process.Too many shear key arrangements will reduce the overall shear performance,and in the early process of the load,the shear key near the load end may yield prematurely.Finally,using the calculated welding studs and PBL shear key shear resistance results,a local model of the transition section of the bridge was established,the most unfavourable load condition was analyzed,and the structure of the bearing plate was optimized.By simplifying the stress state during the working period of the joint section,the component load ratio under the proximal axial force and the distal axial force and the change with the thickness of the bearing plate are analyzed.The results show that the thickness of the bearing plate needs to be ensured to provide sufficient rigidity to give full play to the connection effect of the prestress on the beam and to make the load distribution more uniform.At the same time,calculations show that the performance will be effectively improved when a rib is added near the prestress opening of the bearing plate. |
