Analysis Of Transverse Prestressing Effect And Reinforcement Design For Hollow Slab Bridge

Precast concrete hollow slab bridge has become one of the main bridge types for short to medium span in China, the United States and Japan, because of its fast construction speed and low cost advantages. With the increase of service time, the cracks in the joints of the hollow slab bridges have been widespread in China and leads to the decrease of the transverse connection ability, even become a single slab, which seriously threates the safety of the bridge and traffic system. To solve the problem of single slab, based on the principle of shear friction, the transverse prestress is putted in the mid depth of the beam to recover the shear force transfer capability of joints with crack and improve the transverse distribution of the hollow slab bridge, and the last, achieve the purpose of reinforcement. Based on numerical test, the main research contents of this paper are as follows:Firstly, the software ANSYS is used to establish a finite element model of the hollow slab bridge. The cracking surface of the joints are simulated by contact element. The relationship among the transverse prestressing force, the friction coefficient, and the vertical deflection of the slab is calculated and analyzed. Then, the transverse distribution of the hollow slab bridge with the different compression height of joints is given and the results are compared with the results of the hinge-connected slab method.Secondly, a finite element model of hollow slab with double cavities is established and used to analysis the stress distribution of the joints about the influence of bridge width, length, the number and force of prestressing tendons, and the vehicle load. The results showed that in the direction of the slab height, with the effect of the slab hollow and the dead load, the compression stress is mainly distributed in the top 20 cm of the joints; In the long direction of the bridge, the compression range does not change with the increase of the prestress. Under vehicle load, when the transverse prestressing is set up properly, the relative slip between the cracks will tend to zero. The whole hollow slab bridge will bear load together.Last, basis on the previous, a bridge consist of seven standard hollow slabs with a span of 13 m is used to reinforcement design. Detailed calculation and analysis process for bridge reinforcement design is given. First, analysis of the scope of the compressive stress caused by prestressing, and then calculate the position of the prestressed reinforcement by utilizing the scope of the compressive stress. In order to determine the required force of the prestress under the vehicle load, the maximum relative slip value of the key joints is being used as a control parameter. The software ANSYS is use for calculate the maximum relative slip value of the key joints, Increase the prestressing force and calculate again until the maximum relative slip value of the key joints under various loading conditions meet the requirements and then the minimum force is the prestress design value. Finally, the effectiveness and feasibility of the bridge reinforcement design method based on the principle of the shear friction is proved by calculating the transverse distribution and single point loading of hollow slab bridge. Result shows that the transverse distribution of the reinforced concrete slab bridge is in good agreement with the results of the hinge-connected slab method.