Research On Integral Mechanical Behavior Of Hinged Voided Slab Bridge

Hinged voided slab bridge is a kind of bridge that has been widely used in Chinese small to mid-span bridge. During practical application, the diseases of hinged joint is the most common disease that can be found in the superstructure, it can lead to the failure of transverse connection till the sigle beam bearing phenomenon appears which could pose big threat to the service life and transportation safety of bridge. With the aim of better understanding for the integral mechanical behavior of hinged voided slab bridge, and providing basis of improvment for new-built hinged voided slab bridge, the experiment and finite element analysis on hinged joint were proceeded, main work and main conclusions of this paper are listed as follows:(1) The development history of hinged slab bridge was concluded, the similarities and differences of hinged voided slab bridge were gained by comparison of standard drawing by the code of 1989 and 2004. The structural parameters of voided slab and hinged joint in new-built hinged voided slab bridge were counted, it can provide the basic reference and bsasis for subsequent research.(2) The experimental model were made according to the 8m hinged voided slab bridge in the standard drawing by new code, the experiment on mechanical behavior of hinged voided slab bridge under vehicle load was proceeded. It shows that:when the load reached 70kN, the bottom part of mortar in the mid-span section of hinged joint appeared cracks, the transmission of force declined due to the cracks of hinged joint, the transverse distribution of deflection of voided slab was uneven; When the load reached 80kN, bottom part of mid-span section of three voided slabs appeared transverse cracks; When the load reached 300kN, the bottom part of 1/4 section to 3/4 section of voided slab appeared many transverse cracks, the bottom of motar in hinged joint appeared longitudinal crack.(3) ABAQUS software was uesd to establish solid model of hinged voided slab bridge, the deflection of voided slab, the transverse opening of hinged joint, longtitudinal strain of voided slab, longitudinal strain of main steel bar,strain of constructional reinforcement at junction surface and cracks results from model agreed well with experimental results, the nonlinear finite element model could be used to do mechanical analysis and parameter analysis for integral mechanical behavior. There are three directions at the interface, which are normal direction, vertical direction and longitudinal direction, the vertical relative slippage of the interface should be the index of bonding failure of the interface. As the cracking appears firstly than the voided slab and hinged joint, the weakest part of hinged voided slab bridge is the interface between voided slab and hinged joint.(4) The influence on integral mechanical behavior by gantry steel bar, strength of concrete and rigidity of bonding-slip were analyzed. The results show that the gantry steel bar at the interface between voided slab and hinged joint in the drawing by new code could not improve the cracking load, but the load that vertical straight crack appears could be postponed, and the development of cracks at the interface could also be limited. The increasing of the diameter of gantry steel bar could not affect the cracking load, the load that straight crack appears and the distribution of cracks at interface. The increasing of strength of concrete could limitedly improve the mechanical behavior of interface. The increasing of rigidity of bonding-slip could not improve the cracking load clearly, but it could improve the load that straight crack appears, and the distribution of vertical cracks at interface and the longitudinal crack at the bottom of interface could be limited.