A Study Of Some Mechnical Problems On The Road-Bridge Damage And Failure

Taking the advantage of high strength, good durability, long service life and being suitable for various of vehicles to pass, cement concrete road surface was widely used. Meanwhile, problems emerged, such as surface breaking-away, contact of surface layers, management of surface gaps and so on. The service properties and the working-life would be seriously influenced if these problems were not well settled. The first part of this study is to investigate some of those problems deeply and a series of important conclusions are obtained which have the benefit for actual engineering.Furthermore, ship-bridge-impact accidents took place frequently, causing serious pollution and grievous loss of people and possessions. The damage would be much worse while the abutment collapses due to a ship impact. The other part of this study is to investigate the ship-bridge-impact problem and provide some useful data for the designers, through simulating the impact of a real ship to the main abutment and the protecting device.The main contents of this study includes the following,1. Obtain a new slurry material for surface breaking-away grouting, made of cement, calcareousness, plaster, early strength admixture, high efficiency water reducing agent and swelling agent etc.. It possesses many outstanding properties, such as good workability and fluidity, high early strength and low elastic modulus after coagulation, minimum inflation, etc., which almost satisfies all the requirement to be kind of surface breaking-away grouting material. It was revealed in the experiment that this new material could effectively prolong the service life of the road surface.2. Investigate the deflection of the breaking-away and grouted road surface under impact load with LS-DYNA3D, a powerful dynamics nonlinear FEA program. Results indicated that the elastic modulus of the grouting material had a great effect on the breaking-away road surface, and it should be similar to the modulus of the original stabilized gravel layer to avoid an irregularly distributed stress field or a higher stress point, and this would take place even if the grouting modulus is lower. A universal basic equation was established for the deformation of the cement concrete road surface on an elastic foundation. The analytic solution of the deflection of the road surface was obtained while the differential settlement occurred on the foundation.3. Simulated the cement concrete road surface with the ANSYS program, with the contact of the inner layers taken in account. The following results were available. The coefficient of friction resistance between layers greatly influenced the mechanical response of the surface layer and the foundation layer. The enhanced adhesive effect between layers would be good for the transfer and diffusion of the loads. The coefficient of friction resistance between layers also greatly influenced the mechanical response of the surface layer during the early shrinking period. If the layers of the road were continuous, a great amount of micro-cracks would appear at the bottom of the foundation layer before the road was put into traffic. That would greatly decrease the service performance of the road surface, like inducing fracture at low stress level. The fracture mechanics properties of the cement concrete road surface were studied, through combining the FEA results and the linear elastic fracture mechanics analysis. Results indicated that the main reason of the appearance of the early cracks on the road surface was due to the restriction of the foundation layer against the shrinking of the surface layer.4. Employ the FEA method to study the dynamic respons of HX type sandwich copolymer modified asphalt concrete road seam under various vehicle loads, the mechanical properties of the asphalt road surface seam, the deflection transfer capability and the maximum deformation of the seam, etc.. The following results were available. HX type sandwich copolymer modified asphalt concrete had a wide elastic load-supporting range, which means it could satisfy the requirement of the road seam design. Calculation also indicated that emergent braking of vehicles could easily cause permanent damage of the road surface, and overloaded vehicles often result in greater vertical deflection and permanent tracks. Thus, those conditions should be avoided or restricted. Furthermore, the conception of'material modulus'and'deflection capability'were brought forward. The seam could be well sealed through proper design of the material properties, and no damage would occur on the adhesive surfaces or in the sealant itself. And a new road surface seam-sealing material and the corresponding construction tools were invented, with which the service life of the road could be 3 times increased.5. Simulate impact of a 5000DWT bulk carrier against the abutment from different angles at 4m/s speed with LS-DYNA3D. The results of impact with and without abutment protection devices were compared, which showed that the protection devices effectively weakened the direct damage against the abutment and decreased the peak value of the impact force. The maximum impact force and deformation of the abutment could be restricted through proper design of protective structures and the stiffness. The protection structures could prolong the interactional time so that the ship had enough time to turn around and the impact part of the whole kinetic energy could be as low as possible. The deformation of the protection devices played the leading role in absorbing the impact energy. Thus the damage of the bulk carrier could be reduced to the lowest level.