Research And Application Of Lateral Load Distribution Factor Calculating Method For Small And Medium-span Bridges

The small and medium span bridge is a widely used type in road network construction because of its lower building height, convenient precast and economic material.This bridge type usually adopt package type construction. The calculation of its transverse load distribution is an important content of highway bridge design as a practical approximate method of spatial inner forces calculation,it is related to the structural safety and reliability.The theoretical derivation of approximate method used in engineering design have some physical and mathematical hypothesis,it is different from the actual situation,therefore its results have some errors with the actual values.The assembly prestressed cored slab bridge constructed in the 1970s and 1980s usually have the problem of low carrying capacity and the hinge joints have defects.With the rapid development of modern economy,the problem of heavy and overload truck is increasing severe.So in the recent years,the exiting diseases of hinge joints such as the crushing ,abscission and leakage cause the failure of bridge transverse joint,the exiting of the phenomenon of single beam bearing poses great harm to the driving safety of the road.Therefore,the research on the discrimination of single beam bearing have great practical importance.Before the research of calculation of the transverse distribution factor,we firstly introcuced the practical spatial analysis theory,and have a briefly describtion of the calculation theory.With the development of the technology,the finite element analysis theory and computer are wildly used in bridge design.So it is essential to calculate the transverce distribution factor from the finite element model of the bridge structure.In this paper we conduct the theoretical analysis and building of the finite element model aiming at the standard hinge supported slab bridge and simply supported T bridge..According to this,we calculate the theoretical solution and the numerical solution.By contrast with the results,we get some conclution.At last,we analyze the reason of the disease of single beam bearing.With the help of the MIDAS/Civil combined with the concept of the transverce distribution factor,we studied the appearance as well as the damage degree of the single beam bearing.We finally put forward the prevention measures.This thesis is composed of 5 chapters,the third and forth chapter are the core part.The research content are as follows:The first chapter:We analyzed the research status and summarized the research purpose and significance.The second chapter:The calculating method of transverse distribution factors all have its basic assumption and scope of application according to its theoretical analysis.In order to make the calculation of load transverse distribution better adapted to the specified joint structure,we need to draft the correspongding calculation method according to the different simplified calculation model of the bridge.For the lever analogy,it is always used for the calculation of the distribution factor at the fulcrum section.The eccentric compression method, hinge-jointed plate method, rigid-jointed plate method and rigid-jointed beam method are usually used for the calculation at the mid span section.We can choose corresponding method according to the main girder section type,the transverse connection type, the width-span ratio and so on.The finite element method is the most widely used method in the numerical calculation,and it is also the most common method used in bridge structural spatial analysis.It can be divided into several methods according to discrete form such as space beam element, shell finite element method, three dimensional solid element method and beam grid method.Based on the ANSYS design language APDL,we can simulate the model of the structure, we can also realize the verification of the accuracy of load transverse distribution calculation and the simulation of the bridge structure.The third chapter:We got several conclution as follows according to comparative analysis between the results of simplified calculation and the spatial theory.Firstly,we found that the results of eccentric compression method, hinge-jointed plate method, rigid-jointed plate method are consistent with the numerical simulation.Therefore,it is reasonable to use these methods to conduct bridge design.We also found that it is feasible to use finite element model to analysize the plate and T-beam bridge,it can also used to calculate the transverse distribution factor when the type of the plate or beam is various or it is not contained in the available calculating sheet.The simplified and practical calculating method is an usful tool.The tranverse distribution is a practical calculating method,it solve the spatial problem to simplify the spatial issue into the plane ones.So it is limited to use the finite element method to conduct the design,instead the it is popular to use the calculation of the transverse distribution factor.In this thesis,we also verify the accuracy of the simplified method. The forth chapter:The phenomenon is incidental at the place of carriageway plate of some highway simply supported medium-small span bridge.It mainly shows as the damage of the hinge and bridge deck pavement,it greatly influence the safe service.The research showed that the simply supported small span bridge is considered as the hinged slab in the design,but the hinge always damaged before the main girders because of the weakness of the hinge,so it is not feasible to use the designed factor to conduct the calculation,it greatly affect the normal use and cause the damage of the main girder especially the carriageway plate.So it is rational to structural optimization design of the hinge in order to strength the ability of load transverce distribution especially in the overload condition.We should increase the transverse rigidity of the bridge such as thickening the cement concrete overlay,strengthing the pavement mesh reinforcement,improving the quality of the hinge and so on to prevent the damage of the hinge and length the life of the bridge.The method of comparative analysis between the measured data and finite element model data is feasible to identify the location and degree of the hinge damage,it is usful to provide effective reference and method for structure damage identification maintenance and reinforcement.The fifth chapter:We firstly summarize the work of this paper,secondly,we put forward the future research content and direction.