| Recently, the structural damage detection is becoming a hot research subject in the present engineering field. There have been mature methods for damage diagnosis and determination simple structures, however not like this for the large complex structures. In this paper, based on ultimate bearing capacity and reinforcement problem of Zhong-hua bridge, creating damaged finite element model of large steel reinforced concrete structural bridge to accurately analyze the damaged bridge via two steps. First step:with comprehensive bridge detection technology so called direct damage diagnosis method finding out probable damage locations and degree, and then analyzing specific structures further more to prepare for the second step; two step:using model updating based on optimization design and sensitivity analysis technology to optimize the geometric and physical parameters in order to create comprehensive and accurate large finite element bridge model. The main contents include:(1) Field detection for damaged Zhong-hua bridge. Zhong-hua bridge is pre-stressed reinforced concrete structural bridge. Estimating created bridge service property and bearing capacity, researching on mechanics behaviors of structures etc. are on the premise of bridge detection. Firstly, with non-destructive testing technology detecting concrete strength and defect of T main beams to prepare for the comparison of detected model and finite element model; Secondly, with detecting instrument detecting structural components such as main beams, bridge piers, bearers etc., evaluating damaged degree of structural components based on comparison of detected results, even getting main damaged style; Last, via static test and dynamic test getting the deflection of (1/4,1/2,3/4) span and stress, strain to prepare for creating damaged model accurately.(2) Creating primary damaged model of bridge. Defining damaged styles which are directly related with bridge bearing capacity, and using 3-d elastic-plastic entity finite element method considering on concrete crack to create primary damage model of bridge. Further more, researching on the concrete crack nature and simulating damaged ribbon strips and pre-stressed anchor end precisely, and then, choosing material constitutive relation which are not predefined from ANSYS but from strength test value of concrete core-sample.(3) Model updating based on optimization theory. In this paper, updating the primary finite element modal of bridge with first order optimization method based on optimization theory and sensitivity analysis. Firstly, according to sensitivity analysis, choosing the most sensitive structural design parameters such as volume of killed ribbon strips element, finite element meshing size, concrete modulus of elasticity, structures size etc., which is beneficial to improve computational efficiency. Outstanding optimization theory model updating can use optimization module of ANSYS to deal with complicated calculation of multi-element complex structure.(4) Solving the updated finite element model of bridge and researching on crack, yield and destroy of T main beam including stress, strain and deflection on the pre-cracking, post-cracking and ultimate condition. After getting the ultimate bearing capacity of bridge, further more analyzing remaining bearing capacity of bridge and evaluating the safety of bridge.(5) Researching on damaged bridge reinforcement. Based on bearing capacity evaluation of Zhong-hua bridge, reinforcing the seriously damaged ribbon strips. There are three main measures, including pouring concrete, steel welding, steel plate welding reinforcement method. And then, creating reinforced finite element model, and calculating reflection of main beam and relevant stress, strain, comparing with non-reinforced damaged model to prove that reinforcement method is very efficient. |
