Study On Key Technology Of Assessment And Reinforcement Of In-service Stone Arch Bridge

As an old bridge type, stone arch bridge is widely used in China. According to statistics, the number of existing stone arch bridges have reached four million seats. Because of natural environment, overloading, design, construction, natural disasters and other factors, stone arch bridges have been seriously damaged, and even collapsed. So it is of great practical significance to carry out systematic research work on assessment, maintenance, reinforcement, design and other key technical system and method for in-service stone arch bridge. Main works are as follows:1. The corresponding damage model was presented based on study of damage mechanism of stone masonry, Two-parameter Weibull parameters were used to describe damage variable and by introducing the peak secant modulus a general constitutive equation was derived and established. Then the stress-strain relationship during the whole compression process could be expressed by a single expression. It was of simple form and less parameters. It was continuous derivable, easy to practice, and better meet the actual stress-strain relationship.2. The spatial entity finite element model of long-span stone arch bridge was built based on Ansys. The geometric nonlinearity, double nonlinear and ultimate bearing capacity of injured stone arch bridge were studied, using established stress-strain relationship. The variation of ultimate bearing capacity and failure modes were comprehensively analyzed for stone arch bridge in a variety of load conditions, different design parameters and initial geometric imperfections and damage. It provided theoretical guidance for the assessment and reinforcement of in-service stone arch bridge.3. The analysis on ground motion response of stone arch bridge was done according to typical seismic waves in different site and specification-based artificial waves. The effects of different arch axis and rise-span ratio on seismic behavior of stone arch bridge were discussed. Based on engineering practice, the analysis and comparison of seismic reinforcement methods of stone arch bridge were carried out and the preferred method of seismic reinforcement was put forward for increasing carrying capacity for stone arch bridge.4. In view of huge damage identification training samples and inefficient problem, the concept of sub-structure identification of stone arch bridge was proposed. With the combination of detecting means and mathematical methods, by introducing natural frequency and static displacement as combined parameter, sub-structure damage identification method based on probabilistic neural network PNN was established. It provided a reliable mathematical method for monitoring and evaluation of stone arch bridge.5.Based on reliability theory, by introducing the theory of time-varying reliability, aiming at common reinforcement methods of stone arch bridge, the concept of resistance varying of composite section of stone arch bridge was proposed, the changes of load effect and structural resistance with time were analyzed and life prediction method after reinforcement was built. Bridge maintenance decisions were analyzed and the optimal maintenance strategy judging method based on Markov process was given for reinforced stone arch bridge. Ihe optimal maintenance strategy was arranged according to different states. It saved cost and provided scientific basis for the reinforcement and maintenance.