Model Test On Damage Sensitivity Of Suspension Bridges For Health Diagnosis

With the development of design theories, construction techniques, and the application of high-strength materials, bridges grow longer and more flexible. Having merits of large spanning ability, light weight and aesthetical structure, suspension bridges are the first choice for ultra-long-span bridges.As bridges are operated constantly, various damages may occur and lead to the reduction of bearing capability and durability inevitably, and even affect the safety of operation. There have been several bridges collapsed or destroyed in the world;it makes people pay more attention to detect the work state of bridges. In order to ensure the safety and durability of long-span bridges, monitoring must be conducted in construction and operation period. In recent years, health monitoring and diagnosis for large-scale construction projects have been a hot topic among the academic and engineering circles, both at home and abroad. But there is little experimental research on health diagnosis using integral model test for bridge structure, especially for suspension bridges.A test model for a span of 1000m suspension bridge has been established, by gathering the design data of suspension bridges in the world. Static load experiment and damage simulation test have been performed on suspension bridge model in the proportion 1:100 with the original bridge. By means of test model and finite element model, static and dynamic properties of the suspension bridge model have been analyzed. The damage cases involved abnormality, which are possible to occur, have been simulated. The static and dynamic responses have also been observed and recorded. Based on the testing, theoretical and numerical analysis, the variations of static and dynamic responses and sensitivity characteristics of suspension bridges have been studied. Through experimental research and finite element analysis, the following conclusions are come to:1. The deflection of the stiffening girder is sensitive to cable damage, and shows negligible reaction to local damage;2. Stress-train variations are sensitive to local damage;3. The cable tension located in archors and both sides of towers possesses high sensitivity to cable damage, especially archors, which should be paid more attention to;4. Cable damage has influence on the bridge configuration and cable tension, whereas hanger damage only induces the variance of cable tension whose position is close to the damage part;5. The natural frequencies can detect the damage, but it is difficult to identify the location and extent of damage.