Study On Envelope Diagram Of Inner Force In The Long Span Cable-stayed Bridge

The principle of the structural health monitoring (SHM) of long-span bridge is mainly to obtain the bridge structures daily true responses on-line by sensors disposed in structures, and then deduce the state of the bridge structures by making use of those obtained information and evaluate the bridge safety and security synthetically. SHM can ensure traffic safety of long-span bridge and supply economy inspection schemes. Background on the Runyang Yangtze River Bridge, this paper study inner force distribution and inner force amplitude of variation, form envelope diagram, define region of high stress and fatigue, and propose to the economy optimal local strain sensor placement. This thesis includes seven chapters: Chapter 1: A brief summarizing of the development and achievement of bridge health monitoring are introduced. This paper presents the components and flowchart of the SHM. Conclude that the optimal sensor placement is first problem of SHM. It is the foundation to solve this problem to define region of high stress and fatigue. Chapter 2: Analysis the reasons and character of fatigue damage in long-span bridge. According to the character of fatigue pulsating stress, the main cause of fatigue damage is the maximum stress value and amplitude. It propose sensor placement to obtain stress envelope and variation , draw envelope diagram . Chapter 3: In this paper, the formulas are deduced to calculate influencing surface of bridge structure on the base of the virtual work principle. In this method, influencing surface is substituted by the deflection surface of the whole structure. Compare with influence lines, it show that influence surface is safer. Chapter 4: According to the finite element modeling theory, three-dimensional finite plane and beam element model of the cable-stayed bridge of Runyang Yangtze River Bridge is given. It can describe accurately the deformation and inner force of bridge structure . Chapter 5: Static analysis is done for the Runyang Yangtze River Bridge. There is the bridge equilibrium position at the action of dead weight and cable load. This position is the initial of live load analysis. The live load analysis process: First, calculate influence surface. Second, apply vehicular load in the method of dynamic programming. Obtain the maximum and minimal inner force. Last, draw inner force envelope diagram, define the focal monitoring points of local strain transducer. Chapter 6: Load-on and calculate on the finite element model of the cable bridge. Made comparison between calculation and testing result. Chapter 7: Address the main conclusion of the thesis and the pending problem.