Construction Risk Analysis And Countermeasures Research Of Long Span Cable-Stayed Bridges

The remarkable development of long span cable-stayed bridges has taken place in recent years due to their beautiful shapes and unique structural qualities. With the innovations of structures and the increase of the span length, all kinds of uncertainty have been arisen, and the engineering construction is faced to unprecedented high risk. The engineering accidents which endangers safety of structures, properties and people's lives, might take place if enough attention have not be paid. This dissertation focuses on the construction risk of long span cable-stayed bridges, which includes the following aspects:1. The theoretical skeleton. In this part, the risk conception and its analysis principle are discussed. The definition of risk and the selection principle of risk analysis methods are put forward, and the theoretical skeleton of construction risk analysis for bridges is built on the basis of giving definition of structure risk of bridges during construction.2. Construction risk identification. The principle and the process of construction risk identification for bridges are discussed. Due to the complicated characteristic of construction risk factors of bridges and the lack of practical data for construction accidents, a simple and practical AHP method for construction risk identification of bridges is presented, which is an ideal method for construction risk identification, combining the qualitative method and the quantitative method.3. Construction risk probability estimation. The principle of construction risk probability estimation for bridges is discussed. Due to the performance functions of bridges are implicit and higher order nonlinearity, and the limitations of conventional reliability methods to solve this problem, a method, combining finite element methods and artificial neural network and Monte-Carlo simulation, is presented, which is called F-A-M. This method can solve the couple problems between stochastic simulation and finite element numerical calculation, and can increase the efficiency of risk probability estimation.4. Construction risk consequences estimation. The principle of construction risk consequences estimation for bridges is discussed. The construction risk consequences of bridges are first investigated systemically and completely. The principle for build a model of risk consequences estimation is presented. The model of risk consequences estimation for bridges is built. A risk consequences equivalent estimation method combined with the model of risk consequences estimation to realize quantitative estimation for construction risk consequences of bridges is put forward.5. Construction risk assessment and its index system. The principle of construction risk assessment for bridges is discussed. The principle for building a model of risk assessment is presented. The model of comprehensive risk assessment for bridges is built. The principle for establishing risk assessment indices is put forward. The construction risk assessment index system for bridges, which includes risk acceptance criteria and risk grade assessment standard, is built. This make it possible to comprehensively assess construction risk of bridges in an allround way.