Small And Medium-sized Highway Concrete Bridge Carrying Capacity Assessment Study

It is well known that quite a few existing bridges have been not appropriate for application at present, while the demand of loading level and drive conditions are always increased with road traffic development. Recently, health state of existing bridges has received publicity. How to assess load-carrying capacity of existing bridge is the important part of the work for bridges safety evaluation. The main work of this paper is to set up a practical method for quick assessing load-carrying capacity of the middle-small-scale bridge.In the first part of this paper, based on the background of the research project, difference between large-scale and middle-little-scale condition assessment is depicted, some ongoing implementations of bridge load-carrying capacity evaluation are introduced, the content of this thesis is presented also.Chapter 2 introduces the conception of load-carrying capacity coefficient firstly. A method is presented to deal with several factors, such as actual ultimate strength of structural member, dead load and live load behavior, and structural damages, etc., those influence the load-carrying capacity coefficient. Application of Non-damage detection methods to bridges is introduced. In the last part of this chapter, application value of load-carrying capacity is illustrated in assessment of actual bridge.Chapter 3 and chapter 4 mainly do research about load-carrying capacity of bending structure, which is common in middle-little-scale bridges.Based on analysis of many damages on concrete bridges and the whole process curve of concrete during pressing test, chapter 3 modifies the calculation formulae for normal section strength in current standard. A new method is adopted to bridge assessment, and how structure damages in existing bridges influence their normal section strength is considered.Chapter 4 introduces basic formulae of oblique section strength for simple supported bridge, continuous bridge, ox-leg structure and deep beam. Four factors, dimension effect, loading type, T-sharp beam, straightforward and oblique crack as well, are discussed. Finally, in according to mechanical feature and extent of damage of existing bridge, a method to assess oblique section strength of existing reinforced concrete bridge is proposed.Chapter 5 introduces the regulations, guides and maintenance means of the bridge examination and assessment. The analysis model is modified with all useful messages from bridge field test in assessment. Meanwhile, based on the quantity and quality of test messages, strategies of hierarchy analyses are provided.Chapter 6 presents a bridge assessment example, and illustrates how to use load-carrying capacity coefficient in middle-small-scale bridges assessment.The main contribution and conclusion of this work is summarized in Chapter 7 where some problems to be addressed about the research is set forward.