Research Of Composite Grider Cable-stadyed Bridge Static Stability

Based on the research results summarized by Chinese and foreign scholars and the design specifications at home and abroad, the problems of the stability in the whole construction process of the cable-stayed bridge are studied with the research experiences of stability in China. The thesis is divided into two parts depending on structure and content.The first part is from Chapter 2 to Chapter 4 ,the basic theories of cable-stayed bridge with composite beam, stability, and the three-dimensional creep of the concrete are introduced, which is belong to the aspect of theory and method; the second part is from Chapter 5 to Chapter 7, the development of interface program of the general finite element software for the study of Stability is made, the calculation of overall, local stability and interactive stability, the research and summary of the regular pattern are provided, which is belong to the aspect of research and application. The main aspects of work in the paper as follows:1) From chapter 1 to Chapter 4, the historys of the cable-stayed bridge and steel - concrete composite beam, application status, the key technical issues, and basic theorys of composite beam cable-stayed bridge are mainly introduced, the main reasons of the stability of cable-stayed bridge, the classification of stability, the main research content and research methods of stability are discussioned; the problems of three-dimensional creep in concrete are studied, and the computation method of concret creep under the state of three-dimensional are analyzied particularly and introduced in detail depend on the theory of three-dimensional viscoelastic theory.2) In order to achieve the special function of bridge structure, the general finite element analysis software need to develop a professional interface program, In chapter 5, the method and process are researched as following: achieving target forces of tendons using cooling method in Abaqus; achieving failure of stayed cable in the ultimate bearing capacity analysis process; and exerting Residual Stress through integration points in the element of beam; Moreover, because of the inheritance existed in the status of construction, the method and process of developing the professional interface procedure are researched to make the former result as the initial state of the latter analysis, then materials and element amouts can be changed when changing the results in the different categories of analysis.3) The main content of the chapter 6 is the discussion of first and second category of overall static stability of cable-stayed bridge in the whole construction process with the view of the engineering background. The law of safety factor and buckling mode in the first category stability in the whole construction process are studied and summarized by referencing the stability regular of several important bridges; according to the concrete examples of calculation, the laws of variety of the safety factor of different construction content in the same state and the same content in different Beam Segment are studied; After compairing the affect produced by changing different stayed cable material, some conclusions are obtained; the impact produced by concrete constitutive relation on the second category overall stability are researched; how to impact the second category overall stability and the law through the whole construction process are put forward; the stability calculation results of the two different models (single -Main beam and double-girder of the main beam) are compared and the reasons causing the difference are discussioned; Discussion and evaluation are made regarding the impact degree of some Influencing Factors Such as Shear Studs, Residual Stress of the main beam, Initial State of the structure, installation method of the element (tangent method, zero-displacement method); Concrete Slab possess time-dependent effect, creep will take place as time goes on,but because of the transformation constrainted by steel beam, stress redistribution of Concrete Slab and steel beam is produced, thus, the influence of stability caused by Creep Effect are studied and evaluated.4) In Chapter 7, based on the specific engineering background, the problems of the first category and second category of local static stability through the whole construction process are researched, it is mainly studied the effect on the stability produced by initial imperfection of structure; The Local Stability under the most dangerous state of cross beam , tensile anchor plate, Bridge Deck, and steel girder are researched.5) In chapter 8, combing the results of global stability and local stability, the sequence of the whole stability and partial stability in the whole construction process are conclused; the relativity of the whole stability and partial stability when reducing the element length and considering the stress complex region is researched by establishing refined model.Finally, summarize the research work on this paper, and point out the issues which be studied further, carry on the discussion for this.