| Today, the material of reinforced concrete in bridge project have gotten plenty of applications, however, the brittleness of concrete material that is suitable for pressing and is unsuitable for tensile has decided to appear cracking problem in the course of usage. In the bearing structure of reinforced concrete, the technology of pre-stressed force has solved the problem of tensile cracking, so the structure of pre-stressed force concrete has emerged as the times requiring. With the fast development of science and technology, construction is asked to enlarge the application of steel structure, and should economize steel material as far as possible. The major key that solves the contradiction is: continue research and improve the existing type and the design theory of steel structure, and create the new form of steel structure (Including combination or compound structure). Besides economizing steel material and alleviating self-weight, still enlarging the scope of its application, creating new unique bridge style. In this course, the technique of pre-stressed force is essential, and some researches and applications of composite beam have emerged. Pre-stressed steel-concrete composite beam bridge is a new type structure developed from the conventional composite structure. The material elastic scope is enlarged by externally pre-stressed to steel, thus the high tensile material performance is substantially brought into play. According to the difference of exerting order of pre-stressed force, the technique can again be divided into the two combination beam of pre-stressed force-before pre-stressing and late pre-stressing, the before pre-stressing is the tensioning steel of pre-stressed force on steel beam, then pour concrete slab on this steel beam, and form the before pre-stressing steel -concrete composite beam finally. The late pre-stressing is after concrete combination beam forming to tension pre-stressing steel beam in composite beam and forms finally the steel -concrete composite beam of late pre-stressing. Test study and theory analysis indicate that it is a kind of structure with the merits of safety, high efficiency, economic and easy construction, especially adapting to large span, heavy load bridge structure. Comparing with conventional steel beam, it can economize investment for about 20%. For the above advantages, this type of bridge is competitive and wide used in the construction of long span or mid span bridges. It is proved that the technique of externally pre-stressed with unbound stress is a method with simply construction, high efficiency and applicable. In china, a lot of existing railway bridges, highway bridges and composite bridges need to be reinforced or maintained, so it has the big market. For the advantage of economy, simply construction, convenience maintenance, it has great social benefit in the building of pre-stressed steel concrete composite bridges. It reduces the engineering work of concrete by using the lightweight steel material replacing the big bulk concrete web plate, reduces the environmental pollution when construction. It is well known that the construction period is short in the north area because of low temperature, but this type of bridge is rapidly constructed and can be easy built by the simple machine, it is significant to progress the construction speed of highway and railway engineerings. The study of pre-stressed steel concrete composite beam bridge is still in the stage of beginning, some fundamental works are done in domestic such as Tsinghuauniversity, Tongji university, Westsouth traffic university, Fuzhou university, East-south university, Harbin institute of technology and so on. A foundation of essential theory and experiment is formed. The aspect of the basic research, theoretical reserve and innovation structural system of the steel-concrete pre-stressed force composite beam bridge has a gap between our country level and international level for this field, domestic and international development is not enough. This project will be studied structural behavior of bearing strain further more, establish calculating theory and designing analysis method, and enlarge this application field. Study accomplishment will be expected, promote and realize bridge structure, space structure and building structural for stepping the direction development of big span, big space, of heavy duty, this is important theoretical meaning, application prospect and considerable economic benefits for simplifying construction and reducing cost. It is reason that this paper chose the steel-concrete pre-stressed force composite beam bridge to go into the detailed theoretical calculation and analysis research further. With the rapid developing of economic, the amount of this type of buildings will also increase rapidly. So it is useful to present a series of calculation theory and design method in China. It is very necessary for developing the research work of the steel-concrete pre-stressed force composite beam bridge. The static behaviors of pre-stressed steel-concrete composite beam bridges are discussed in the paper, the main contents, techniques and results of the research are summarized as follows: Firstly, based on elastic theory, the shearing force's lag phenomenon of girder and T beam's flange slab are analyzed by variational method. It indicates that the theory results have good accordance with the test results. It provides the necessary basis of analyzing the bending processing of composite beam by the method ofbending curvature. The solution of this calculating question will play important role to improve the theory study and design calculation of the pre-stressed steel-concrete composite beams. Secondly, the shearing strain's difference between steel and concrete under vertical concentrated loading is analyzed based on elastic theory, and results is compared with ideal solution under vertical distributing loading and the test results. It indicates that computing formula concluded from the paper of shearing strain's difference for composite beam is believable. After the pre-stressed force is equivalent outside loading, the calculating method is convenient to the influence of calculate pre-stressed force for shearing slip strain. Thirdly, based on the elastic-plastic theory, the analysis model of composite beam bending process is established considering the nonlinear of material and geometry, the shearing forces lag phenomena of flange concrete slab, the shearing strain difference between steel and concrete, and the calculating program is compiled, the calculating results have the well agreement with the test results. This method can be calculated efficiently the difference of the non-claying outside pre-stressed force with the change of loading. Fourthly, static load tests are done of eight pre-stressed steel-concrete composite simply supported beams and two steel -concrete composite simply supported beams, the stress change of pre-stressed tendons and the shearing strain's difference between steel and concrete, the shearing force lag phenomena at flange concrete slab and laws of section strain change are studied, some valuable conclusions are obtained. Lastly, the simplified formulation of calculating bending capacity and displacement of pre-stressed steel-concrete composite beams are presented. It also analyzed some problems existed in the design work, discussed and commented the... |
PDF Full Text Request