The Research On Bearing And Deflection Ability Of Simply Supported Composite Steel-Light Weight Concrete Beam

In recent years, the composite steel-concrete beam (CSCB) is applied and developed more quickly than ever before, and applying the light weight aggregate concrete (LWAC) in the beam will be a tendency of improvement to the composite structure. The loading capacity and the transforming capacity of CSCB is relevant to some factors, such as cutting section size, the ratio of high to long, the slipping and shearing between the concrete beam and steel gird, and the partial yielding-stress of steel gird, etc. Whether the CSCB can be applied in the bridge construction on a large scale, the analysis on the loading capacity and the transforming capacity will become the main design according to and point to be attended to. So this article on the bases of the research result of the CSCB in the common concrete makes systematical research on the composite steel-light weight aggregate concrete beam.This article mainly studied the structural behavior of the target beam under symmetry and concentrated force, and put forward simplification formulation of deformation, then carried on a simulation with the finite element method, validated the feasibility of the formulation. The full article is divided into five chapters totally, among them, chapter 4 is a textual core part, and concrete research contents are as follows:Chapter 1 recapitulated the purpose and significance of the article. The application of LWAC in CSCB is the new development of the composite structure, the characteristic of the LWAC is the key to whether the beam can be large-scale to apply. This part of contest introduces the characteristic and domestic and international development of the LWAC, analyzing the development foreground and the application values of the LWAC. Basing on the advantage of the LWAC, such as light weight but high and strong quality, durable good, the anti- earthquake good and good etc, the application of LWAC in CSCB will exert the two kinds of materials more adequately than each from of advantage themselves. By analyzing the technique capacity of the CSCB, the application of LWAC to composite beam has good feasibility, comparing the good applied advantage in the composite steel-concrete, the applying foreground will be extensive.Chapter 2 introduced the applied advantage of the LWAC in composite beam firstly, and then recapitulated the related theories about loading capacity of the composite beam, and in detail respectively introduced the development of the related theories, applied condition and calculating methods, also compared a few different and similar of method. Later, this chapter designed a composite steel-light weight concrete beam model, namely designed the shear conjunction form, form and sizes of the sections of the composite beam, and then carried on the theories calculation. For the loading ability of the model beam, this article carried on the analysis with elastic-extreme limit method and plastic-extreme limit method separately, and fixed the relationship of stress among key points, took the results as the reference to the theory and model beam simulation.Chapter 3 mainly analyzed the deformation of the composite steel-light weight concrete beam. First of all, the chapter introduced the calculation theory and the development of the theory about the beam. This article analyzed the deformation of light-weight composite beam respectively by adopting the convert-section method, the minishing rigidity method, the minimum potential energy method and formulation considering slipping, and built up the calculation formula to solve the deformation of the middle part of the composite beam, base on the transform formulation. Then contrast above several kinds of calculation methods to confirm that it is feasible and answering the act to adopt the last method in calculating the middle deformation of the composite steel-light weight concrete beam. For the deformation of every section, adopt the elastic-extreme limit theory to analysis, applied the model that designed in Chapter 2, and originally validated the correctness of the formula of this article. Calculating results also showed that, because of the convert-section method doesn't consider the slippage of the interface, the calculation value that caused transform is partially small, in actual design is in insecure. Assuring the factors that influences composite beam loading ability and transform ability included: the distance and form of shear conjunctions, the strength grade of the concrete and the size of steel section, etc.Chapter 4 is the textual core part, putting forward more reasonable infinite element calculating model, and verified the formula that this article put forward. For analyzing the loading capacity, transform capacity and the influence factors about the composite beam by the finite element method, this chapter designed four modal beams, changing the section size, the distance of the shear conjunctions and the type of the concrete, and carried on a non-linear analysis by finite element method. Comparing the results of the model imitating, it showed that: the calculation values match well, the bigger the steel beam in every aspect to accumulate, the longer the distance of the shear conjunctions, the higher the loading capacity and the transform capacity of the composite have. The extreme load of the light weight concrete composite beams approached to the plastic-extreme load, so we should betake the extreme limit method to design beams, in order to avoid the waste of material by using the convert-section method. The deformation of the target beam can be divided into three stages approximately: the flexible stage, the elastic-plastic stage and the stage of plastic. For the flexible mold quantity of LWAC is lower than common concrete, the medium deformation of the modal beam was greater than the common beams. Corresponding to every stage of loading, the formula that this article put forward on calculating the medium deformation fit together better. Comparing with the convert-section method, the result of this article was more adjacent to the real deformation, the result was more secure, but a little smaller than the minishing rigidity method. The textual calculation results can provide certain theories about calculation and design for the aftertime composite beam to according to.Chapter 5 is the summary of the full article, sum up the process of completing the article, at the same time put forward the contents and the direction that still need to continue in the work of carrying on the research.