Simply Supported Steel - Concrete Composite Beams Elastoplastic Effective Width Analysis

Composite structure develops quickly in recent years. Steel-concrete composite beam are its basic members. It is used to resist bending moment by means of integrating concrete slab and steel joist to through shear connectors. It takes advantages of the respective properties of tension of steel and compression of concrete, and is used widely in those structures under heavy loads, request long span and low depths of beams. Steel-concrete composite beams are simple and common members in engineering.In the theory of steel-concrete composite beams, the effective width of concrete slab is a very important parameter of the section. Its value influences the bearing capacity and vertical deflection of the beam directly. As the shear lag effect, the stress distribution across section of concrete flange is not same as obtained in mechanics of materials which is even everywhere. The value of stress near the middle of the concrete slab is larger than it further. The study about effective width in and abroad are mostly based on theory of elasticity. Now the regulation of it in codes are derived from elastic theories. But the moment resistance of composite beam at ultimate limit state could be increased greatly because of the re-distribution of stress. So, the computing method of the ultimate limit resistance with effective width exists errors. The factor influencing effective width is very complicated. Owing to the financing short, it is very difficult to analyze it in detail by experiments.Recently many kind of finite element soft develops quickly with the deeply research into finite element method. The high capacity of fast solving equations of the computer make it possible to solve nonlinear equations within a certain precision. Scholars are using this method to replace experimental research more and more, and it becomes a study means chosed by engineers. This paper adopted nonlinear finite element method to simulate the whole loading process of four composite beams provided by researchers. It can be obtained clearly that the result is accurately enough and can satisfy the demands of engineering.To analyze the effective width of concrete slab in plastic ultimate limit stage under the complicated influents mentioned above, this paper designed scores of steel-concrete composite beams. Some dominant parameters are analyzed on the influence of effective width, such as width-span ratio of the composite beams, width of concrete slab, shear connection legree, concrete strength, steel's yielding strength, form of the loads. The whole loading crocess on the composite beam is simulated by nonlinear finite element method, and the effective width of concrete slab are computed under different loads. The conclusion is that the alue of effective width in plastic ultimate limit stage is larger than the that of in elastic...