The Experiment And Analysis Of Effective Width In Steel-Composite Beams

The composite structure has some merits, such as light weight, better economical efficiency and constructs convenience. It's widely used in engineering practice. In the design of steel-concrete composite beams, the effective width of concrete slab is a very important parameter of the section. Shear strain of concrete slab makes stress not uniform. We use the concept of effective width to solve this problem. The effective width is a transformed width, but is not the real width of slab and the yielding width. Up to now we make the concept of effective width on the base of elastic condition. The effective width changes as the load grows. In plastic stage, the distributing of stress becomes uniform. The value of effective width in plastic stage is larger than that in elastic stage.Go ahead in this basis, this paper completed experimental study of two composite beams with different width and span under static concentrate vertical loads. The damaging shape, deforming nature, cross-section stress, slip feature, specially the stress and strain of concrete slab was observed.This paper adopted nonlinear finite element method to simulate the whole loading process from two 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 analytical samples of steel-concrete composite beams. Some dominant parameters are analyzed on the influence of effective width, such as width-span ratio of the composite beam; the thickness of concrete slab, shear connection degree, concrete strength, and yielding strength of steel, form of the loads and so on. The whole loading process on the composite beams was simulated by nonlinear finite element method, and the effective width of concrete slab is computed under different loads. The conclusion is that the value of effective width in plastic ultimate limit stage is larger than that in elastic stage. The reason is the re-distribution of stress at ultimate limit stage, and the distribution goes to even everywhere across the section of the concrete slab, and so the value of the width of effective width increase. The current and range of increase is different along with the different parameter varies.With comparing the effective flange width provisions between several countries, some simple equations which applied in the effective width of concrete flange in the elastic stage and plastic stage was suggested.