Study On The Effective Flange Width Of Steel-concrete Composite Beam

Steel-concrete composite structure is a newly structure type based on reinforced concrete structure and steel structure. Lately, engineering practices indicate this structural type both has the advantage of reinforced concrete structure and steel structure .Because of its significant economic and social effect, Steel-concrete composite structure develops to one of the most important structural type.In a composite section, the concrete slab acting as a flange in the composite girder. The shear strain and stress in the concrete slab causes the longitudinal displacement in the parts of the slab remote from the webs lag behind that near the webs and the normal stress in the parts of the slab near the grid webs bigger than that remote from the webs. This phenomenon, termed shear-lag, can result in an incorrect calculation of the displacement and extreme fiber stresses when using only the elementary theory of beam bending. The effective width concept has been introduced, widely recognized, and implemented into different codes of practice around the world as a simplified practical method for design and evaluation of structural strength and stiffness while accounting for shear-lag effects indirectly. 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. There are many factors influence it, such as width-span ratio of the composite beam, form of the loads, concrete slab depth, concrete strength, and steel's yielding strength. Each code implements different ideas and approaches for specifying effective width, and they varied greatly .most of the research of this point based on elastic in plastic phase, because of redistribution of stress, the effective width enhanced. Both In elastic phase and plastic phase the effective width adopted by the codes is inclined to less than the actual effective width. Study how the factors influence the effective width in elastic phase especially in plastic phase has significant meaning.A parametric study was conducted based on finite-element methodology to find the truth that how the factors above influence the slab effective width. Regressive equation based on the elastic data was proposed and revised in plastic phase. The Chinese code refers to Steel-concrete composite structure's effective width was compared and analyzed among other countries and equations proposed by author. Then some advice on the effective width can be applied to the analysis and design of Steel-concrete composite structure.