Analysis Of The Sidespin’s Composite Beams Effective Width In The Composite Frame Structure’s Negative Moment Region

Steel-concrete composite frame is a framework which made up by steel-concrete composite components, it mainly includes the composite beams with steel columns, composite beams with composite column and composite column with steel beam etc. The steel-concrete composite frame beam mentioned in this paper is a frame structure which is constituted by combination frame beam and pure steel column. The reinforced concrete floor and steel beam can work together by the effective connectivity through the stud shear connector, then they the combination frame beam.The effective width of concrete slab is a very key parameter which will affect the value of the bearing capacity and deformation of the composite frame beam when we calculate it. In the code for design of steel structure (GB50017-2003), it increases the calculation of the negative moment of steel-concrete composite beam, it means that the design of the composite beam has extended to the continuous beam and beam-column connection area of the frame structure. In the code, the effective width values of the positive moment region and negative moment region are the same. But in the negative moment region of the combination of frame structure, the bearing capacity in the negative moment of the composite beams will be greatly influenced due to the edge of the concrete board members constraint is different. Then, the effective width should also take different values for the concrete slab.According to the present situation, this paper chooses and set models on the edge across of the steel-concrete composite frame system by the finite element software. And it simulates and analyses the factors of the effective width in the negative moment region of the composite frame, then the influence of the coefficient of calculation height, the longitudinal reinforcement ratio, the connection constraint of the side beam and the lateral stiffness and wrest resistant stiffness of the side are particularly considered. Then it contrasts and analyses the effective width and bearing capacity between combination frame beam and truss beam on the same side beam constraints. On the basis of the above analysis, this paper summarize the formulas of the effective width of the combination frame beam in the largest negative moment section respectively in the elastic and plastic limit state. Finally, this paper chooses many models and gets the section flexural strength according to current theories of formula and the flexural strength of the finite element calculation on the elastic limit respectively in state and the plastic limit state. Through the contrast analysis, it is found that the introduction of the concept of effective width can be good for analysis the negative moment region in the edge of the combination frame beams on the elastic and plastic limit bearing capacity.