Interface Slip And Full Process Analysis Of Double Steel-Concrete Composite Beam Under Negative Bending

Double steel-concrete composite beam is a new structual system born in 1980s. Besides the concrete roadway slab, there is a concrete bottom slab connected with the bottom steel flange through studs where this section suffers negative bending moment. In this way, the concrete slab helps to share with the compress stress, which is taken on by the bottom steel flange and web alone in the traditional continuous steel-concrete composite beam, hence improving the rigid flexibility and bending strength of the beam. Therefore it is a reasonable and effective measure to improve the performance of the steel-concrete composite beam under negative bending. The thesis makes an exploratory research on the interface slip of the double steel-concrete composite beam under negative bending with the primary mechanical principle and the boundary method of stain distributions respectively. The slip's formulas along the span direction are obtained and an example is used to make a comparison between the slip features of the double steel-concrete composite beam and the traditional continuous steel-concrete composite beam. A full process from loading to destruction of the double steel-concrete composite beam under negative bending is analyzed in the thesis. The cracking of concrete, yielding of steel, stiffness of shear connectors and interface slip are taken into account in the analysis. A numeral iterative program is drawn up for the calculation of moment-curvature curves. This program is not only suitable for the double steel-concrete composite beam,but also for the traditional composite beam. Through the program, the M -φ of some examples are calculated and analyzed. Furthermore, they are compared with the traditional continuous steel-concrete composite beams and prestressed composite beams. In addition, an example is given to compare the full process of the double steel-concrete composite beams with full-interaction and partial-interaction. Through the study, we can gain a preliminary insight into the mechanical behaviour of the double steel-concrete composite beam which provide a base to further researches.