چكيده لاتين
The use of composite beams compared to steel beams alone has advantages such as higher stiffness and flexural strength and can provide a more economical design. For this reason, it is considered one of the most widely used elements in the construction industry. These composite beams which are composed of concrete slabs, steel beams, and several shear connectors, with the steel section being in tension and the concrete slab being in compression, the efficiency of the steel sections has increased, and this advantage is especially important in the case of cold-formed steel (CFS) sections. One of the effective factors in the design process of composite beams is the correct estimation of the minimum degree of shear connection, which somehow expresses the minimum amount of shear interface used in these beams. These parts create a type of integration between the concrete slab and the steel beam, which must be strong enough not to be damaged during loading and not have brittle behavior. To have a safe and economical composite beam design, the minimum degree of shear connection must be determined. For some specific sections in hot-rolled beams, this coefficient is determined by the design codes. In recent decades, Cold-formed steel (CFS) frames have become increasingly popular in the building industry due to their advantages such as being lightweight and relatively easy to construct. In addition, the cold-formed corrugated decks reduce construction time and cost and can act as a steel tensile element and play a role in increasing the bending capacity of the composite beam. In this study, using bolts as a cold-formed composite beam connector, in addition to compatibility with other components and no need for welding, creates a demountable set that the steel beam can be separated during use or after. This provides less waste and easier collection than other connections and they are a suitable option for short-term buildings that require demolition.
In this research, four full-scale composite beam specimens comprising cold-formed double-lipped channel sections, profiled steel sheeting, concrete slabs, and bolted shear connectors were examined. Of particular interest were the thickness and height of CFS beams. These beams are defined by partial shear connection and after the test, the shear connections remain undamaged and the results show that the analytical and experimental moments are close to each other. Then, comparing the results obtained from the finite element models by developing a three-dimensional numerical model using Abaqus software, the validation of the numerical models is done against the available experimental results. Then, some numerical studies were conducted to investigate the effects of different parameters on the behavior of the composite beam and, the results are discussed. These results showed that the presence of profiled steel sheeting improves the bending behavior of the composite beam by 15-20% and changing its thickness does not have a significant effect on the behavior of the composite beam. Only by increasing the thickness of the profiled steel sheeting from 0.7 to 1.5 mm in the composite beam, between 5 and 10 percent increase in the moment capacity occurs. In the end, As the main and most important goal of this study, the minimum degree of shear connection is formulated for this type of composite beams by different length spans and cross sections and the influence of various parameters such as load configuration, span length, geometry and cross section of composite beams was investigated and finally, relations in this field were suggested. The given relations are for concentrated loading and should be approximately doubled for distributed loading.
