Yield Line Method Applied to Slabs with Different Supports

In very ancient decades and up to a rather recent time, concrete in its known composites; cement, aggregate and sand, was not a well-known material to those of major concern of building construction field. Nevertheless, most of the formally constructed buildings were basically made of woods, stones, clay, steel and the like of the available materials at the time later and in an outrageous development, concrete has become, in no noticeable time, the most important material in building construction field. Nowadays, more than 65% of the structures in the world are made of concrete. This research aims to study reinforced concrete slabs in different boundary conditions by analyzing the applied forces in order to determine reason why this research deals only with reinforced concrete slabs is that the quantity of concrete used in constructing them is more than that used in foundations, columns, beams and other reinforced concrete members. From the other hand, slabs, at most times, unless designed properly, are the main cause of failure of reinforced concrete structures. There are multiple procedures to determine the forces applied on slabs. The Yield Line theory which is an ultimate load analysis, is used here as one easy and ideal method of analysis based on Virtual Work and Equilibrium Methods. Nevertheless, one should have in mind that when the slabs are restrained against lateral movement by stiff boundary elements compressive forces are induced in the plane of slab causing a rather considerable increase in the slab strength. These induced forces are known as membrane action and are studied here in the light of former studies. Further in this research, the features of cracks, ultimate loads and deflection values are obtained theoretically using reinforced concrete slab models differ in fixing conditions and steel reinforcement densities, applied to loads increasing gradually until failure. The experimental results are then compared with the theoretical results obtained sooner in the research and the factor of safety is satisfactory. Thus, we recommend the yield line method of analysis to be used taking into consideration the membrane\e action as it leads to reduce the volume of concrete by reducing the thickness of the slab and consequently reduce the cost of the structure