An Analytical Procedure For R.C. Beams Strengthened By New Concrete Layers

A common problem in high seismicity areas is the need for flexural strengthening of the weak reinforced concrete elements. A popular technique for increasing the flexural capacity of reinforced concrete elements involves the casting of a new concrete layer, reinforced or not, on the tensile or the compressive side of the element. Slip at the interface between the old and the new concrete affects the behaviour of the composite element. However, it is common practice in design to ignore slip and consider the strengthened element as monolithic. In the present paper, an approximate estimation of the maximum values of sliding, slip strain and shear stress of the strengthened element is presented. In addition, an analytical procedure for prediction of the distribution of sliding and slip strain along the interface between the initial beam and the new layer of concrete is presented. Finally, the results of these two methods are compared.