Structural analysis of cracked R.C. members subjected to sustained loads and imposed deformation

A structural analysis of cracked R.C. members under instantaneous or sustained loads and<br />imposed displacements is presented. In the first part of the paper the problem of deriving feasible<br />moment-curvature diagrams for a long term analysis of R.C. sections is approached in an exact way by<br />using the Reduced Relaxation Function Method in state I uncracked and the method suggested by CEB in<br />state II cracked. In both states the analysis of the main parameters governing the problem has shown that<br />it is possible to describe the concrete creep behaviour in an approximate way by using the algebraic<br />formulation connected to the Effective Modulus Method. In this way the calculations become quite simple<br />and can be applied in design practice without introducing significant errors. Referring to continuous<br />beams, the structural analysis is then approached in a general way, applying the Force Method and the<br />Principle of Virtual Works. Finally, considering single members, the structural analysis is performed by<br />means of a graphical procedure based on the application of feasible moment-rotation diagrams which<br />allow to easily solve various structural problems and to point out the most interesting aspects of the long<br />term behaviour of cracked R.C. members with rigid or elastically deformable redundant restraints.