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 andimposed displacements is presented. In the first part of the paper the problem of deriving feasiblemoment-curvature diagrams for a long term analysis of R.C. sections is approached in an exact way byusing the Reduced Relaxation Function Method in state I uncracked and the method suggested by CEB instate II cracked. In both states the analysis of the main parameters governing the problem has shown thatit is possible to describe the concrete creep behaviour in an approximate way by using the algebraicformulation connected to the Effective Modulus Method. In this way the calculations become quite simpleand can be applied in design practice without introducing significant errors. Referring to continuousbeams, the structural analysis is then approached in a general way, applying the Force Method and thePrinciple of Virtual Works. Finally, considering single members, the structural analysis is performed bymeans of a graphical procedure based on the application of feasible moment-rotation diagrams whichallow to easily solve various structural problems and to point out the most interesting aspects of the longterm behaviour of cracked R.C. members with rigid or elastically deformable redundant restraints.