EFFECT OF SHRINKAGE AND CREEP IN REINFORCED AND PRESTRESSED CONCRETE MEMBERS

Abstract

Shrinkage and *reap have got practical importance in the sign of reinforeed. and, prestressed concrete struct:•res. It has be observed ithat time str-ain creep may amount several tims more daformttons than the c,-formations undr direct stresSe5 a Earlier in designs the effect. of Shrirflage and cr,:p on the reWorcel concrete sturetures was incorporates as a provision of reforcement for tepertare anI &rthke, in of prestressed concrete members Natioml Building Cone has pit given expressions to calculate shrinkage and creep effects. In several cases, tine iepen&nt stresses do not aUbet the load currying capacity of a bcr.'fiure is con trol2i by large strains that develop at collapse regariless of the previous strain hi story. However when stability is a factor shrinkage and creep may affect the failure load. In designs provision has been made to overcome the effect of shriniAge and creep =4 vrious studies )ave been made to Incorporate the time ani environment dependent *AM"• charactersUc of concrete, vi. Approach, Glanville sni. Thomas approach and Graduck approach etc. As in these aiwroathes for &u'inkage and creep effects calculations involve much time, a neei was felt to make them computerised, With this viev in mini, a computer programme has been made for the metloi, recommcned by C (Comite iuropean due Beton), In this dissertation an attempt is made to compute the time dependent deformations in re1norc.e4 and prestressed concrete members, using a crnputez progze. The approach recommended by C.B. has been used to expressed the ihrinkage and creep coefficients. The time dependent characteristic Of concrete-bas been assumed to be known in a conenient forn* The affect of preatmasing. form has been Incorporated as dead load. Few examples Of reinforced concrete %embers such as beams, colwnns have Wen analysed and effect of percentage reinforcement variation has been studied by a general computet • The re suits obtained. are compared vith affective modulus method and the results obtained from C.E.B. approach are found to be more reliable., Few examples of prestressed concrete members have also ben analysed by the general computer programme in Uhich the effects of shrinkage ani creep have been studied keeping In view the vartous parameters of minimum weight design.. .Thee results are also comparable with the elastic strain method results and with the results obtained from the expressions gIven: In National Building Code for shrinkage and creep to account for age of umber and relative humidity. Thus me general computer programme can be used to find otit the ects of shrincage and creep on both reinforcel and preetrefs(. d concrete members