Time-dependent deformations and stresses in prestressed concrete structures

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The objective of this investigation is to develop an accurate method for the evaluation of the time- dependent effects of creep and shrinkage of concrete and relaxation of steel in prestressed concrete beams and frames. The analysis uses a step-by-step numerical procedure in which the service life of the structure is divided into discrete time intervals. In each interval the time-dependent effects on stresses and strains in the preceding intervals are accounted for, thus updating the data at each step. The step-by-step procedure gives accurate results but is unsuitable for hand computation common in many applications. The thesis is divided into two main parts. The first one deals with noncomposite statically determinate members. A simple, but accurate, design method is developed for the evaluation of axial strain, curvature and prestress loss using a chart derived by a step-by-step procedure. When the first two are calculated for various sections in the member, they can be used to find displacements. ing and midspan deflection in beams. with other available methods. Formulae are given for axial shorten- The proposed method is compared In the second part, a general analysis is developed for the solution of composite continuous structures. A computer program is presented for use as a design aid. It can be used, among other applications, to determine t he time-dependent effects in bridges made up of precast pretensioned members placed freely on supports (or falsework) and then made continuous by cast-in-situ deck and second stage post-tensioning. The analysis gives the time development, of the stresses in concrete and steel, and of the displacements (translations and rotations), at various locations along the centroidal axis of the structure. The proposed design procedures are verified by comparison with experimental results in the literature, and demonstrated by numerical examples.
Bibliography: p. 119-125.
Tadros, M. K. (1975). Time-dependent deformations and stresses in prestressed concrete structures (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/15899