Time Effects in Concrete Structures: (Developments in Civil Engineering S.)

The inability of designers of concrete structures to recognize and quantify the non-linear effects of cracking, creep and shrinkage is a common cause of serviceability failure. Such failures include excessive deflection, camber and/or shortening of members and excessive cracking which may cause aesthetic or durability problems. This book provides practising engineers with practical and usable techniques for predicting the non-linear effects of creep and shrinkage on the in-service behaviour of concrete structures. Both cracked and uncracked reinforced, prestressed, and composite members subjected to sustained loads or sustained deformations are considered. Analytical procedures are developed for the calculation of instantaneous and time-dependent stresses and deformations on cross-sections in both simple and continuous members. Numerous self-contained worked examples which clearly illustrate the analytical procedures are included. A wide variety of practical situations is considered. Listings of microcomputer programs for a number of the analyses are also presented.

Table of Contents:
1. Introduction. Background. Typical concrete strain magnitudes. Effects of creep. Effects of shrinkage. Time analyses - the basic problem. 2. material behaviour. Introduction. Deformation of concrete. Instantaneous strain. Creep strain. Shrinkage strain. Methods for predicting the creep coefficient and shrinkage. Steel reinforcement. References. 3. Methods for the time analysis of structures. Introduction. The effective modulus method (EMM). Age-adjusted effective modulus method (AEMM). Rate of creep method. Improved dischinger method. Superposition - Step-by-step method. Comparison of methods. References. 4. Time analyses of cross-sections. Introduction. Parts: I. Uncracked cross-sections. Time-varying axial load on a symmetrically reinforced section. Relaxation of a symmetrically reinforced section. Longitudinally restrained shrinkage in an uncracked member. Singly reinforced or prestressed section in sustained bending. Combined axial force plus bending moment on a reinforced or prestressed section with multiple layers of reinforcement. Combined axial force plus bending moment on a composite steel-concrete cross-section. Combined axial force plus bending moment on a composite concrete-concrete cross-section. Non-linear temperature variation on a general cross-section. II. Cracked Cross-Sections. The effects of cracking - general. Short-term analysis of fully-cracked cross-sections. Time-dependent analysis of fully-cracked cross-sections. An `average' cracked section. 5. Time analyses of members and structures. Designing for serviceability. Statically determinate members. Statically indeterminate members. Temperature effects in indeterminate structures. Two-way slab systems. Direct tension cracking and crack control. Slender reinforced concrete columns. Concluding remarks. References. Appendices - Some Useful Computer Software. Appendix 1 - Analysis of cross-sections. Appendix 2 - Slender reinforced concrete columns. Author index. Subject index.