Concrete Structures Stresses and Deformations

Concrete Structures Stresses and Deformations

Concrete structures must have adequate safety factor against failure and must
also exhibit satisfactory performance in service. This book is concerned with
the checks on stresses and deformations that can be done in design to ensure
satisfactory serviceability of reinforced concrete structures, with or without
prestressing. The following are qualities which are essential for a satisfactory
1 No excessive deflection should occur under the combined effect of pre-
stressing, the self-weight of the structures and the superimposed dead
2 Deflections and crack width should not be excessive under the above
mentioned loads combined with live and other transitory loads, settle-
ment of support and temperature variations. This makes it necessary to
control stress in the reinforcement, which is one of the main parameters
affecting width of cracks. Durability of concrete structures is closely
linked to the extent of cracking.

Because of creep and shrinkage of concrete and relaxation of prestressed
reinforcement, the stresses in the concrete and in the reinforcement vary with
time. In addition, when the structure is statically indeterminate the reactions
and the internal forces are also time dependent. The strains and consequently
the displacement change considerably with time due to the same effects and
also due to cracking. The purpose of this text is to present the most effective
methods for prediction of the true stresses and deformations during the life
of the structure.
The mechanical properties that enter in calculation of stress and strain are
the modulus of elasticity, creep and shrinkage of concrete and modulus of
elasticity of reinforcements. These properties differ from project to project
and from one country to another.


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