الفهرس 
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Abstract
Reinforced concrete elements are exposed to direct and indirect actions. Direct action refers to applied loads; weight of the structure and its contents, or pressures due to wind, water, or earth, etc. The opposite is indirect action which is a movement or deformation that through does not result from applied loads, will cause stresses in a structure. Strains due to volume changes due to shrinkage or thermal variation and similar effects are examples for indirect action. If a reinforced concrete structure in any way is hindered to deform due to volume changes, shrinkage, temperature variation and creep, restraining forces will appear. The deformation can be restrained internally due to the reinforcement bars or externally due to the supports. The prevented deformation results in tensile or compressive stresses, which will result in cracking if the concrete tensile strength is reached. Currently, in most design codes, the restraining effect due to concrete volume changes should be considered in combination with other loads (such as gravity and lateral) if their presence adversely affects the structural safety. Restraint of movements associated with volume changes can cause significant internal forces in a structure. Several strategies can be followed to accommodate movements; e.g., expansion joints and construction closure strips. Nevertheless, such measures have negative effect on the structure performance with regard to durability, ease of construction, …, etc. For better performance of long span structures, accounting for restraint stresses, without having to introduce expansion joints or closure strips, would be the best option. In this study, the effect of shrinkage and temperature variation on the behavior of long span reinforced concrete structures as flat plate system, raft foundation supported directly on soil or piles, continuous beams and bare frames has been examined via the nonlinear finite element analysis. The nonlinear finite element, with the aid of the software Abaqus (2017), is utilized in performing the modeling and analysis. The results of analysis revealed that material nonlinearity plays a major role in the response of the structure for temperature and shrinkage effects since its presence remarkably reduced the adverse effect of the two factors. Shrinkage and temperature variation had more significant effect on slabs than on rafts. Their effect on concrete stresses was not critical in slabs and had no significance in rafts. On the other hand, such effect on steel reinforcement was noticeable in rafts and significant in slabs. This led to the conclusion that the effect of both temperature variation and shrinkage can be accommodated by additional reinforcement. In continuous beams, restrained stresses may have a significant effect on the concrete compressive stresses and reinforcement tensile stresses. As for the reinforcement compressive stresses the effect is drastic. In frames, noticeable effect may take place in concrete compressive stresses and girder reinforcement tensile or compressive stresses, but the effect on the stresses of column reinforcement and deflection is significant.