Traffic jams have become a significant problem with increasing population. In order to overcome this problem, roads and bridges are required to be designed targeting high quality. Since structural safety, low-cost and short construction period are significant issues for the construction of bridge type structures, using prestressed reinforced concrete beams which allow carrying high loads and passing large spans with relatively smaller cross sections, become forward. Due to the fact that bridges are designed for long term usage, it is also essential to examine their time-dependent behaviours. Besides, realistic and reliable results can be achieved by determination of time-dependent behaviours as accurately as possible. Creep, shrinkage and relaxation parameters are components of time-dependent behaviour. Shrinkage is affected by the characteristics of the material, environmental and boundary conditions. Creep is not only affected with these conditions but also affected with loading type and cases. In this study, time-dependent stress and strain behaviours of prestressed reinforced concrete member are determined at immediately after prestress transfer and 1000 days. Creep and shrinkage effects are calculated by using Eurocode 2, ACI 209R-92 and CEB-FIP and relaxation is determined according to AASHTO practical design principles. Curvature, strain and stress values for several locations on the beam are calculated for each design code approach. Likewise, deflections at mid span and time relationship are presented in graphic. Analysis results show that time-dependent behaviour have substantial effects on structural behaviour of prestressed reinforced concrete members.
Anahtar Kelimeler: Creep, shrinkage, relaxation, reinforced concrete
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