The stresses in concrete and steel of a reinforced concrete slab are continuously changed with time due to creep of concrete. In general, reinforced concrete structures are designed to resist the tensile force by reinforcement and the compressive force by concrete. Therefore, the deformations and forces due to creep with time of reinforced concrete slab at underground level which carries the compressive force due to the pressure of water and soils have to be considered in analysis and design.
The purpose of this study is to propose the model equation of aging coefficients for the slab under flexural moment and axial force. Aging coefficients which are used for aging adjusted effective modulus method(AEMM) in analysis of reinforced concrete structures are obtained by calculating and comparing the curvature from step-by-step method and AEMM. Some parameters like initial loading time, loading duration, notional creep coefficient, reinforcement ratio and axial force are considered to analyze the aging coefficients. From the analysis, the curvature is larger when initial loading time is earlier, loading duration is longer, notional creep coefficient is larger, the ratio of compression steel to tensile steel is smaller and axial force is larger. The aging coefficients are smaller in the case of earlier initial loading time, longer loading duration, larger notional creep coefficient, smaller reinforcement ratio, and larger axial force.
Comparing the relationships between the parameters and considering the similarities and tendencies, a model equation of aging coefficients which is able to reasonably predict the long term deformation is finally proposed.