Study on two-dimensional creep effects of RC slab structures

• Creep in RC slabs causes major deflection and stress rise in both directions. • Longitudinal reinforcement affects deflection little but redistributes stress. • Transverse reinforcement affects deflection & stress, redistributing stress. • Validation of 2D creep analysis methods using the finite element method . Reinforced concrete (RC) slab structures are common in civil engineering, yet they are susceptible to creep under sustained loading. The creep effects significantly impact the biaxial stress distribution of reinforced concrete slabs. Existing creep analysis and computation methods for these structures have some limitations. Therefore, exploring an appropriate two-dimensional creep analysis approach is essential. The two-dimensional stress creep properties of concrete and Poisson's ratio of creep are used to create a two-dimensional creep transformation matrix. A two-dimensional creep calculation formula using the age-adjusted effective modulus method is established to improve reinforced concrete slab creep analysis. Based on the stress states and geometrical characteristics of RC slabs , two-dimensional creep calculation methods are suitable for plain concrete slabs, reinforced concrete slabs with longitudinal reinforcement, and reinforced concrete slabs with both longitudinal and transverse reinforcement. Deflection rises due to the creep effect in the plain concrete slab, although the longitudinal and transverse stresses increase relatively slightly. The effect of the longitudinal reinforcement on deflection in RC slabs is negligible; as the longitudinal stress in concrete decreases, reinforcement stress rises with obvious stress redistribution; the lateral stress decreases compared with plain concrete but rises. The transverse reinforcement of RC slab affects concrete deflection and transverse stress twice as much as longitudinal reinforcement. Prolonged loading considerably redistributes longitudinal and transverse stresses in the reinforced concrete slab's concrete and steel reinforcing.