Parametric investigation of restrained reinforced concrete slabs subjected to combined gravity loads and volumetric changes

This study is based on a developed Nonlinear Finite Element Analysis (NLFEA) technique for analysing the effect of Combined Gravity Loading and Volumetric Changes (CGLVC) on Reinforced Concrete (RC) slabs. A validated NLFEA technique serves as the foundation for the investigation of CGLVC condition. Based on that technique, the present paper performs parametric study to assess the impact of volumetric changes and vertical element stiffness on the serviceability behaviour of continuous RC floors. The NLFEA analyses were conducted with the Concrete Damaged Plasticity (CDP) model for simulating cracking, stiffness degradation and stress redistribution. Outcomes of this investigation show that volumetric changes due to concrete shrinkage and temperature changes notably affect axial stiffness reductions ranging from 60 to 85%. This was resulting for volumetric changes equivalent to temperature variations between − 20 °C and − 50 °C, respectively, that depends on column stiffness and slab arrangement. High stiffness of the vertical members caused 25% higher values of restraint factor, which in turn led to increased reinforcement stresses and wider cracks, especially over internal supports. The findings of this research also indicate a direct link between crack width evolution and stiffness reduction, with crack width as critical parameter in serviceability and durability consideration. The results highlight the most significant drawbacks found on previous research and international design code provisions, which do not account for stiffness loss due to cracking nor address interactions between volumetric changes and gravity loads. The proposed crack-based stiffness evaluation scheme contributes to improving design guidelines concerning CGLVC condition. These guidelines can lead to more durable structures as well as more economic design practice of restrained RC slabs under the influence of concrete shrinkage and temperature variation.