Deformation control of reinforced concrete slabs and moment-resisting frame buildings

Abstract

Design of reinforced concrete (RC) slabs is governed by deflection limits associated with serviceability requirements, whereas design of RC moment-resisting frame (RC-MRF) buildings is governed by inter-story drift ratio limits associated with performance objectives. This thesis investigates deformation behavior in RC structures by addressing vertical deflections in one-way slabs and lateral displacements in RC-MRF buildings through analytical, experimental, and comparative approaches. Vertical deflections in one-way RC slabs were analyzed through a parametric study to quantify the influence of geometrical, material, and construction parameters on immediate and long-term deflections. The parameters considered include slab thickness, reinforcement ratios, concrete mechanical properties at loading time, creep and shrinkage effects, loading and drying time, and applied load level. Long-term deflections are estimated using an effective moment of inertia formulation that incorporates time-dependent effects. The results show that slab thickness and tension reinforcement ratio are the dominant parameters controlling both immediate and long-term deflections. Vertical deflections in one-way RC slabs were also analyzed through experimental and analytical studies. These studies evaluated short- and long-term deflections of slabs constructed with conventional concrete (CC) and self-compacting concrete (SCC). Slab specimens with different reinforcement ratios were tested under monitored environmental conditions. Mechanical properties were experimentally determined, and measured deflections are compared with analytical predictions. SCC slabs showed lesser long-term deflections than CC slabs, primarily due to higher stiffness and reduced shrinkage. Analytical models accurately estimated short-term deflections but underestimated long-term deflections when environmental conditions were not included in the analysis. This research also focused on the drift requirements of buildings located in seismic regions. Lateral displacements of RC-MRF buildings were analyzed through a comparative study of seismic design codes to evaluate drift requirements for such buildings in six countries. Drift limits are expressed in terms of the maximum allowable fundamental period of vibration, enabling direct comparison of stiffness requirements across codes, soil conditions, and seismic hazards. Results show significant variability of the maximum allowable fundament period for RC-MRF buildings required by the six design codes.