Influence of cover thickness in structural frames exposed to fire and service loads

This paper deals with the effect of cover thickness in a reinforced concrete columns of 3-D (three dimensional) frame structures under progressive collapse assessment. The concrete cover protects the reinforcements of structural elements from corrosion and other environmental effects. Even under thermal effects, the concrete cover plays a vital role by preventing the temperature to reach the reinforcements which are present inside. An optimum amount of cover thickness must be provided to the structural elements to withstand sufficient loads and sustain environmental conditions. To study the influence of cover thickness in frame structures, a single-bay single-story 3-D reinforced concrete frame was analyzed under fire scenarios using ABAQUS (FEA). Two nominal cover thicknesses were adopted likely 40 mm and 45 mm for the columns in the frame structure as they are the main load-carrying element. The important structural aspects such as axial load-carrying capacity, thermal expansion, deformation, stiffness, bending moment, and shear force were studied under the considerations of frames with slab and masonry infill wall. It was observed that the nominal cover thickness of 45 mm increases the structural performance and thermal resistance, and can sustain other environmental conditions in a better way.