Successive sustained loading effect on the long-term deflection of flat slab
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Successive sustained loading effect on the long-term deflection of flat slab A. Fuzail Hashmi1 · M. Shariq1 · A. Baqi1 Received: 26 April 2020 / Accepted: 14 October 2020 © Springer Nature Switzerland AG 2020
Abstract The research work presents the experimental long-term behaviour of reinforced concrete (RC) flat slab specimens at 1:2 scale, subjected to uniformly distributed sustained load in successive phases up to 90 days. The sustained load was applied in two stages, in the first stage, it was 3 kN/m2 for 30 days, whereas in the second stage, it was increased from 3 kN/m2 to 6 kN/m2 for the next 60 days. Age-dependent strength of cement mortar and concrete as used in RC flat slabs has been determined using the method as per the Indian code of practice. The contribution of creep and shrinkage deflection in total deflection for the column strip, middle strip, and cantilever portion has been observed in the range of 34% to 42% at the end of 90 days. After the first 30 days, the mid panel deflection of the flat slabs was larger as compared to column strip and cantilever deflection. At 90 days, the cantilever portion experienced the highest deflection as compared to middle strip and column strip deflection. The measured deflection has also been compared with the IS code procedure and it is found that the code underestimates the long-term deflection of the flat slab. Further, the finite element modelling using ABAQUS has also been carried out on the RC flat slab to validate the experimental results of the same slab within the elastic range. The present study gives an idea to the designer for fixing the thickness of the slab by considering the long-term deflection criteria in the design of the RC flat slab based on its behaviour under sustained loading. Keywords RC flat slab · Sustained loading · Long-term deflection · Numerical modelling
1 Introduction The reinforced concrete (RC) flat slab is a thin structure concerning its span length and the design is mainly governed by stiffness rather than strength. The deflection in the RC slab mainly depends on the non-linear and inelastic properties of concrete. Nowadays, the flat slab floor system is considered one of the most popular forms of construction due to its easiness in construction with a comparatively lower cost. The engineers and designers are mainly focusing to design efficient slab which has larger spans. Flat slabs have a variety of practical applications in various fields such as in different floor situations, ramps, irregular column layouts, etc. The advantage of
the flat slab over other slab includes flexibility in plan and column layout, lesser depth, reduced dead weight, and faster rate of construction. The flexibility of flat slab construction results in economical construction with more freedom to the architect and designers. It provides easy formwork arrangement, plain ceiling surface with a better diffusion of light and larger head-room or shorter storey height with pleasing appearance e.g. large halls, library, commercial building, etc. Few exp
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