Assessment on the structural impact of the slabs with joists used in the reinforced concrete structures in Burundi

Abstract

Introduction. This paper addresses the effect of reinforced concrete slabs with joists on the behavior of reinforced concrete buildings.
 
 Materials and methods. Firstly, models of 3-storey, 6-storey, 9-storey and 12-storey buildings were used to determine internal longitudinal forces in the most heavily loaded column on the ground floor and to identify the unloading action of slabs with joists. Secondly, natural periods of the structures were identified by solving the modal equation of vibration in reinforced concrete building models to identify the effect of the unloading action on the flexibility of a reinforced concrete building. Tables and diagrams were used to analyze and interpret the results.
 
 Results. For the ratio of 4.72 between the weight of one square meter of a reinforced concrete slab and the weight of joists used in one square meter of the slab, the unloading effect varies from 15.18 to 16.78 % and from 15.74 to 16.10 % in the columns, respectively, for the ultimate limit state and the serviceability limit state of a reinforced concrete building. The unloading action, induced by the slabs with joists, reduces the flexibility of a reinforced concrete building. Flexibility reductions are illustrated by reductions of the values of the natural periods from 6.74 to 6.98 % for the 3-storey building, from 5.77 to 6.74 % for the 6-storey building, from 5.36 to 6.56 % for the 9-storey building and from 4.26 to 7.84 % for the 12-storey building.
 
 Conclusions. The use of slabs with joists reduces the mass by 15 % and has an unloading effect on a reinforced concrete structure; it also boosts the building flexibility by 6 % and deteriorates the deformability due to the non-linear behaviour of concrete.