Effects of Pit-Sand on Resistance Capacities of Reinforced Concrete Space Framed Structures

Abstract

This paper used the existing formulae in estimating resistance parameter of reinforced concrete structure to assess the effect of concrete produced from pit-sand in Akure metropolis, on the resistance parameters of a collapsed building in Oba-Ile, Akure. Site inspections were carried out on the collapsed building, and concrete samples were taken. Both destructive and non-destructive methods were used to determine the structure’s concrete strength. The number of reinforcements in each structural element was determined by exposing them. Resistance parameters such as moments of resistance for slab (M RS ), for beam (MR B ) and shear capacity (V C ) of the structural elements were estimated using existing formulae and, compare the results with the structure’s actual resistance parameters. The average concrete strength was 8.5 N/mm 2 which was less than 20 N/mm 2 , the prescribed concrete strength for construction of the building. The estimated resistance parameters M RS , M RB and V C based on 8.5 N/mm 2 concrete strength are 18.2 kN · m, 46.3 kN · m and 64.4 kN respectively. Also the estimated resistance parameters M RS , M RB and V C based on 20 N/mm 2 concrete strength are 20.6 kN · m, 54.1 kN · m and 90.73 kN respectively. The actual M RS , M RB and V C at collapse were 6.67 kN · m, 13.6 kN · m and 18.88 kN respectively. The existing formulae for predicting resistance parameters did not give accurate resistance parameters for the building at collapse. The collapse of the building was by shear failure, since shear failure capacity will be reached first before any of the other resistance parameters.