Volume 11, No. 4, 2017
Received: 2017/08/27, Accepted:
Authors:
Abubakar Idris; Aliyu Ibrahim;
Abstract:
This work focused on the development of Iso-safety (Isolated Safety) design charts for flexural design of singly reinforced concrete sections at predefined reliability levels in accordance with EN 1992-1-1 (2004) design criteria. Constitutive models for reinforcing steel and concrete were selected in accordance with the EN 1992-
1-1 design requirements and subsequently the flexural limit state function was derived. Charts were developed for the flexural design of rectangular reinforced concrete sections with respect to the position of neutral axis ( ) for each concrete grade (fck) and steel grade (fyk). Uncertainties in loading and geometrical properties were
obtained and a program was developed taking into consideration Eurocode 2 design requirements. A safety index β value of 1.81 was achieved for various points on each of the generated curves using First Order Reliability Method (FORM). Reliability-based design charts, called Iso-safety charts, were produced to target safety indices; βT of 3.3, 3.8 and 4.3 as the minimum recommended for the three failure consequence classes by EN 1990 (2002). This recommendation shows that EN 1992-1-1 design of singly reinforced concrete sections considering flexural failure with a safety index value of 1.81 provides designs that are below the recommended target safety indices. A singly reinforced concrete section was there after being designed using the charts and it was shown that for the same loading and geometrical considerations, the area of flexural
reinforcement required increased by 40%, 55% and 75% over EN 1992-1-1 design for corresponding target safety indices of 3.3, 3.8 and 4.3, respectively.
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