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Civil-Comp Proceedings
ISSN 1759-3433
ISSN 1759-3433
CCP: 96
PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
PROCEEDINGS OF THE THIRTEENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping and Y. Tsompanakis
Paper 145
Optimal Design Comparisons for a Prestressed Concrete Beam Designed using the ACI Code, BS8110 and Eurocode Requirements
K.A. Taib1, N. Kasim1,2 and N. Mohamad Basir1
1Department of Civil and Structural Engineering, National University of Malaysia, Bangi, Malaysia
2Public Works Department, Kuala Lumpur, Malaysia
Full Bibliographic Reference for this paper
K.A. Taib, N. Kasim, N. Mohamad Basir, "Optimal Design Comparisons for a Prestressed Concrete Beam Designed using the ACI Code, BS8110 and Eurocode Requirements", in B.H.V. Topping, Y. Tsompanakis, (Editors), "Proceedings of the Thirteenth International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 145, 2011. doi:10.4203/ccp.96.145
Keywords: optimisation, non-linear programming, piecewise linearisation, prestressed concrete beam.
Summary
This paper presents a comparison between the American Concrete Institute (ACI), British Standard (BS) and Eurocode (EC) used for the optimal design of a simply supported prestressed concrete beam. The problem to be solved in this optimisation design involve finding a solution to a non-linear programming problem. In getting the solution to the nonlinear problem, the technique utilised in this research is the piecewise linearisation method. In this approach, the non-linear equations are being simplified to linear ones which then produce a linear programming problem and it is eventually solved using the conventional algorithm. The simply supported prestressed beam involved in this study has an I-cross-sectional area with the flange width, the flange thickness, the web thickness, the beam height, and the area of the prestressing steel as the unknown parameters. The objective of the optimisation is to minimise the weight of the beam which at the same time will optimise the amount of materials used and therefore will produce the most cost-saving beam. The constraints are developed from the design requirements, restrictions and limits as stipulated in the relevant code of practices. The optimisation process involves several iteration cycles, of which each cycle will produce a new and an updated set of values of the variables. The process is terminated and thus the optimisation is achieved once at least the last three values of each of the unknown parameters converge to a single figure. To verify that the values constitute a global minimum, several other initial trial values are being fed into the program and the results obtained are compared with the earlier ones. From the results obtained in this study, it has been found that the prestressed concrete design based upon the ACI code requirements is more economical than that of EC, with BS8110 requirements being the least economical design. The cross-sectional size of the prestressed concrete beam adhering to the ACI code requirements is about 20% improvement in cost saving compared to the beam design that complied to the EC,, whilst the beam designed based upon EC is about 8% more economical than that designed according to the BS 8110 code requirements. These differences are mainly due to the less stringent limiting stresses stipulated in the ACI code compared to those limits imposed by the BS and EC requirements.
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