Minimum Cost Design of PSC Post-Tensioned I-Girder for Short to Medium Span Bridges
Devashree Sawant1, N. G. Gore2, P. J. Salunke3

1Miss Devashree Uday Sawant, M.E. Structure student, Department of Civil Engg.,  M.G.M. College of Engineering & Tech., Kamothe, Navi Mumbai (Maharashtra), India.
2Prof. N. G. Gore, (Guide) Department of Civil Engg., M.G.M. College of Engineering & Tech., Kamothe, Navi Mumbai (Maharashtra), India.
3Prof. P. J. Salunke, (Guide) Department of Civil Engg., M.G.M. College of Engineering & Tech., Kamothe, Navi Mumbai (Maharashtra), India.

Manuscript received on 20 March 2014 | Revised Manuscript received on 25 March 2014 | Manuscript published on 30 March 2014 | PP: 112-115 | Volume-3 Issue-1, March 2014 | Retrieval Number: A1036033114/2014©BEIESP
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Abstract: Post-tensioned simply supported pre-stressed concrete (PC) I-girder bridges are widely used bridge system for short to medium span (20m to 50m) highway bridges due to its moderate self -weight, structural efficiency, ease of fabrication, low maintenance etc. In order to compete with steel bridge systems, the design of PC I-girder Bridge system must lead to the most economical use of materials. In this study, minimum cost design approach of a post-tensioned PC I-girder is presented. The objective is to minimize the total cost in the design process of the bridge system considering the cost of materials. For a particular girder span and bridge width, the design variables considered for the cost minimization of the I-girder, are top flange width, girder depth, bottom flange thickness, number of cables i.e. X1, X2, X3, X4 respectively. Design constraints for the optimization are considered according to AASHTO (American Association of State Highway and Transportation Officials), IS: 1343-1980 and Geometrical design requirements. The optimization problem is solved by having a combination of continuous, discrete and integer sets of design variables and multiple local minima. For An optimization purpose Matlab Software with SUMT (Sequential Unconstrained Minimization Technique) is used that is capable of locating directly with high probability the minimum design variables. The proposed cost optimization approach is validated which leads to a considerable cost saving while resulting in feasible design.
Keywords: Constraints, Design variables, Pre-stressed concrete, Structural optimization.

Scope of the Article: Low-power design