Optimum Design of Box and T Shape Pre-stressed Concrete Beam with Genetic Algorithm

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Abstract

Pre-stressed concrete beams are frequently used in structures such as bridges etc. The theory for analysis and design of these structures has been developed in recent decades. Furthermore; optimization in design has recently been considered with the aim of energy conservation. Optimization of pre-stressed concrete beams (OPCB) with box and T shapes is presented in this paper. For this purpose Genetic Algorithm Optimization method is used in which design properties such as cost, weight and section characteristics are included in the objective function. Furthermore; the cost objective function represented by the overall cost of the OPCB in terms of concrete, pre-stressing steel, mild steel, formwork and construction pre-stressing and placing of concrete is minimized subjected to 14 reliability constraints and 4 geometrical constraints. The design variables consist of three or five dimensions relative to section shape (T and box shapes respectively), two items that represent the percentage and amount of pre-stressing and three or seven items for tendon profile related to number of spans. Analysis is performed using a computer program with an automated design optimization package in which new exact equations are developed to calculate pre-stressing force losses analytically. Using this program, the design of an optimized pre-stressed concrete beam can be carried out according to the provisions specified by the British Standard (BS8110 and BS5400).

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