Optimum design of prestressed steel beams via genetic algorithm

Abstract

The objective of this article is to present an optimization problem formulation to reduce the total structural cost of prestressed doubly-symmetric and monosymmetric I-shaped steel simply supported beams with straight tendons. The optimization problem was implemented via MATLAB's native Genetic Algorithm. The validation and evaluation processes adopted two examples from literature. The design method follows the Brazilian standard NBR 8800:2008 for the Ultimate and Serviceability Limit States. The best result was found for a monosymmetric case by up to 20.00% and 25.70%. Saving in material weight and installation of tendons, without exceeding the security limits, was also effective. Furthermore, the results presented an efficient alternative for structural engineering, providing a significant model for similar analyzes.

Optimizing the CO2 emission of composite steel‐concrete beams with external prestressing

“…The second stage aimed to analyze our optimization technique. As in Netto, Calenzani, and Alves [17], prestressed steel beams were used as reference to compare optimizations by analyzing their CO2 emissions. Although the selected example is not a prestressed composite beam, we managed to validate the selected optimization technique.…”

“…Figure 8 shows the total emission normalized in relation to the result by Netto, Calenzani, and Alves [17]. The genetic algorithm with an unshored structure was the model that generated the best solution, reducing total emissions by 57.2%.…”

“…Among the existing optimization algorithms, the genetic algorithm (GA) proposed by Holland [15] and the particle swarm algorithm (PSO), originally proposed by Kennedy and Eberhart [16], stand out for their scope and wide use. In recent years, several structural optimization studies with GA and PSO have been developed, such as Netto, Calenzani, and Alves [17], which assessed prestressed steel beams; Breda, Pietralonga, and Alves [18], which evaluated composite beams with flat web profiles; Erdal, Doan, and Saka [19], which analyzed composite cellular steel beams; Senouci and Al-Ansari [20] and Govindaraj and Ramasamy [21], which aimed at optimizing a large range of structures; and Arpini and Alves [22] and Poitras, Lefrançois and Cormier [23], which appraised composite floor systems.…”

“…For a comparative analysis of the optimization process, the prestressed steel beam (Figure 7) optimized by Netto, Calenzani, and Alves [17] was analyzed as a prestressed steel-concrete composite beam; In this study, we re-optimized the steel beam. The input data considered were 150-kN 3-point loads applied at 11, 12.5, and 14 meters from the left support; with a 3-kN/m overload; a 12.86-kN/ permanent load m; a 15-kN/m serviceability overload; a 25-m L; 15.2-mm tendons set 100 mm below the inferior flange bottom; a 345-MPa fy; and a 205000-MPa E. The analysis in this study considered that the load corresponding to the weight of the slab would be included in the 12.86-kN/m value of the permanent load.…”

“…The best result for the doubly symmetric profile consisted of a profile with a 1580mm height, 410-mm upper and lower flanges, whose thickness and web equaled 22.4mm and 12.5mm, respectively, and nine 15-mm diameter tendons. Table 3 shows a comparative analysis of the optimization result of the prestressed composite beam in relation to the result by Netto, Calenzani, and Alves [17] for a pure steel beam. Table 4 shows the obtained emission, displacement, compression, and traction stresses values.…”