OPTIMIZACIÓN DE LOSAS ALVEOLARES PRETENSADAS EN SITUACIÓN ACCIDENTAL DE INCENDIO

Abstract

[EN] Prestressed hollow core slabs are precast concrete elements used for floors when large span and high load level are required, due to their high ratio between height and available span. Hollow core slabs are manufactured in industrial facilities, therefore finding optimal geometries and reinforcement configurations are feasible thanks to their repeatable production process. Few research works have been focused on geometry and reinforcement optimization for hollow core slabs, and no one was related to their optimization under fire conditions. Based on what was observed in the state of the art of this research, this paper applies the theory called simulated annealing optimization (Simulated Annealing, SA). This theory tries to minimize an objective function based on a cost structure. This heuristic technique was chosen to reach the aim of the work using the maximum number of variables to define the cross-section and the reinforcement configuration. All the Spanish standards requirements were cheeked. The experimental plan is based on finding optimal geometries of hollow core slabs considering requirements in the fire situation for 30, 60, 90 and 120 minutes of fire resistant ratio, compared with more representative commercial manufacturer series. The study was carried out using 2.0 kN / m2 of dead load and 5.0 kN / m2 of live load. To achieve the objective, the SA algorithm was calibrated, establishing a movement of 6 variables with an initial temperature calculated for an initial acceptance of 60%. A Markov chain length of 1000 was established, with a stop condition that freezes the algorithm when the last Markov chain obtain an accepted solution ratio lower than 0.8%. The cooling schedule fixed was a temperature decrease of 0.95% from the previous temperature step. A sensibility analysis was performed, studying the influence on the solution of the concrete price fluctuations, the strength of the materials used, as well as the layout and number of hollows. Hollows geometry was also varied depends on the manufacturing technology employed. As a result, hollow core slab designs which fulfill with all standard requirements, at room temperature and in the fire situation, were obtained. These new designs can reach an economic reduction cost from 7.21 % to 21.45 %.; [ES] Las placas alveolares pretensadas son elementos prefabricados de hormigon armado pretensado, que se utilizan como elemento resistentes en forjados unidireccionales, cuando se requiere cubrir grandes luces y con un nivel de carga elevado, ya que la relacion canto del elemento con respecto a la luz cubierta es muy alto. Las placas alveolares son productos industrializados para edificacion, por tanto, su materializacion se realiza en instalaciones industriales, lo que hace que la busqueda de geometrias y armados optimos, para la misma, sea factible dada la repetitividad en la produccion. Son pocos los trabajos de investigacion que se han encaminado hacia la busqueda de la optimizacion geometrica y del armado de las placas alveolares, y ninguna hacia la…