Fernando Gómez-Martínez

The objective of architecture and engineering cannot be limited only to the elaboration of projects that comply with the limitations of the problem to be solved. It is necessary to go further and choose, from among the multiple design proposals capable of meeting the requirements of the problem, those that comply to a greater extent with a set of suitability criteria (economic, environmental, sustainability, ...). The optimization of a building structure involves analysing a large number of possible structural configurations. The computational burden of these repeated analyses and the need to automate the process require specific calculation and validation tools and highly efficient computing environments. This paper presents the metaheuristic optimization tool VTAM and a set of unique building cases in which VTAM has been able to provide structural solutions that are much more efficient than those built at the time.

According to the Spanish National Annex to Eurocode 8, the use of reinforced concrete wide-beam frames is forbidden for medium and high seismicity. Previously, the Spanish NCSE-02 and Italian NTC codes established a cap to the behaviour factor considering its disadvantages: deficient transmission of forces to the column and lower stiffness, ductility, dissipation, joint resistance and column-to-beam hierarchy. Mediterranean trend is contrary to European and International codes, which allows the use of wide beams of controlled cross-section width and larger columns in order to provide enough lateral stiffness. The review of codes and experimental evidence suggests that the width limit provision is enough to provide proper transmission and dissipation, while two analytic studies show that the increase of overstrength and ductility due to the use of larger columns provides similar global seismic capacity to conventional deep-beam frames. Thus, wide-beam frames could be a feasible structural option in seismic-prone areas. El Anejo Nacional al Eurocódigo 8 prohíbe el uso de vigas planas de hormigón para sismicidad media y alta, y tanto NCSE-02 como la norma italiana NTC impedían su proyecto en ductilidad alta, por desventajas como: transmisión deficiente de esfuerzos al pilar y menor rigidez, ductilidad, disipación, resistencia de nudos y jerarquía pilar-viga. Esta tendencia mediterránea es opuesta a la europea e internacional, donde se permiten las vigas planas con límite de anchura y suficiente sobredimensionando de pilares para garantizar la rigidez lateral. La revisión normativa y experimental sugiere que la limitación de ancho garantiza la transmisión y disipación, mientras que la realización de dos estudios analíticos apunta a que el incremento de sobrerresistencia y ductilidad causados por el engrosamiento de pilares garantiza una capacidad global al menos equiparable a los pórticos de vigas de canto, sugiriendo que el uso de vigas planas podría ser una opción en zona sísmica.

Performance-based seismic codes ensure proper inelastic behaviour of reinforced concrete frames through capacity design, among others. This strategy relies not only on avoiding brittle failures and providing ductility to plastic hinges but also in their distribution within the frame aimed at a greater number of storeys involved in the eventual collapse mechanism. Although codes are generally in agreement to some basic principles in order to ensure capacity design, they show some discrepancies regarding the specific strategies. In this paper, capacity design provisions proposed by some European current codes—Eurocode 8, Italian NTC, and Spanish NCSE-02—are compared, and their effectiveness is discussed. The alternative formulation proposed by Italian code for “strong column–weak beam” turns out to be not suitable under specific circumstances, such as with large gravity loads or significant cantilever deformation in lower storeys. Regarding the value of axial load in columns to be considered for the calculation of shear and moment capacities, provisions in the three codes could eventually cause unconservative design for perimeter columns. The Spanish whole set of provisions is proved to not be effective due to their different fundamentals—they are based on overstrength instead of capacity. For all the three cases, some alternative procedures are suggested in this work.

Current formulations proposed by Eurocode 8 part 3 for the inelastic deformations of existing reinforced concrete members are assessed separately for wide beams (WB) and conventional deep beams (DB). The current approach, based on a large experimental database of members, predicts larger ultimate chord rotation but lower chord rotation ductility for WB rather than for DB despite the similar curvature ductility, due to lower plastic hinge lengths in WB. However, if the data are disaggregated into DB and WB, predicted chord rotations are consistently conservative for DB and not conservative for WB if compared with experimental values, especially at ultimate deformation. Thus, plastic hinge length may be even greater for DB in comparison to WB. Therefore, some feasible corrections of the formulations for chord rotations are proposed, in order to reduce the bias and thus increase the robustness of the model for cross-section shape variability.

Se ofrece una hipótesis de comportamiento de los edificios porticados de hormigón armado de Lorca ante el terremoto de 2011, mediante la aplicación del método FAST, procedimiento de estimación simplificada de la vulnerabilidad a gran escala de dichos edificios contando con la contribución estructural de la tabiquería de fábrica. Este terremoto tuvo una aceleración de pico (PGA) tres veces superior a la básica de proyecto; sin embargo, se caracterizó por la práctica ausencia de colapsos. Se estudian las propiedades del evento sísmico y las particularidades de la edificación para, a través de la aplicación de FAST, tratar de confirmar que dicha ausencia de colapsos pudiera deberse a la contribución estructural de la tabiquería, a pesar de no ser proyectada con ese fin ni regulada por las sucesivas regulaciones normativas. Los resultados obtenidos confirman en buena medida dicha hipótesis, siendo el nivel medio de daño previsto consistente con el escenario real.