Francisco López-Almansa

Francisco López-Almansa
Universitat Politècnica de Catalunya | UPC · Department of Structural Architecture (EA)

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102
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Publications

Publications (102)
Article
This paper presents a state-of-the-art review on seismic tests of adjustable pallet rack systems: on particular components of racks, subassemblies, full racks and stored goods. The tested particular components are the most critical connections: beams-to-uprights, braces-to-uprights, and floor-to-uprights; subassemblies also include beam-to-upright...
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Base isolation solutions are efficient alternatives for seismic protection of buildings and for enhancing resilient capacity. Currently, seismic isolation is focused principally on the critical infrastructure of public health, transportation, education, etc. Despite these considerations, the current worldwide implementation of this technology is st...
Article
This paper proposes an innovative seismic design approach for shallow rectangular cut-and-cover underground subway or railway stations. The traditional approach is to design rigid frame-like structures by connecting rigidly the main horizontal and vertical structural elements (side walls, top, bottom and intermediate slabs, and central columns); on...
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In this study, with the objective to develop a reliability-based seismic design tool, ductility and dissipated hysteretic energy uniform annual failure rate (UAFR) spectra are obtained and compared using the spectral acceleration at first mode of vibration of the structure Sa(T1) and the well-known spectral shape-based intensity measure INp. Notice...
Article
This paper presents numerical simulations of a suite of cantilever seismic tests of speed-lock connections between beam and upright members of adjustable pallet rack systems. The tested specimens differ in the endplate-to-beam weld beads geometric configuration; the experimental results show that each weld configuration leads to different behavior,...
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This paper presents seismic cantilever monotonic and cyclic tests of speed-lock (boltless) beam-to-upright connections of adjustable pallet rack systems; the objective of the monotonic tests is to obtain the bounds that are employed to define the loading protocol of the subsequent cyclic tests. The beam-to-upright connections consist of welding the...
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In this study, the optimal seismic design of traditional and buckling-restrained braces (BRBs) 3D-reinforced concrete (R/C) buildings is compared. The optimal buildings are obtained through the non-dominated sorting genetic algorithm (NSGA-II) multi-objective technique. Unlike most of this type of studies, the complete design of the 3D frames will...
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This article presents a design method for the improvement of steel structures stability by modifying their structural elements parameters. The available parameters can be selected from a predefined list of stiffness and ultimate capacities for joints and steel members. The proposed procedure is based on determining the critical load factor (ratio b...
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This paper is the result of both experimental and numeric analyses on pallet rack components. Two cyclic testing protocols for beam-end connectors of adjustable racking systems are compared; such experiments are named as “code type” and “Castiglioni”. Both protocols share the same test mock-up: an assembly of a doubly-pinned upright segment with a...
Conference Paper
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This paper discusses the vibrations engendered on a composite (concrete-steel) building slab by a machine for automated production of plastic bags; the slab is rather flexible, lightweight, lightly damped, and rests on steel columns (RSS). That machine has a number of rotating parts; in one of them (for plastic welding), an impact is generated at e...
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Base (seismic) isolation is a promising technology for seismic protection of buildings and other constructions. Nowadays, it is accepted that such a technique is efficient and reliable; however, it has two major limitations: soft foundation soil, and tall buildings. The first issue restrains the seismic isolation spreading, given that soft soil is...
Article
This paper presents a simplified stability-based method for practical structural predesign of down-aisle unbraced frames of selective racks. Given the uniformity of actual racks, only a single upright and its adjoining half beams were modeled, discretized with two-dimensional (2D) beam elements; the flexibility of the upright-beam and upright-floor...
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In this paper, various moment-resisting steel frames (MRSFs) are subjected to 30 narrow-band motions scaled at different ground motion intensity levels in terms of spectral acceleration at first mode of vibration SaT1 in order to perform incremental dynamic analysis for peak and residual interstory drift demands. The results are used to compute the...
Conference Paper
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The energy demand on a given construction is commonly determined, in terms of equivalent velocity, from smoothed design spectra that are ordinarily derived after dynamic analyses on SDOF systems. The application to actual multi-story buildings is far from trivial, given that their behavior must be characterized with MDOF models; in this context, a...
Article
This paper presents a parametrical study on seismic pounding between pairs of RC frames with 3 and 5 stories and aligned slabs. The performance indices are the maximum inter-story drift, absolute acceleration, and story shear force, and the cumulated hysteretic energy. The distinctive features are the selection of parameters and of performance indi...
Conference Paper
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Este artículo describe ensayos dinámicos unidireccionales de golpeteo (impacto) sísmico de una estructura tridimensional de hormigón efectuados en un simulador de terremotos ("shaking table"). Se consideraron dos excitaciones (escaladas con distintos factores): un acelerograma sísmico y una onda armónica. El espécimen analizado es una porción a esc...
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Base seismic isolation is a seismic protection technique for buildings, successful and with great use worldwide. In Colombia there are currently some buildings that incorporate this technique, which have been designed under the requirements of American regulations in force at the time, such is the case of ASCE 7-10. Aforementioned regulation has be...
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There are no local regulations in Colombia for the design of buildings with seismic (base) isolation; the limited number of base isolated buildings that exist in Colombia have been designed with some of the American documents endorsed by the Colombian seismic design code (NSR-10). However, using in Colombia foreign regulations without a detailed an...
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The damping modification factors are utilized to alter the design spectral ordinates for constructions whose damping differs significantly from 5%, this being the level that is routinely considered by most codes. Such factors are habitually evaluated after suites of historical inputs representing the local seismicity. However, such records may not...
Article
Seismic pounding between adjoining buildings frequently causes serious damage; although collision can be avoided with proper separation, can still occur due to code non-fulfillment, loose requirements of old codes, and seismicity underestimation. Inside this context, this work deals with collision between two buildings with aligned slabs. The simul...
Conference Paper
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This paper describes unidirectional shaking table tests on seismic pounding of a 3-D RC building structure. Two inputs were considered: a seismic accelerogram and a harmonic wave. The tested specimen is a one-and-a-half-story 2/5 scaled portion of a RC building structure consisting of waffle slabs and columns. The instrumentation consisted of strai...
Article
In simplified seismic structural analyses, not all the deterioration modes are adequately considered. This work discusses the relation among the hidden failure modes of columns of non-ductile reinforced concrete building frames and their global collapse mechanism. With this aim, a numerically efficient model is developed and implemented in OpenSEES...
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This paper presents a new strut-and-tie model on steel fiber reinforced concrete (SFRC) members under uniform (Saint Venant) torsion. This truss model is intended to reproduce the structural behavior in ultimate limit state, once concrete is cracked. The proposed model is based on previous formulations developed by other researchers; the main novel...
Article
Collision between adjoining buildings with aligned slabs is relevant, since the huge impact forces significantly modify the buildings dynamic behavior. The separation required by the regulations avoids pounding; however, even in recent buildings, impact can occur due to not fulfillment of codes and seismicity underestimation. Given the importance o...
Article
The behavior of reinforced concrete structures under severe demands, as strong ground motions, is highly complex; this is mainly due to the complexity of concrete behavior and to the strong interaction between concrete and steel, with several coupled failure modes. On the other hand, given the increasing awareness and concern on the worldwide seism...
Conference Paper
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RESUMEN Los apoyos elastoméricos son dispositivos empleados ampliamente para aislamiento sísmico de edificaciones. Su gran aceptación puede deberse, entre otros factores, al buen comportamiento evidenciado y a su costo inferior respecto a los aisladores basados en fricción. Dentro de los aisladores elastoméricos, se encuentran principalmente los de...
Article
The behavior of reinforced concrete (RC) structures under severe demands, as strong ground motions, is highly complex; this is mainly due to joint operation of concrete and steel, with several coupled failure modes. Furthermore, given the increasing awareness and concern for the important seismic worldwide risk, new developments have arisen in eart...
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Se considera en este trabajo un edificio sismorresistente aporticado de hormigón armado, de 21 niveles, diseñado para Guayaquil, Ecuador. El objetivo del estudio es desarrollar un procedimiento de diseño de un sistema de disipación pasiva de energía (barras de pandeo restringido) para mejorar los parámetros de respuesta de la estructura original. S...
Conference Paper
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This work presents a parametrical numerical study of pounding between short-to-mid height RC framed buildings with aligned slabs. The study consists in analyzing the dynamic response of four 3 and 5-storey prototype colliding buildings to four representative accelerograms.
Conference Paper
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A 6-story RC building with base isolation using rubber bearings and viscous dampers has been recently built in Shanghai. Since the building is founded on soft soil, concern regarding base isolation suitability arose; even the Chinese design code does not recommend this solution for soft soil. To clarify this issue, nonlinear time-history analyses a...
Conference Paper
Full-text available
A 6-story RC building with base isolation using rubber bearings and viscous dampers has been recently built in Shanghai. Since the building is founded on soft soil, concern regarding base isolation suitability arose; even the Chinese design code does not recommend this solution for soft soil. To clarify this issue, nonlinear time-history analyses a...
Conference Paper
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Nonlinear dynamic analysis of reinforced concrete structures requires a thorough understanding of behavior of structural elements for all levels of performance, especially collapse. Main reason is that reinforced concrete is a mixed material having complicated nonlinear behavior, each element having several coupled degradation modes that influence...
Conference Paper
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This study evaluates the damping coefficient, the effective damping and the energy dissipated of a structure with and without buckling-restrained braces (BRB), subjected to 30 seismic records with different characteristics. These results are compared with the damping coefficient given by an international standard. The structure was modelled with a...
Article
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RESUMEN El aislamiento de base es una exitosa medida de protección sismorresistente para edificios y puentes. En Japón, China, Italia y USA existe una gran cantidad de estructuras aisladas; en Latinoamérica, en Chile, Colombia, Ecuador y Perú se han realizado importantes avances en la implementación de esta tecnología. La mayoría de estos países, c...
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Lorca earthquake (11-05-2011) is most destructive event recorded in Spain, causing nine fatalities and other severe consequences. Its important intensity was rather unexpected, and serious concern arose regarding risk of building stock in Spain. This paper analyzes performance, under Lorca earthquake, of RC buildings with one-way slabs with wide be...
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Buckling-restrained braces are commonly installed in building structures as concentric diagonal or chevron braces to protect the main construction from seismic actions. These elements have shown repeatedly their usefulness for reducing the seismic response, both from theoretical and experimental studies; and a number of practical applications have...
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Se evalúa cualitativamente el riesgo sísmico para un asentamiento informal en Mérida («La Milagrosa») y se proponen estrategias de rehabilitación sísmica. Se eligen cuatro edificios prototipo que representan a la gran mayoría de los de «La Milagrosa». El comportamiento estructural de estos edificios se analiza en profundidad y se concluye que los e...
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This paper describes a new seismic protection system for timber platform frame buildings, either for new construction or retrofit. The system consists in connecting the timber frame to a steel structure that includes hysteretic energy dissipators designed to absorb most of the seismic input energy thus protecting the timber frame and the other stee...
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The existing seismic isolation systems are based on well-known and accepted physical principles, but they are still having some functional drawbacks. As an attempt of improvement, the Roll-N-Cage (RNC) isolator has been recently proposed. It is designed to achieve a balance in controlling isolator displacement demands and structural accelerations....
Conference Paper
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This study aims to investigate the capacity of simplified and advanced numerical models to reproduce the nonlinear monotonic behavior of reinforced concrete framed structures. The considered simplified models are commonly used in earthquake engineering and are based either on concentrated or distributed plasticity. The considered advanced models ar...
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En el laboratorio E-Defense de Japón se ensayó durante 2007 un prototipo de edificio, a escala real, cuya estructura estaba conformada por pórticos metálicos resistentes a momentos. Ese prototipo fue sometido a diferentes escalas de las tres componentes del acelerograma registrado en la estación de Takatori, durante el terremoto de Kobe de 1995. El...
Article
This work presents a numerical model of the cyclic structural behavior of dissipative buckling-restrained braces, commonly used as an alternative to classical concentric braces for seismic protection of building frames and other structures. Such devices are usually composed of a slender steel core embedded in a stockiest casing that is intended to...
Article
The recent earthquake in Lorca (11-05-2011) was the most destructive recorded event in Spain, despite its moderate magnitude. This paper describes the numerical simulation of the dynamic response to the main record of the Lorca earthquake of six 3 and 6-story buildings with one-way concrete slabs with wide beams; these buildings were designed witho...
Article
A number of mid-height steel buildings have been erected recently in Bogotá. Their seismic risk might be high, given the present microzonation of Bogotá and the lack of comprehensive previous studies; noticeably, the response reduction factors were commonly obtained only from general recommendations. The objective of this work is to investigate the...
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This paper describes a numerical study of the efficiency of energy dissipators for seismic protection of thinplated timber buildings; the dissipators are based on plastification of metals and are newly designed. This research belongs to a project to promote the use of timber in seismic regions; this project involves experiments and advanced numeric...
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This work proposes design energy spectra in terms of an equivalent velocity, intended for regions with design peak acceleration 0.3 g or higher. These spectra were derived through linear and nonlinear dynamic analyses on a number of selected Turkish strong ground motion records. In the long and mid period ranges the analyses are linear, given the r...
Article
A significant number of short-to-mid height RC buildings with wide beams have been constructed in areas of moderate seismicity of Spain, mainly for housing and administrative use. The buildings have a framed structure with one-way slabs; the wide beams constitute the distinctive characteristic, their depth being equal to that of the rest of the sla...
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Resumen Este artículo presenta un algoritmo para resolver las ecuaciones del movimiento de edificios de varias plantas que incorporan disipadores de energía friccionales como protección sismorresistente. El comportamiento de los disipadores se representa mediante modelos de Coulomb de rozamiento seco; estos introducen no linealidades severas en el...
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This paper presents the results from unidirectional shaking table tests of two reduced scale steel models of a building frame, with one and two fl oors, respectively. These frames incorporate friction dissipators at every fl oor. The inputs are sine-dwells and artifi cial and registered earthquakes. This study is part of a larger research project a...
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Dans ce travail, une méthodologie simplifiée a été proposée afin d’évaluer la vulnérabilité sismique des bâtiments en béton armé. La démarche s’appuie sur une surface de réponse obtenue à partir de calculs pushover du bâtiment. L’analyse pushover a été effectuée sous le logiciel ZeusNL. Une étude de cas a été réalisée sur un bâtiment type en utilis...
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This work presents a numerical model of the cyclic structural behavior of dissipative buckling-restrained braces, commonly used as an alternative to classical concentric braces for seismic protection of building frames and other structures. Such devices are usually composed of a slender steel core embedded in a stockiest casing that is intended to...
Article
In Latin America there is an urgent need for housing; thus, during the last few years a relevant number of mid-height buildings (usually, up to five stories) with thin RC shear–walls have been constructed for low-cost dwellings in Bolivia, Colombia, Ecuador, Mexico, Peru, Venezuela, and other countries located in seismic-prone regions. These walls...
Article
Seismic risk scenarios are obtained for an informal settlement in Mérida (Venezuela), which is representative of an important number of urban areas in earthquake-prone regions of the developing world. The vulnerability indices of the buildings range between 0.64 and 0.80 on a scale of 0 to 1. In an intensity IX earthquake scenario, more than 32% of...
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Energy input spectra applicable to the seismic design of structures in moderate-to-high seismicity regions are proposed. Such design inputs are derived from the bilinear envelope of individual spectra obtained for 144 ground motions recorded in Colombia. In the short period region the spectra account for the increase of input energy, due to plastif...
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This work deals with short to mid span-length light vaults made of reinforced brick masonry. The research is oriented at proposing semi-prefabrication and construction techniques. Numerical models for predicting the structural behavior of this type of structures are developed. Experimental research is performed with the following three main objecti...
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Seismic retrofit of reinforced concrete pre-code buildings is considered in this work. Nonlinear static pushover analysis is performed by means of specialized finite element software to obtain building response under the code prescribed seismic design load. Performance states that were considered include limitations of the total building roof displ...
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This paper describes structural tests of thin vaults made of reinforced brick masonry. The experiments consist of concentrated loading tests of 14 full-scale laboratory vaults. These vaults are designed to include common situations such as short- to midspan length, low-mid-high rise, rigid-flexible-sliding supports, instantaneous-sustained loading,...
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Evaluation of seismic performance of buildings is considered in this work. Surface response concept is used to derive explicitly the failure function in order to assess reliability of seismic design durability of reinforced concrete buildings. The failure function is considered to be the building maximum inter story displacement. Finite element com...
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This work aims to foster the mass use of buckling restrained braces, mainly in developing countries. To reach this goal, two major objectives are pursued: (i) to contribute to a better understanding of the structural behavior of such dissipators and (ii) to propose cheap and simple yet efficient devices, suitable for the intended applications. Such...
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Reinforced brick masonry has experienced only scarce use as a fully structural material due to, among other reasons, the lack of design criteria and calculation tools allowing a scientific, but also practical, engineering approach to design and assessment. Aiming at contributing to a more widespread use of this material, a simplified method for the...
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This paper presents a new algorithm to simulate the seismic response of N-story building frames incorporating friction energy dissipators; a device per floor is considered. The frames with the dissipators are described by 2D lumped masses models with two degrees of freedom per floor, namely the horizontal displacements of the main structure and of...
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This paper presents a general strategy to select the numerical values of the coefficients defining an uniaxial tensioned concrete equivalent constitutive relationship to simulate, under serviceability conditions, the instantaneous and time-dependent flexural behavior of reinforced and prestressed concrete members. Such values are determined by a le...