Space structures for sports buildings: Tien T. Lan and Yuan Zhilian (eds). Elsevier Applied Science Publishers, The Netherlands, 1987

This book review states that parts of this interesting volume may prove useful as a reference for designers and researchers in the field, though it lacks somewhat in unity and various important topics are not covered.

Mejora del comportamiento t��rmico de los morteros de cal aditivados y su empleo en la rehabilitaci��n de inmuebles = Improvement of thermal behaviour of additived lime mortars and their use in rehabilitation of buildings

La envolvente de la edificaci��n es la responsable de equilibrar el intercambio energ��tico entre el interior y el exterior, por lo tanto cualquier actuaci��n encaminada a la reducci��n del consumo energ��tico ha de establecer, como uno de sus objetivos prioritarios, la mejora del comportamiento de la misma. Las edificaciones anteriores a 1940 constituyen la mayor parte de las existentes en ��reas rurales y centros urbanos. En ellas, la repercusi��n de la fachada sobre las transmitancias globales pone de manifiesto la necesidad de intervenci��n. Sin embargo, su elevada inercia t��rmica y los importantes saltos t��rmicos caracter��sticos de gran parte de Espa��a plantean la importancia de que aqu��lla se efect��e por el exterior. A tal respecto, la falta de disponibilidad de espesor suficiente para implantar sistemas tipo SATE deriva en que, frecuentemente, la ��nica soluci��n viable sea la de aislar por el interior perdiendo con ello la capacidad de acumulaci��n t��rmica del muro y con el asociado riesgo de condensaciones. La amplia tradici��n en el empleo de revestimientos, especialmente en base de cal, permiten que ��stos sean utilizados no s��lo como elemento est��tico o de protecci��n de la obra de f��brica antigua sino tambi��n para la mejora del comportamiento t��rmico del soporte, si se aprovecha el mecanismo de transmisi��n t��rmica por radiaci��n. ��ste es el objetivo de la presente Tesis Doctoral en la que se estudia la modificaci��n de las propiedades radiantes de los morteros de revestimiento para la mejora de la eficiencia energ��tica de las construcciones hist��ricas, principalmente las constituidas por muros monol��ticos, aunque podr��a ser de aplicaci��n a otro tipo de construcciones compuestas por diversas capas. Como punto de partida, se estudi�� y revis�� la documentaci��n disponible sobre las investigaciones de las tres ��reas cient��fico-tecnol��gicas que convergen en la Tesis Doctoral: rehabilitaci��n, material y comportamiento t��rmico, a partir de lo cual se comprob�� la inexistencia de estudios similares al objeto de la presente Tesis Doctoral. Complementariamente, se analizaron los revestimientos en lo concerniente a los materiales que los constituyen, la composici��n de las mezclas y caracter��sticas de cada una de las capas as�� como al enfoque que, desde el punto de vista t��rmico, se estimaba m��s adecuado para la obtenci��n de los objetivos propuestos. Bas��ndonos en dichos an��lisis, se preseleccionaron ochenta materiales que fueron ensayados en t��rminos de reflectancia y emisividad para elegir cuatro con los que se continu�� la investigaci��n. ��stos, junto con la cal elegida para la investigaci��n y el ��rido marm��reo caracter��stico de la ��ltima capa de revestimiento, fueron caracterizados t��rmicamente, de forma pormenorizada, as�� como qu��mica y f��sicamente. Los fundamentos te��ricos y los estudios preliminares desarrollados con distintos materiales, en estado fresco y endurecido, fueron empleados en la dosificaci��n de componentes de las mezclas, en dos proporciones distintas, para el estudio del efecto del agregado. ��stas se ensayaron en estado fresco, para comprobar su adecuaci��n de puesta en obra y prever su VI adherencia al soporte, as�� como en estado endurecido a 28 y 90 d��as de curado, para conocer las propiedades que permitieran prever su compatibilidad con aqu��l y estimar el alcance de la reducci��n de transferencias t��rmicas lograda. Adem��s, se estudiaron las caracter��sticas generales de las mezclas que sirvieron para establecer correlaciones entre distintas propiedades y entender los resultados mec��nicos, f��sicos (comportamiento frente al agua) y energ��ticos. Del estudio conjunto de las distintas propiedades analizadas se propusieron dos mezclas, una blanca y otra coloreada, cuyas caracter��sticas permiten garantizar la compatibilidad con la obra de f��brica antigua, desde el punto de vista f��sico y mec��nico, y preservar la autenticidad de los revestimientos, en cuanto a la t��cnica de aplicaci��n tradicional en sistemas multicapa. El comportamiento t��rmico de las mismas, sobre una obra de f��brica de 40 cm de espesor, se estim��, en estado estacionario y pseudo-transitorio, demostr��ndose reducciones del flujo t��rmico entre 16-48%, en condiciones de verano, y entre el 6-11%, en invierno, en funci��n de la coloraci��n y de la rugosidad de la superficie, en comparaci��n con el empleo de la mezcla tradicional. Por lo que, se constata la viabilidad de los materiales compuestos propuestos y su adecuaci��n al objetivo de la investigaci��n. VII ABSTRACT The envelope is responsible for balancing the energy exchange between the inside and outside in buildings. For this reason, any action aimed at reducing energy consumption must establish, as one of its key priorities, its improvement. In rural areas and urban centers, most of the constructions were built before 1940. In them, the impact of the fa��ade on the global transmittance highlights the need for intervention. However, its high thermal inertia and fluctuation of temperatures in the majority of Spain bring up that it should be placed outside the insulation. In this regard, the lack of availability of enough thickness to implement systems such as ETICS results in that often the only viable solution is to isolate the interior, losing thereby the wall���s heat storage capacity with the associated risk of condensation. The tradition in the use of renders, especially lime-based, allows us to use them not only as an aesthetic element or to protect the ancient masonry, but also for improved thermal performance of the support by taking advantage of the heat transfer mechanism by radiation. This is the aim of this Doctoral Thesis in which the modification of the radiative properties of lime mortars for renders to improve the energy efficiency of historic buildings, mainly composed of monolithic walls, is studied, although it could be applied to other structures composed of several layers. As a starting point, the available literature in the three scientific-technological areas that converge at the Doctoral Thesis: rehabilitation, material and thermal behaviour, was reviewed, and confirmed the absence of researches similar to this Doctoral Thesis. Additionally, the renders were studied with regard to the materials that constitute them, the composition of the mixtures and the characteristics of each layer, as well as to the approach which, from a thermal point of view, was deemed the most suitable for achieving the objectives sets. Based on thre aforementioned analysis, eighty materials tested in terms of reflectance and emissivity were pre-selected, to choose four with which the research was continued. Common marble sand, used in the last layer of the renders, together with the appointed materials and hydrated lime were characterized thermally, in detail, as well as chemically and physically. The theoretical bases and preliminary studies with different materials, in fresh and hardened state, were used in the dosage of the composition of the mixtures. In order to study their effect they were used in two different proportions, that is, ten mixtures in total. These were tested in their fresh state to evaluate their setting-up suitability and foresee their adhesion to the support, as well as in their hardened state, at 28 and 90 days of curing, to establish the properties which enabled us to anticipate their compatibility with the old masonry walls and estimate the scope of the reduction of heat transfers achieved. In addition, the general characteristics of the mixtures used to establish correlations and to understand the mechanical, physical and energy results were studied. Two mixtures, one white and one colored, were proposed as the result of the different properties analysed, whose characteristics allow the guarantee of mechanical and physical compatibility VIII with the old masonry and preserve the authenticity of the renders. The thermal behavior of both, applied on a masonry wall 40 cm thick, was estimated at a steady and pseudo-transient state, with heat flow reductions between 16-48% during summertime and 6-11% during wintertime, depending on the color and surface roughness, compared to the use of the traditional mixture. So, the viability of the proposed composite materials and their fitness to the aim of the research are established.

Dynamique des structures. Vuln��rabilit�� aux b��timents. Construction parasismique

La le��on s'addresse �� la comprehension du comportement des b��timents soumis �� l'acc��leration s��ismique, et pr��sente une introduction au comportement dynamique de oscillateurs (un ou plusieurs d��gr��s de libert��), du comport��ment hyst��r��tique des structures (selon modes de dissipation) et aux param��tres s��ismiques relevants �� la conception parasismique, notamment aux spectres de r��ponse et de d��mande, et sa relation avec la capacit�� de la structure (courbe de capacit��) o�� on peut identifier les niveaux de dommage -ou les crit��res de performance- pour des intensit��s s��ismique pr��vues au projet. Elle consid��re aussi les m��thodes de d��finition et d��termination de la vuln��rabilit��, fa��e aux s��ismes, des diff��rentes typologies constructives, avec l'inclusion finale des typologies pour les sist��mes de contreventement et recomandations vis��es �� ��viter aux m��mes la concentration de dommage d'origine s��ismique. Lecture's goal focuses in the understanding of the behaviour of buildings under seismic excitation. It presents an introduction of dynamics (single or multiple degrees of freedom oscillators) and the hysteretic behaviour of ductile structures, introducing the seismic parameters relevant to the structural design, mostly in the context of response and demand spectra and their relations with capacity curves of structures. On the capacity curve obtained in pushover analysis, points representing the design objectives in terms of performance levels can be identified and related with seismic demand. Lecture deals also with methods on vulnerability analysis for building construction typologies and the behaviour (and related recommendations) of seismic resistant structural typologies, having the distribution of dissipative energy and damage in mind.

Shaking table tests of structures with hysteretic dampers: experimental results vs. prediction using non-linear static methods

The use of seismic hysteretic dampers for passive control is increasing exponentially in recent years for both new and existing buildings. In order to utilize hysteretic dampers within a structural system, it is of paramount importance to have simplified design procedures based upon knowledge gained from theoretical studies and validated with experimental results. Non-linear Static Procedures (NSPs) are presented as an alternative to the force-based methods more common nowadays. The application of NSPs to conventional structures has been well established; yet there is a lack of experimental information on how NSPs apply to systems with hysteretic dampers. In this research, several shaking table tests were conducted on two single bay and single story 1:2 scale structures with and without hysteretic dampers. The maximum response of the structure with dampers in terms of lateral displacement and base shear obtained from the tests was compared with the prediction provided by three well-known NSPs: (1) the improved version of the Capacity Spectrum Method (CSM) from FEMA 440; (2) the improved version of the Displacement Coefficient Method (DCM) from FEMA 440; and (3) the N2 Method implemented in Eurocode 8. In general, the improved version of the DCM and N2 methods are found to provide acceptable accuracy in prediction, but the CSM tends to underestimate the response.

Seismic vulnerability analysis of wide-beam buildings in Spain

A number of short-to-mid height RC buildings with wide beams have been constructed in moderate-seismicity areas of Spain. The seismic behavior in the direction of the wide beams appears to be deficient because of low lateral strength, low ductility of the wide beams, big strut compressive forces inside the column-beam connections, and unreliable contribution of the spandrel zones of the wide beams. In the orthogonal direction, the behavior is worse since only the joists and the fa��ade beams contribute to the lateral resistance. The objective is to assess the seismic capability of these structures; further research will involve proposing retrofit strategies. The research approach consists of selecting a number of representative buildings and evaluating their vulnerability by code-type, push-over and dynamic analyses. The cooperation of the masonry infill walls is accounted for. The main conclusion is that the seismic behavior of these buildings is inadequate in most of the situations.

Damage assessment on building structures subjected to the recent near-fault earthquake in Lorca (Spain)

The city of Lorca (Spain) was hit on May 11th 2011 by two consecutive earthquakes with 4.6 and 5.2 Mw respectively, causing casualties and important damage in buildings. Lorca is located in the south-east region of Spain and settled on the trace of the Murcia-Totana-Lorca fault. Although the magnitudes of these ground motions were not severe, the damage observed was considerable over a great amount of buildings. More than 300 of them have been demolished and many others are being retrofitted. This paper reports a field study on the damage caused by these earthquakes. The observed damage is related with the structural typology. Further, prototypes of the damaged buildings are idealized with nonlinear numerical models and their seismic behavior and proneness to damage concentration is further investigated through dynamic response analyses.

Crack width control in RC elements with recycled steel fibres and applications to integral structures : theoretical and experimental study

El presente trabajo trata de elementos reforzados con barras de armadura y Fibras Met��licas Recicladas (FMR). El objetivo principal es mejorar el comportamiento a fisuraci��n de elementos sometidos a flexi��n pura y a flexi��n compuesta, aumentando en consecuencia las prestaciones en servicio de aquellas estructuras con requerimientos estrictos con respecto al control de fisuraci��n. Entre ��stas ��ltimas se encuentran las estructuras integrales, es decir aquellas estructuras sin juntas (puentes o edificios), sometidas a cargas gravitatorias y deformaciones impuestas en los elementos horizontales debidas a retracci��n, fluencia y temperatura. Las FMR son obtenidas a partir de los neum��ticos fuera de uso, y puesto que el procedimiento de reciclado se centra en el caucho en vez que en el acero, su forma es aleatoria y con longitud variable. A pesar de que la eficacia del fibrorefuerzo mediante FMR ha sido demostrada en investigaciones anteriores, la innovaci��n que representa este trabajo consiste en proponer la acci��n combinada de barras convencionales y FMR en la mejora del comportamiento a fisuraci��n. El objetivo es por tanto mejorar la sostenibilidad del proyecto de la estructura en HA al utilizar materiales reciclados por un lado, y aumentando por el otro la durabilidad. En primer lugar, se presenta el estado del arte con respecto a la fisuraci��n en elementos de HA, que sucesivamente se ampl��a a elementos reforzados con barras y fibras. Asimismo, se resume el m��todo simplificado para el an��lisis de columnas de estructuras sin juntas ya propuesto por P��rez et al., con particular ��nfasis en aquellos aspectos que son incompatibles con la acci��n de las fibras a nivel seccional. A continuaci��n, se presenta un modelo para describir la deformabilidad seccional y la fisuraci��n en elementos en HA, que luego se ampl��a a aquellos elementos reforzados con barras y fibras, teniendo en cuenta tambi��n los efectos debidos a la retracci��n (tension stiffening negativo). El modelo es luego empleado para ampliar el m��todo simplificado para el an��lisis de columnas. La aportaci��n consiste por tanto en contar con una metodolog��a amplia de an��lisis para este tipo de elementos. Seguidamente, se presenta la campa��a experimental preliminar que ha involucrado vigas a escala reducida sometidas a flexi��n simple, con el objetivo de validar la eficiencia y la usabilidad en el hormig��n de las FMR de dos diferentes tipos, y su comportamiento con respecto a fibras de acero comerciales. Se describe a continuaci��n la campa��a principal, consistente en ensayos sobre ocho vigas en flexi��n simple a escala 1:1 (variando contenido en FRM, ��/���s,eff y recubrimiento) y doce columnas a flexi��n compuesta (variando contenido en FMR, ��/���s,eff y nivel de fuerza axil). Los resultados obtenidos en la campa��a principal son presentados y comentados, resaltando las mejoras obtenidas en el comportamiento a fisuraci��n de las vigas y columnas, y la rigidez estructural de las columnas. Estos resultados se comparan con las predicciones del modelo propuesto. Los principales par��metros estudiados para describir la fisuraci��n y el comportamiento seccional de las vigas son: la separaci��n entre fisuras, el alargamiento medio de las armaduras y la abertura de fisura, mientras que en los ensayos de las columnas se ha contrastado las leyes momento/curvatura, la tensi��n en las barras de armadura y la abertura de fisura en el empotramiento en la base. La comparaci��n muestra un buen acuerdo entre las predicciones y los resultados experimentales. Asimismo, se nota la mejora en el comportamiento a fisuraci��n debido a la incorporaci��n de FMR en aquellos elementos con cuant��as de armadura bajas en flexi��n simple, en elementos con axiles bajos y para el control de la fisuraci��n en elementos con grandes recubrimientos, siendo por tanto resultados de inmediato impacto en la pr��ctica ingenieril (dise��o de losas, tanques, estructuras integrales, etc.). VIIIComo punto final, se presentan aplicaciones de las FMR en estructuras reales. Se discuten dos casos de elementos sometidos a flexi��n pura, en particular una viga simplemente apoyada y un tanque para el tratamiento de agua. En ambos casos la adicci��n de FMR al hormig��n lleva a mejoras en el comportamiento a fisuraci��n. Luego, utilizando el m��todo simplificado para el an��lisis en servicio de columnas de estructuras sin juntas, se calcula la m��xima longitud admisible en casos t��picos de puentes y edificaci��n. En particular, se demuestra que las limitaciones de la pr��ctica ingenieril actual (sobre todo en edificaci��n) pueden ser aumentadas considerando el comportamiento real de las columnas en HA. Finalmente, los mismos casos son modificados para considerar el uso de MFR, y se presentan las mejoras tanto en la m��xima longitud admisible como en la abertura de fisura para una longitud y deformaci��n impuesta. This work deals with elements reinforced with both rebars and Recycled Steel Fibres (RSFs). Its main objective is to improve cracking behaviour of elements subjected to pure bending and bending and axial force, resulting in better serviceability conditions for these structures demanding keen crack width control. Among these structures a particularly interesting type are the so-called integral structures, i.e. long jointless structures (bridges and buildings) subjected to gravitational loads and imposed deformations due to shrinkage, creep and temperature. RSFs are obtained from End of Life Tyres, and due to the recycling process that is focused on the rubber rather than on the steel they come out crooked and with variable length. Although the effectiveness of RSFs had already been proven by previous research, the innovation of this work consists in the proposing the combined action of conventional rebars and RSFs to improve cracking behaviour. Therefore, the objective is to improve the sustainability of RC structures by, on the one hand, using recycled materials, and on the other improving their durability. A state of the art on cracking in RC elements is firstly drawn. It is then expanded to elements reinforced with both rebars and fibres (R/FRC elements). Finally, the simplified method for analysis of columns of long jointless structures already proposed by P��rez et al. is resumed, with a special focus on the points that conflict when taking into account the action of fibres. Afterwards, a model to describe sectional deformability and cracking of R/FRC elements is presented, taking also into account the effect of shrinkage (negative tension stiffening). The model is then used to implement the simplified method for columns. The novelty represented by this is that a comprehensive methodology to analyse this type of elements is presented. A preliminary experimental campaign consisting in small beams subjected to pure bending is described, with the objective of validating the effectiveness and usability in concrete of RSFs of two different types, and their behaviour when compared with commercial steel fibres. With the results and lessons learnt from this campaign in mind, the main experimental campaign is then described, consisting in cracking tests of eight unscaled beams in pure bending (varying RSF content, ��/���s,eff and concrete cover) and twelve columns subjected to imposed displacement and axial force (varying RSF content, ��/���s,eff and squashing load ratio). The results obtained from the main campaign are presented and discussed, with particular focus on the improvement in cracking behaviour for the beams and columns, and structural stiffness for the columns. They are then compared with the proposed model. The main parameters studied to describe cracking and sectional behaviours of the beam tests are crack spacing, mean steel strain and crack width, while for the column tests these were moment/curvature, stress in rebars and crack with at column embedment. The comparison showed satisfactory agreement between experimental results and model predictions. Moreover, it is pointed out the improvement in cracking behaviour due to the addition of RSF for elements with low reinforcement ratios, elements with low squashing load ratios and for crack width control of elements with large concrete covers, thus representing results with a immediate impact in engineering practice (slab design, tanks, integral structures, etc.). Applications of RSF to actual structures are finally presented. Two cases of elements in pure bending are presented, namely a simple supported beam and a water treatment tank. In both cases the addition of RSF to concrete leads to improvements in cracking behaviour. Then, using the simplified model for the serviceability analysis of columns of jointless structures, the maximum achievable jointless length of typical cases of a bridge and building is obtained. In XIIparticular, it is shown how the limitations of current engineering practice (this is especially the case of buildings) can be increased by considering the actual behaviour of RC supports. Then, the same cases are modified considering the use of RSF, and the improvements both in maximum achievable length and in crack width for a given length and imposed strain at the deck/first floor are shown.

Vulnerability analysis of RC buildings with wide beams located in moderate seismicity regions

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 slab, thus providing a flat lower surface, convenient for construction and the layout of facilities. Seismic behavior in the direction of the wide beams appears to be deficient because of: (i) low lateral strength, mainly because of the small effective depth of the beams, (ii) inherent low ductility of the wide beams, generated by high amount of reinforcement, (iii) the big strut compressive forces developed inside the column-beam connections due to the low height of the beams, and (iv) the fact that the wide beams are wider than the columns, meaning that the contribution of the outer zones to the resistance of the beam-column joints is unreliable because there is no torsion reinforcement. In the orthogonal direction, the behavior is worse since the only members of the slabs that contribute to the lateral resistance are the joists and the fa��ade beams. Moreover, these buildings were designed with codes that did not include ductility requirements and required only a low lateral resistance; indeed, in many cases, seismic action was not considered at all. Consequently, the seismic capacity of these structures is not reliable. The objective of this research is to assess numerically this capability, whereas further research will aim to propose retrofit strategies. The research approach consists of: (i) selecting a number of 3-story and 6-story buildings that represent the vast majority of the existing ones and (ii) evaluating their vulnerability through three types of analyses, namely: code-type, push-over and nonlinear dynamic analysis. Given the low lateral resistance of the main frames, the cooperation of the masonry infill walls is accounted for; for each representative building, three wall densities are considered. The results of the analyses show that the buildings in question exhibit inadequate seismic behavior in most of the examined situations. In general, the relative performance is less deficient for Target Drift CP (Collapse Prevention) than for IO (Immediate Occupancy). Since these buildings are selected to be representative of the vast majority of buildings with wide beams that were constructed in Spain without accounting for any seismic consideration, our conclusions can be extrapolated to a broader scenario.

Assessment of expected damage on buildings subjected to Lorca earthquake through an energy-based seismic index method and nonlinear dynamic response analyses

The city of Lorca (Spain) was hit on May 11th, 2011, by two consecutive earth-quakes of magnitudes 4.6 and 5.2 Mw, causing casualties and important damage in buildings. Many of the damaged structures were reinforced concrete frames with wide beams. This study quantifies the expected level of damage on this structural type in the case of the Lorca earth-quake by means of a seismic index Iv that compares the energy input by the earthquake with the energy absorption/dissipation capacity of the structure. The prototype frames investigated represent structures designed in two time periods (1994���2002 and 2003���2008), in which the applicable codes were different. The influence of the masonry infill walls and the proneness of the frames to concentrate damage in a given story were further investigated through nonlinear dynamic response analyses. It is found that (1) the seismic index method predicts levels of damage that range from moderate/severe to complete collapse; this prediction is consistent with the observed damage; (2) the presence of masonry infill walls makes the structure very prone to damage concentration and reduces the overall seismic capacity of the building; and (3) a proper hierarchy of strength between beams and columns that guarantees the formation of a strong column-weak beam mechanism (as prescribed by seismic codes), as well as the adoption of counter-measures to avoid the negative interaction between non-structural infill walls and the main frame, would have reduced the level of damage from Iv=1 (collapse) to about Iv=0.5 (moderate/severe damage)

Determination of the influence of specific building regulations in smart buildings

The automation of domestic services began to be implemented in buildings since the late nineteenth century, and today we are used to terms like ���intelligent buildings���, ���digital home��� or ���domotic buildings���. These concepts tell us about constructions which integrate new technologies in order to improve comfort, optimize energy consumption or enhance the security of users. In conjunction, building regulations have been updated to suit the needs of society and to regulate these new facilities in such structures. However, we are not always sure about how far, from the quantitative or qualitative point of view, legislation should regulate certain aspects of the building activity. Consequently, content analysis is adopted in this research to determine the influence of building regulations in the implementation of new technologies in the construction process. This study includes the analysis of different European regulations, the collection and documentation of such guidelines that have been established and a study of the impact that all of these have had in the way we start thinking an architectural project. The achievements of the research could be explained in terms of the regulatory requirements that must be taken into account in order to achieve a successful implementation of a home automation system, and the key finding has been the confirmation of how the design of smart buildings may be promoted through specific regulatory requirements while other factors, such as the global economic situation, do not seem to affect directly the rate of penetration of home automation in construction.

A methodology to calibrate structural finite element models for reinforced concrete structures subject to blast loads

Civil buildings are not specifically designed to support blast loads, but it is important to take into account these potential scenarios because of their catastrophic effects, on persons and structures. A practical way to consider explosions on reinforced concrete structures is necessary. With this objective we propose a methodology to evaluate blast loads on large concrete buildings, using LS-DYNA code for calculation, with Lagrangian finite elements and explicit time integration. The methodology has three steps. First, individual structural elements of the building like columns and slabs are studied, using continuum 3D elements models subjected to blast loads. In these models reinforced concrete is represented with high precision, using advanced material models such as CSCM_CONCRETE model, and segregated rebars constrained within the continuum mesh. Regrettably this approach cannot be used for large structures because of its excessive computational cost. Second, models based on structural elements are developed, using shells and beam elements. In these models concrete is represented using CONCRETE_EC2 model and segregated rebars with offset formulation, being calibrated with continuum elements models from step one to obtain the same structural response: displacement, velocity, acceleration, damage and erosion. Third, models basedon structural elements are used to develop large models of complete buildings. They are used to study the global response of buildings subjected to blast loads and progressive collapse. This article carries out different techniques needed to calibrate properly the models based on structural elements, using shells and beam elements, in order to provide results of sufficient accuracy that can be used with moderate computational cost.

Piezoelectric sensing and non-parametric statistical signal processing for health monitoring of hysteretic dampers used in seismic-resistant structures

The paper proposes a new application of non-parametric statistical processing of signals recorded from vibration tests for damage detection and evaluation on I-section steel segments. The steel segments investigated constitute the energy dissipating part of a new type of hysteretic damper that is used for passive control of buildings and civil engineering structures subjected to earthquake-type dynamic loadings. Two I-section steel segments with different levels of damage were instrumented with piezoceramic sensors and subjected to controlled white noise random vibrations. The signals recorded during the tests were processed using two non-parametric methods (the power spectral density method and the frequency response function method) that had never previously been applied to hysteretic dampers. The appropriateness of these methods for quantifying the level of damage on the I-shape steel segments is validated experimentally. Based on the results of the random vibrations, the paper proposes a new index that predicts the level of damage and the proximity of failure of the hysteretic damper