Search

The external envelope walls of a significant percentage of the residential building stock in Southern European countries is commonly constituted by infill masonry walls. However, thousands of square meters of this masonry wall typology presents severe issues of cracking and instability, related to the incorrect and deficient support conditions of the outer brick panel of the double-leaf wall solution. In this work, an experimental campaign divided in two phases has been performed to evaluate the effectiveness of two different remedial wall ties retrofitting techniques (Solution A and Solution B) used for double leaf horizontally hollowed clay brick masonry fa&ccedil, ades. The first phase of the experimental campaign was performed on 120 isolated specimens of horizontally hollowed clay bricks, resorting to post- and pre-NP EN 771-1 brick exemplars (that is, new and pre-existent aged bricks, respectively), as well as on 4 square wallettes, with a side length of 1.20 m, considered as representative of a real scale scenario, for evaluating the two remedial wall ties retrofitting techniques. The second phase of the experimental campaign was performed to fully characterize the different failure types as well as the slipping phenomena observed in the first phase of the experimental campaign, focusing solely on the retrofitting technique Solution B and comprises 24 tests performed on isolated specimens, resourcing to new and pre-existent aged bricks as well. The results obtained by the use of these techniques revealed an average anchorage strength value ranging from 0.25 to 2.5 kN for each tested tie-bar. Solution B reveals an increase of double of the anchorage strength value in comparison to Solution A. In this sense, the global results revealed a suitable applicability of both retrofit studied solutions.

Infill walls, which are generally assumed as dead loads in building design, affect the lateral resistance, stiffness, and energy consumption of the frames. Investigations conducted after earthquakes show that the infill walls, whose effects are neglected in the design, can change the earthquake behavior of the structure and cause unforeseen damages in the buildings and even collapses in some cases. In order to match the behavior of designed and built frames, the technique of isolating the infill wall from the RC frame with non-interacting infill was adopted. In this study, in-plane behavior of bare, traditionally infilled frames and a frame with non-interacting infill wall were investigated experimentally under reversed cycling loads, then their numerical models were calibrated. As a result, in contrast to the traditionally infilled frame, it has been seen that the frame with non-interacting infill behaves close to the bare frame in the initial drifts and maintains its lateral resistance without a damage until further drifts. Therefore, it has been found that constructing the infill wall with non-interacting joint improves the in-plane behavior.

Lateral stiffness provided by infill walls to the building structures is generally neglected in designs. Infill walls, which are only included in the calculations as dead loads, significantly affect the lateral resistance, stiffness and energy dissipation of the frames. Both the studies in the literature and the infill wall damages observed after the earthquake support the existence of these unforeseen effects in the design. It is an important problem to reflect the infill wall effects to the site application as designed. In this study, the solution to isolate the infill walls from the load-carrying frames is adopted. Three different flexible connection elements designed in this context were examined experimentally and numerically, their in-plane behavior was compared with bare and traditionally infilled frames. As a result of the study, it was observed that the frames with flexible connections behaved close to the bare frame in the initial drifts, unlike the fully infilled frame behavior, which significantly lost its lateral resistance in the initial drifts, and continued its lateral resistance without any damage until further drifts. It is thought that the flexible connections will be an important development in terms of compatibility of design and site applications.

Masonry infill walls are commonly used in the frames of reinforced concrete (RC) buildings around the world. The seismic performance of these buildings is strongly affected by the presence of the infill walls and partitions, as shown by the post-earthquake damage in many cases. The effect of these components is particularly important for RC frame constructions underdesigned for seismic actions that usually are characterized by deformable frames magnifying the contribution of the infill walls to the seismic response. Also the flexibility of the floors could be influenced by the collaboration of the infill walls to the transversal stiffness of the building. The paper addresses the seismic assessment of a typical infilled RC frame building designed only for gravity loads in the 1960s in the Southern of Italy that currently is a high-seismic zone. The structural identification of the building based on ambient vibration test has been already done pointing out the significant role of infill walls and partitions through the updating of the numerical model. Based on the results of the calibrated model, the effect of the floor flexibility on the dynamic behavior of the structure is discussed, and the seismic capacity at life safety limit state (LSLS) is assessed by means of the linear dynamic analyses. The effects of the infill walls on the seismic performance of the building are discussed in detail considering a strengthening solution that involves the infill panels as masonry walls cut from the RC columns to avoid the local interaction but strengthened by composite grids in mortar matrix (FRCM).

In Italy, most of the residential buildings (77%) were constructed before 1981, when only 25% of the national territory was classified as seismic. Further, the first provisions addressing thermal performance criteria were introduced in 1991, when about 88% of the existing Italian buildings had already been realized. Therefore, the Italian building stock is characterized by a large deficit in terms of both seismic capacity and thermal insulation. The large number of buildings having inadequate performance, both seismic and thermal, calls for rehabilitation interventions that are based on an integrated and sustainability-oriented approach. In the paper, the influence on seismic performance deriving from some retrofitting techniques, generally adopted to enhance the thermal performance of infill walls, has been evaluated. A common residential RC building representative of existing buildings designed only for vertical loads has been studied. The seismic performances have been evaluated through Incremental Dynamic Analyses (IDA). A first comparison is related to a thermal retrofitting intervention made by replacing the existing masonry infill walls with new elements that are able to ensure an adequate thermal protection. Further, a retrofitting intervention based on the “double skin” technique, where new infilled RC frames are added and connected to the existing ones, has been investigated in terms of seismic and thermal performance.

The paper describes the results of quasi-static tests performed on a real-scale adobe masonry infill wall partitioned into sub-panels by means of the introduction of vertical wooden planks, acting as sliding joints. The specimen was tested both in-plane and out-of-plane, exhibiting good performance in terms of both stability against out-of-plane actions and in-plane deformation capacity and damage control. The results emphasize the applicability of adobe masonry as material for infill walls in seismic prone regions, coupling the good structural response with the inherent positive performance in terms of indoor ambient comfort and production sustainability demonstrated in literature.

In 1999 Marmara and 2011 Van earthquakes in Turkey, majority of the existing buildings either sustained severe damage or collapsed. These buildings include masonry infill walls in both the interior and exterior R/C frames. The material of the masonry infill is the main variant, ranging from natural stones to bricks and blocks. It is demanding to design these buildings for satisfactory structural behavior. In general, masonry infill walls are considered by its weights not by interaction between walls and frames. In this study, R/C buildings with infill walls are considered in terms of structural behavior. Therefore, 5 and 8-story R/C buildings are regarded as the representative models in the analyses. The R/C representative buildings, both with and without infill walls were analyzed to determine the effects of structural behavior change. The differences in earthquake behavior of these representative buildings were investigated to determine the effects of infill walls leading structural capacity. First, pushover curves of the representative buildings were sketched. Aftermath, time history analyses were carried out to define the displacement demands. Finally, fragility analyses were performed. Throughout the fragility analyses, probabilistic seismic assessment for R/C building structures both with and without infill walls were provided. In this study, besides the deterministic assessment methodology, a probabilistic approach was followed to define structural effect of infill walls under seismic loads. © 2013 Techno-Press, Ltd.

University of Minho is a partner of the INSYSME research project (Innovative Systems for earthquake resistant masonry enclosures in RC buildings), funded by the European Commission. The main aims of this project are to study new systems for masonry infill walls, which combine simplicity with low cost, and to propose recommendations and calculation procedures for their design to seismic actions, filling an existing gap in current regulations. At University of Minho a new construction system for masonry enclosures was developed, being composed of a new commercial unit and vertical steel reinforcement placed in ceramic brick frogs, connected to top and bottom beams. In this paper, the experimental work developed at the University of Minho for validation of the solution proposed for masonry infills is presented and discussed. The experimental validation process of the solution for the masonry enclosure walls was based on in-plane and out-of-plane static cyclic tests. The tests were carried in four specimens built at reduced scale (1:1.5). In order to assess the in-plane behaviour, two specimens have been tested. The first test was done, in a specimen with masonry infill, until maximum drift. In the second test, only reinforcement concrete frame was tested, to access the contribution of masonry infill. For out-of-plane direction two specimens were tested one without reinforcement, and other with reinforcement. The out-of-plane test was carried using an airbag system. In this case only positive direction was considered. In-plane and out-of-plane tests were performed under displacement control according to a load pattern defined based on the FEMA 461 recommendations., FCT -Fuel Cell Technologies Program(606229)

Tese de doutoramento em Engenharia Civil, The work presented in this thesis was developed at the Department of Civil Engineering of University of Minho. This work involves experimental and numerical campaigns and intends to give a contribution for a better understanding of the effect of explosions. Blast loading is a subject of much actuality and considerable lack of expertise. Europe has never been so rich and safe, where the violent years of the first half of the 20th century lead to an unprecedented period of peace and stability. Despite the terrorist decades, e.g. connected to ETA and IRA in Europe, the attacks of Madrid (2004), London (2005) and worldwide (New York, Oklahoma, Mumbai) had a major psychological effect in the societies. Clearly, the understanding about the effect of blast loading in structures and their subsystems saves lives and reduces damage in buildings. The Buncefield explosion (2005) resulted in tremendous damage to the outlying area and huge fires involving 23 large oil fuel tanks. Experimental and finite element analyses are carried out for the static and dynamic response of lightweight metal boxes that are similar to the steel junction boxes on the site of this explosion. During the Buncefield Explosion Mechanism Phase I research, the lightweight steel junction boxes on the site located within the area covered by the gas cloud are compared with similar boxes tested under a range of different loading conditions using hydrostatic pressure, gas explosions and high explosive charges. The residual plastic deformations for these boxes are recorded and used to validate a finite element based modelling approach. The predicted pressure-time history is in reasonably good agreement with the measurements. Further parametric studies are then conducted to produce iso-deformation curves which can be used in accident investigations to back track the blast loading from structure deformations. Investigation of the dynamic properties of construction materials is critical for structural engineering. The strain rate effect influences the properties on most constructions materials. This effect on materials such as concrete or steel has been intensively investigated. However, such studies on masonry materials such as clay bricks cannot be found in the open literature easily. Understanding the strain rate effect on masonry materials is important for proper modelling and design of masonry structures under high velocity impacts or blast loads. This work aims to study the behaviour of masonry and its individual components in compression at different strain rates. A Drop Weight Impact Machine is used at different heights and weights introducing different levels of strain rate. The strain rate effect on the compressive strength, Young’s modulus, strain at peak strength and compressive fracture energy is determined from the experimental results. Empirical relations of dynamic increase factors (DIF) for these material properties are also presented. The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The dynamic behaviour of masonry infill walls subjected to dynamic out-of-plane loading is experimentally investigated in this work. In the present study water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, are used as confined underwater blast wave generators (WBWG). Tests are performed in unreinforced walls with 1.7 by 3.5 m, which are 1:1.5 scaled, and the results presented. These results are used to calibrate numerical models using ABAQUS Explicit dynamics, allowing a detailed study on this kind of masonry panels under dynamic out-of-plane loading in the form of parametric studies. Two different reinforcement solutions are studied in the numerical model and the results are presented. The results are used to create pressure-impulse (P-I) diagrams which can help the designer to estimate the response of these elements under different loading conditions. Protection is not an absolute concept and there is a level of protection where the cost of the protection provided with respect to the cost of potential loss is in balance. On one hand, protection cannot offer full guarantee of safety and, on the other hand, too much protection is a waste of resources with regard to what is expected to be saved. The purpose of protective construction is to improve the probability of survival of people and other contents in a given facility for a given threat, to an adequate level. In order to improve this probability, one must first understand the threat and accordingly analyse the facility. In this work risk assessment is addressed and applied to a large Public Transport Operator. This assessment allows identifying potentially critical infrastructure, which are studied and its structural security is evaluated for different scenarios regarding blast loading., O trabalho apresentado nesta tese foi desenvolvido no Departamento de Engenharia Civil da Universidade do Minho. Este trabalho envolve campanhas experimentais e numéricas, e pretende ser uma contribuição para uma melhor compreensão do efeito das explosões. As explosões são um tema atual e de conhecimento muito reduzido. A Europa nunca esteve tão rica e segura, sendo que os anos violentos da primeira metade de século 20 conduziram a um período sem precedentes de paz e estabilidade. Apesar de décadas de terrorismo, por exemplo da ETA e do IRA na Europa, os ataques de Madrid (2004), Londres (2005) e em todo o mundo (Nova York, Oklahoma, Mumbai) têm tido um impacto psicológico muito elevado nas sociedades. Claramente, a compreensão sobre o efeito da ação das explosões nas estruturas e nos seus subsistemas salva vidas e reduz os danos nas construções. A explosão de Buncefield em 2005 resultou num dano impressionante nas proximidades e fogos imensos em 23 grandes depósitos de combustível. Campanhas experimentais e numéricas são executadas para estudar o comportamento dinâmico de caixas metálicas semelhantes às encontradas em Buncefield. Durante a investigação do incidente de Buncefield, as caixas presentes na área coberta pela nuvem de vapor são comparadas com caixas semelhantes sujeitas a diferentes tipos de ações, usando pressão hidrostática, explosões de gás e explosivos de grau militar. As deformações permanentes são registadas e usadas para validar modelos numéricos com recurso ao Método dos Elementos Finitos. A previsão dos perfis de pressão é adequada aos dados obtidos durante a investigação do acidente. Os modelos numéricos obtidos são usados para criar curvas de iso-dano que podem ser usadas para auxiliar em investigações pós-acidente relacionando a deformação nessas subestruturas com o perfil de pressões atuante. A investigação das propriedades dinâmicas dos materiais de construção é considerada crítica para a engenharia. O efeito das velocidades de deformação influencia as propriedades da maior parte dos materiais de construção. Este efeito tem sido estudado em betão e aço. No entanto, estudos sobre este efeito em alvenaria, e seus componentes, são reduzidos na literatura. A compreensão destes efeitos em alvenaria é crucial para uma modelação e dimensionamento adequado destes materiais quando sujeitos a impactos ou explosões. Este trabalho pretende estudar o comportamento da alvenaria, e dos seus componentes individuais, em compressão a diferentes velocidades de deformação. Para o efeito uma torre de queda é usada com diferentes alturas e pesos de impacto, introduzindo no sistema diferentes velocidades de deformação. O efeito das velocidades de deformação é determinado pelos resultados experimentais, e estudado para a resistência à compressão, módulo de elasticidade, extensão em compressão máxima e energia de fratura em compressão. Relações empíricas sob a forma de fatores de incremento dinâmico (FID) são apresentadas para estas propriedades mecânicas. A vulnerabilidade da envolvente em alvenaria dos edifícios quando sujeita a explosões é considerada crítica devido ao risco de perdas humanas. O comportamento de paredes de enchimento quando sujeitas a ações dinâmicas fora do seu plano é investigado neste trabalho. São usados reservatórios de água com uma carga explosiva no seu centro para atuar como geradores de onda de choque. São executados testes em paredes de enchimento de alvenaria com 1.7×3.5 metros (escala de 1:1.5). Os resultados obtidos são usados para calibrar modelos numéricos com recurso ao software ABAQUS Explicit. Isto permite uma análise alargada do comportamento destes elementos quando sujeitos a ações dinâmicas fora do plano, sob a forma de estudos paramétricos. Duas soluções de reforço são estudas numericamente e os resultados apresentados. Os resultados obtidos nas tarefas anteriores são usados para criar diagramas de pressãoimpulso (P-I) que auxiliam os técnicos que pretendam estimar a resposta deste tipo de paredes quando sujeitas a diferentes tipos de ação. A proteção não é um conceito absoluto e há um nível de proteção em que o custo da proteção em relação às perdas possíveis está em equilíbrio. Por um lado, não é possível garantir proteção e segurança absoluta, por outro lado, demasiada proteção pode ser um desperdício de recursos em relação ao que se espera proteger. O objetivo de proteção, no caso de estruturas, é melhorar a probabilidade de sobrevivência dos seus ocupantes e seu conteúdo, para uma ameaça específica, obtendo uma probabilidade adequada. Para isto ser possível é necessária uma compreensão detalhada da ameaça e da estrutura. Neste trabalho a avaliação de risco é estudada e uma metodologia é aplicada a um Operador de Transportes Públicos. Esta avaliação de risco permite identificar infraestruturas críticas, tendo sido avaliada a segurança estrutural de uma destas a diferentes cenários de explosão., This experimental work was performed under the financial support of the research project CH-SECURE funded by the Portuguese Foundation of Science and Technology (FCT). The financial support provided by the Portuguese Foundation of Science and Technology (FCT) under the PhD grant SFRH/BD/45436/2008, is also gratefully acknowledged.

The vulnerability of the masonry envelop under blast loading is considered critical due to the risk of loss of lives. The behaviour of masonry infill walls subjected to dynamic out-of-plane loading was experimentally investigated in this work. Using confined underwater blast wave generators (WBWG), applying the extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, allowed a surface area distribution avoiding also the generation of high velocity fragments and reducing atmospheric sound wave. In the present study, water plastic containers, having in its centre a detonator inside a cylindrical explosive charge, were used in unreinforced masonry infills panels with 1.7m by 3.5m. Besides the usage of pressure and displacement transducers, pictures with high-speed video cameras were recorded to enable processing of the deflections and identification of failure modes. Additional numerical studies were performed in both unreinforced and reinforced walls. Bed joint reinforcement and grid reinforcement were used to strengthen the infill walls, and the results are presented and compared, allowing to obtain pressure-impulse diagrams for design of masonry infill walls., This work was performed under Project CH-SECURE, with reference PTDC/ECM/120118/2010, funded by the Portuguese Foundation of Science and Technology - FCT. The authors acknowledge the support. The first author also acknowledges the support from his PhD FCT grant with the reference SFRH/BD/45436/2008.

The performance of various composite materials applied to strengthen hollow masonry panels under out-of-plane actions is compared here. The strengthening solutions belong to three reinforcement Externally Bonded (EB) wet lay-up systems: (i) bidirectional composite meshes applied with inorganic matrices, i.e., Textile Reinforced Mortars (TRM); unidirectional composite textiles applied with (ii) inorganic matrices, i.e., Steel Reinforced Grouts (SRG), or (iii) organic (epoxy) matrices, i.e., Fibre Reinforced Polymers (FRP), Steel Reinforced Polymers (SRP) and Natural FRPs. Carbon FRP, flax and hemp NFRP, and basalt and glass-based TRM were examined. As inorganic matrix, a cement-based mortar was used for TRMs; in the case of SRGs, comparisons with a magnesia-based matrix were also carried out. Twenty-seven specimens were subjected to simplified four-point monotonic bending tests, aimed at reproducing in the laboratory the failure condition of infill masonry walls under out-of-plane actions. The results are compared in terms of failure mode and mechanical improvement, and provide an analytical evaluation of moment–curvature behaviour according to bilinear laws.

The objective of this paper is to study the effects of structural non-linear behaviour on Floor Response Spectra (FRS) of existing reinforced concrete frames. This study examines how the FRS vary with the level of post-elastic behaviour in buildings of different number of stories and masonry infill wall configurations. The effect of damping modelling assumptions is also investigated. Differences and similarities with findings from the literature are discussed. On the basis of the obtained results, a commentary on the adequacy of basic assumptions used in predictive equations proposed by different seismic codes is offered.

This paper discusses the issue of performance requirements and construction criteria for masonry enclosure and infill walls. Vertical building enclosures in European countries are very often constituted by non-load-bearing masonry walls, using horizontally perforated clay bricks. These walls are generally supported and confined by a reinforced concrete frame structure of columns and beams/slabs. Since these walls are commonly considered to be nonstructural elements and their influence on the structural response is ignored, their consideration in the design of structures as well as their connection to the adjacent structural elements is frequently negligent or insufficiently detailed. As a consequence, nonstructural elements, as for wall enclosures, are relatively sensitive to drift and acceleration demands when buildings are subjected to seismic actions. Many international standards and technical documents stress the need for design acceptability criteria for nonstructural elements, however they do not specifically indicate how to prevent collapse and severe cracking, and how to enhance the overall stability in the case of moderate to high seismic loading. Furthermore, a review of appropriate measures to improve enclosure wall performance and both in-plane and out-of-plane integrity under seismic actions is addressed.

In designing and implementing earthquake resistance for clay block masonry infill integrated into a structural frame, with or without openings, the infill wall should be taken into account. Presumably, simplified models, acceptable for practical use, could be applied for that purpose. However, the anisotropy of clay block masonry units, masonry mortar joints, and unit contact properties as well as the high variance of material properties limit their ability to describe the actual earthquake resistance of clay block masonry. In this work, we consider a three-dimensional micromodel of a clay block masonry wall, with the inclusion of masonry unit anisotropy and masonry mortar joint and unit contact properties. To avoid the excessive calibration procedure of the wall micromodel, the wall constituents were calibrated separately beforehand, which resulted in a high correlation of computational and experimental results without further need for calibration. Using a calibrated micromodel, the influence of variance in material properties on the wall’s resistance was investigated. The influence was showed not to be negligible, which may significantly affect the presumed behaviour of the whole structure.

Annual Meeting Architecural Institute of Japan, September 1-3, 2005, Osaka, Japan