The analysis of buildings constructed in the last 20 years, designed following modern
standards, may lead to worrying conclusions. Images of out-of-plane expulsions and in-plane
failures of infill walls in recent seismic activities around the world reminded engineers of the
consequences of bad practice, wrong solutions or inadequate design.
With the above in mind, a research program is being conducted as a partnership between
University of Minho and the National Laboratory for Civil Engineering (LNEC), which
includes a shaking table experimental program of framed concrete buildings with masonry
infill walls, reinforced and unreinforced.
Herein the shaking table program and the tested solutions are detailed, along with the
discussion of the results, focusing on the local behaviour of the infills and the global
behaviour of the concrete structure.
The building envelope in Europe is usually made of masonry walls, with enclosure and infill
functions. Masonry walls have a major economical importance and contribute significantly to
the building performance. Even if infill walls have no load-bearing function, they contribute
significantly to the seismic behavior of buildings. Therefore, their adequate structural
performance is needed, avoiding the occurrence of severe in-plane damage, with very large
economical losses, and the out-of-plane expulsion, which additionally represents a large risk
for human life.
Recent earthquake codes in Europe require the safety assessment of non-structural elements
(parapets, veneer masonry walls, infill walls, etc.), when their collapse entails risks for people
or for the main structure. The Eurocode standards, entering the mandatory stage now,
incorporate new requirements to be fulfilled by buildings or their parts. Such is the case of
masonry infilled RC frames whose panels, according to Eurocode 8, are explicitly required to
withstand the out-of-plane movement induced by earthquakes. Appropriate measures should
be taken to avoid brittle failure and premature disintegration of the infill walls, as well as the
partial or total out-of-plane collapse of slender masonry panels.
This paper presents the experimental work and results achieved by applying cyclic out-ofplane
loads to damaged masonry infilled RC frames. The masonry panels were previously
damaged by applying an in-plane cyclic load after which the cyclic out-of- plane loads were
applied. The frames and panels tested follow the traditional Portuguese RC structure
construction system to which different types of reinforcement have been introduced in the
This work presents a brief review on the seismic behavior on non-loadbearing masonry walls used as masonry infills. O Some examples of inefficient performance are shown based on information available of recent earthquakes. Additionally, a literature overview on the techniques for retrofitting existing masonry infills is provided. Finally, alternative braided reinforced composite materials are briefly described and pointed out as an alternative solution for retrofitting masonry infill walls.
The vulnerability of unreinforced masonry walls (URM) under seismic events, causing huge loss of money and human lives, has revealed the enormous need for an efficient strengthening material. In this context, the present paper reports the development of a new reinforcing material for masonry walls based on braided fibrous structures. These fibrous materials were developed through braiding of polyester yarns around a core made of either glass or carbon fiber (core reinforced braid) or without any core (simple braid). Masonry walls were fabricated by placing these braided materials on the surface of clay brick walls in a mesh like configuration and covering with a mortar layer. The flexural behavior of developed masonry walls was compared with URM and walls reinforced with more commonly used glass fiber laminates using the same configuration and process.
Dissertação de mestrado integrado em Engenharia Civil (área de especialização em Perfil de Estrutura e Geotecnia); Atualmente, têm-se registado inúmeros eventos sísmicos que comprovaram a vulnerabilidade
das paredes de enchimento inseridas em pórticos de betão armado. A vulnerabilidade é
essencialmente devida à inexistência de regras de dimensionamento e à não utilização de
detalhes construtivos adequados durante a construção. Por isso, é importante avaliar técnicas
de reforço que possam ser implementadas nas paredes existentes ou a ser construídas, de
maneira a melhorar o seu desempenho, evitando as roturas frágeis, e por outro lado possam
potenciar benefícios ao nível do comportamento global do edifício à ação sísmica.
Este trabalho apresenta uma sugestiva adaptação da técnica de reforço de paredes de alvenaria
designada na literatura inglesa por Textile Reinforced Mortar (TRM) com vista ao
melhoramento das paredes a ações fora do plano. A malha é constituída por varões
compósitos cujo núcleo é ocupado por fibras resistentes que são envolvidas numa estrutura de
entrançado têxtil, sendo uma alternativa ao uso de materiais compósitos aplicados através de
diferentes técnicas. Esta técnica apresenta a vantagem da possibilidade de dimensionamento
da constituição da malha de acordo com determinadas exigências mecânicas...
Dissertação de mestrado integrado em Engenharia Civil (área de especialização em Perfil de Estruturas e Geotecnia); Toda a história humana encontra-se recheada de eventos sísmicos que fustigaram as
populações e a suas cidades de forma mais ou menos grave, dependendo da intensidade
do sismo e da preparação das estruturas para resistirem. Perderem-se nesta luta travada
contra a natureza e a sua implacável redundância um número bastante significativo de
vidas humanas e danos materiais. Portugal, ao longo dos tempos, já prestou o seu tributo
a esta triste causa e poderá no futuro encontrar-se novamente perante um evento sísmico
de grandes proporções. A grande preocupação perante esta eventualidade é claramente o
facto de o património edificado não estar a altura deste evento. Dentro dos edifícios
modernos a maior preocupação, desencadeada em grande parte por recentes sismos em
países vizinhos com resultados catastróficos, é a vulnerabilidade das paredes em
alvenaria, pelo facto de poderem ceder segundo vários tipos de mecanismos de colapso.
O objetivo deste trabalho é contribuir para o conhecimento da engenharia civil sobre o
funcionamento destes elementos em particular e a sua influência no comportamento
global das estruturas. Para tal...
The Commission of the European Communities has recently funded a research project
for the benefit of Associations of Small and Medium Enterprises (SME-AGs), aimed at developing
innovative systems for masonry enclosures. More in general, the project deals with external partition
systems for reinforced concrete framed buildings, such as infill walls and envelopes, and with internal
partitions. The project involves sixteen partners from seven European countries, among which there
are seven universities and research centres, five industrial associations, and four small and medium
enterprises. In the present contribution, an overview of the main objectives and steps of the project is
given. A general summary of the various construction systems that are being developed and designed
is given. The future developments in terms of experimental programs, numerical analyses, and final
expected outcomes of the project are described.
The latest earthquake codes in Europe require the safety assessment of no-structural elements (parapets, masonry wall’s veneer, infill walls, etc.), as their collapse entails risks for people or for the main structure stability. This work made possible th e development of a design method, supported by previous experimental researches by applying cyclic out-of-plane loads to damaged masonry infill in RC frames. Panels tested reproduce Portuguese traditional RC structure construction system and two reinforced solutions were created as innovative solutions. The experimental campaign was carried out in order to determine: masonry properties; out-of-plane panel behaviour with previous in-plane damage; building behaviour subjected to dynamic tests
performed in shaking table. Using finite element method to reproduce experimental tests and to broaden the range of samples it was possible to figure out equations according to parametric analysis which was able to reproduce in-plane and out-plane behaviour leading to an estimated load bearing capacity of each model and to determine frame strength and its stiffness. Those equations permit to design or verify the masonry infill panels in RC frames subjected to seismic loads.
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 was experimentally investigated in this work. Confined underwater blast wave generators (WBWG) allows applying an extremely high rate conversion of the explosive detonation energy into the kinetic energy of a thick water confinement, which, in turn, allows a surface area distribution avoiding 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. Tests were performed in unreinforced walls with 1.7 by 3.5 m, which are 1:1.5 scaled. Besides the usage of pressure and displacement transducers, pictures were recorded with high-speed video cameras to process the deflections and identify failure modes.
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 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. Studies were performed in both unreinforced and reinforced walls with 1.7 by 3.5 meters. Bed joint reinforcement and grid reinforcement were used to strengthen the infill walls. 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. Two different strengthening solutions were studied under blast loading and the results are presented and compared.
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...
Tese doutoramento em "Civil Engineering"; Several factors influence the behaviour of infilled frames, which has been studied in the last fifty years. One might assume that so many years of research in one theme might be enough to nearly fully understand it but this is not the case. The new generation of design standards, namely the Eurocode 8 (EC8), impose the use of reinforcement in these walls in order to prevent a brittle collapse and makes the structural engineer accountable for this requirement, yet it fails to provide enough information for the design. Motivated by the stated reasons, this thesis aims at understanding the seismic behaviour of infill walls when designed following the prescriptions of the EC8, therefore reinforced with bed joint and plaster reinforcement, and compares them to the seismic behaviour of the infill walls considered as a standard in the last three decades in Portugal, which is an unreinforced double leaf. For this purpose, three RC concrete buildings were constructed at a scale of 1:1.5 and tested on the shaking table of the National Laboratory for Civil Engineering, Portugal, each with a different infill solution but with the same geometry. Next, the experimental results were compared, in terms of demand and capacity...
In structural analyses, masonry infill walls are commonly considered to be non structural elements. However, the response of reinforced concrete buildings to earthquake loads can be substantially affected by the influence of infill walls. In this article, an improved numerical model for the simulation of the behavior of masonry infill walls subjected to earthquake loads is proposed and analyzed. First, the proposed model is presented. This is an upgrading of the equivalent bi-diagonal compression strut model, commonly used for the nonlinear behavior of infill masonry panels subjected to cyclic loads. Second, the main results of the calibration analyses obtained with two series of experimental tests are presented and discussed: one on a single frame with one story and one bay tested at the LNEC Laboratory; and the second, on a full-scale four story and three-bay frame tested at the ELSA laboratory.
The presence of masonry infill walls in RC buildings is very common. However, and even today, in the design of new buildings and in the assessment of existing ones, these infill walls are usually considered as non-structural elements and their influence in the structural response is generally ignored. For horizontal loading, infill panels can drastically modify the response, attracting forces to parts of the structure that have not been designed to resist them. This paper presents an improved non-linear numerical simulation model for the influence of the masonry infill walls in the seismic behavior of structure. The model is implemented in the PORANL program. After the implementation and calibration of the proposed masonry model, a series of non-linear dynamic analyses of a building representative of Modern Architecture in Europe were carried out. The main objective was to investigate the behavior of this type of building, and any weakness under seismic loading. The building geometry and the dimensions of the RC elements and infill walls were set in the original project, and confirmed in the technical visits. The building under study has nine storeys and the structure is mainly composed of 12 plane frames oriented in the transversal direction. The building was analyzed with a simplified plane model...
This paper approaches the issue of performance requirements and construction criteria for masonry enclosure and
infill walls. Vertical building enclosures in European countries include, very often, non-loadbearing masonry
walls, using horizontally hollowed clay bricks. These walls are generally supported and confined by a reinforced
concrete frame structure of columns, beams or slabs. Since these walls are commonly considered to be
non-structural elements, and their influence over the structural response is ignored, their consideration in the
design of structures as well as its linkage to the surrounding structure is often negligent or insufficiently detailed.
In consequence, non-structural 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
alert to the need of acceptability criteria for non-structural walls, however they do not specifically indicate how to
prevent collapse and severe cracking and how to enhance the overall stability for severe seismic loading. In this
paper, appropriate measures are proposed to improve both in-plane and out-of-plane integrity and the performance
behaviour under seismic actions of external leaf of double leaf cavity walls as well as premature disintegration of
the infill walls.
It is a common misconception considers that masonry infill walls in structural RC buildings can only increase the overall lateral load capacity, and, therefore, must always be considered beneficial to seismic performance. Recent earthquakes have showed numerous examples of severe damages or collapses of buildings caused by structural response modification induced by the non-structural masonry partitions.
From a state-of-the-art review of the available numerical models for the representation of the infill masonry behaviour in structural response, it was proposed an upgraded model. The proposed model is inspired on the equivalent bi-diagonal compression strut model, and considers the non-linear behaviour of the infill masonry subjected to cyclic loads. The model was implemented and calibrated in a non-linear dynamic computer code, VISUALANL.
In this paper, it is presented the proposed model and the results of the calibration analyses are briefly introduced and discussed.
Cracks that form at the interfaces between masonry structures are common uncontrolled occurrences in buildings. Numerous methods have been proposed by the construction industry to address this problem. Cracks continuously form in the joints between concrete columns and masonry infill walls. In this study, the most common methods for preventing these types of cracks were evaluated in laboratory experiments. Column masonry models were constructed using different types of joints between concrete columns and masonry infill walls, such as steel bars and steel mesh. The efficiency of each type of joint method was evaluated by performing direct tensile tests (pullout tests) on the models and monitoring the evolution of the crack opening in the joint between the column and wall, as a function of load applied to the model. The results from this study indicate that the model composed of "electrowelded wire mesh without steel angles" is the best model for controlling cracking in the joints between concrete columns and masonry infill walls.
Tipo: EUR - Scientific and Technical Research ReportsFormato: CD-ROM
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The purpose of the present study was to investigate possible seismic retrofit options for use in the seismic upgrade of a reinforced concrete frame building with brick masonry infill walls. The building is typical of a Mediterranean European country (e.g., Greece, Italy, Portugal) and while designed according to the state-of-the-art over 40 years ago, it does not meet the present day seismic design requirements and contains a number of now ¿well-recognised¿ seismic design deficiencies and problems. The overall aim of this project was to identify the optimal combination of retrofit options that would enable the building to meet the present-day ¿life-safety¿ performance criteria for buildings subject to a design magnitude earthquake. As part of this study, a detailed review of the broader literature in the area of seismic rehabilitation was undertaken in conjunction with a preliminary assessment of the building¿s seismic capacity.; JRC.G.5-European laboratory for structural assessment
In order to investigate the out-of-plane behaviour of masonry infill walls, quasi-static testing was performed on a masonry infill walls built inside a reinforced concrete frame by means of an airbag system to apply the uniform out-of-plane load to each component of the infill. The main advantage of this testing setup is that the out-of-plane loading can be applied more uniformly in the walls, contrarily to point load configuration. The test was performed under displacement control by selecting the mid-point of the infill as control point. Input and output air in the airbag was controlled by using a software to apply a specific displacement in the control point of the infill wall. The effect of the distance between the reaction frame of the airbag and the masonry infill on the effective contact area was previously analysed. Four load cells were attached to the reaction frame to measure the out-of-plane force. The effective contact area of the airbag was calculated by dividing the load measured in load cells by the pressure inside the airbag. When the distance between the reaction walls and the masonry infill wall is smaller, the effective area is closer to the nominal area of the airbag.
Deformation and crack patterns of the infill confirm the formation of arching mechanism and two-way bending of the masonry infill. Until collapse of the horizontal interface between infill and upper beam in RC frame...
This work intends to present a newly developed test setup for dynamic out-of-plane loading using underWater Blast Wave Generators (WBWG) as loading source. Underwater blasting operations have been, during the last decades, subject of research and development of maritime blasting operations (including torpedo studies), aquarium tests for the measurement of blasting energy of industrial explosives and confined underwater blast wave generators. WBWG allow a wide range for the produced blast impulse and surface area distribution. It also avoids the generation of high velocity fragments and reduces atmospheric sound wave. A first objective of this work is to study the behavior of masonry infill walls subjected to blast loading. Three different masonry walls are to be studied, namely unreinforced masonry infill walls and two different reinforcement solutions. These solutions have been studied previously for seismic action mitigation. Subsequently, the walls will be simulated using an explicit finite element code for validation and parametric studies. Finally, a tool to help designers to make informed decisions on the use of infills under blast loading will be presented.