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
The stresses induced in a structure by a seismic action have a low probability of occurrence and their magnitude is such that the structure is forced beyond the ultimate limit state. The effective standards in Portugal, and the ones that will be effective shortly, consider the possibility of a seismic action in all the territory, fact that has been neglect by designers and authorities in the last years. This new standard, Eurocode 8, Design of structures for earthquake resistance, defines new standards for infill walls, imposing the use of reinforcement but failing to give detailed information besides the type of reinforcement. Furthermore, the structural designer is the responsible for these non-structural elements. Therefore, with the goal of contributing to the creation of simple design rules for these infills, a shaking table test program of reinforced concrete frame buildings with infill walls, reinforced and unreinforced, will be carried out. Predeceasing these tests, different numerical simulations of the buildings were carried out, with two main objectives: i) understand the behavior of the structure when subjected to a seismic action, in order to more accurately define the experimental program; ii) using different computational programs and numerical elements to perform static non-linear analyses...
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.
Half-timbered buildings represent an important historical heritage in many countries. They are diffused in various regions for different reasons, such as availability of materials, to lighten a structure, low cost and the strength they offer, and as a construction element able to resist seismic actions. This latter issue is the research topic analysed here, as half-timbered buildings have been specifically used in reconstruction plans as earthquake-resistant buildings
in many countries, such as Portugal, India, Greece, etc. The aim of this paper is to study the behaviour under cyclic loading of such half-timbered walls, with typical connections, materials and geometries encountered in existing buildings.
Traditionally, different types of infill could be applied to half-timbered walls depending on the country, namely brick masonry, rubble masonry, hay, mud, etc. The focus of this paper is to study and compare the seismic behaviour of the walls considering two different infill typologies, as well as the possibility of having no infill, i.e. considering only the timber frame. Cyclic test were performed on traditional walls and their behaviour was studied in terms of ultimate capacity, deformability, energy dissipation and stiffness.; Fundação para a Ciência e a Tecnologia (FCT)
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...
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 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...
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.
Reinforced concrete (RC) buildings in Nepal are constructed as RC frames with masonry infill panels.
These structures exhibit a highly non-linear inelastic behaviour resulting from the interaction between
the masonry infill panels and the surrounding frames. In this context, the paper presents an extensive
case study of existing RC-framed buildings in a high seismic risk area in Nepal. A sensitivity analysis
of the structures with masonry infill is performed. For this, the influence of different material
properties is studied, namely diagonal compressive stress, modulus of elasticity and tensile stress of
masonry infill panels. Result shows the influence on the structural behaviour particularly by variation
of the diagonal compressive strength of infill masonry panels.
Water production in the early life of Coal Seam Gas (CSG) recovery makes these reservoirs different from conventional gas reservoirs. Normally, a large amount of water is produced during the early production period, while the gas-rate is negligible. It is essential to drill infill wells in optimum locations to reduce the water production and increase the gas recovery. To optimise infill locations in a CSG reservoir, an integrated framework is developed to couple the reservoir flow simulator (ECLIPSE) and the genetic algorithm (GA) optimisation toolbox of (MATLAB). In this study, the desired objective function is the NPV of the infill drilling. To obtain the economics of the infill drilling project, the objective function is split into two objectives. The first objective is the gas income; the second objective is the cost associated with water production. The optimisation problem is then solved using the multi-objective solver. The economics of the infill drilling program is investigated for a case study constructed based on the available data from the Tiffany unit in San Juan basin when gas price and water treatment cost are variable. Best obtained optimal locations of 20 new wells in the reservoir are attained using this optimisation framework to maximise the profit of this project. The results indicate that when the gas price is less than $2/Mscf...
The aim of this thesis is to investigate innovate approaches that can help to improve methane recovery and production rate from coalbed methane (CBM) reservoirs. The results of two following subjects are presented and discussed. First, thermally enhanced gas recovery from gassy coalbeds is introduced. Second, an integrated reservoir simulation-optimization framework is developed and employed to optimize infill well locations across coalbed reservoirs. When coalbed methane and geothermal activities coexist in the same field, coalbeds can be thermally treated prior to the gas production using available underground geothermal resources. Feasibility of this method is investigated both using methane sorption tests on Australian coal samples at different temperatures and also reservoir simulation. The impact of temperature elevation on methane sorption and diffusion in coal is investigated by running sorption experiments on two the Australian coal samples using a manometric adsorption apparatus. Experiments are performed to indicate that how the difference between original reservoir pressure and critical desorption pressure is decreased at elevated reservoir temperatures. Lower pressure gradient is required to extract methane from coalbed when it is thermally treated prior to gas production. Following the experimental study...
Many existing flat-plate buildings are seismically deficient and pose a threat to life safety if subjected to ground motions of even low to moderate intensity. Failure in such structures is typically the result of punching failure at the slab-column connection. Because of this, performance-based retrofit procedures are needed to upgrade these non-ductile buildings. This investigation evaluated the use of lightweight pumice stone concrete (LWPSC) infill panels as a retrofit alternative for flat-plate buildings.
Six four-tenth-scale slab-column subassemblies were designed and detailed based on ACI 318-63 and current performance-based testing requirements. Except for one bare frame specimen, all the subassemblies were retrofitted with prefabricated LWPSC infill panels and subjected to quasi-static loading conforming to FEMA 273. The geometry of the individual units was governed by weight limitations for handling and erection. Among the variables studied were connections between the slabs and the infill wall and the addition of uniformly distributed perforations (circular and rectangular openings).
All of the retrofitted specimens had significant increases in both strength and stiffness over that of the bare frame. The behavior of the specimen with the infill panels not attached to the slabs was similar to that of a masonry wall without any connections to the frame. Although diagonal tension cracks formed within the recessed region...
This investigative study presents results on the
socioeconomic impact of infill drilling recovery from carbonate
reservoirs in the Permian Basin. The amount of incremental oil and gas production from infill drilling in 37 carbonate reservoir
units is established using decline curve analysis. The increase in incremental recovery is used to compute the amount of increased revenue and taxes (local, state and federal). A job market analysis
is performed to determine the impact of these increased revenues on primary jobs in the oil industry and secondary jobs in the
community. Secondary jobs are generated by oil industry workers
spending money in the community. The appropriation of the
estimated taxes is analyzed to determine which government
agencies benefit most from the infill drilling.
The observations from this research are that most of the San
Andres and Clearfork carbonate reservoir units in the Permian
Basin are potentially profitable to infill drill. The incremental oil and gas production from infill drilling could maintain or create
many primary jobs within the local oil industry and also secondary
jobs in the community. The incremental production could generate
taxes which would greatly benefit certain local, state, and federal
government agencies. ernment agencies.
This research proposal presents a methodology to calculate
the amount of incremental oil and gas production from infill
Timber frame buildings are well known as an efficient seismic resistant structure
and they are used worldwide. Moreover, they have been specifically adopted in codes and
regulations during the XVIII and XIX centuries in the Mediterranean area. These structures
generally consist of exterior masonry walls with timber elements embedded which tie the
walls together and internal walls which have a timber frame with masonry infill and act as
shearwalls. In order to preserve these structureswhich characterizemany cities in theworld it
is important to better understand their behaviour under seismic actions. Furthermore, historic
technologies could be used even in modern constructions to build seismic resistant buildings
using more natural materials with lesser costs. Generally, different types of infill could be
applied to timber frame walls depending on the country, among which brick masonry, rubble
masonry, hay and mud. The focus of this paper is to study the seismic behaviour of the walls
considering different types of infill, specifically: masonry infill, lath and plaster and timber
frame with no infill. Static cyclic tests have been performed on unreinforced timber frame
walls in order to study their seismic capacity in terms of strength...
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...