Numerical modelling of masonry-infilled reinforced concrete frames : model calibration and parametric study

Generally two methods are proposed for analyzing the infilled frames; Micro modelling approach which finite element method is used to take into account local effects in detail and Macro modelling approach which is a very simplified method that takes into account the global behavior of the structure by replacing the infill with diagonal strut. In the present study a numerical analysis is carried out on a one bay one storey reinforced concrete frame with masonry infill under in-plane loading by using finite element modelling through the DIANA software. The numerical model was calibrated based on experimental results and then a parametric study was carried out, taking into account variation of material properties of infill and its height to length ratio. It is concluded that compressive strength and height to length ratio of the masonry infill has dominant role on the in-plane behavior of these types of masonry infilled frames. Increasing the compressive strength of the masonry enhances the lateral strength of the infilled frames while increasing the height to length ratio of the infill panel results in decrease of their lateral strength and initial stiffness.Fundação para a Ciência e a Tecnologia (FCT

Out-of-plane response of masonry infilled RC frames: effect of workmanship and opening

Publicado em "Brick and block masonry: trends, innovations and challenges. ISBN 978-1-138-02999-6Out-of-plane response of typical South European masonry infilled frames was investigated by testing three reduced scale specimens to investigate the effect of workmanship and presence of opening on the out-of-plane behaviour. The tests were performed considering an airbag to apply the uniform out-of-plane loading for each mass of the infill and by imposing pre-defined values of displacements in the out-of-plane direction in the control point taken at mid height and mid length of the masonry infill wall. Quasi-static cyclic testing was performed just in one direction to be able to monitor the propagation of the cracks and performance of the interfaces during out-of-plane loading. It was concluded that the workmanship is an important factor that may change the out-of-plane response of the specimen by changing the initial stiffness and lateral strength of the specimen. Another important contribution of the workmanship is the change of the collapse pattern of the infill by formation of twoway arching mechanism or one way arching mechanism. When the upper boundary condition of the infill in contact with RC frame is filled properly with mortar, two way arching mechanism was observed otherwise one-way horizontal arching mechanism was formed which exhibits lower out-of-plane resistance. The specimen with a central opening exhibits lower deformation capacity with respect to the reference wall but any decrease in its lateral strength was not recorded.FCT (Portuguese Foundation for Science and Technology), within ISISE, project UID/ECI/04029/2013Portuguese Foundation of Science and Technology for the funding of the project RetroInf—Development of innovative solutions for seismic retrofitting of masonry infill walls (PTDC/ECM/122347/2010

Experimental evaluation of a constructive system for earthquake resisting masonry enclosure walls

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

Out-of-plane strengthening of masonry infills using textile reinforced mortar (TRM) technique

Published online: 29 May 2021The out-of-plane collapse of masonry infills during seismic actions resulted in human life losses and huge repair or reconstruction costs. These problems will result in disturbance of the operational functions of the buildings. The main scope of this research is to analyze the efficiency of different strengthening techniques based on textile reinforced mortar (TRM) technique and using steel connectors in the out-of-plane direction. To accomplish the objectives, four half-scale specimens were tested under uniform out-of-plane loads applied by an airbag to each mass of the infill cyclically. The performance of the textile reinforced mortar technique by using two different meshes was also evaluated experimentally. Besides the protection of the infill from collapsing and protection of human lives, using TRM technique enhances the out-of-plane response of the specimen but its connection to the infill has to be deeply investigated.Fundação para a Ciência e Tecnologia (FCT

Performance of textile reinforced mortar as strengthening solution of masonry infill walls to seismic action

A elevada vulnerabilidade sísmica das paredes de enchimento em alvenaria tem conduzido à necessidade de reforço deste tipo de paredes, utilizando técnicas convencionais ou usando materiais inovadores. Os Fiber reinforced polymers (FRP’s) são utilizados principalmente como materiais inovadores para o reforço de estruturas. Apesar das vantagens associadas ao uso deste tipo de materiais, esta técnica de reforço apresenta algumas desvantagens, como problemas de aderência, mau comportamento à humidade e ao fogo. Uma solução possível para os problemas associados a estes materiais, pode passar pela substituição de agentes ligantes orgânicos para os inorgânicos, tais com argamassas à base de cimento. As interações entre as fibras e a matriz e também as condições de aderência em compósitos cimentícios pode ser melhorado através da utilização de malhas de reforço embebidas na argamassa de reboco, técnica habitualmente designada em língua inglesa por textile reinforced mortar (TRM). Esta técnica é relativamente nova (utilizada desde dos anos 80), tendo sido estudada por vários investigadores em diferentes aplicações. Neste artigo, investiga-se a utilização desta técnica no reforço de paredes de enchimento de alvenaria para ações no plano que simulam a ação sísmica. Foram ensaiados no plano, três provetes à escala reduzida, representativos da construção dos anos 70 em Portugal, um provete de referência, um provete reforçado com uma malha comercial e um provete reforçado com uma malha de reforço desenvolvida para o efeito. Neste caso as malhas de reforço foram desenvolvidas na Universidade do Minho no departamento de engenharia têxtil. A eficácia da técnica desenvolvida foi comparada com soluções comerciais.The high seismic vulnerability of masonry infilled frames have lead to their in-plane and out-of-plane strengthening by means of conventional techniques or by using innovative materials. Fiber reinforced polymers (FRP’s) are mostly used as innovative materials for retrofitting of structures. In spite of many advantages associated with use of FRPs, this retrofitting technique is not problem-free One possible solution to the problems of FRPs could be the replacement of organic binders with inorganic ones such as cement based mortars. Fiber-matrix interactions and also the bond conditions in cementitious composites could be improved if the fibers replaced with textile sheets. This lead to the formation of textile reinforced mortar (TRM) technique. This technique is relatively a new technique (it was started to use in early 1980s) and was studied by few researchers. In this paper, in-plane retrofitting of the infilled frames was investigated by using textile reinforced mortar (TRM) technique. Three half scale specimens which are representative of construction of 1970s in South European countries, were tested in the in-plane direction, a reference specimen, specimen retrofitted by commercial TRM technique and specimen retrofitted with developed TRM technique. In the developed TRM technique the textile meshes were developed and produced in the Textile Department. The effectiveness of the developed technique was compared with commercial solutions

Seismic performance of Portuguese masonry infill walls: From traditional systems to new solutions

The use of masonry infill walls in reinforced concrete structures are a common solution in Portugal and other European countries for more than 50 years. These walls are used as exterior enclosures to build the envelope of the buildings, or as interior partitions to divide the different spaces of the houses. In the building construction practice these walls are built only after the hardening of the reinforced concrete elements. For that reason, they are assumed as non-structural elements, and not considered in the structural design of the building. However, when buildings are subjected to seismic action, these walls assume a structural behavior. This leads in many cases to the existence of an unsatisfactory behavior of infill walls, resulting in damage of the walls, which put human lives in dangerous and cause extensive economic losses. This seismic vulnerability of masonry infill walls is well recognized by the scientific community and has been observed in many works carried out in the last decades, as well as the recent earthquakes in southern Europe. In the case of a seismic event of high intensity in Portugal, it is expected that similar problems will occur in the Portuguese masonry infill walls, given the similarity of the construction typologies, in southern Europe. It is therefore important to study the masonry infill walls used in Portugal over the years, to fully understand their seismic behavior, and thus be able to propose and study reinforcement systems for existing walls and new masonry infill systems for new construction. Thus, in this paper is made a characterization of masonry infill walls typologies used in Portugal over the years. A review of the mechanical behavior of masonry infill walls is carried out using several In-Plane and Out-of-Plane tests performed at the University of Minho and other studies carried out in Portugal. Several strengthening techniques possible to be used in this type of walls are presented, as well as some mechanical characterization tests of these strengthening solutions applied on Portuguese infills walls. Finally, are presented two proposals for new systems of masonry infill walls to be used in new construction, with the objective of present a better seismic behavior in this type of elementsEuropean Union’s Seventh Framework Program for research, technological development and demonstration under grant agreement No 606229, which support this work. This work was also supported by FCT (Portuguese Foundation for Science and Technology, within ISISE, project UID/ECI/04029/2013, and through a doctoral scholarship reference SFRH/BD/125094/201

Paredes de alvenaria de enchimento e a ação sísmica: reabilitação e inovação

Neste trabalho apresentam-se os principais resultados da investigação efetuada na Universidade do Minho relacionada com a análise do comportamento de paredes de enchimento sujeita a ações sísmicas e metodologias de reforço com a proposta de um novo material desenvolvido na perspetiva de reabilitação destas paredes construídas em regiões sísmicas. Apresentam-se também algumas possibilidades para construção nova de paredes de enchimento que visam um desempenho melhorado quando sujeitas a ações sísmicas

Out-of-plane behavior of masonry infill walls

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, the infill bends in two directions but the failure of that interface which is known as weakest interface due to difficulties in filling the mortar between bricks of last row and upper beam results in the crack opening trough a well-defined path and the consequent collapse of the infill

Molecular and Seroepidemiological Survey of Visceral Leishmaniasis among Humans and Domestic Dogs in Mazandaran Province, North of Iran

Background: New cases of visceral leishmaniasis (VL) have been reported recently in some parts of Mazandaran Province, north of Iran where the first human case of VL was reported in 1949. This study aimed to determine the present status of Leishmania infantum infection among humans and domestic dogs using serological and molecular methods in central parts of Mazandaran Province. Methods: In this cross-sectional study, blood samples were randomly collected from 402 humans and fortynine domestic dogs throughout 2009 and 2010 in the central part of Mazandaran Province including Semeskadeh and Kiakola districts where recent cases of human visceral leishmaniasis had been reported there. All the collected samples were tested by direct agglutination test (DAT) for the detection of anti-Leishmania infantum antibodies as well as convenience PCR assay on whole blood samples for detection of leishmanial infection and identification of Leishmania species. Results: None of 402 collected human (402) and dog (49) blood samples showed anti Leishmania infantum antibodies at titers 1:3200 and 1:320 as cut-off values of DAT, respectively but only 2 of domestic dogs (4.1 %) were found PCR-positive corresponding to L.infantum. Conclusion: This study confirms the circulation of L. infantum at least among domestic dogs an

Epidemiological Aspects of Visceral Leishmaniasis in Baft District, Kerman Province, Southeast of Iran

Background: Visceral leishmaniasis (kala-azar) is an endemic disease in some areas of Iran. A cross- sectional study was conducted for sero-epidemiological survey of visceral leishmaniasis (VL) in Baft district from Kerman Province, southeast of Iran.Methods: Blood samples were collected from children up to 12 years old and 10% of adult population from Baft villages with a multi-stage randomized cluster sampling. In addition, blood samples were collected from 30 domestic dogs from the same areas. All the collected blood sam­ples were tested by direct agglutination test (DAT) for the detection of anti-Leishmania antibod­ies in both human and dog using the cut-off value of ≥1:3200 and ≥ 1:320, respectively. Parasitologi­cal, molecular, and pathological were performed on infected dogs. Chi-square and Fisher exact tests were used to compare sero-prevalence values.Results: From 1476 collected human serum samples, 23 (1.55%) showed anti-Leishmania antibod­ies at titers of 1:800 and 1:1600 whereas 14 (0.95%) showed anti-Leishmania infantum antibodies at titers of ≤ 1:3200. No statistically significant difference was found between male (1.18 %) and female (0.69%) sero-prevalence (P=0.330). Children of 5-8 years showed the high­est sero-prevalence rate (3.22%). Seven out of 30 domestic dogs (23%) showed anti-Leishmania antibodies at titers ≤1:320. Leishmania infantum was identified in five infected dogs by nested - PCR assay.Conclusion: It seems that visceral leishmaniasis is being endemic in southern villages of Baft district, southeast of Iran