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Seismic behaviour of an asymmetric three-dimensional steel frame with base isolation devices

Barros, R.C.; Braz César, M.T.
Fonte: Civil-Comp Press Publicador: Civil-Comp Press
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.36%
A parametric study on the use of base isolation devices in frame building structures is undertaken. Frames were analysed with regular geometry starting from a baseframe (BF), from which more complex frames were created by association of BF in height above a certain asymmetric plant. The modularity of the BF facilitates the analysis of the results, allowing for parametric studies on the use of base isolation devices in more complex geometries. To conduct the computational studies the commercial software SAP2000 was used. Three-dimensional (3D) structures were analyzed with asymmetries in plant and in elevation. Some of the results of the parametric study are presented graphically, identifying the importance of positioning the seismic isolation devices used in each structural configuration.

Influence of the location of resistant cores on the seismic response of a reinforced concrete three-dimensional frame equipped with HDRB base isolation devices

Braz César, M.T.; Barros, R.C.
Fonte: Civil-Comp Press Publicador: Civil-Comp Press
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.48%
The present work addresses the structural behaviour of three-dimensional reinforced concrete buildings with concrete cores of resistant walls and seismic isolation. In this study a single asymmetric concrete core was placed in a 10 floor 3D building and then a set of numerical analyses were made for several geometric arrangements without and with High-Damping Rubber Bearings (HDRB). This base isolation system is used in order to reduce the structural seismic response and its associated damage. In order to evaluate the importance of the basic location of these structural elements, a parametric study was carried out changing the in-plan core location associated with symmetrical and asymmetrical structural distribution of the in-plan stiff core. The buildings were modelled using the commercial package SAP-2000 and the seismic analyses were carried out in accordance with the new European Code for seismic analysis and design: Eurocode 8 (EC8); the national annex was used to define the Portuguese elastic spectra.

Modelling connections of moment resisting steel frames for seismic analysis

Mota, L.; Silva, A. T. da; Rebelo, C.; Silva, L. Simões da; Lima, L. de
Fonte: Federal University of Rio de Janeiro; State University of Rio de Janeiro Publicador: Federal University of Rio de Janeiro; State University of Rio de Janeiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
46.52%
The seismic response of moment resisting steel frames depends on the behaviour of the beamto- column connections, in particular when these are considered to be dissipative zones. This paper aims to contribute to a better understanding of modelling joints of steel moment resisting frames concerning their seismic behaviour. The modified Richard-Abbott constitutes a sophisticated model and is used here to reproduce the cyclic behaviour of the steel joints. A parametric study is carried out in order to evaluate the influence of stiffness degradation, strength degradation and hardening effect of the connections in global response of the structure. For the study case the maximum global displacements increase for higher hardening effect. This conclusion can be relevant because for moment resisting frames the horizontal displacement is usually the controlling design criterion in seismic design.

Ductile connection characterization regarding seismic retrofitting of masonry buildings

Carles, Tristan Hamilton
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Dissertação de Mestrado
Publicado em //2012 ENG
Relevância na Pesquisa
46.65%
Dissertação de mestrado em Structural Analysis of Monuments and Historical Constructions; Anthropological reasons apart, earthquakes are one of the most devastating causes of damage to monuments and historical constructions, and, as a consequence, lead to significant cultural, human, and economical losses. Protection of such structures against seismic excitations is thus an important factor regarding life safety and the conservation of our historical heritage. Efficient connections between structural elements can highly reduce the seismic vulnerability of masonry buildings by enhancing the out of plane behaviour of the walls regarding lateral loads which are presented as the principal cause of failure in this type of structure. In spite of the importance of structural connections regarding the global behaviour of historical constructions under seismic actions, research in this field is almost nonexistent and needs to be developed. The objective of this thesis is to study the seismic response to a ductile connection used to connect tie-rods to masonry walls in the scope of seismic retrofitting of historical constructions and to analyse its behaviour in comparison to the behaviour of the other structural elements. In seismic vulnerability assessment...

Assessment of the seismic behaviour of unreinforced : traditional half-timbered walls

Poletti, Elisa; Vasconcelos, Graça
Fonte: Sociedade Portuguesa de Engenharia Sísmica Publicador: Sociedade Portuguesa de Engenharia Sísmica
Tipo: Conferência ou Objeto de Conferência
Publicado em //2012 ENG
Relevância na Pesquisa
56.41%
Half-timbered buildings represent an important historical heritage in many countries. They are diffused in various regions for different reasons, among which for being able to resist seismic actions. Despite the great popularity of this kind of structures, few studies are available on their global behaviour or on that of their single structural elements. The aim of this paper is to study the behaviour under cyclic loading of traditional half-timbered walls, with connections, materials and elements dimensions encountered in existing buildings. Cyclic tests have been performed in order to evaluate the performance of distinct traditional retrofitting techniques of the connections, namely: (1) increasing the number of nails at the connection; (2) use of steel bolts; (3) use of steel plates. The idea is to compare the performance in terms of hysteresis loops and the assessment of the improvements of the cyclic response in terms of ductility and energy dissipation.

An overview on the seismic behaviour of timber frame structures

Vasconcelos, Graça; Lourenço, Paulo B.; Poletti, Elisa
Fonte: Tampone, Ruggieri and Zinno Publicador: Tampone, Ruggieri and Zinno
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
Relevância na Pesquisa
46.41%
Traditional timber frame walls are an important structural element of many buildings and are usually composed of vertical posts and horizontal beams with bracing diagonal elements. In Portugal the timber frame walls, known as frontal walls, are usually part of Pombalino buildings, which were introduced by the Marquis of Pombal, who was responsible for the reconstruction of Downtown Lisbon after the great earthquake of 1755, which partially destroyed the city. Given the increasing interest of the research community to this structural system, it is important to promote the discussion of the main findings that can contribute to the advance on the knowledge of the mechanical behaviour of timber frame buildings to seismic action. Therefore, this paper intends: (1) to give an overview of the different solution of timber frame structures in different countries with special focus on the frontal walls characteristic of Pombalino buildings; (2) provide some examples of the reasonable behaviour of timber frame buildings in past earthquakes; (3) to summarize the experimental research carried out in the recent years in analysis of the behaviour to in-plane cyclic loading.

Characterization of the seismic behaviour of traditional timber frame walls

Poletti, Elisa
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 20/12/2013 ENG
Relevância na Pesquisa
46.48%
Tese de doutoramento Engenharia Civil - Estruturas; Timber frame structures constitute an important cultural heritage of many countries, since they represent a typical anti-seismic construction adopted worldwide. Therefore, the preservation of these structures is of the utmost importance. Although recent earthquakes have pointed out the good seismic behaviour of this kind of structures, few experimental studies are available on the performance of traditional half-timbered walls and their retrofitting solutions. Aiming at filling this research gap and at better understanding the behaviour of these historic elements under seismic loads, an extensive experimental campaign has been carried out, performing in-plane cyclic tests on real scale half-timbered and timber frame walls, adopting connections and dimensions found in real structures and considering different infill types (brick masonry and lath and plaster). Moreover, considering possible damages caused by earthquakes, after the unreinforced tests, the walls were retrofitted and re-tested to compare the efficiency of the retrofitting solutions in terms of maximum load, ductility, cyclic stiffness, energy dissipation and equivalent viscous damping. Both traditional and innovative retrofitting techniques were adopted...

Seismic behaviour of masonry infill walls : test and design

Leite, João C.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Tese de Doutorado
Publicado em 28/07/2014 ENG
Relevância na Pesquisa
46.41%
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...

Seismic behaviour and strengthening of existing reinforced concrete structures

Varum, H.; Rodrigues, H.; Fernandes, C.; Costa, A.; Arêde, A.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
56.6%
The seismic vulnerability associated to existing reinforced concrete buildings, constructed until the late 1970’s, in urban areas of many European countries with moderate to high seismic hazard, is of extreme importance. In that period, reinforced concrete buildings were designed and constructed without considering adequately earthquake provisions, constituting therefore a significant source of risk for our cities. Recent major earthquakes around the world have evidenced that this type of existing buildings lacking appropriate seismic resisting characteristics are very vulnerable. The present paper focus in four important subjects regarding the seismic behaviour of reinforced concrete buildings, first the importance of the experimental studies on full-scale buildings in particular with two full-scale four-storey reinforced concrete frames tested, in these tests two problems were under study the presence on infill masonry panels in the structure and the use of smooth reinforcement bars, that induces a sudden loss of concrete-steel bond is one of the sources of brittle failure in RC elements. For the presence infill masonry panels it’s presented a simplified macro-model that is able of represents the global behaviour of infill masonry panels and its interaction with RC elements and its application to a case study. Regarding the study of RC buildings smooth reinforcement bars it’s presented the experimental campaign ongoing and the first results and conclusions. Another identified problem in the seismic behaviour of RC buildings is the behaviour of axially loaded reinforced concrete members under biaxial bending moment. It’s presented the actual lack of experimental studies and the nonexistence of simplified models able to represent these effects and the experimental study of RC columns under uniaxial and biaxial bending.

Seismic behaviour characterization of reinforced concrete buildings

Varum, H.; Rodrigues, H.; Fernandes, C.; Costa, A.
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
56.41%
The seismic vulnerability assessment associated to existing reinforced concrete buildings, constructed until the late 70’s in many European countries with moderate to high seismic hazard, designed and constructed without considering adequately earthquake provisions, is of extreme importance. They constitute a significant source of risk for our cities. In this paper are presented the main results of research developed in the field of seismic assessment and retrofitting of existing RC buildings.; Stanovení seismické zranitelnosti železobetonových budov postavených do konce sedmdesátých let v mnoha evropských zemích s mírným až vysokým seismickým nebezpečím, projektovaných a postavených bez přiměřených protiseismických opatření, má extrémní význam. Tyto budovy představují významný zdroj rizika pro naše města. V článku se uvádějí hlavní výsledky výzkumu na úseku stanovení seismické zranitelnosti a modernizace existujících železobetonových budov.

Numerical models for simulation of the seismic behaviour of RC structures: a case study

Varum, H.; Costa, A.; Rodrigues, H.
Fonte: UMSNH, aSMMNI, CIMNE Publicador: UMSNH, aSMMNI, CIMNE
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
46.51%
Seismic analysis of RC structures requires realistic but simple analytical models. In this paper are presented two models proposed and implemented in the program PORANL, to represent the RC buildings behaviour under earthquake loading. The first model represents the bending behaviour of slender RC elements, and the second model represents the influence of infill walls in the global building response. The models are calibrated with test results on full-scale specimens. It is studied the vulnerability of one building, representative of the Modern Architecture, in Lisbon. Non-destructive tests on materials and natural frequencies measurement were performed to calibrate the model. The building was studied, with the proposed non-linear models, and the seismic safety was evaluated according to recently proposed assessment procedures. Additionally, it is proposed and studied a retrofitting solution, to improve the seismic performance of the building, based on a bracing system with a damping device associated.

Seismic evaluation of old masonry buildings: performance and strengthening

Varum, H.; Vicente, R.; Rodrigues, H.; Silva, J. A. R. Mendes da
Fonte: Civil-Comp Press Publicador: Civil-Comp Press
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
46.48%
The concern and need to assess seismic vulnerability, particularly of the traditional masonry buildings under seismic actions is a key issue, that should be a priority in the mitigation of the seismic risk, definition of strengthening requirements needs and minimization of possible damages due to seismic actions, in the identification of critical buildings and safeguarding of built heritage. This paper provides information on the constructive and structural details of the traditional buildings in Coimbra, Portugal, and interprets the potential structural damage and discusses its seismic behaviour, identifying structural fragilities and consequently their vulnerability. It also presents the main results obtained in the numerical studies, and verifies the global stability and dynamic response to seismic actions. Three different strengthening techniques to improve the global behaviour of these buildings were modelled and analysed. Efficiency of the strengthening strategies is also discussed in terms of deformation demands and cost-benefit analysis.

Structural behaviour and retrofitting of adobe masonry buildings

Varum, H.; Tarque, N.; Silveira, D.; Camata, G.; Lobo, B.; Blondet, M.; Figueiredo, A.; Masood Rafi, M.; Oliveira, C.; Costa, A.
Fonte: Springer Berlin Heidelberg Publicador: Springer Berlin Heidelberg
Tipo: Parte de Livro
ENG
Relevância na Pesquisa
46.37%
Earth is one of the most widely used building materials in the World. Different types of adobe dwellings are made to assure protection and wellbeing of the population according to the diverse zones needs. Therefore, it is importantstudy the structural behaviour of the adobe masonry constructions, analysing their seismic vulnerability, which may help in preventing social, cultural and economic losses. In the present chapter, an explanation of the seismic behaviour of adobe buildings, a summary of recent research outputs from experimental tests conducted on adobe masonry components and from numerical modelling of fullscale representative adobe constructions are reported. In addition, different rehabilitation and strengthening solutions are presented and results from the testing of retrofitted adobe constructions and components are discussed.

Experimental research on the seismic behaviour of precast r/c structures: the role of ASSOBETON and ELSA

COLOMBO Antonella; NEGRO Paolo
Fonte: Politecnico of Milan Publicador: Politecnico of Milan
Tipo: Contributions to Conferences Formato: Printed
ENG
Relevância na Pesquisa
46.58%
The traditional single-storey structures for industrial buildings, made of an assemblage of precast components, have a large diffusion all over Europe, due to their low costs associated to a very good ser-viceability. In Italy they cover almost all the market of industrial buildings and an important percentage of commercial structures. In spite of the large use of this type of buildings, some uncertainties are still connected with their seismic behaviour. Since some years ASSOBETON, in close collaboration with Politecnico of Mi-lan and the ELSA Laboratory, participate actively to national and European research programmes devoted to the investigation of the seismic behaviour of precast structures. The first research project is dated 1994. As a part of the project twenty columns, characterised by different re-inforcement configurations and axial load, have been subjected to cyclic loads of increasing amplitude. The results of the experimental campaign demonstrated that precast columns are able to dissipate a large amount of energy up to important ductilities with stable loops. After the qualification of the seismic behaviour of sin-gle elements, a research programme aimed at demonstrating the equivalence between the behaviour factor of precast and cast in situ single-storey industrial buildings was carried out in collaboration with other associa-tions interested in the field. The results of the tests demonstrated the excellent capacity of precast buildings to behave during earthquakes without suffering important damage. The study of the seismic behaviour of single-storey precast buildings was extended to the investigation of the effects of the presence of cladding panels within the PRECAST STRUCTURES EC8 project. The results of the study provided important data for the evaluation of the stiffening effect of panels together with information about the diaphragmatic behaviour of precast roofs. The results obtained within the previously mentioned research project will be extended to multi-storey structures as a part of the SAFECAST project recently financed by the European Commission. This paper is intended to provide an overview of the main results of these research projects.; JRC.DG.G.5-European laboratory for structural assessment

Recent Collaborative Research Activities Between Europe and China on the Seismic Behaviour of Precast Structures

COLOMBO Antonella; NEGRO Paolo; ZHAO Bin; LU Xilin
Fonte: University of Beijing Publicador: University of Beijing
Tipo: Contributions to Conferences Formato: Printed
ENG
Relevância na Pesquisa
46.43%
With the support from both European Commission and Chinese Government, a series of collaborative research activities on the seismic behaviour of precast reinforced concrete structures have been carried out between the European Laboratory for Structural Assessment (ELSA), Joint Research Centre, European Commission, and the State Key Laboratory for Disaster Reduction in Civil Engineering (SKLDRCE), Tongji University, Shanghai, P.R. China. The seismic behaviour of this worldwide used structural system is discussed, based on the outcomes of the experimental activity. It is concluded that well-conceived and designed precast reinforced concrete structures have almost the same seismic capacities as the cast-in-situ reinforced concrete structures. The motivations for further ongoing activities are discussed.; JRC.DG.G.5-European laboratory for structural assessment

Seismic behaviour of traditional timber frame walls: experimental results on unreinforced walls

Poletti, Elisa; Vasconcelos, Graça
Fonte: Springer Verlag Publicador: Springer Verlag
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
Relevância na Pesquisa
46.51%
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...

Strengthening to seismic action of reinforced columns with rectangular cross-section

Marques, Pedro Gonçalo Faustino
Fonte: Universidade Nova de Lisboa Publicador: Universidade Nova de Lisboa
Tipo: Tese de Doutorado
Publicado em /07/2015 ENG
Relevância na Pesquisa
46.39%
The first part of this research work regards the assessment of the mathematical modelling of reinforced concrete columns confined with carbon fibre (CFRP) sheets under axial loading. The purpose was to evaluate existing analytical models, contribute to possible improvements and choose the best model(s) to be part of a new model for the prediction of the behaviour of confined columns under bending and compression. For circular columns, a wide group of authors have proposed several models specific for FRP-confined concrete. The analysis of some of the existing models was carried out by comparing these with several tested columns. Although several models predict fairly the peak load only few can properly estimate the load-strain and dilation behaviour of the columns. Square columns confined with CFRP show a more complex interpretation of their behaviour. Accordingly, the analysis of two experimental programs was carried out to propose new modelling equations for the whole behaviour of columns. The modelling results show that the analytical curves are in general agreement with the presented experimental curves for a wide range of dimensions. An analysis similar to the one done for circular columns was this turn carried out for square columns. Few models can fairly estimate the whole behaviour of the columns and with less accuracy at all levels when compared with circular columns. The second part of this study includes seven experimental tests carried out on reinforced concrete rectangular columns with rounded corners...

Seismic behaviour of the Dead Sea fault along Araba valley, Jordan

Klinger, Y.; Avouac, J. P.; Dorbath, L.; Karaki, N. Abou; Tisnerat, N.
Fonte: Royal Astronomical Society Publicador: Royal Astronomical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /09/2000
Relevância na Pesquisa
46.43%
The Dead Sea fault zone is a major left-lateral strike-slip fault. South of the Dead Sea basin, the Wadi Araba fault extends over 160 km to the Gulf of Aqaba. The Dead Sea fault zone is known to have produced several relatively large historical earthquakes. However, the historical events are unequally distributed along the fault and only four events have been reported in the Araba valley over the last few thousands of years. Magnitudes estimated from the historical record are probably slightly smaller than that of the M_w ∼ 7.3 earthquake that struck the Gulf of Aqaba in 1995. The fault cuts straight across Pleistocene to Holocene alluvium and shows morphologic evidence for essentially pure strike-slip motion. Regional seismic monitoring reveals little microseismicity along the fault except around the Dead Sea and Gulf of Aqaba, where the fault splays into complex pull-apart basin fault systems. We have investigated the fault zone at several sites selected from SPOT images and the study of aerial photography. At the site of the now destroyed Tilah Castle, a well-preserved wall, dated to be about 1200 yr BP (^(14)C age on charcoal), is cut by the fault and offset by 2.2 m. Comparison with offset gullies at a nearby site 3 km to the north and at three other sites...

Seismic behaviour of portuguese rammed earth buildings

Barros, Ricardo Freitas Lima da Silva; Varum, Humberto; Rodrigues, Hugo; Correia, Mariana; Vasconcelos, Graça; Lourenço, Paulo B.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em /07/2015 ENG
Relevância na Pesquisa
56.37%
Rammed earth is one of the oldest building materials in the world and is present in the Portugal with a particular focus in the South of the country. The mechanical properties and the structural behaviour of rammed earth constructions have been the subject of study of many researchers in the recent years. This study is part of a broader research on vernacular seismic culture in Portugal. Numerical analyses were carried out on a rammed earth masonry construction representative of the vernacular heritage of Alentejo region. Variations in the geometry, constructive characteristics and material properties were implemented and the main conclusions of the non-linear static and modal analysis are presented. Analysing the damage framework allowed interpreting the weaknesses of this type of constructions and consider the most appropriate reinforcement methodologies.

Seismic behaviour assessment of vernacular isolated buildings

Ortega Heras, Javier; Vasconcelos, Graça; Lourenço, Paulo B.; Rodrigues, Hugo; Varum, Humberto
Fonte: Taylor & Francis Group Publicador: Taylor & Francis Group
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
56.41%
This paper presents the numerical seismic analysis of isolated vernacular buildings characteristic of the Alentejo region, which is considered a medium seismic hazard region in Portugal.A representative isolated building was selected from a database, and a geometric model was defined for the numerical pushover analysis. Subsequently, a parametric analysis was carried out to assess the influence of distinct parameters on the seismic behaviour of such buildings.