Neste trabalho o comportamento sísmico das partes internas de um equipamento de proteção ambiental é estudado. O equipamento, um precipitador eletrostático, é composto basicamente de uma grande caixa de metal elevada, que contem eletrodos positivos e negativos responsáveis pela coleta de material particulado no fluxo de gases industriais. Esses componentes se comportam como pêndulos. No modelo foram considerados os deslocamentos sísmicos horizontais em duas direções ortogonais. De especial interesse está o fato de os eletrodos terem a liberdade de oscilar no plano de uma direção, mas não no seu plano perpendicular. Serão analisados quatro modelos com um, dois, três graus de liberdade, e um com três graus de liberdade linearizado. O modelo mais completo considera como graus de liberdade e coordenadas generalizadas os dois deslocamentos horizontais, e o deslocamento angular do pendulo. Foi adotada a formulação Lagrangeana para derivar as equações de movimento do modelo. As equações diferenciais do movimento de segunda ordem obtidas apresentam um comportamento não linear. Os movimentos sísmicos, que são estocásticos por natureza, serão simulados por meio de um registro sísmico existente, arbitrariamente escolhido. A obtenção dos parâmetros do modelo a ser estudado é de especial interesse para a melhor previsão do comportamento do equipamento quando solicitado a esforços sísmicos. A integração numérica do modelo matemático é efetuada...
Historical city buildings are an integral part of the built heritage to be preserved, and their safety is a primary requirement in seismic areas. Collapse of ancient masonry buildings due to seismic actions occur mostly due to overturning of the perimeter walls. This paper addresses the issue of seismic analysis and vulnerability of historical city centers, with a specific case study: the 18th century downtown part of Lisbon, Portugal. The finite element method was adopted for a number of different analyses, introducing non-linear behavior of the materials. From the analysis, the following issues have been addressed: (a) seismic vulnerability of this type of constructions; (b) influence of the group of buildings on the seismic behavior of the individual buildings that compose a single compound; and (c) methodology for action. It is believed that the conclusions obtained with respect to the seismic assessment of masonry buildings can be extrapolated for the wide variety of historical city centers.
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 current paper deals with the analysis of the results yielded by a series of tests performed to evaluate the seismic behaviour of a model log construction. The study was based on an experimental investigation performed to improve the existing knowledge on log houses subject to seismic events. The main part of the experimental work is based on a full scale shaking table test, conducted on a two-storey log house designed by the Portuguese company Rusticasa® in compliance with design rules for timber buildings. The test was performed by the University of Minho within the framework of the SERIES Project ‘Multi-storey timber buildings’ and was coordinated by the University of Trento, at LNEC, Lisbon, Portugal.
The geometry of the specimen, the design of the test, the setup and the instrumentation layout are first presented in this paper. The test procedure was conducted in stages with maximum accelerations (bi-directional) of 0.07g, 0.28g and 0.5g. The experimental results of each test have been analyzed and the resultant values of inter-storey drift, wall slippage and uplift measurements, shear deformations and hold-down forces measured are presented. Most importantly, the dynamic properties (fundamental period and mode shapes) of the system have been determined.
This paper presents a study of the seismic behavior of the “Old Municipal Chambers” building in Christchurch, which was damaged by earthquakes in 2010 and 2011. In view of its seismic vulnerability and retrofitting, finite element and equivalent frame models were used for pushover analysis. Predictions allow identifying the weak parts of the building and its expected failure modes, which are in agreement with the observed damage. Computations seem however conservative, because the building capacity curves provide insufficient strength to survive the registered earthquakes. By considering the floors as bidirectional diaphragms in the simplified model, a better behavior is observed.
Dissertação de mestrado em Structural Analysis of Monuments and Historical Constructions; The study of the vulnerability of ancient buildings is receiving much attention in the recent decades due to the
increasing interest in the conservation of the built heritage and the awareness that life and property must be
preserved. The different types of masonry present common features that provide high seismic vulnerability to
these buildings, such as the high specific mass, the low tensile strength, the low to moderate shear strength
and the low ductility. In addition to the influence of the material properties, the seismic behavior of ancient
masonry buildings depends on factors such as the geometry of the structure, connections between orthogonal
walls, connections between structural walls and floors, connections between walls and roof, the foundation
behavior, the stiffness of the floors and the behavior of the non-structural elements.
The present study aims at evaluating the variation on response of the structure varying the material and
geometrical properties of the ancient masonry buildings. The response is obtained through the non linear
dynamic and static analysis with time integration and is focused on the dynamic behavior of the masonry walls
and timber floors. First...
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 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...
Adobe constructions represent a high percentage of the national patrimony, with high historical, cultural and architectonic value. Well preserved adobe structures can exhibit a particular architecture with very attractive geometric characteristics while also incorporating natural materials. However, the behavior of these structures is deficient under horizontal loads, such as those induced by an earthquake, which endangers their structural integrity and human lives. To develop a seismic retrofit solution, a real-scale wall was characterized and tested by considering permanent vertical actions with cyclic horizontal forces of increasing amplitude. To retrofit the wall, repair and seismic reinforcement solutions were developed and combined to evaluate their efficiencies. To repair the damages, hydraulic lime gum was injected by pressure into the cracks. The reinforcement solution included the use of a synthetic mesh in the wall. The retrofitted wall was then tested, and the results indicated that the retrofit solutions significantly improved the seismic performance of the wall. This study contributes to the characterization of walls constructed with adobe masonry and their behavior under horizontal actions. Furthermore, an economic, sustainable and efficient solution is presented for the retrofitting of adobe walls...
Seismic design loads for tunnels are characterized in terms of the deformations imposed on the structure by surrounding ground. The free-field ground deformations due to a seismic event are estimated, and the tunnel is designed to accommodate these deformations. Vertically propagating shear waves are the predominant form of earthquake loading that causes the ovaling deformations of circular tunnels to develop, resulting in a distortion of the cross sectional shape of the tunnel lining. In this paper, seismic behavior of circular tunnels has been investigated due to propagation of shear waves in the vertical direction using quasi-static analytical approaches as well as numerical methods. Analytical approaches are based on the closed-form solutions which compute the forces in the lining due to equivalent static ovaling deformations, while the numerical method carries out dynamic, nonlinear soil-structure interaction analysis. Based on comparisons made, the accuracy and reliability of the analytical solutions are evaluated and discussed. The results show that the axial forces determined using the analytical approaches are in acceptable agreement with numerical analysis results, while the computed bending moments are less comparable and show significant discrepancies. The differences between the analytical approaches are also investigated and addressed.
As part of a multi-university research program funded by NSF, a comprehensive experimental and analytical study of seismic behavior of hybrid fiber reinforced polymer (FRP)-concrete column is presented in this dissertation. Experimental investigation includes cyclic tests of six large-scale concrete-filled FRP tube (CFFT) and RC columns followed by monotonic flexural tests, a nondestructive evaluation of damage using ultrasonic pulse velocity in between the two test sets and tension tests of sixty-five FRP coupons. Two analytical models using ANSYS and OpenSees were developed and favorably verified against both cyclic and monotonic flexural tests. The results of the two methods were compared. A parametric study was also carried out to investigate the effect of three main parameters on primary seismic response measures. The responses of typical CFFT columns to three representative earthquake records were also investigated.
The study shows that only specimens with carbon FRP cracked, whereas specimens with glass or hybrid FRP did not show any visible cracks throughout cyclic tests. Further monotonic flexural tests showed that carbon specimens both experienced flexural cracks in tension and crumpling in compression. Glass or hybrid specimens...
This paper reports on the first experimental study on the seismic behavior of FRP-concrete-steel composite double-skin tubular columns (DSTCs). Six DSTCs that were made of high-strength concrete (HSC) were tested under constant axial compression and reversed-cyclic lateral loading. The main parameters of the experimental study included the axial load level, level of confinement, concrete strength and thickness of inner steel tube. Test results indicate that DSTCs are capable of developing very high inelastic deformation capacities under simulated seismic loading, which makes them attractive alternative for construction of new earthquake-resistant columns. Examination of the test results have lead to a number of significant conclusions in regards to the influence of the important column parameters on the performance of DSTCs. These results are presented together with a discussion on the influence of the main parameters on the seismic behavior of DSTCs.; Yunita Idris and Togay Ozbakkaloglu
The prediction of the seismic behavior of waterfront structures has been considered as a challenging problem and attracted significant research interest, especially after the severe damage of such structures in Niigata, Japan, during the 1964 Niigata Earthquake.
The objective of the present study is to improve our understanding of the effects of the backfill material and the wall-soil interface on the seismic behavior and safety performance of retaining walls. The nonlinear analyses are conducted by using an explicit finite-difference formulation for large-deformation analysis of soil-structure systems subjected to seismic excitation.
The effects of separation at the wall-soil interface are investigated assuming a fix-based rigid wall and a linearly elastic backfill material. These effects are found to be significant, resulting to wall forces and moments that may be, respectively, 25 and 40% larger than those based on the assumption of no separation.
The effects of nonlinearity of a typical saturated backfill soil in a waterfront structure are investigated by considering three different materials, namely, loose sand, medium sand and dense sand. The study examines the effects of relative density, intensity of base excitation, frequency of base excitation and number of cycles of loading on the wall pressures...
In this study the issue of stability of elastomeric bearings subjected to extreme dynamic loading is studied in detail and response reduction strategies in structures both fixed base and base-isolated structures using a negative stiffness device (NSD) are evaluated. For response reduction, the composite response spectrum approach is utilized to provide a comprehensive representation of the trade-offs associated with each choice of design strategies. A comprehensive database of strong ground motion is used to study the suitability of NSD for seismic protection. The spectral characteristics of all the ground motions selected are identified using a mathematical model and the characteristics of the ground motion that affect the structural assembly and the response reduction strategies considered are evaluated. The results of the study are organized based on the identified characteristics of ground motion to demonstrate the effectiveness of the negative stiffness device for response reduction. The analytical study takes into account both linear fixed base structures as well as base-isolated structures equipped with linear and nonlinear dampers.
For stability of elastomeric bearings, detailed analytical models that capture the nonlinear behavior of the bearings under extreme axial loads and horizontal displacements are developed...
Tese de doutoramento em Engenharia Civil; Masonry buildings are one of the most representative constructive systems since the early ages of
civilization. Through time, they have exhibited worldwide structural deficiencies, severe damage and
collapse during strong earthquake events. It is known that their brittle behavior together with its low
frictional resistance, which is mainly due to the combination of low tensile strength, large mass and
insufficient connection between structural elements, are the main limitations for its structural
implementation in residential buildings. Nevertheless, masonry also offers several advantages like
thermal and acoustic efficiency, excellent fire behavior, economy, durability and a simple
construction technology. Then, if the deficiencies are overcome, it can be effectively considered as
an alternative low cost structural solution.
Following past researches dealing with the proposal of an innovative solution in structural masonry
for low to medium rise residential buildings, based on concrete block masonry units and truss type
reinforcement, the main objective of the present work is to study the seismic behavior of masonry
buildings built with this system. For this, an enlarged experimental campaign and numerical analysis
were planned. It is commonly found that research on masonry under seismic loading has been
mostly focused on experimental and numerical analyses of structural masonry elements...
Considering that vernacular architecture may bear important lessons on hazard mitigation and that well-constructed examples showing traditional seismic resistant features can present far less vulnerability than expected, this study aims at understanding the resisting mechanisms and seismic behavior of vernacular buildings through detailed finite element modeling and nonlinear static (pushover) analysis.
This paper focuses specifically on a type of vernacular rammed earth constructions found in the Portuguese region of Alentejo. Several rammed earth constructions found in the region were selected and studied in terms of dimensions, architectural layout, structural solutions, construction materials and detailing and, as a result, a reference model was built, which intends to be a simplified representative example of these constructions, gathering the most common characteristics.
Different parameters that may affect the seismic response of this type of vernacular constructions have been identified and a numerical parametric study was defined aiming at evaluating and quantifying their influence in the seismic behavior of this type of vernacular buildings. This paper is part of an ongoing research which includes the development of a simplified methodology for assessing the seismic vulnerability of vernacular buildings...
The seismic behavior and plasticity spreading of a neotype column-slab high pier are researched in this paper. Four scale model tests of a web slab with two boundary columns are carried out under cyclic inelastic lateral displacements simulating seismic response. The test results show that the neotype column-slab high pier has strong and stable bearing capacity, good ductility, and energy dissipation capacity. The experimental values pertaining to the spread of plasticity are derived. An approach for deriving the spread of plasticity analytically is deduced and applied to the four tests. This method accurately assesses a pier's spread of plasticity for most ductility levels. At nearly all ductility levels, the mean difference between analytical assessments of the spread of plasticity and results from 4 large-scale tests is 12% with a 9% coefficient of variation.
Timber frame construction is characteristic of several historic city centres as well as of vernacular architecture in several countries around the world, either motivated by the availability of materials and construction traditions or by the need of reducing the seismic vulnerability of buildings, namely in south European countries, where this construction technique was adopted for seismic-resistance purposes. From past earthquakes, it has been seen that timber frame construction can be viewed as an interesting technology as it has exhibited a very reasonable behaviour when compared to other traditional construction techniques such as masonry walls.
This chapter provides an overview of the main insights on the seismic performance of timber frame buildings from the evidences of past earthquakes and provides the main results of recent research focused on the in-plane cyclic behavior of timber frame walls with distinct geometrical configurations. Additionally, the main seismic performance indexes of timber frame walls, both unreinforced and retrofitted, are presented and discussed in detail.
Given the fact that using timber frame structures has proven to improve the seismic behavior of
vernacular architecture, as has been reported in past earthquakes in many countries, its
preservation as a traditional earthquake resistant practice is important. This paper firstly intends
to evaluate whether the use of timber frames as a traditional seismic resistant technique for
vernacular architecture in the South of Portugal, traditionally a seismic region, is still active.
Secondly, the city of Vila Real de Santo António was selected as a case study because it also
followed a Pombaline development contemporary to the reconstruction of Lisbon. The plan
included the provision of timber frame partition walls for some of the buildings and, thus, an
overview of the type of constructions originally conceived is provided. Finally, the alterations
done in the original constructions and the current state of the city center are described and the
effect of these changes on the seismic vulnerability of the city is discussed.