A preliminary investigation is presented on a pushover analysis used for the seismic
performance of metallic braced frames equipped with diagonal X-bracing and K-bracing
Three steel frames were analysed corresponding to 3, 6 and 10 floor regular buildings. The
frames were modelled in the MIDAS/Civil finite element software and in the analyses nonlinear
static methods were used to obtain the pushover curve.
The principal objective of this article is to compare the evaluation of the structural performances
of these buildings with respect to the proposed N2-method, and so also of the consequent
convenience of using pushover methodology for the seismic analysis of structures.
This paper presents the numerical study that aims at the seismic evaluation of the performance of typical Portuguese “gaioleiro” buildings. The numerical modeling was performed with resource to a model of finite elements on 1:3 reduced scale and it was calibrated in agreement with experimental results obtained in the tests done in the LNEC 3D shaking table.
With the purpose to define an adequate strategy for seismic performance evaluation nonlinear dynamical analysis with time integration and pushover analyses were carried out. In the dynamic analysis, each earthquake is composed by two uncorrelated artificial accelerograms compatible with design response spectrum of EC8. In the pushover analyses it was considered that the seismic action is simulated through a set of proportional horizontal forces to the mass of structure and to the 1st vibration mode according with the direction in study.
Dissertação de mestrado em Construção e Reabilitação Sustentáveis; Através dos eventos sísmicos que têm ocorrido nas mais variadas partes do mundo, tem-se
demonstrado que a alvenaria simples (não armada) não apresenta um desempenho adequado
face à ocorrência de sismos, podendo apresentar roturas frágeis e pouca capacidade de
dissipação de energia. Por outro lado, a alvenaria armada pode conduzir a um desempenho
estrutural, quer em termos de resistência, quer em termos de ductilidade. Uma solução
recentemente desenvolvida em alvenaria estrutural de blocos de betão prevê a utilização de
armadura de junta combinada com armadura vertical inserida no interior das células dos blocos
ou alternativamente na junta vertical e o uso de argamassa de assentamento modificada para
preenchimentos das células armadas.
O objectivo principal deste trabalho consistiu em avaliar o desempenho global da solução recente
em comparação com uma solução tradicional não armada à acção sísmica, que só poderá ser
efectuado através de ensaios em mesa sísmica, de modo a poder determinar as propriedades
dinâmicas. Neste trabalho pretende-se avaliar também o comportamento mecânico da alvenaria
ao corte com diferentes configurações de armadura vertical e horizontal.
Para o efeito foi planeada e realizada uma campanha de ensaios experimentais...
This paper aims to assess and improve the seismic performance of an existing masonry building with ﬂexible
ﬂoors, representative of a Portuguese building typology—‘gaioleiro’ buildings. The study involved seismic
tests and dynamic identiﬁcation tests of two models (nonstrengthened and strengthened) in the shaking table.
Each model was subjected to several seismic tests with increasing amplitude. . Before the ﬁrst test and after
each seismic test, the dynamic identiﬁcation of the model was carried out, aiming at obtaining their seismic
vulnerability curves based on a damage indicator obtained from the decrease of the frequencies of the
modes. In the strengthened model, steel elements were used to improve the connection between walls and
ﬂoors, together with ties in the upper stories. The results show that adopted strengthening technique is effective for reducing the seismic vulnerability of ‘gaioleiro’ buildings, namely for improving the out-of-plane behavior of the facades.
Ancient masonry structures are usually associated to a high seismic vulnerability, mainly due to the properties of the materials (low tensile and moderate shear strengths), weak connections between floors and load-bearing walls, high mass of the masonry walls and flexibility of the floors. For these reasons, the seismic performance of traditional masonry structures has received much attention in the last decades.
This paper presents the sensitivity analysis taking into account the deviations on features of the “gaioleiro” buildings - Portuguese building typology. The main objective of the sensitivity analysis is to compare the seismic performance of the structure as a function of the variations of its properties with respect to the response of a reference model. The sensitivity analysis was carried out for two types of structural analysis, namely for the non-linear dynamic analysis with time integration and for the pushover analysis proportional to the mass of the structure. The Young’s modulus of the masonry walls, Young’s modulus of the timber floors, the compressive and tensile non-linear properties (strength and fracture energy) were the properties considered in both type of analysis. Additionally, in the dynamic analysis...
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...
This paper presents a sensitivity analysis taking into account possible variations on the features of
masonry buildings. The main objective of the analysis is to compare the seismic performance of a typology
of buildings in Lisbon as a function of the changes of its properties with respect to a reference model
calibrated from experimental tests. The sensitivity analysis was carried out using non-linear dynamic
analysis with time integration and using pushover analysis with distribution of forces proportional to
the inertial forces of the structure. The deviations on the seismic response were mainly analysed in terms
of maximum load capacity and collapse mechanisms. The results show that the Young’s modulus of the
masonry walls, the Young’s modulus of the timber floors and the compressive non-linear properties are
the parameters that most influence the seismic performance of this type of tall and weak existing
masonry structures. Furthermore, it is concluded that the stiffness of the timber floors significantly influence
the strength capacity of the building and the type of collapse mechanism.
The increase in housing demand and the construction cost of the necessary houses for its satisfaction have motivated the study of economical and efficient solutions aiming at developing new construction methods. A new solution for the construction of residential houses is presented. Dynamic seismic tests by using a shaking table were performed on two masonry buildings. The first experimental model incorporates steel reinforcement according to the Eurocodes, while the second was tested as an unreinforced solution. A numerical model for the unreinforced solution was prepared by using macro-modelling approach. Five non-linear phased dynamic analyses with time integration representing the same seismic amplitude tests implemented during the experimental campaign were made. In terms of experimental results, the quantitative parameters for both models and the crack patterns are presented. Comparisons between the experimental results and those from the numerical simulations are also presented.; Portuguese Agency of Innovation (ADI).
Tese de Doutoramento em Engenharia Civil; Unreinforced masonry construction is predominant in many urban areas world-wide. Many of
these constructions are vulnerable to earthquakes, which are the main cause of damage and loss
of cultural heritage. Lessons learned from earthquake surveys proved that a satisfactory seismic
performance is attained when the structure behaves as a monolithic box.
This thesis tackles the problem of earthquake-impact on heritage masonry construction, starting
from the basic consideration that efficient protection and strengthening can only be achieved with
the proper knowledge of the behaviour of the structural elements and its connections. A numerical
approach is proposed aiming at studying and further characterize the behaviour of stone masonry
walls and anchors injected in masonry walls (used to strengthen connections between structural
components). The knowledge provided by these studies is then applied in the seismic assessment
of a typical masonry building.
The numerical study of the in-plane behaviour of masonry walls was carried out based on an
experimental programme carried out at EUCENTRE. The finite element models, considering
walls with distinct slenderness ratios and pre-compression levels...
Earthen structures present very appealing characteristics regarding a more sustainable practice with the
preservation of our natural resources. However, when subjected to earthquake ground motions, this type of
construction may present a deficient performance, which may cause significant human losses and important
structural damage. The seismic response of earthen structures is typically characterized by fragile failures. There
are several examples of recent earthquakes that affected earthen buildings in a severe way, evidencing the
vulnerability of this type of construction, like the El Salvador earthquake, in 2001, the Bam, Iran earthquake, in
2003, the Pisco, Peru earthquake, in 2007 and the Maule, Chile earthquake, in 2010.
The construction of earth structures on earthquake-prone areas must be carefully studied and should include
seismic reinforcement solutions in order to improve their seismic performance.
In this paper, the performance of earthen structures in recent earthquakes will be examined, analyzing failure
modes inherent to these particular construction materials and associated construction techniques. Also, seismic
reinforcement approaches and techniques will be presented in a comprehensive manner. Examples of tests conducted for the assessment of retrofitting solutions efficiency will be presented...
The effectiveness of reinforced concrete (RC) column jacketing for improving the seismic performance of existing RC
building structures were studied. Four three storey buildings with different structural conﬁguration and detailing were
selected for seismic assessment and retroﬁtting purpose. The response of structures (original and retroﬁtted) was
evaluated in terms of capacity curve and inter-storey drift. The case studies also intend to verify the effect of P-delta
effects and bi-axial response of columns under non-linear time history analysis. The nature of the capacity curve
represents the strong impact of the P-delta effect, leading to a reduction of the global lateral stiffness and reducing
the strength of the structure. Finally, a seismic safety assessment is performed based on the drift limit proposed by
FEMA-356. The assessment of original building structures indicates that they may exhibit inadequate seismic
performance. However, RC column jacketing highly improves seismic performance of all the structures and results
maximum drift demand within the drift limit proposed by FEMA-356.
The present paper analyses the design procedure and its impact on seismic
safety of the structures. For this, a representative reinforced concrete frame building
(WDS) is designed and the results are compared with similar buildings detailed with:
i) Current Construction Practices (CCP); ii) the Nepal Building Code (NBC) and iii)
the Modified Nepal Building Code (NBC+) recommendations. The seismic
performance evaluation is done with global strength, inter-storey drift and
displacement of the structures. Likewise, the sensitivity of the structural and
geometrical parameters of the RC frame building is studied through nonlinear analysis.
The study parameters considered for parametric analysis are column size, beam size,
inter-storey height, bay length, bay width, and compressive strength of concrete. The
results show that the influence on the structural behaviour, particularly by variation in
column size and inter-storey height. Additionally, the influence of the seismic zone
factor on reinforcement demand of the structure is studied. The result shows that
structures designed for high to medium seismic hazard demands double the
reinforcement in beams compared to structures in low seismic zone.
This PhD thesis is focused on the characterisation of the out-of-plane seismic
performance of stone masonry walls, where the development of an innovative
fragility-based approach, founded on solid experimental outputs, analytical
formulation and post-earthquake damage observation, was outlined as main
objective. In order to achieve it, two groups of specific objectives were
distinguished in function of the genesis of the work, and are discussed
throughout the seven chapters that compose this document. The first chapter
presents a brief introduction to the main topic of the work, the description of the
general and specific objectives to be achieved and each one of the tasks
performed to fulfil them. Chapter 2 presents a compact state-of-art review
wherein the principal methodologies proposed to assess the out-of-plane
behaviour of unreinforced masonry structures are presented and discussed.
The experimental part of this research begins in the third chapter, where an in
situ experimental campaign, performed on three masonry wall piers of an
existing building, is presented. Chapter 4 aims at describing an experimental
program conducted in laboratory environment to characterise the out-of-plane
behaviour of unreinforced masonry piers. In the scope of this experimental
This paper proposes an indicator of seismic performance based on life-cycle cost of a building. It is expressed as a ratio of lifetime damage loss to life-cycle cost and determines the seismic performance of isolated buildings. Major factors are considered, including uncertainty in hazard demand and structural capacity, initial costs, and expected loss during earthquakes. Thus, a high indicator value indicates poor building seismic performance. Moreover, random vibration analysis is conducted to measure structural reliability and evaluate the expected loss and life-cycle cost of isolated buildings. The expected loss of an actual, seven-story isolated hospital building is only 37% of that of a fixed-base building. Furthermore, the indicator of the structural seismic performance of the isolated building is much lower in value than that of the structural seismic performance of the fixed-base building. Therefore, isolated buildings are safer and less risky than fixed-base buildings. The indicator based on life-cycle cost assists owners and engineers in making investment decisions in consideration of structural design, construction, and expected loss. It also helps optimize the balance between building reliability and building investment.
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...
Highway bridges are an important part of transportation networks. They provide connectivity across waterways, ravines and other roadways, reducing commuting times and facilitating social community. The disruption of their effective operation caused by earthquake damage has lasting effects based on repair costs, road closure times, traffic rerouting causing extended commute times and additional CO2 emissions, and the potential prevention of emergency responders being able to reach affected regions.
Bridge expansion joints have historically been recognized as the most vulnerable component in the bridge system during these seismic events, causing dramatic disruption to bridge functionality because of their location in bridges (points of discontinuity in deck systems). Expansion joint systems are placed in these locations of discontinuity and accommodate bridge movements from thermal effects while facilitating safe driving surfaces across large gaps in the roadway. Commonly installed systems are not designed to survive seismic events, instead failure is assumed and replacement necessary to return the bridge to its functional state. When damaged, the large gaps they span can be un-crossable without external intervention, resulting in non-functioning bridges even when the structural system remains sound. Expensive and complex expansion systems exist...
As an alternative to transverse spiral or hoop steel reinforcement, fiber reinforced polymers (FRPs) were introduced to the construction industry in the 1980's. The concept of concrete-filled FRP tube (CFFT) has raised great interest amongst researchers in the last decade. FRP tube can act as a pour form, protective jacket, and shear and flexural reinforcement for concrete. However, seismic performance of CFFT bridge substructure has not yet been fully investigated. Experimental work in this study included four two-column bent tests, several component tests and coupon tests. Four 1/6-scale bridge pier frames, consisting of a control reinforced concrete frame (RCF), glass FRP-concrete frame (GFF), carbon FRP-concrete frame (CFF), and hybrid glass/carbon FRP-concrete frame (HFF) were tested under reverse cyclic lateral loading with constant axial loads. Specimen GFF did not show any sign of cracking at a drift ratio as high as 15% with considerable loading capacity, whereas Specimen CFF showed that lowest ductility with similar load capacity as in Specimen GFF. FRP-concrete columns and pier cap beams were then cut from the pier frame specimens, and were tested again in three point flexure under monotonic loading with no axial load. The tests indicated that bonding between FRP and concrete and yielding of steel both affect the flexural strength and ductility of the components. The coupon tests were carried out to establish the tensile strength and elastic modulus of each FRP tube and the FRP mold for the pier cap beam in the two principle directions of loading. A nonlinear analytical model was developed to predict the load-deflection responses of the pier frames. The model was validated against test results. Subsequently...
Vertical inclusions of expanded polystyrene (EPS) placed behind rigid retaining walls were investigated as geofoam seismic buffers to reduce earthquake-induced loads. A numerical model was developed using the program FLAC and the model validated against 1-g shaking table test results of EPS geofoam seismic buffer models. Two constitutive models for the component materials were examined: elastic-perfectly plastic with Mohr-Coulomb (M-C) failure criterion and non-linear hysteresis damping model with equivalent linear method (ELM) approach. It was judged that the M-C model was sufficiently accurate for practical purposes. The mechanical property of interest to attenuate dynamic loads using a seismic buffer was the buffer stiffness defined as K = E/t (E = buffer elastic modulus, t = buffer thickness). For the range of parameters investigated in this study, K ≤ 50 MN/m3 was observed to be the practical range for the optimal design of these systems. Parametric numerical analyses were performed to generate design charts that can be used for the preliminary design of these systems.
A new high capacity shaking table facility was constructed at RMC that can be used to study the seismic performance of earth structures. Reduced-scale models of geosynthetic reinforced soil (GRS) walls were built on this shaking table and then subjected to simulated earthquake loading conditions. In some shaking table tests...
Haselton, Curt B.; Goulet, Christine A.; Mitrani-Reiser, Judith; Beck, James L.; Deierlein, Gregory G.; Porter, Keith A.; Stewart, Jonathan P.; Taciroglu, Ertugrul
Fonte: Pacific Earthquake Engineering Research CenterPublicador: Pacific Earthquake Engineering Research Center
Tipo: Report or Paper; PeerReviewedFormato: application/pdf
Publicado em /08/2008
Relevância na Pesquisa
This report describes a state-of-the-art performance-based earthquake engineering methodology
that is used to assess the seismic performance of a four-story reinforced concrete (RC) office
building that is generally representative of low-rise office buildings constructed in highly seismic
regions of California. This “benchmark” building is considered to be located at a site in the Los
Angeles basin, and it was designed with a ductile RC special moment-resisting frame as its
seismic lateral system that was designed according to modern building codes and standards. The
building’s performance is quantified in terms of structural behavior up to collapse, structural and
nonstructural damage and associated repair costs, and the risk of fatalities and their associated
economic costs. To account for different building configurations that may be designed in
practice to meet requirements of building size and use, eight structural design alternatives are
used in the performance assessments.
Our performance assessments account for important sources of uncertainty in the ground
motion hazard, the structural response, structural and nonstructural damage, repair costs, and
life-safety risk. The ground motion hazard characterization employs a site-specific probabilistic
seismic hazard analysis and the evaluation of controlling seismic sources (through
disaggregation) at seven ground motion levels (encompassing return periods ranging from 7 to
2475 years). Innovative procedures for ground motion selection and scaling are used to develop
acceleration time history suites corresponding to each of the seven ground motion levels.
Structural modeling utilizes both “fiber” models and “plastic hinge” models. Structural
modeling uncertainties are investigated through comparison of these two modeling approaches...