PERFORMANCE-BASED SEISMIC VULNERABILITY EVALUATION OF EXISTING BUILDINGS IN OLD SECTORS OF QUEBEC
Author: Amin KARBASSI | Size: 4 MB | Format:PDF | Quality:Unspecified | Publisher: McGill University – Department of Civil Engineering and Applied Mechanics THIS THESIS WAS PRESENTED AND DEFENDED BEFORE A BOARD OF EXAMINERS AND PUBLIC June 15, 2010 AT ÉCOLE DE TECHNOLOGIE SUPÉRIEURE | Year: JULY 20, 2010
To perform a seismic vulnerability evaluation for the existing buildings in old sectors of
Quebec, two major tools at two different levels are missing: first, in the context of the
seismic vulnerability assessment of a group of buildings, an updated rapid visual screening
method which complies with the Uniform Hazard Spectra presented in the 2005 version of the National Building Code of Canada (NBCC) does not exist; and second, in the context of loss estimation studies, capacity and fragility curves which are developed based on the specific building typologies present in those sectors are required. In this research work, in the first place, a building classification for the existing buildings in old sectors of Quebec considering the masonry as the main construction material is proposed. Later, an updated rapid visual screening method—in the form of vulnerability indices for different typologies and cities in Quebec—which is adapted to the Uniform Hazard Spectra in NBCC 2005 is proposed. The structural vulnerability indices (SVI) are calculated through the application of the improved nonlinear static analysis procedure in FEMA 440 Improvement of nonlinear static seismic analysis procedures for three levels of seismic hazard. A set of index modifiers are also presented for the building height, irregularities, and the design and construction year. To deal with the second problem, on the other hand, a performance-based seismic vulnerability evaluation method is applied to examine the structural performance of two buildings—a 6-storey industrial masonry building and a 5-storey concrete frame with masonry infill walls, as two of the building classes constructed vastly in old sectors in Quebec—at multiple seismic demand levels. The results of such an assessment are used to develop dynamic capacity and fragility curves for the target buildings. The Applied Element Method is used here as an alternative to FE-based methods to conduct a thorough 4-step performance-based seismic vulnerability evaluation. To this end, the Incremental DynamicAnalyses (IDA) for the buildings are carried out using various sets of synthetic and real ground motions representing three M and R categories. Consequently, the fragility curves are developed for the three structural performance levels—Immediate Occupancy, Life Safety, and Collapse Prevention. Finally, the mean annual frequencies of exceeding those performance levels are calculated by combining the data from the calculated fragility curves and those from the region’s hazard curves. The proposed method is shown to be useful to conduct seismic vulnerability evaluations in regions for which little observed damage data exists.
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In order to learn how to analyze typical reinforced concrete buildings, understand their seismic
behavior and to learn how guidelines such as ASCE 41, ATC-40 and FEMA could apply to buildings in
Pakistan, the project team idealized a typical Karachi residential-commercial mixed use building as
the pilot case study building. For simplicity, the team investigated the behavior of two-dimensional
frame models with and without infill walls, and simplified certain structural details. A separate
report describes a study of the three dimensional model of the building.
The building upon which the idealized case study structure is based is located in Gulistan-e-Johar, a
densely populated area in Karachi. This building consists of reinforced concrete framed building with
five storeys including the ground floor. The building has shops located at the ground floor, while the
above floors have residential apartments. The building was constructed before the 2005 Kashmir
Earthquake. Project participants selected this building as the pilot case study because it has several
seismic vulnerabilities common to mixed-use residential buildings in Karachi: a weak story created by
open shop fronts at the ground floor, an eccentrically located reinforced concrete core, and heavy,
stiff unreinforced masonry infill walls that were not considered during the structural design of the
building.
The case study team assessed the building’s potential seismic vulnerabilities using the US Federal
Emergency Management Agency (FEMA) Prestandard 310 Tier 1 Checklist modified for Pakistan
conditions, as well as the American Society of Civil Engineers (ASCE) Standard 31 Tier 2 and 3
analyses and acceptance and modeling criteria from ASCE 41. The building was found to be
inadequate for seismic zone 4 and requires retrofitting to rectify the soft storey at the base and
provide lateral stability to the building.
The team examined a number of potential retrofit solutions for both seismic performance and
economic considerations. In order to provide a cost-effective and minimally intrusive retrofit, the
team selected a rocking spine retrofit solution. A spine of existing infill panels reinforced with
shotcrete above a reinforced concrete wall at the open ground storey prevents the building from
collapsing. The spine provides stability and strength without extensive foundation work. This retrofit
solution promises to be an innovative and cost-effective alternative for buildings in Pakistan.
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SEISMIC PERFORMANCE OF REINFORCED CONCRETE BUILDINGS IN THE 22 FEBRUARY CHRISTCHURCH (LYTTELTON) EARTHQUAKE
Author: Weng Y. Kam , Stefano Pampanin , Ken Elwood3 | Size: 5.9 MB | Format:PDF | Quality:Unspecified | pages: 40
Six months after the 4 September 2010 Mw 7.1 Darfield (Canterbury) earthquake, a Mw 6.2 Christchurch
(Lyttelton) aftershock struck Christchurch on the 22 February 2011. This earthquake was centred approximately 10km south-east of the Christchurch CBD at a shallow depth of 5km, resulting in intense seismic shaking within the Christchurch central business district (CBD). Unlike the 4 Sept earthquake
when limited-to-moderate damage was observed in engineered reinforced concrete (RC) buildings [35], in the 22 February event a high number of RC Buildings in the Christchurch CBD (16.2 % out of 833) were severely damaged. There were 182 fatalities, 135 of which were the unfortunate consequences of
the complete collapse of two mid-rise RC buildings.
This paper describes immediate observations of damage to RC buildings in the 22 February 2011 Christchurch earthquake. Some preliminary lessons are highlighted and discussed in light of the observed performance of the RC building stock. Damage statistics and typical damage patterns are
presented for various configurations and lateral resisting systems. Data was collated predominantly from
first-hand post-earthquake reconnaissance observations by the authors, complemented with detailed assessment of the structural drawings of critical buildings and the observed behaviour. Overall, the 22 February 2011 Mw 6.2 Christchurch earthquake was a particularly severe test for both
modern seismically-designed and existing non-ductile RC buildings. The sequence of earthquakes since
the 4 Sept 2010, particularly the 22 Feb event has confirmed old lessons and brought to life new critical
ones, highlighting some urgent action required to remedy structural deficiencies in both existing and
“modern” buildings. Given the major social and economic impact of the earthquakes to a country with
strong seismic engineering tradition, no doubt some aspects of the seismic design will be improved based
on the lessons from Christchurch. The bar needs to and can be raised, starting with a strong endorsement
of new damage-resisting, whilst cost-efficient, technologies as well as the strict enforcement, including
financial incentives, of active policies for the seismic retrofit of existing buildings at a national scale.
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COMPONENT BASED SEISMIC VULNERABILITY ASSESSMENT PROCEDURE FOR RC BUILDINGS
Author: EMRAH ERDURAN | Size: 1.8 MB | Format:PDF | Quality:Unspecified | Publisher: Ph.D., Department of Civil Engineering Supervisor: Assoc. Prof. Dr. Ahmet Yakut | Year: JULY 2005
In the last fifteen years, Turkey has lost tens of thousands of its citizens and huge amounts of economic properties in moderate and severe earthquakes. Moreover, most of the population and industry of Turkey is under the threat of a possible major earthquake since they are located in earthquake prone regions. The current seismic code of Turkey [1] was rewritten in 1998 to enable the satisfactory performance of the structures and thus to reduce loss after a major earthquake. However, a vast majority of the structures in Turkey had been constructed before the adaptation of the 1998 Turkish Earthquake Code [1]. Moreover, newstructures are not generally designed and/or constructed according to the provisions of this code resulting in a huge number of deficient structures. As a result the engineers in Turkey, like most of their colleagues in the world, are faced with a critical question which must be answered immediately: Which buildings are safe and which must be strengthened or even demolished? For decades researchers have been studying on developing seismic vulnerability assessment procedures to overcome this problem. These vulnerability assessment procedures can be categorized in three according to the level of complexity they contain. The first level of seismic assessment procedures is known as the walk-down survey or street survey and is the quickest and simplest way of ranking the buildings in a building stock relative to each other based on their certain attributes. The typical parameters used in this type of assessment procedures are the number of stories, the age of the building, vertical
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Dynamic behavior of masonry structures under pyroclastic flows
Author: Junji KIYONO , Robin J.S. SPENCE and Tadayoshi NAKASHIMA | Size: 0.31 MB | Format:PDF | Quality:Unspecified | Publisher: Journal of Natural Disaster Science, Volume 28, Number 2, 2006, pp73-83 | Year: 2006 | pages: 11
Pyroclastic flow is a dangerous hazard for people and houses so buildings have to provide a measure of protection
to the occupants. In order to improve the structural strength of buildings, we need to know the structural
behavior against the lateral pressure of the flow. In this study, dynamic behavior of unreinforced masonry structures
affected by pyroclastic flows was analyzed using 2-dimensional (2D) Distinct Element Methods (DEM).
DEM is a numerical analysis technique, in which the positions of elements are calculated by systematically solving
equations. The structure is modeled as an assembly of distinct elements connected by virtual springs and dashpots
where elements come into contact. Masonry structures with simple structural elements; walls, floors, a roof,
and furniture were modeled. The strength of mortar was varied to check the effect of pyroclastic flow on the structural
behavior under different conditions. Pressure acting on a wall due to pyroclastic flow was modeled as a simple
time function of which the peak value was varied from 0.1 MPa to 10 MPa. A pressure model of which intensity
changes with height was also treated. Tilting, lateral movement, collapse and swept away within several seconds
are the typical collapse process of a weak masonry structure even when the lateral pressure is 1 KPa. collapse of the masonry structure is controlled by the relation between the overturning moment due to the lateral
pressure and the resistant moments due to gravity and mortar joint strength.
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Seismic Risk Assessment of Unreinforced Brick Masonry Buildings System of Northern Pakistan
Author: MOHAMMAD JAVED | Size: 6.8 MB | Format:PDF | Quality:Unspecified | Publisher: Department of Civil Engineering, N-W.F.P. University of Engineering and Technology | Year: 2009 | pages: 230
This research work was aimed at assessing the seismic risk of unreinforced brick masonry buildings’
system of Northern Pakistan, constructed in stone dust mortar. To accomplish this, four series of
unreinforced brick masonry piers constructed in stone dust mortar were tested in the in-plane direction
using quasi-static method of testing. Each pier series comprised of three piers with identical properties
and thus a total of twelve piers were tested. Aspect ratio and pre-compression were kept as the main
variables. Various properties such as displacement ductility factors, ultimate drift ratios, coefficient of
equivalent viscous damping, stiffness degradation and modulus of rigidity were determined using the
experimental data from quasi-static cyclic tests on the piers. The effect of pre-compression on the
coefficient of equivalent viscous damping and stiffness degradation were studied. Similarly, the effect
of drift ratio on the coefficient of equivalent viscous damping was also studied. Various performance evels for unreinforced brick masonry piers, in relation to drift ratios, were also recommended. Based on the results of experimental work, a methodology was proposed for lateral strength assessment of unreinforced brick masonry buildings. The developed methodology produced satisfactory results when compared with the results of full-scale unreinforced masonry (URM) buildings tested at University of Pavia, Italy [MKC 95] and Georgia Institute of Technology, USA [ Yi 04]. Although the proposed methodology was used for brick masonry buildings, it can be applied to other types of masonry (such as stone and concrete block masonry constructed in cement: sand mortar, lime mortar, etc.) if the properties required to quantify the seismic performance (e.g., displacement ductility factors and ultimate drift ratios of masonry piers, etc.) are experimentally known. Various performance levels for unreinforced brick masonry buildings were also recommended in relation to drift ratios. Finally, seismic capacities of thirty-one buildings were evaluated. The buildings’ stock consisted of seventeen single-story and fourteen double-story buildings. The buildings were selected keeping in view their common typological use in urban areas of Northern Pakistan. Fragility curves, showing the probabilities of reaching or exceeding various performance levels at various levels of ground shaking, were drawn for various performance limit states. It was found by studying the fragility curves that the probability of occurrence for various performance levels of single- and double- story buildings do not differ significantly. It was also concluded that unreinforced brick masonry, if
properly constructed, can be safely used in localities placed in seismic zone 2b [BCP 07] and below.
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SHEAR STRENGTH OF PARTIALLY GROUTED SQUAT MASONRY SHEAR WALLS
Author: JAMAL H. ELMAPRUK | Size: 10.5 MB | Format:PDF | Quality:Unspecified | Publisher: WASHINGTON STATE UNIVERSITY Department of Civil and Environmental Engineering | Year: august 2010 | pages: 117
Unreinforced masonry systems consist of a composite of bricks, often made from clay or concrete blocks, and mortar joints. Across the past centuries, masonry has been described as one of the most reliable and durable building systems that humans have built in many historic civilizations throughout the world, although they lack sufficient strength to resist strong ground motions. Nevertheless, the wide demand for such building systems also comes from their ease of construction and formation. Obviously, masonry systems are designed to carry out and resist vertical and the horizontal loads. However, during past and the recent earthquakes, the vulnerability of traditional masonry systems has been addressed. It has been noticed that the resistance of masonry buildings to tension or lateral
dynamic loads, as well as vertical or compressive loads, is significantly different than inthe case of isotropic or homogeneous materials. Despite the wide use of some modern building materials such as steel and reinforced concrete, masonry building systems are still used. However, the development of a modern masonry construction system using fully reinforced or partially grouted masonry has improved the performance of masonry systems in terms of resisting the
tension and the shear forces generated in high seismic activity regions.
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URBAN SEISMIC RISK ASSESSMENT IN DEHRADUN CITY USING REMOTE SENSING AND GEOINFORMATION TECHNIQUES
Author: DEBARATI ROY | Size: 2.2 MB | Format:PDF | Quality:Unspecified | Publisher: Indian institute of Remote Sensing National Remote Sensing Agency Dept. of Space, Govt. Of India Dehradun, 248001, India | Year: 2007 | pages: 108
“Although the incidence of major natural disasters has not increased, their effects are becoming more severe in the Third World because of the growing numbers of people and structures located in hazard-prone areas. Millions people in these expanding urban populations are potential victims of disasters cataclysmic proportions, and even the political and economic stability of many nations in Africa, Asia and Latin America can be threatened.” – Spencer W Havlick Modern man, for all his intellectual development, his technological sophistication and even his technical abilities, is still at the mercy of natural forces. The scale and complexity of economic development makes man more and more dependent on the smooth functioning of very broad economic systems and technical facilities. Therefore, he may now not only be vulnerable to direct blows by natural disasters, but also indirectly vulnerable to catastrophes geographically distant areas. The city of Dehradun is the interim capital of Uttaranchal in North India and has short-listed by United Nations Development Programme (UNDP) as one of the most earthquake prone city in the country. Direct relationships between the damage of civil structures such as buildings to the number of casualties have been found. The frequent occurrence of damaging earthquakes clearly demonstrates the urgent need of study of earthquake risk assessment (ERA) methods of buildings to effectively reduce the impact of earthquake in the city. India, till date, no precise risk evaluation model of earthquake risk and damage assessment has been developed. Thus, in order to reduce risk, models developed by other countries have been adopted.
The secretariat of the International Decade for Natural Disasters
Reduction (IDNDR 1990-2000), United Nations, Geneva, therefore, launched the RADIUS (Risk Assessment tools for Diagnosis of Urban areas against Seismic disasters) initiative in 1996, with financial assistance from the Government Japan. It was aimed to promote worldwide activities for reduction of seismic disasters in urban areas, particularly in developing countries. The present study has been done with an aim to use RADIUS for analyzing the life and property damage in an urban area. In doing so, mitigation measures have been planned. This thesis work had been divided in three parts. The first part tries to assess the amount of urban densification that has occurred in the area, over a span of years. The second part deals with quantification of life and property damage the various magnitude of earthquake. The third part involves mitigation
measures that could be made in case of a crisis.
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EARTHQUAKE-RESISTANT CONFINED MASONRY CONSTRUCTION
Author: Svetlana Brzev Department of Civil Engineering British Columbia Institute of Technology Burnaby, BC, Canada | Size: 2.5 MB | Format:PDF | Quality:Unspecified | Publisher: NATIONAL INFORMATION CENTER OF EARTHQUAKE ENGINEERING Indian Institute of Technology Kanpur Kanpur (India) | Year: DECEMBER 2007 | pages: 90
This document is written for building professionals interested
in learning more about confined masonry construction and for
those who would like to promote its application in countries
without prior experience related to this construction practice.
Confined masonry has evolved over the last 100 years
through an informal process based on its satisfactory
performance in past earthquakes in countries and regions of
extremely high seismic risk. It is used both for non-engineered
and engineered construction; its field applications range from
one or two storey high single-family dwellings to six storey
apartment buildings. Design and construction provisions for
confined masonry are included in building codes in several
countries.
Building technologies are closely related to local conditions,
and their successful application depends on several factors,
including the availability and cost of building materials, the
skill level of construction labour and the availability of
construction tools and equipment. Introducing new
construction practices, or even improvements in existing ones,
can be daunting tasks. In India and many other countries,
masonry and reinforced concrete (RC) are the technologies of
choice for housing construction, with the design applications
ranging from one-storey family houses to multi-storey
apartment buildings. However, past earthquakes in India and
other countries have revealed weaknesses associated with
both masonry and reinforced concrete frame construction.
Confined masonry offers an alternative to both unreinforced
masonry and RC frame construction for applications in
earthquake-prone areas of the world. The fact that confined
masonry construction looks similar to RC frame construction
with masonry infills and that it uses the same components
(masonry walls and RC confining members) is expected to
assist in an easy transition from the construction perspective.
Confined masonry construction practice does not require new
or advanced construction skills or equipment, but it is
important to emphasize that quality construction and sound
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Line 1 of the ReLUIS 2005-2008 Framework Project consisted of a coordinated research on the evaluation and reduction of seismic vulnerability of existing masonry buildings. The research, which involved nineteen different research units, has developed along five main topics: the assessment and strengthening of structural units within building aggregates, the methods for assessment of mixed masonry-reinforced concrete structures, the strategies and techniques for strengthening of masonry buildings, considering both horizontal (floors, roofs, vaults) and vertical (walls) structural elements, the methodologies for modelling the seismic response of masonry structural systems. Within each topic several subtasks were considered, involving surveying, modelling, in-situ and laboratory testing. Within the project also some large scale static and dynamic testing was carried out, involving shake table tests on building models and structural components. In this paper the developments and outcomes of the project are synthesized.
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