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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Seismic Analysis of a Typical Masonry Building from Barcelona’s Eixample District
Author: Christopher Potter | Size: 5.2 MB | Format:PDF | Quality:Unspecified | Year: 2011 | pages: 154
The historic Eixample district of Barcelona is characterised by its beautiful avenues, laid out in grid across the city. At first impression, the buildings lining these avenues appear identical, an unending façade built to house the new Barcelona of the 20th Century. The unreinforced masonry buildings that typify the development remain in use today, largely unaltered since their construction. Unreinforced masonry buildings are among the most vulnerable structures to damage from seismic actions. For the masonry buildings of the Eixample that house over 15% of the population of Barcelona, this is no exception. This study performs a seismic analysis on a typical masonry building of the Eixample to estimate and assess this damage. By doing so, it aims to estimate the likely damage due to seismic actions, to identify critical elements of the structures and to quantify the need for seismic risk maintenance and response plans.
The analysis uses the N2 Capacity Spectrum Method (Fajfar, 2000), adopted by Eurocode 8, to determine the displacement demand of possible earthquake scenarios. A seismic hazard analysis determines the seismic demand using deterministic, probabilistic and current European and Spanish code provisions. The seismic demand is then compared to the results of a non-linear pushover analysis completed using software DIANA (Version 9.4). The model geometry was based upon plans of a building that well represents the typical unreinforced masonry buildings of the Eixample.Results indicate a displacement demand to Spanish code provisions that corresponds to a substantial
level of damage, in accordance with the European Macroseismic Scale (EMS 98) damage criteria. A moderate level of damage is derived from the probabilistic seismic scenario. Similar to previous studies, these results indicate a significant risk of seismic damage. The analysis has isolated critical structural elements that control the global response and damage during seismic action. This information can be used to develop inspection and maintenance plans to limit the risk of seismic damage. This study highlights the real risk of seismic damage to the typical unreinforced masonry buildings of the Eixample district. It determines appropriate building maintenance procedures, and reinforces the
need for seismic response planning to best manage the significant expected social and infrastructure
demands should such a disastrous event ever occur.
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IDENTIFYING CONFIGURATION AND CONNECTION DETAILS OF UNREINFORCED MASONRY STRUCTURES IN MID-AMERICA
Author: Ty A. Stokes University of South Carolina REU at the University of Illinois at Urbana-Champaign Advisor: Professor Y. K. Wen | Size: 0.84 MB | Format:PDF | Quality:Unspecified | pages: 16
Experience from past earthquakes indicates that some structures perform better than others under similar ground motion conditions. This disparity leads to the conclusion that some structures will be safer, and thus less likely to require repair or cause harm, than others. In order to describe this phenomenon quantitatively, vulnerability functions are developed. Vulnerability functions describe a structure in terms of its likelihood (probability) of exceeding a certain limit state at a specified ground motion condition accounting for the uncertainty in both excitation and structural capacity. Indeed, there are several sources of uncertainty that cannot be eliminated, but in order to create the most accurate relationship possible, any uncertainty that can be reduced, should be reduced. Therefore, the goal of this particular part of this project is to remove some of the uncertainty in the nature of the buildings that are being modeled. By understanding better of a typical unreinforced masonry (URM) building, it is possible to accomplish this goal and create a vulnerability function which may better describe a larger percentage of the population of URM structures in
Mid-America.
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Behavior and Vulnerability of Reinforced Masonry Shear Walls
Author: Ehsan Minaie in partial fulfillment of the requirements for the degree of Doctor of Philosophy | Size: 18.6 MB | Format:PDF | Quality:Unspecified | Publisher: Drexel University | Year: august 2009 | pages: 488
The overarching goal of the research presented herein was to establish the key behavior mechanisms and seismic vulnerabilities of reinforced masonry (RM) shear walls. Currently, there are knowledge gaps related to partially grouted masonry shear walls, regarding their failure mechanisms, applicability of current code provisions to PG walls, and influence of bidirectional loading on the behavior of such walls. To bridge these gaps a research program that integrated both experimental and analytical approaches was conducted. The centerpiece of the experimental program was a series of full-scale, quasi- static cyclic tests of both PG and FG masonry shear walls. Key test parameters included the level of vertical stress, wall aspect ratio, and mortar formulation. Following these experiments a series of nonlinear finite element models were developed and correlated with the experimental results. These models were then used to examine the influence ofbi-directional loading through a series of parametric studies with out-of-plane drift, wall aspect ratio and vertical stress as variables. Results of this study indicated a potentially significant seismic vulnerability of PG masonry shear walls that is not reflected in current design provisions. The PG masonry shear walls tested displayed shear strengths less than half of the capacity estimated by current design methods. The modeling component of this research developed an efficient nonlinear finite element modeling approach that proved capable of simulating the capacity (within 10%), failure modes and hysteretic response of both PG and FG masonry shear walls. This modeling approach was also validated for the prediction of out-of-plane response, and then used to examine the bi- directional response of PG masonry shear walls. Results from this study indicated that out-of-plane drifts corresponding to the collapse prevention limit state may reduce the in- plane capacity of PG walls by more than 20%. Although the capacity of PG walls is influenced by out-of-plane drifts, their hysteretic responses, and in particular, energydissipation and ductility capacities remain nearly unchanged. As a result, the seismic response of PG masonry walls is likely only nominally affected by bi-directional ground motions.
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Article/eBook Full Name: A Review of the No Erosion Filter Test
Author(s): Soroush, Abbas & Shourijeh, Piltan Tabatabaie
Edition: Volume 32, Issue 3
Publish Date: 2009
ISBN: DOI: 10.1520/GTJ101588
Published By: Geotechnical Testing Journal (ASTM)
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