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1
Cornick, Steven M. Carleton University Dissertation Engineering Civil. "MASON; a rule based damage assessment system for masonry walls." Ottawa, 1985.
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2
Wijanto, Ludovikus Sugeng. "Seismic Assessment of Unreinforced Masonry Walls." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2007. http://hdl.handle.net/10092/1680.
Full textAbstract:
This thesis focuses on the seismic performance of unreinforced masonry wall perforated with
a door opening representing typical URM walls of many aged masonry buildings in
Indonesia. To obtain a test result that will be able to represent the local conditions, the
experiments have been conducted in the Research Institute for Human Settlements (RIHS)
laboratory in Bandung-Indonesia.
Two 75 % unreinforced masonry (URM) walls with a 1½-wythe of solid clay-brick were
constructed in Dutch bond configuration and tested until failure under quasi-static-reversed
cyclic loading. Both units were loaded vertically by constant loads representing gravity loads
on the URM wall’s tributary area. Both models were constructed using local materials and
local labours. Two features were taken into account. First, it accommodated the influence of
flanged wall and second, the URM wall was built on the stone foundation. The first URM
wall represent the plain existing URM building in Indonesia and second strengthened by
Kevlar fibre.
It was observed from the test results that the URM wall Unit-1 did not behave as a brittle
structure. It could dissipate energy without loss of strength and had a post-elastic behaviour in
terms of “overall displacement ductility” value of around 8 to 10. As predicted, the masonry
material was variable and non homogeneous which caused the hysteresis loop to be non
symmetrical between push and pull lateral load directions. It can be summarized that Kevlar
fibre strengthening technique is promising and with great ease of installation. Although
Kevlar material is more expensive when compared to other fabrics as long as it was applied at
the essential locations and in limited volumes, it can significantly increase the in-plane URM
wall capacity. With appropriate arrangements of Kevlar fibre, a practicing engineer will be
able to obtain a desired rocking mechanism in the masonry structure. Another advantage for
the architectural point of view, very thin Kevlar fibres do not reduce the architectural space.
Studies have also been undertaken to analyze the in-plane response of plain URM wall before
and after retrofiting using the current seismic standard and the Finite Element Method (FEM).
3
White, Kevin Andrew. "Sandwich action in foam filled masonry cavity walls." Thesis, Nottingham Trent University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245632.
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Minaie, Ehsan Moon Franklin. "Behavior and vulnerability of reinforced masonry shear walls /." Philadelphia, Pa. : Drexel University, 2009. http://hdl.handle.net/1860/3163.
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Wirth, John Michael. "An Exploration of the Masonry Wall." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/46170.
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The teaching of the user through the clear understanding of the building they encounter on a daily basis is the intent of this thesis. Can a user learn how a brick wall is constructed, by looking and interacting with the brick wall they sleep within at night? Is it easier for one to understand his/her built environment if the construction is done in a manner that makes the means transparent, versus hidden tricks within the materials. Through the study of honest and truthful use of materials and construction methods, this project explores if a building can teach.<br>Master of Architecture
6
Vaughan, Timothy Phillips. "Evaluation of masonry wall performance under cyclic loading." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Spring2010/t_vaughan_042310.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, May 2010.<br>Title from PDF title page (viewed on July 14, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 72-73).
7
Moradi, Lee. "Resistance of membrane retrofit concrete masonry walls to lateral pressure." Birmingham, Ala. : University of Alabama at Birmingham, 2007. https://www.mhsl.uab.edu/dt/2009r/moradi.pdf.
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Thesis (Ph. D.)--University of Alabama at Birmingham, 2007.<br>Title from PDF title page (viewed Feb. 4, 2010). Additional advisors: James S. Davidson, Robert J. Dinan, Alan E. Eberhardt, Jason T. Kirby, Talat Salama, Houssam A. Toutanji. Includes bibliographical references (p. 139-146).
8
Haider, Waheed, and haiderw@connellhatch com. "INPLANE RESPONSE OF WIDE SPACED REINFORCED MASONRY SHEAR WALLS." Central Queensland University. Centre for Railway Engineering, 2007. http://library-resources.cqu.edu.au./thesis/adt-QCQU/public/adt-QCQU20070421.130337.
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Wide spaced reinforced masonry (WSRM) walls that contain vertical reinforced cores at horizontal spacing up to 2000mm are commonly used in high wind zones of Australia although their inplane shear resistance is not well understood. This thesis aims at providing better insight into the behaviour of WSRM walls subjected to inplane lateral loading through experimental and numerical investigations.
The interactions between the unreinforced masonry (URM) panels and vertical reinforced cores are first determined using an elastic finite element analysis and the potential failure paths hypothesized. The hypotheses are then validated using a series of full-scale WSRM and Non-WSRM wall tests under monotonic and cyclic lateral loading by keeping the spacing between the vertical reinforced cores as the main design variable. Load-displacement response of these shear walls indicates that the current classification of the WSRM in AS3700 (2001) as those walls containing vertical reinforced grouted cores at 2000mm maximum spacing is appropriate.
A finite element model (FEM) based on an explicit solution algorithm is developed for predicting the response of the masonry shear walls tested under static loading. The FEM has adopted macroscopic masonry failure criteria and flow rules, damaged plasticity model for grout and tension-only model for reinforcing bars reported in the literature, and predicted crack opening and post-peak load behaviour of the shear walls. By minimising the kinetic energy using appropriate time scaling, the FEM has provided reasonable and efficient prediction of load flow, crack patterns and loaddisplacement curves of the shear walls. The FEM is further validated using full-scale tests on WSRM walls of aspect ratios and pre-compression different to that tested before.
The validated FEM is used to examine the appropriateness of the prescriptive design details for WSRM concrete masonry shear walls provided in AS3700 (2001) allowing for a large scatter in material properties. It is shown that the inplane shear capacity formula provided in AS3700 (2001) for squat WSRM shear walls is non-conservative.
9
Lunn, Dillon Stewart. "Behavior of Infill Masonry Walls Strengthened with FRP Materials." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-04282009-143603/.
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Collapse of unreinforced masonry (URM) structures, including infill walls, is a leading cause of property damage and loss of life during extreme loading events. Many existing structures are in need of retrofit to bring them in compliance with modern design code provisions. Conventional strengthening techniques are often time-consuming, costly, and add significant weight to the structure. These limitations have driven the development of alternatives such as externally bonded (EB) glass fiber reinforced polymer (GFRP) strengthening systems, which are not only lightweight, but can be rapidly applied and do not require prolonged evacuation of the structure. The objective of this research program was to evaluate the effectiveness of strengthening infill masonry walls with externally bonded GFRP sheets to increase their out-of-plane resistance to loading. The experimental program comprises fourteen full-scale specimens, including four un-strengthened (control) specimens and ten strengthened specimens. All specimens consisted of a reinforced concrete (RC) frame (which simulates the supporting RC elements of a building superstructure) that was in-filled with solid concrete brick masonry. The specimens were loaded by out-of-plane uniformly distributed pressure in cycles up to failure. Parameters investigated include the aspect ratio, the strengthening ratio, the number of wythes, and the type of FRP anchorage used. The type of FRP anchorage was found to greatly influence the failure mode. Un-strengthened specimens failed in flexure. However, strengthened specimens without overlap of the FRP onto the RC frame failed due to sliding shear along the bed joints which allowed the walls to push out from the RC frames in a rigid body fashion. In the case where GFRP sheets were overlapped onto the RC frames, the aforementioned sliding shear caused delamination of the GFRP sheets from the RC frames. Use of steel angles anchored along the perimeter of the walls as shear restraints allowed these walls to achieve three times the service load without any visible signs of distress. GFRP strengthening of infill masonry walls was found to be effective, provided that proper anchorage of the FRP laminate was assured.
10
Mjelde, Jon Zachery. "Performance of lap splices in concrete masonry shear walls." Online access for everyone, 2008. http://www.dissertations.wsu.edu/Thesis/Spring2008/Jon_Mjelde.042508.pdf.
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O'Gara, Martin. "Numerical modelling of masonry compartment walls in fire situations." Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342400.
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12
Gandia, Jordan. "Blast Retrofit of Unreinforced Masonry Walls Using ECC Shotcrete." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39070.
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Blast loads on buildings can originate from accidental explosions or from targeted attacks. Design against blast loads has become an increasingly important topic due to the current political climate. Unfortunately, many older buildings are constructed with unreinforced masonry (URM) walls which are particularly susceptible to out of plane failures caused by blast loads. One solution to increase the safety of these buildings is to retrofit them with advanced materials that can increase their out-of-plane stiffness and resistance. This thesis investigates the potential of using a high-performance shotcrete as a retrofit system for URM walls against blast effects. The shotcrete used in this study is made from Engineered Cementitious Composite (ECC), a special type of fiber-reinforced cementitious material, with high ductility and high energy-absorption capacity. The ECC shotcrete replaces aggregates with synthetic microfibers to increase tensile strength and ductility. A welded wire mesh was embedded in the shotcrete to provide ductile behavior.
The testing program includes a total of six large-scale unreinforced masonry wall specimens. Two walls were constructed using concrete masonry unit (CMU) blocks to be retrofitted. The first specimen was built as an infill wall, experiencing no axial load, while the second specimen was built as a load bearing wall, with 10% axial load. Four more walls were built out of stone blocks. Two of the stone walls were controls: one infill and one load bearing (4% axial load). The other two stone walls were retrofit with the shotcrete system: one infill and one load bearing (4% axial load).
The blast loads were simulated using the University of Ottawa’s Shock Tube. The walls were restrained at the top and bottom with a shear restraint to induce one way bending. Pressure, displacement and strain data were acquired with the use of pressure gauges, LVDT’s, strain gauges and cameras.
The specimens were subjected to gradually increasing blast pressures until failure. The performance of the specimens was observed by analyzing the displacement, crack widths, fragmentation and failure mode. The results indicate the benefits of using ECC shotcrete as a retrofit system. The displacements of the retrofit walls were very small compared to the control walls, and fragments were limited. The specimens with axial load were found to have increased resistance. While the failure mode was brittle for the retrofit walls, this can be avoided with the use of a mesh with a larger area of steel.
A SDOF analysis was performed to predict the blast response of the test walls. The analysis was done by generating resistance functions for the walls through analytical models. The analysis was found to agree reasonably well with the experimental data.
13
Zessin, Jennifer Furstenau. "Collapse analysis of unreinforced masonry domes and curving walls." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70879.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2012.<br>This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.<br>Cataloged from student-submitted PDF version of thesis.<br>Includes bibliographical references (p. 176-182).<br>The safety and assessment of historic masonry structures continues to be a challenge for most analysts, especially for more complex buildings. Historic masonry structures have great cultural and economic value, but engineers have not examined the collapse modes for many masonry elements. This thesis examines the collapse of unreinforced masonry structures in response to large support displacements and constant horizontal ground accelerations. Two different structural forms are studied and collapse conditions are established for each. The aim of this research is to allow simple, but meaningful, analytical models and experimental results to inform each other in an effort to better define masonry collapse mechanisms. The first structural form to be analyzed is the masonry dome. For historical masonry domes, small outward movements of the supports will cause cracking and may lead to collapse. The critical span increase to cause collapse of a hemispherical dome is determined for domes with varying thicknesses using two small-scale physical models. In addition, the critical value of constant horizontal acceleration to cause collapse of a hemispherical dome is also examined, simulated by tilting the two domes on a plane. In both cases, a mechanism forms, rendering the dome unstable and collapse ensues. Simple analytical models, emphasizing the relationship between geometry and equilibrium, are able to accurately predict the failure limits and mechanisms. The second structural form to be analyzed is the curving masonry wall. In an effort to better understand the origins and perceived benefits of curving masonry walls, their stability is measured relative to the amount of curvature in the wall. The critical value of constant horizontal acceleration to cause collapse of a curving wall is determined using multiple equilibrium methods and compared with both full-scale and small-scale experiments for dry-stacked bricks. Based on these results, new limits for the stability of these structures are proposed.<br>by Jennifer Furstenau Zessin.<br>Ph.D.
14
Dillon, Patrick. "Shear Strength Prediction Methods for Grouted Masonry Shear Walls." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/4395.
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The research in this dissertation is divided between three different approaches for predicting the shear strength of reinforcement masonry shear walls. Each approach provides increasing accuracy and precision in predicting the shear strength of masonry walls. The three approaches were developed or validated using data from 353 wall tests that have been conducted over the past half century. The data were collected, scrutinized, and synthesized using principles of meta-analysis. Predictions made with current Masonry Standards Joint Committee (MSJC) shear strength equation are unconservative and show a higher degree of variation for partially-grouted walls. The first approach modifies the existing MSJC equation to account for the differences in nominal strength and uncertainty between fully- and partially-grouted walls. The second approach develops a new shear strength equation developed to perform equally well for both fully- and partially-grouted walls to replace and improve upon the current MSJC equation. The third approach develops a methodology for creating strut-and-tie models to analyze or design masonry shear walls. It was discovered that strut-and-tie modeling theory provides the best description of masonry shear wall strength and performance. The masonry strength itself provides the greatest contribution to the overall shear capacity of the wall and can be represented as diagonal compression struts traveling from the top of the wall to the compression toe. The shear strength of masonry wall is inversely related to the shear span ratio of the wall. Axial load contributes to shear strength, but to a lesser degree than what has been previously believed. The prevailing theory about the contribution of horizontal shear reinforcement was shown to not be correct and the contribution is much smaller than was originally assumed by researchers. Horizontal shear reinforcement principally acts by resisting diagonal tensile forces in the masonry and by helping to redistribute stresses in a cracked masonry panel. Vertical reinforcement was shown to have an effect on shear strength by precluding overturning of the masonry panel and by providing vertical anchorages to the diagonal struts.
15
Nazir, Shahid. "Studies on the failure of unreinforced masonry shear walls." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/82792/1/Shahid_Nazir_Thesis.pdf.
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This thesis aims at studying the structural behaviour of high bond strength masonry shear walls by developing a combined interface and surface contact model. The results are further verified by a cost-effective structural level model which was then extensively used for predicting all possible failure modes of high bond strength masonry shear walls. It is concluded that the increase in bond strength of masonry modifies the failure mode from diagonal cracking to base sliding and doesn't proportionally increase the in-plane shear capacity. This can be overcome by increasing pre-compression pressure which causes failure through blocks. A design equation is proposed and high bond strength masonry is recommended for taller buildings and/ or pre-stressed masonry applications.
16
IENTILE, SILVIA. "Sensitivity and dinamic identification of damaged unreinforced Masonry Walls." Doctoral thesis, Università IUAV di Venezia, 2017. http://hdl.handle.net/11578/278742.
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Behrens, Christina. "Assessment of thermal properties of AAC masonry walls and panels." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1453187421&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Nolph, Shawn Mark. "In-plane shear performance of partially grouted masonry shear walls." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Thesis/Summer2010/s_nolph_050710.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, May 2010.<br>Title from PDF title page (viewed on July 21, 2010). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 96-97).
19
Davis, Courtney Lynn. "Evaluation of design provisions for in-plane shear in masonry walls." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/C_Davis_120508.pdf.
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Thesis (M.S. in civil engineering)--Washington State University, December 2008.<br>Title from PDF title page (viewed on Feb. 19, 2009). "Department of Civil and Environmental Engineering." Includes bibliographical references (p. 56-57).
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Daou, Yehia Anis. "Behaviour of post-tensioned brickwork cantilever fin walls." Thesis, University of Sheffield, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389923.
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Erdogdu, Murat. "In Plane Seismic Strengthening Of Brick Masonry Walls Using Rebars." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610114/index.pdf.
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About half of the total building stock in Turkey is masonry type building.
Masonry buildings in Turkey, especially in rural areas, are constructed without any
engineering knowledge mostly by their own residents. They generally have heavy
roofs. Masonry type buildings also have thick and heavy wall materials. Heavy
roof and wall material generate large inertial forces in the case of an earthquake.
Brittle failure of walls leads to total failure of whole system followed by sudden
collapse of heavy roof. The aim of this thesis is to understand failure mechanisms
of brick masonry walls, prevent their brittle failure and allow the walls to dissipate
energy during an earthquake. Furthermore, ultimate capacity increase was also
targeted by using low cost and easy to obtain material.
In order to find an economical and effective way in strengthening of brick masonry
walls in their in-plane direction, steel rebars were used as post-tensioning materials
in brick masonry walls and house tests. Springy connections were utilized in the
reinforcing and post-tensioning bars in order to prevent early loss of post-tension
due to wall cracking or rebar yielding. Separate tests were conducted with and
without rebars and springs in order to compare their results.
v
The test results indicated that the ultimate lateral load capacity of 6m long brick
masonry house increased up to about 6 times with respect to its nominal value.
Energy dissipation also increased up to about 10 times of the original house.
Lateral load capacity increase in 2m long rebar post-tensioned brick masonry walls
were measured as about 17 times when compared with the original wall. The
energy dissipation capacity was also increased about 30 times the nominal value.
A general procedure was developed to assess the vulnerability of single storey
masonry houses, which calculates the earthquake demand acting on each wall
segment. Comparison of capacity versus demand enables evaluation of wall
segments and leads strengthening calculations if necessary. Derived formulas were
used to calculate post-tensioning force and design vertical and diagonal rebars. The
procedure was demonstrated using properties of an existing house and
strengthening cost was found to be about 10% of the building cost.
The results of the conducted tests have shown that rebar post-tensioning of brick
masonry walls is an effective and cost-efficient way of strengthening the walls in
their in-plane direction and can be used as an economical and simple technique for
seismically vulnerable masonry houses. Spring based connection detail has
improved the post cracking performance of the walls at large deformations by
keeping the wall reaction higher after ultimate strength has reached as well as
increased the energy dissipation capacity of the walls.
22
Aridru, Gabriel G. "Effective flexural rigidity of plain and reinforced concrete masonry walls." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ29463.pdf.
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Willis, C. R. "Design of unreinforced masonry walls for out-of-plane loading /." Title page, abstract and table of contents only, 2004. http://web4.library.adelaide.edu.au/theses/09PH/09phw7342.pdf.
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GEREN, REBECCA. "CALCULATING FIRE-RESISTANCE RATINGS OF CONCRETE MASONRY UNIT (CMU) WALLS." Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/618764.
Full textAbstract:
This paper serves as a statement accompanying a capstone project for a degree in
Information: Science and Technology. It details the work that went into creating the
web page dedicated to helping specifications and codes writers to calculate fire resistance
ratings of concrete masonry unit (CMU) walls. It briefly examines what a
CMU wall is and the calculations that are involved in calculating fire-resistance
ratings. The paper delves into how the site itself works, what the user can expect to
see when first accessing the page and how to follow the steps in order to get the
correct output. Without getting too technical, the paper also describes the four
programming languages that were involved with coding the web page and what
they handle in accordance with the page’s design and implementation. Finally, the
paper concludes with an appendix containing the URL that will lead the reader to
the web calculator and provides some practice problems that will allow the reader
to test the calculator’s abilities.
25
Rahman, Ahmad Habibur Carleton University Dissertation Engineering Civil. "Thermal stresses in intersecting masonry walls; a finite element study." Ottawa, 1986.
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Burnett, Steven. "Impact resistance of masonry walls : materials characterisation & numerical modelling." Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412723.
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Noor-E-Khuda, Sarkar. "Studies on the out-of-plane behaviour of masonry walls." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/93197/1/Sarkar_Noor-E-Khuda_Thesis.pdf.
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The prime aim of this PhD thesis is to contribute to the current body of knowledge on the out-of-plane performance of masonry walls through systematic investigation of the key parameters and provide insight into the design clauses of Australian Masonry Standard (AS3700-2011). The research work has been carried out through numerical simulation based on a 3D layered shell element model. The model demonstrated capability to simulate various forms of new and existing masonry systems commonly constructed in Australia such as unreinforced, internally and externally reinforced, confined and dry-stack masonry. In addition, the model simultaneously simulates in-plane and out-of-plane responses.
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Ozturk, Mehmet Selim. "Effects Of Masonry Infill Walls On The Seismic Performance Of Buildings." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606753/index.pdf.
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In Turkey, in most of the reinforced concrete buildings, hallow masonry infill walls are used as a non-structural element, during design stage, their contribution to overall building behavior is not well known. Observations made after the earthquakes revealed that these non-structural elements had beneficial effects on the lateral capacity of the building.
In this study, the contribution of the hallow masonry infill walls to the lateral behavior of reinforced concrete buildings was investigated. For this purpose, two different buildings were chosen as case studies. Three and six story symmetric buildings are modeled as bare and infilled frames. The parameters that were investigated are column area, infill wall area, distribution of masonry infill walls throughout the story. To determine the effect of each parameter, global drift ratios are computed and are compared for each case.
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Riahi, Zahra. "Backbone model for confined masonry walls for performance-based seismic design." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32195.
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Nonlinear models are of paramount importance in the emerging field of performance-based earthquake engineering. In this study, an analytical model is developed capable of
simulating the measured backbone of typical confined masonry (CM) walls whose
response under lateral loads is mainly governed by shear deformations. Equations are
developed for the cracking and maximum shear strength, and the cracking and ultimate
deformation capacities. This model is based on the results of both monotonic and
reversed cyclic experiments assembled in an extensive database, and developed through
an iterative linear regression analysis.
Owing to their anomalies, specimens with compression diagonal loading, height-to-length aspect ratio greater than 1.2, axial stress to masonry compressive strength ratio
larger than 0.12, and those with column longitudinal reinforcement ratio below 1%, are
not considered for the purpose of creating the, empirical equations.
Several statistical and graphical tools are utilized to identify the most significant panel
and tie column design variables; to set the functional forms that best relate them to model
parameters; and to diagnose influential points that may exert undue impact on the
analysis results.
The effect of openings and panel aspect ratio on the strength characteristics of CM walls,
the capability of existing equations to predict the observed backbone response, and the
limitations of the proposed equations are discussed in detail. Model variability is also
presented in lognormal fragility curves for different model parameters and at all limit
states.
The proposed backbone model is found to simulate reasonably well the seismic behaviour
of CM walls whose properties conform to the assumptions of the model. However, it fails
to track the observed backbone response of anomalous or atypical CM walls.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
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Albert, Michael Lewis. "Rehabilitation of unreinforced masonry walls with externally applied fiber-reinforced polymers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0002/MQ34330.pdf.
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Ciornei, Laura. "Performance of Polyurea Retrofitted Unreinforced Concrete Masonry Walls Under Blast Loading." Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23180.
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Unreinforced masonry walls subjected to blast loading are vulnerable to collapse and fragmentation. The objective of this thesis is to conduct experimental and analytical research for developing a blast retrofit methodology that utilizes polyurea. A total of four unreinforced masonry walls were constructed and tested under various shock tube induced blast pressures at the University of Ottawa Shock Tube Testing Facility. Two of the retrofitted walls had surface-sprayed polyurea. The results indicate that the use of polyurea effectively controlled fragmentation while significantly increased the load capacity and stiffness of masonry walls. Polyurea proved to be an excellent retrofit material for dissipating blast induced energy by providing ductility to the system and changing the failure mode from brittle to ductile. Single degree of freedom (SDOF) dynamic analyses were conducted as part of the analytical investigation. The results show that the analytical model provides reasonably accurate predictions of the specimen response.
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Silveira, Dora Susana Gomes da. "Constructive and mechanical characterisation of adobe masonry walls of existing buildings." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17313.
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Doutoramento em Engenharia Civil<br>Earthen construction has been widely used throughout the world, since
approximately 10000 years ago and until the present day. A significant part of
the world earthen built heritage – including many properties inscribed on the
UNESCO’s World Heritage List –, however, is at risk.
In Portugal, earth was also a widely used construction material until the middle
of the 20th century. In Aveiro district, in particular, adobe construction was very
common. Currently, there are still a great number of adobe constructions in this
region, a large part of which are in use. Many of the existing buildings are of
social, cultural, and architectural value. Despite their value, however, many of
these buildings are in a poor state of conservation, suffering from various
structural and non-structural defects.
The problems observed in existing adobe buildings result in large part from a
lack of knowledge regarding the materials and building systems used in this
type of construction. There is, in particular, a lack of knowledge about the
properties and behaviour of adobe masonry walls, which are key structural
elements that influence the overall behaviour of buildings. The main aim of the
research developed and discussed in this thesis is thus to contribute to this
knowledge, focusing, in particular, on the adobe buildings of Aveiro district.
For this purpose, a visual and dimensional inspection of the facade walls of
twenty-one representative adobe buildings was conducted. With this inspection,
it was possible to carry out a detailed analysis of the facade walls – including
their structural system, coatings, and traditional masonry materials – and to
assess the vulnerabilities, common defects, and state of conservation of these
elements.
A series of experimental tests were also carried out. Simple compression tests
were performed on cylindrical and cubic adobe specimens, flexural tests on
adobe bricks, and splitting tests on cylindrical specimens. Simple compression
and diagonal compression tests were also conducted on ten full-scale adobe
masonry wall panels, built with adobes taken from an existing construction.
Finally, an in-plane horizontal cyclic test was performed on a full-scale double-T
shaped adobe wall, also built with adobes from an existing construction. With
the tests carried out, it was possible to characterise the strength, stiffness,
stress-strain relationships, and common damage pattern of the test specimens,
and to assess correlations between different mechanical properties. It was also
possible to develop a comparison between the strength values obtained and
the limits indicated in existing standards for earthen construction, and between
the results obtained and those determined by other authors for test specimens
representative of adobe construction in other countries.
The results presented and discussed in this thesis contribute to the enrichment
of knowledge that is considered essential to support the conservation and
rehabilitation of existing adobe buildings, not only in Portugal, but also in other
regions of the world.<br>A construção em terra tem sido muito utilizada em todo o mundo, desde há
cerca de 10000 anos atrás e até aos dias de hoje. Uma parte significativa do
património mundial construído com terra, incluindo vários bens inscritos na
Lista de Património Mundial da UNESCO, encontra-se, no entanto, em risco.
Em Portugal, a terra foi também um material de construção muito utilizado até
meados do século XX. No distrito de Aveiro, em particular, a construção em
adobe era muito comum. Atualmente, existe ainda um elevado número de
construções em adobe nesta região, grande parte das quais se encontram em
uso. Muitos dos edifícios existentes são de valor social, cultural e arquitetónico
reconhecido. No entanto, apesar do seu valor, muitos destes edifícios estão
em mau estado de conservação, apresentando anomalias estruturais e não
estruturais variadas.
Os problemas observados nos edifícios existentes de adobe resultam, em
grande parte, de falta de conhecimento sobre os materiais e sistemas de
construção utilizados neste tipo de edificação. Há, em particular, falta de
conhecimento sobre as propriedades e o comportamento das paredes de
alvenaria de adobe, que são elementos estruturais principais que influenciam o
comportamento global dos edifícios. Assim, o trabalho de investigação
desenvolvido e discutido nesta tese tem como principal objetivo contribuir para
este conhecimento, debruçando-se, em particular, sobre as construções em
adobe do distrito de Aveiro.
Para este efeito, foi realizada uma inspeção visual e dimensional das paredes
de fachada de vinte e um edifícios de adobe representativos. Com esta
inspeção, foi possível analisar de forma detalhada as paredes de fachada –
incluindo o seu sistema estrutural, revestimentos e materiais de alvenaria
tradicionais – e avaliar as vulnerabilidades, anomalias comuns e estado de
conservação destes elementos.
Uma série de ensaios experimentais foi também levada a cabo. Foram
realizados ensaios de compressão simples sobre provetes cilíndricos e cúbicos
de adobe, ensaios de flexão sobre blocos de adobe e ensaios de compressão
diametral sobre provetes cilíndricos. Foram ainda realizados ensaios de
compressão simples e compressão diagonal sobre dez painéis de alvenaria de
adobe à escala real, construídos com adobes recolhidos de uma construção
existente. Por fim, realizou-se o ensaio de uma parede à escala real em forma
de ‘duplo T’, construída também com adobes de uma construção existente,
sob a ação de uma carga horizontal cíclica, aplicada no plano da parede. Com
os ensaios realizados, foi possível caracterizar a resistência, a rigidez, as
relações de comportamento tensão-deformação e o padrão comum de dano
dos elementos ensaiados, e avaliar as correlações entre diferentes
propriedades mecânicas. Foi ainda desenvolvida uma comparação entre os
valores de resistência obtidos e os limites indicados nas normas existentes
para a construção em terra, bem como entre os resultados obtidos e aqueles
determinados por outros autores para a alvenaria de adobe representativa da
construção em adobe noutros países.
Os resultados apresentados e discutidos nesta tese contribuem para o
enriquecimento de conhecimento que é considerado essencial para apoiar a
conservação e reabilitação dos edifícios de adobe existentes, não só em
Portugal, mas também noutras regiões do mundo.
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Tapsir, Siti Hamisah. "Time-dependent loss of post-tensioned diaphragm and fin masonry walls." Thesis, University of Leeds, 1994. http://etheses.whiterose.ac.uk/11263/.
Full textAbstract:
This thesis reports an investigation on time-dependent loss of post-tensioned masonry box and tee sections representing diaphragm and fin walls, respectively. The prestress loss due to creep and shrinkage of masonry, and relaxation of steel bars were quantified separately and the main influencing factors considered were geometry and masonry type. For each type of masonry three diaphragm and three fin walls were built to determine prestress loss (decreasing load), creep (constant load) and shrinkage (zero load). The walls were constructed from undocked clay, calcium silicate and concrete block units with grade (ii) mortar with cementlime:sand in the proportions of 1:½:4½ and water/cement ratio of 1.27. Creep and shrinkage were also measured on unbonded masonry units and mortar prisms for predicting the deformations in the masonry walls by using a previously developed composite model. The mal;onry units and mortar prisms were partly sealed to simulate the corresponding volume/surface ratio of the bonded masonry units and mortar joints in the masonry walls. The calcium silicate walls exhibited the highest prestress loss, creep and shrinkage compared with the clay and concrete block diaphragm and fin walls. The current methods of prediction of prestress loss for masonry are only suitable for specific types of masonry for which they were developed. On the other hand, the methods developed for prestressed concrete gave reasonable predictions for all the masonry types investigated, with one particular method being very accurate. For all test results it was confirmed that long-term deformations were influenced by geometry, fin walls exhibiting greater deformations than diaphragm walls. The composite model did not predict shrinkage very well in calcium silicate and concretc block walls because some moisture in the mortar was absorbed by the masonry units. As a result the partly sealed unbonded mortar prisms had higher water content than the mortar bed joint in the walls, and thus a higher shrinkage in the partly sealed mortar prisms occured. Consequently, when the creep and shrinkage of the partly sealed mortar prisms was applied to the model, the masonry deformation was overestimated. A modified water absorption test was carried out which confirmed that for units laid dry the mortar bed joint had a reduced shrinkage compared to the unbonded mortar prisms. From the results, creep and shrinkage adjustment factors were correlated with unit water absorption, and when adjusted creep and shrinkage were incorporated with the composite model, satisfactory predictions of masonry deformations were achieved.
34
Lazzarini, Daniel Louis. "Seismic Performance of Unreinforced Masonry Walls Retrofitted with Post-Tensioning Tendons." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/143.
Full textAbstract:
Unreinforced masonry (URM) structures have historically been regarded as structurally unsound in response to seismic events. The tendency for URM walls to collapse out-of-plane in a brittle manner is continually cause for concern. Retrofit of these walls is necessary in order to prevent severe damage and injury to occupants.
This paper is concerned with the retrofit of unreinforced masonry (URM) walls in response to out-of-plane loading. A retrofit design was developed and verified through structural testing. The selected retrofit technique incorporates vertical coring of URM walls to allow for the insertion of a single post-tensioning (PT) tendon. Tendons are spaced at a regular interval and anchored at the top of the wall parapet and at the lower diaphragm level. Tensioning of the tendons imparts a compressive stress to the wall that effectively increases the wall cracking moment strength, ultimate moment strength and displacement capacity. Additionally, the insertion of PT tendons allows the wall to behave in a ductile manner in response to out-of-plane ground motion.
Extensive research was conducted in order to accurately portray the material properties and construction methods of unreinforced masonry walls in San Luis Obispo, California. Various mortar mix designs were generated and tested so that a mix design could be selected to best reflect the target URM structures. Seismic parameters were generated to reflect a URM structure in San Luis Obispo.
An unreinforced masonry wall was constructed by a professional mason using the established mortar mix proportions and salvaged bricks from the 1920 era. Having a pin-pin unsupported height of 11 feet, the wall constructed for testing was reflective of the configuration of URM walls in many downtown San Luis Obispo structures. The wall was loaded in the out-of-plane direction by 4 equal point loads mimicking a uniformly distributed load. The testing program consisted of cycling the wall through target internal moments and target displacements.
It was verified through testing that post-tensioning tendons can be successfully introduced in URM walls to resist out-of-plane bending. Testing showed that the addition of PT tendons significantly increased the wall’s cracking moment capacity, giving it the elastic strength to resist twice the forces imposed by the design-level ground motion. PT tendons also increased the nominal strength of the wall, allowing the wall to achieve large displacements without collapse. It was also found that PT tendons provided a restoring force to the wall returning it to almost no residual displacement after each displacement cycle. Thus, the URM wall retrofitted with PT tendons demonstrated significant integrity as a structural system, providing for improved strength and ductility with no residual displacement.
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Song, Mengli. "Effectiveness of steel bars in reinforced masonry walls under concentric compression." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/132724/1/Mengli_Song_Thesis.pdf.
Full textAbstract:
This PhD thesis aims at developing an economical and safe reinforced masonry structural walling system suitable for usage in the heavily loaded lower stories of the multi-storeyed residential or commercial buildings. Through a systematic experimental investigation of more than 50 walls and a finite element modelling incorporating material and geometric nonlinearities, design formulae have been developed and incorporated in the Australian Masonry Design Standard AS3700 (2018). With this significant contribution, the outcomes of this PhD thesis can address some of the recent problems of huge societal costs involving cracked walls in several residential apartments in Australia.
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Arifuzzaman, Shah. "Seismic Retrofit of Load Bearing Masonry Walls with Surface Bonded FRP Sheets." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24233.
Full textAbstract:
A large inventory of low rise masonry buildings in Canada and elsewhere in the world were built using unreinforced or partially reinforced load bearing wall. The majority of existing masonry structures is deficient in resisting seismic force demands specified in current building codes. Therefore, they pose significant risk to life safety and economic wellbeing of any major metropolitan centre. Because it is not economically feasible to replace the existing substandard buildings with new and improved structures, seismic retrofitting remains to be an economically viable option.
The effectiveness of surface bonded carbon fiber-reinforced polymer (CFRP) sheets in retrofitting low-rise load bearing masonry walls was investigated in the current research project. The retrofit technique included the enhancements in wall capacity in shear and flexure, as well as anchoring the walls to the supporting elements through appropriate anchorage systems. Both FRP fan type anchors and steel sheet anchors were investigated for elastic and inelastic wall response. One partially reinforced masonry (PRM) wall and one unreinforced masonry (URM) wall were built, instrumented and tested under simulated seismic loading to develop the retrofit technique. The walls were retrofitted with CFRP sheets applied only on one side to represent a frequently encountered constraint in practice. FRP fan anchors and stainless steel sheet anchors were used to connect the vertical FRP sheets to the wall foundation. The walls were tested under constant gravity load and incrementally increasing in-plane deformation reversals. The lateral load capacities of both walls were enhanced significantly. The steel sheet anchors also resulted in some ductility. In addition, some small-scale tests were performed to select appropriate anchor materials. It was concluded that ductile stainless steel sheet anchors would be the best option for brittle URM walls.
Analytical research was conducted to assess the applicability of truss analogy to retrofitted walls. An analytical model was developed and load displacement relationships were generated for the two walls that were retrofitted. The analytical results were compared with those obtained experimentally, indicating good agreement in force resistance for use as a design tool.
37
Centeno, Jose. "Sliding displacements in reinforced masonry walls subjected to in-plane lateral loads." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/52438.
Full textAbstract:
Seismic design provisions in the Canadian Masonry Code often lead to indications that the governing yield mechanism for a reinforced masonry wall with a height/length (H/L) ratio below 1.0 and under low axial loads will not achieve the design objective of a flexural yield mechanism and instead, will develop a sliding shear mechanism. In addition to this, results of previous experimental research studies indicate that even for squat walls that yield in flexure, the displacements at the top are the result of both flexure and sliding shear mechanisms. Currently, there is a limited understanding on how sliding shear displacements develop and how they affect the response of a building. The following work sets out to study the sliding shear mechanism and to develop tools for determining the corresponding displacements for seismic design. This study proposes to modify the current definition for a sliding shear mechanism, re-classifying yield mechanisms of Reinforced Masonry (RM) walls with sliding displacements into three separate mechanisms: sliding shear (SS) mechanism, dowel-constrained failure (DCF) mechanism and combined flexural-sliding shear (CFSS) mechanism. In addition, a 2D analytical model is developed and calibrated in this study using the experimental test results of wall specimens with recorded sliding shear displacements. This calibrated model simulates sliding in RM walls based on the effects of frictional resistance, dowel action and flexural hinging, which will be the basis for a procedure that can estimate sliding displacements in an RM wall design.<br>Applied Science, Faculty of<br>Civil Engineering, Department of<br>Graduate
38
Taghdi, Mustafa. "Seismic retrofit of low-rise masonry and concrete walls by steel strips." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0003/NQ32457.pdf.
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Kuzik, Marc D. "Out-of-plane cyclic behavior of masonry walls reinforced externally with GFRP." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0015/MQ47054.pdf.
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Rosenboom, Owen Arthur. "Post-Tensioned Clay Brick Masonry Walls for Modular Housing in Seismic Regions." NCSU, 2002. http://www.lib.ncsu.edu/theses/available/etd-07092002-151211/.
Full textAbstract:
From past research post-tensioned concrete masonry walls have performed well due to in-plane loading, yet despite the advantage of being more aesthetically pleasing, post-tensioned clay brick masonry walls have not been investigated under this loading. Five half scale structural specimens using this system were constructed and tested, and the results from these tests plus a proposed force-displacement analysis procedure are included herein. The results show that post-tensioned clay brick masonry walls are well suited for seismic regions when the walls are grouted and unbonded, and the presence of confinement plates in the compression region greatly enhances the overall performance of the wall. In addition, the force-displacement analysis shows that in order to account for the overall behavior of the wall, cyclic degradation characteristics must be included.
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Campbell, Barraza Jaime Andrés [Verfasser]. "Numerical model for nonlinear analysis of masonry walls / Jaime Andrés Campbell Barraza." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1025515250/34.
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Boyle, P. M. "Passive solar energy : modifications of existing masonry walls to improve thermal performance." Thesis, University of Leeds, 1986. http://etheses.whiterose.ac.uk/618/.
Full textAbstract:
Existing brick walls usually have a high U value, one method of improvement is by insulation, but if the wall faces approximately south, it is possible that greater benefits could be obtained by improving the wall's performance as a solar collector. Three solid 225 mm walls were constructed: one glazed, one unglazed, and (since glazing prevents rain penetration) one waterproofed unglazed wall. Two glazed cavity walls were also constructed one glazed with a fan to recover heat from the cavity by forced convection, and one unglazed, with no fan. These walls gave small heat gains. The walls behind the glazing were then insulated on their outer faces, and warm air collected by natural convection. Such a collector was built using a selective surface, a maximum efficiency of about 50% was observed. A theoretical model was developed based on simple steady state theory, this was found to correlate well with experimental data. The theory could be used for any system of low thermal storage, including forced flow collectors. Finally these walls, and others, are compared and their relative merits discussed.
43
Williams, Scott A. "Numerical Analysis of Reinforced Masonry Shear Walls Using the Nonlinear Truss Approach." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/25219.
Full textAbstract:
Reinforced masonry (RM) shear walls are a common lateral load-resisting system for building structures. The seismic design guidelines for such systems are based on relatively limited experimental data. Given the restrictions imposed by the capabilities of available experimental equipment, analytical modeling is the only means to conduct systematic parametric studies for prototype RM wall systems and quantify the seismic safety offered by current design standards. A number of modeling approaches, with varying levels of complexity, have been used for the analysis of reinforced concrete (RC) and masonry wall structures. Among the various methods, the truss analogy is deemed attractive for its conceptual simplicity and excellent accuracy, as indicated by recent studies focusing on RC walls.
This thesis uses an existing modeling method, based on nonlinear truss models, to simulate the behavior of fully grouted reinforced masonry shear walls. The modeling method, which was originally created and used for RC walls, is enhanced to capture the effect of localized sliding along the base of a wall, which may be the dominant mode of damage for several types of RM walls. The truss modeling approach is validated with the results of quasi-static cyclic tests on single-story isolated walls and dynamic tests on a multi-story, three-dimensional wall system. For the latter, the truss model is found to give similar results to those obtained using a much more refined, three-dimensional finite element model, while requiring a significantly smaller amount of time for the analysis.
Finally, truss models are used for the nonlinear static analysis of prototype low-rise walls, which had been analyzed with nonlinear beam models during a previous research project. The comparison of the results obtained with the two modeling methods indicates that the previously employed beam models may significantly overestimate the ductility capacity of RM squat walls, due to their inability to accurately capture the shear-flexure interaction and the effect of shear damage on the strength of a wall.<br>Master of Science
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Ibrahim, Khaled S. (Khaled Sayed) Carleton University Dissertation Engineering Civil and Environmental. "Inelastic behaviour of reinforced masonry shear walls; an experimental and analytical study." Ottawa, 1995.
Find full text
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Janaraj, Thangarajah. "Studies on the in-plane shear response of confined masonry shear walls." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/71899/1/Thangarajah_Janaraj_Thesis.pdf.
Full textAbstract:
The prime aim of this research project is to evaluate the performance of confined masonry walls under in-plane shear with a view to contributing to the national masonry design standard through a set of design clauses. This aim stems from the criticisms of the current provisions of the in-plane shear capacity equations in the Australian Masonry Standard AS3700 (2011) being highly non-conservative. This PhD thesis is an attempt to address this gap in the knowledge through systematic investigation of the key parameters that affects the in-plane shear strength of the masonry walls through laboratory experiments and extensive finite element analyses.
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Asad, Mohammad. "Failure analysis and mitigating strategies for masonry walls subject to vehicular impacts." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/201381/1/Mohammad_Asad_Thesis.pdf.
Full textAbstract:
This thesis demonstrates how new materials and damping technologies were developed and applied to mitigate the adverse effects of vehicular crashes into masonry buildings. Many masonry buildings are vulnerable to vehicular crashes which result in loss of property, loss of habitat or functionality of the building and harm to the occupants of the building and vehicle. Auxetic materials were used in this research with negative Poisson ratio and innovative damping technologies at the wall edges to reduce the accident severity and to save the lives in both the building and the vehicle.
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Nicolini, Luca. "Equivalent Viscous Damping and Inelastic Displacement for Strengthened and Reinforced Masonry Walls." Doctoral thesis, University of Trento, 2012. http://eprints-phd.biblio.unitn.it/819/1/Luca_Nicolini_-_PhD_Thesis.pdf.
Full textAbstract:
The masonry still one of the widespread construction system for low-rise residential buildings even for countries prone to seismic risk. Despite seismic design methods yet in use are force-based, in the last decades was highlighted as the differences in strength between two levels of damage is low, and therefore as the damage is better correlated to the displacement. Also, in recent years, has arose a widespread expectation for being able to control the damage based on the probability of occurrence of an earthquake or being able to base the design on different performance levels ("performance-based design").
In this context, considerable interest is growing regarding the application of these methods to the design of masonry structures. Many questions are still open and need to be studied more in detail. From the experimental results obtained by cyclic shear-compression tests on different types of masonry panels, an analytical model has been developed, that allows to reproduce the in-plane behavior of both the tested types: one is modern reinforced masonry and the other is traditional multi-leaf stone masonry. The developed model has been used to perform a wide number of dynamic analysis with the aim of studying the inelastic characteristics of the described types of masonry. The results of the analysis made it possible to define simple and reliable formulations for the application of displacement-based method to masonry structures. Finally, we studied the dynamic behavior of a large structure, through the finite element analysis, using a damage model that has been shown to be able to reproduce the response obtained from shaking table tests. This phase has the aims of validate the results obtained for stone masonry walls, and giving useful indication for the application of displacement-based method on multi-degree of freedom structures.
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Perez, Garcia Ramon. "Increasing the Blast Resistance of Concrete Masonry Walls Using Fabric Reinforced Cementitious Matrix (FRCM) Composites." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42095.
Full textAbstract:
Unreinforced masonry (URM) walls are often used as load-bearing or infill walls in buildings in many countries. Such walls are also commonly found in existing and heritage buildings in Canada. URM walls are strong structural elements when subjected to axial loading, but are very vulnerable under out-of-plane loads. This type of loading may come from different sources , including seismic or blast events. When subjected to blast, wall elements experience large pressures on one of their faces due to the high pressure produced in the air when an explosion takes place. This wave of compressed air travels in a very short time and hits the wall causing immense stresses, which result in large shear and bending demands that may lead to wall failure, and the projection of debris at high velocities that can injure building occupants. This failure process is highly brittle due to the very low out-of-plane strength that characterize such walls.
In the past years, many investigations have been carried out to enhance the structural behaviour of unreinforced masonry walls under out-of-plane loading. Different strengthening methods have been studied, which include the use of polyurea coatings, the application of advanced fiber-reinforced polymer (FRP) composites or the use of concrete overlays in combination with high performance reinforcement. Fabric-reinforced cementitious matrix (FRCM) is a new composite material that overcomes some of the drawbacks of FRP. This composite material consists of applying coatings which consist of one or more layers of cement-based mortar reinforced with a corresponding open mesh of dry fibers (fabric). This material has been studied as a strengthening technique to improve in-plane and out-of-plane capacity of existing URM walls as well as other structural elements, mostly under seismic actions. This thesis presents an experimental and analytical study which investigates the effectiveness of using FRCM composites to improve the out-of-plane resistance of URM walls when subjected to blast loading.
As part of the experimental program, three large-scale URM masonry walls were constructed and strengthened with 1,2 and 3 layers of FRCM using unidirectional carbon fabrics. In all cases the specimens were built as load-bearing concrete masonry (CMU) walls. To increase shear resistance, two of the walls were also grouted with a flowable self-compacting concrete (SCC) mortar. Blast tests were conducted using the University of Ottawa Shock Tube and the results are compared with control walls tested in previous research at the University of Ottawa. The experimental results show that the FRCM retrofit significantly improved the blast performance of the URM load-bearing walls, allowing for increased blast capacity and improved control of displacements. The performance of the retrofit was found to be dependent on the number of retrofit layers.
As part of the analytical research, Single Degree of Freedom (SDOF) analysis was carried out to predict the blast behaviour of the strengthened walls. This was done by computing wall flexural strength using plane sectional analysis and developing idealized resistance curves for use in the SDOF analysis. In general, the analysis procedure is found to produce reasonably accurate results for both the resistance functions and wall mid-height displacements under blast loading.
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Jung, Hyunchul. "Blast Retrofit of Unreinforced Masonry Walls Using Fabric Reinforced Cementitious Matrix (FRCM) Composites." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40530.
Full textAbstract:
Unreinforced masonry (URM) walls are commonly found in existing and heritage buildings in Canada, either as infill or load-bearing walls. Such walls are vulnerable to sudden and brittle failure under blast loads due to their insufficient out-of-plane strength. The failure of such walls under blast pressures can also result in fragmentation and wall debris which can injure building occupants.
Over the years, researchers have conducted experimental tests to evaluate the structural behaviour of unreinforced masonry walls under out-of-plane loading. Various strengthening methods have been proposed, including the use of concrete overlays, polyurea coatings and advanced fiber-reinforced polymer (FRP) composites. Fabric-reinforced cementitious matrix (FRCM) is an emerging material which can also be used to strengthen and remove the deficiencies in unreinforced masonry walls. This composite material consists of a sequence of one or multiple layers of cement-based mortar reinforced with an open mesh of dry fibers (fabric). This thesis presents an experimental and analytical study which investigates the effectiveness of using FRCM composites to improve the out-of-plane resistance of URM walls when subjected to blast loading.
As part of the experimental program, two large-scale URM masonry walls were constructed and strengthened with the 3-plies of unidirectional carbon FRCM retrofit. The specimens included one infill concrete masonry (CMU) wall, and one load-bearing stone wall. The University of Ottawa Shock Tube was used to test the walls under gradually increasing blast pressures until failure, and the results were compared to those of control (un-retrofitted) walls tested in previous research. Overall, the FRCM strengthening method was found to be a promising retrofit technique to increase the blast resistance of unreinforced masonry walls. In particular, the retrofit was effective in increasing the out-of-plane strength, stiffness and ultimate blast capacity of the walls, while delaying brittle failure and reducing fragmentation.
As part of the analytical research, Single Degree of Freedom (SDOF) analysis was performed to predict the blast behaviour of the stone load-bearing retrofit wall. This was done by computing wall flexural strength using Plane Section Analysis, and developing an idealized resistance curve for use in the SDOF analysis. Overall, the dynamic analysis results were found to be in reasonable agreement with the experimental maximum displacements.
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Williams, Joseph Louis. "Fatigue of Masonry Walls with CFRP Applied Externally for Out-of-Plane Loads." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/153.
Full textAbstract:
This master’s thesis presents an investigation on the effects of fatigue on fiber- reinforced polymers (FRP) when applied to masonry walls subjected to out-of-plane loading. The project aims to provide further research and add to the general testing database of FRP enhanced masonry. An introduction to the problems and solutions associated with unreinforced masonry is discussed along with a literature review on previous testing done in the field of FRP enhanced masonry. The investigation on the effects of fatigue on FRP when applied to masonry walls subjected to out-of-plane loading is performed through experimental testing. A total of four wall specimens (6 ft x 4 ft x 8 in) were constructed. One of the specimens was left unreinforced and used as a baseline for testing while the remaining three specimens were reinforced with carbon fiber reinforced polymer (CFRP) strips designed to take the out-of-plane loads capable of creating the cracking moment in the unreinforced wall. The material testing, construction of the test specimens, and CFRP application are all presented in this thesis.
With the use of an oscillating shake table to generate the out-of-plane loading, the walls were fixed at the base and cantilevered from the shake table. By determining the frequency and amplitude that generated the cracking moment in the baseline unreinforced wall, the remaining three CFRP reinforced walls were tested at the same frequency and amplitude. The results from the testing of the three CFRP reinforced walls are presented along with time histories showing the shake table displacement and wall’s tip displacement versus time. In general, fatigue of masonry walls reinforced with CFRP strips can be managed as long as the out-of-plane reinforcement has sufficient strength and development length. Additional findings were made as a result from the testing. The development length of a vertical CFRP strip can be increased by adding a horizontal CFRP strips near the critical section and surface damage to CFRP may have severe consequences.