¹ Ph.D student, Department of Civil and Resource Engineering, Dalhousie University, Halifax, NS, B3S 1Z1, Canada, xz601190@dal.ca
² Associate Professor, Department of Civil Resource Engineering, Dalhousie University, Halifax, NS, B3S 1Z1, Canada, yi.liu@dal.ca

ABSTRACT
In veneer wall construction, the wall ties play an important role in supporting the veneer and transferring the face loads from wind or earthquakes to the backup wall. Wind pressure or suction and seismic loads result in both tensile and compressive forces in ties. The evaluation of the tie force has been traditionally based on tributary area, which results in prescriptive limits on tie spacing. However, some studies have shown that the distribution of forces in the ties is dependent on a range of factors and tributary area based distribution certainly does not reflect the true force in the ties.
The current Canadian masonry design standard prescribe that for a flexible backing, each tie be designed using a load equal to 40% of the tributary lateral load on a vertical line of ties. The rationale for 40% tributary load was based on elastic analysis assuming the tie infinitely rigid in tension and compression.
This paper presents a finite element study on the distribution of tie forces in veneer wall systems. Parameters considered include support conditions for veneer and back-up walls, load application being either pressure or suction, stiffness ratio of the veneer and backup walls, and stiffness and spacing of ties. The effects of these parameters on the tie force distribution are presented. The redistribution of tie force after tie buckling is also studied. The adequacy of 40% rule specified by the Canadian standard is discussed.

KEYWORDS: veneer wall, tie load, tie stiffness, flexible backup wall, Canadian masonry standard, numerical study

239.pdf

¹ Graduate Student, Department of Civil Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada, bpaxton@rjc.ca
² Senior Heritage Planner, City of Victoria, BC, V8W 1P6, Canada, sbarber@victoria.ca
³ Executive Director, Victoria Civic Heritage Trust, BC, V8W 1P6, Canada, vcht@shaw.ca
⁴ Associate Professor, Department of Civil Engineering, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada, elwood@civil.ubc.ca

ABSTRACT
Victoria, British Columbia, Canada is widely known for its historical downtown core with numerous early 20th century masonry buildings. The city is also located within 100 km of the Juan de Fuca subduction zone, capable of approximately M9 mega-thrust earthquakes. The seismic risk for the region is further heightened due to the potential for smaller, but closer, crustal earthquakes. This seismic environment is not unlike that of Christchurch, New Zealand, where earthquakes in 2010 and 2011 have severely impacted the relatively large population of unreinforced masonry (URM) buildings. This paper briefly compares the history of heritage URM construction in Victoria with that in Christchurch and approaches taken to address the vulnerability of these buildings. Recognizing the life safety risk from these structures in the event of an earthquake, Victoria has taken a voluntary but proactive approach to the seismic retrofit of heritage buildings, including tax incentives. The paper reports on retrofit progress in Victoria, makes comparison to seismic risk mitigation efforts undertaken elsewhere, describes example projects, and introduces an ongoing study to correlate the distribution of URM buildings in the city with ground conditions and population distribution to identify the buildings with the greatest risk of damage in future earthquakes.

KEYWORDS: unreinforced masonry, seismic risk, seismic retrofit, Victoria, Christchurch

479.pdf

¹ MSc. Student, ROSE Programme, UME School, IUSS, Pavia, Italy, annalisa.rosti@umeschool.it
² Assistant Professor, University of Pavia, Department of Civil Engineering and Architecture and European Centre for Training and Research in Earthquake Engineering (EUCENTRE), Pavia, Italy, andrea.pen na@unipv.it
³ Researcher, EUCENTRE, Pavia, Italy, maria.rota@eucentre.it
⁴ Associate Professor, University of Pavia, Department of Civil Engineering and Architecture and Head of the Masonry Structures Section at EUCENTRE, Pavia, Italy, guido.magenes@unipv.it

ABSTRACT
The main advantage of using autoclaved aerated concrete (AAC) blocks for masonry construction is their excellent thermal insulation capacity. This property increases with decreasing material density, which however is inversely proportional to the values of mechanical properties, including compressive strength. Hence, also considering the emerging issues on energy efficiency of buildings for which low density AAC masonry is greatly appreciated, the study of its structural performance becomes a relevant issue for the definition of suitable criteria and limitations for the design of safe masonry buildings, in particular for seismic design purposes. The experimental campaign presented in this paper aimed at investigating the seismic performance of low density AAC masonry. First, characterization tests on blocks, mortar and wallettes were carried out (vertical and diagonal compression tests). In-plane cyclic shear tests on six full-scale unreinforced low density AAC masonry walls were then performed with the aim to obtain a reliable description of the lateral cyclic behavior. Information regarding the displacement capacity, the correlation between experimental and analytical strengths and the dissipative behavior of masonry were derived. The results show a moderate displacement capacity of low density AAC masonry walls, strongly depending on the applied vertical load, and a good correlation between analytical and experimental lateral strengths. At the end of the shear cyclic tests, the residual vertical compression strength of some walls was also evaluated.

KEYWORDS: AAC masonry, experimental testing, seismic design

503.pdf

Keywords:      Infill Walls, University of Alberta

Page Content:

Lead Investigators:     Yasser Korany (University of Alberta)

CMRC Support:         Support has been provided through funding of the endowed MCAA Chair in Masonry Systems as well as financial and in-kind support through local CMRC members.

• NSERC IPS Student Mohammed Ashraf Nazief (Numerical investigation of the behavior of shear infill masonry walls with openings)

Impacts of Research:            The results of this research have helped to further contribute to our understanding of the complex behaviour of masonry infill frames under lateral loads.

References:

Conference Papers:

Nazief, M. and Korany, Y. (2013). “Diagonal strut model for masonry infill shear walls in various standards and codes.” Proceedings of the 12^th Canadian Masonry Symposium, Vancouver, BC, Canada.

Nazief, M. and Korany, Y. (2014). “Finite element modelling for masonry infill shear walls with and without openings.” Proceedings of the 4^th Annual International Conference on Civil Engineering, Structural Engineering and Mechanics, Athens, Greece.

Theses:

Nazief, M. A. (2014). Finite Element Characterization of the Behaviour of Masonry Infill Shear Walls With and Without Openings. Ph.D. – Thesis, Department of Civil and Environmental Engineering, University of Alberta, Edmonton, AB.

ABSTRACT

The development and introduction of the OCBA Quality Assurance Program is based on more stringent requirements than demanded by the material Standard. Key components of the program include increased geometric dimensions, higher design strength criteria, and decreased absorption and absolute shrinkage characteristics. A brief discussion of  test results from standard tests is included and benefits of the program for producers and users are discussed.

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