Track 2: Materials over Time: Points of Change

General Abstract

Rehabilitation of the Exterior Stone Masonry of Toronto’s Union Station Head House

Tuesday, September 25
10:30 AM - 12:00 PM
Location: BNCC- 101BG

The head house of Toronto’s Union Station a Designated Historic Site. It was constructed in the Beaux Art tradition between 1916 and 1920. In 2010 the City of Toronto undertook a major conservation program of the building as part of the Union Station Revitalization Project. NORR Limited of Toronto has been the architect and engineer of record on the project since 2008. The heritage architect was FGMDA of Montreal. The project involves a major transformation of the station which includes new concourses and a retail mall to be constructed underneath the entire train’s viaduct structure and part of the head house. It also includes major restoration, rehabilitation and preservation work of the exterior masonry and almost every exterior and interior component of the heritage building. Structural interventions in the heritage fabric were designed by NORR and led by the author. This paper focuses on the analysis, monitoring and retrofit of the masonry envelop. Significant research was undertaken in addressing the observed conditions and a number of unique solutions were implemented, some we believe for the first time in the industry. The structure is a hybrid of steel frames and stone and brick masonry. This is reminiscent of construction schemes of the turn of the twentieth century. Exploratory openings were reviewed by the author and the heritage architect. Cracks were observed and stone movements were surmised. In particular almost all corners of the building had wide cracks. This was followed by a monitoring program using optical precision surveying equipment. A number of hypotheses were examined for the causes of movement and cracking. Theoretical finite element models were devised and ran to confirm one of these hypotheses, namely thermal contraction of the exterior stone against the more inert interior structure which is environmentally controlled year round. Corner cracking was addressed through the use of up to ten foot long stainless steel bars cored into the stone and bonded with epoxy. An additional and potentially more critical issue was observed in the northwest pavilion of the head house where cracking was observed along the full height of the pavilion from the inside and the outside, particularly at the staircase running the full height of the building. Upon detailed examination it was found that this particular exterior wall was constructed as a load bearing masonry with no steel framing embedded within the wall. Analysis combined with observations prompted a significant structural intervention. This entailed a number of measures including a new foundation wall, reinforced concrete masonry wall, seismic ties, glass fibre reinforced polymer in part of the wall and finally a stainless steel tie back of the masonry wall at roof level. Many lessons were learned from this conservation work which spanned a decade.

Learning Objectives:

Hassan Saffarini, P.Eng., PhD, PMP, LEED AP BD+C

Manager, Structural Engineering
NORR Architects & Engineers Limited

Dr. Saffarini is the head of Structural Engineering at NORR A&E, Toronto. He is a graduate of Leeds University, UK with a Masters Degree and PhD from the University of California, Berkeley. He is a Professor of Civil Engineering and taught for over twenty five years in universities in the US, Middle East and Canada. He is currently an Adjunct Professor at Ryerson University. Hassan has many publications in international journals in the area of structural and earthquake engineering. He has a rich experience with restoration of heritage and archeological sites and served organizations like UNESCO and ACORE.


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Frances Gale

University of Texas at Austin

Frances Gale is an architectural conservator with a Master of Science in historic preservation from Columbia University and over thirty-year’s experience in preserving historic buildings and monuments. Fran was a Senior Lecturer and Conservation Scientist at the University of Texas at Austin School of Architecture for 11years. Other positions have included Architectural Conservator and Training Director for the National Park Service and Director of Technical Services for AMT Laboratories and Prosoco, Inc. Fran’s recent consulting projects include Union Terminal in Cincinnati, the University of Virginia Rotunda, Vanderbilt Mansion National Historic Site in New York, and the Matagorda Island Lighthouse in Texas. Fran was elected to the Association for Preservation Technology International College of Fellows in 2010 and became a Fellow of the American Institute for Conservation of Historic & Artistic Works in 2017.


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Rehabilitation of the Exterior Stone Masonry of Toronto’s Union Station Head House

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