Information from this article was first published in Demolition Magazine and is being reused with permission from the National Demolition Association.
The new Tobin Center for the Performing Arts was planned to be built within the nearly 90-year-old San Antonio Municipal Auditorium. The iconic facade of the building will be incorporated into the new design of the Tobin Center. The 28-month-long construction project began in June 2012.
The demolition phase consisted of removal and salvage of exterior stone façade and other architectural features, interior stripping of all remaining floor space, extensive selective structural demolition in the main entry, removal of the domed roof, removal of all of the “rear of house” facilities including a 10-story stage house, and removal of all concrete foundations, slabs, footings and basements up to the “cut line.” J.R. Ramon & Sons, Inc., the demolition company, was also responsible for the storm water pollution plans, traffic control and universal waste removal.
Historic preservation efforts
Extensive salvage of the exterior stone facade was performed for reuse in the reconstruction. The salvage and recovery of elements in the exterior stone facade was meticulously documented as each and every stone was removed, numbered, palletized and later delivered to an off-site location for long-term storage. Architects worked hand-in-hand with community historic preservationists to preserve as many elements of the original structure as possible, going as far as to design a reconstruction of some of the historic architectural features removed from the outside of the building to incorporate them into an interior dividing wall and display of heritage.
Bracing for demolition
Because the historic front facade, main entry, turrets, rotundas and what later became referred to as crab claws, (the east and west walls), were scheduled to remain, considerable temporary bracing had to be engineered to satisfy the dynamic forces that may be applied to the 90 year old existing structure during not only demolition but construction of the new 9-story building that will be placed inside and around the remaining elements.
Crews drilled, placed, bolted and welded over 15 tons of temporary bracing and shoring to accommodate wind loads, ground hydraulic forces and construction loads anticipated within the two year building schedule. It was critical that all temporary shoring and bracing be in place prior to any mass demolition or dismantling of any component of the structure.
Some areas of the original facade and architectural components had developed hairline cracks from the building's long history. These cracks were identified, documented and monitored during demolition with crack monitors placed at each individual crack and periodically checked to see if the structure was moving or shaking. Vibration monitors were also used on concrete floors and basements to verify that the heavy equipment or the impact of falling debris were not causing extensive vibrations in the stone facade or remaining concrete and steel structure.
Dome removal and mass demolition
Timothy Ramon, J.R. Ramon & Sons vice president and member of the National Demolition Association, said that during the initial site visit they realized the dome roof could be dismantled without the need of a central shoring tower. The dome’s roofing materials - a compilation of over 16-inches of lightweight concrete, foam insulation, built-up roofing material and thin copper sheeting - were removed manually.
Howell Crane of San Antonio supplied two mobile Grove cranes, a 350- and a 550-ton, which were used to gently pick and lower the sectioned Dome roof to the ground. Men in lifts – at heights of 125 feet off the ground – rigged and cut loose the components of the steel skeleton. Weight calculations of each pick were critical as the nearest crane position available was 130 feet from the pick point. Some picks reached out as far as 165 feet from crane center point.