Quiet Determination at UT

Where There's a Wire Saw, There's a Way

By Jeff Hawk

There's nothing like the reverberating sound of a jackhammer to focus the mind on academic pursuits. Fortunately for University of Texas at Austin students, UT officials disagree. The partial demolition of UT's Batts Infill Building could have been a dusty, disruptive affair. But the rare use of a diamond-beaded wire saw minimized the mess.

All that's left of the old Batts Infill Building are the walls

The project called for gutting the narrow 60 by 100-ft. structure, leaving only its historic Texas shell limestone exterior walls. The building "fills in" the space between the newly renovated and presently occupied Mezes Building and the currently under-renovation Batts Classroom Building. The work included removing two levels of structural elements supporting the existing auditorium and classrooms. Glenn Horstmann, project manager for UT's selected construction manager SpawGlass Contractors Inc., said demolishing the structure's interior is "like working in a shoebox."

The Austin office of SpawGlass finished renovating the Mezes and adjacent Benedict buildings last year as part of a two-phase $33 million contract to modernize, re-configure and add on to existing structures within UT's South Mall buildings. The rapidly growing university needed more classrooms, more office space and to bring their outdated buildings up to code, Horstmann said. Built in 1952, the buildings fall under historic preservation requirements stipulating that their exterior walls must remain untouched. In September SpawGlass began the second phase, which includes renovations to the 24,000-sq.-ft. Batts Infill and the 80,000-sq.-ft. Batts Classroom buildings.

The smaller building posed the bigger challenge. SpawGlass had to demolish Batts Infill's 3-ft.-thick and nearly 2-ft.-wide structural concrete beams while causing minimum disturbance to Mezes occupants and minimal damage to the structure's historic walls. Jackhammers and air hammers would typically do such demolition work. But the vibrations, noise and dust caused by such equipment and concerns about weakening the walls forced SpawGlass and its demolition contractor, Southwest Destructors of Austin, to think outside of the box.

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The wire saw provided the solution. The saw uses a diamond-embedded stainless steel cable to loop around the heavy beams. A 24-in.-diameter composite metal wheel drags the cable across the concrete member while a feed-pulley system draws it in. The speed is generally slow but adjustable. Rubber spacers protect the cable; water from a hydraulic pump cools it while it cuts. The device produces little dust and minimal vibration, said David Day, an estimator for Austin-based Austex Drilling and Sawing Inc., which provided and operated the saw for Southwest Destructors.

Perhaps most important, the wire saw greatly reduced the potential of "microscopically cracking" and structurally damaging the existing walls, Day said. Vibrations from air and hydraulic hammers can weaken structures by "separating the steel from the concrete," he added. Wire sawing is faster, safer and more cost-effective than traditional methods, but "it's not often used," Day said.

Prior to cutting, crews assembled a forest of shoring up to the concrete beams and used existing steel bar joists from the roof to build mid-wall box trusses that supported the existing structure.

Workers "hopscotched" the demolition, said SpawGlass project superintendent Jim Williams, referring to sequencing the repeated process of tearing out the 7.5-in. concrete slab floors, building the box truss and then cutting and removing the beam. A tower crane carefully lifted the huge 17-ft. long, 7.5-ton beam sections out of the mesh of trusses and scaffolds.

"What they came up with was clever," said Bob Rawski, senior project manager for UT's facilities, planning and construction office.

The new Batts Infill Building will house four levels of classrooms and offices. A gabled roof surfaced with UT's signature orange clay Ludwici tile will replace the structure's original flat metal roof and provide attic space for mechanical elements. Crews will excavate down 8 ft. to 10 ft. to make room for sub-soil drainage installation.

SpawGlass is simultaneously renovating the connecting Batts Classroom Building. Both structures will receive new fire suppression, fireproofing and fire alarm systems to replace the antiquated fire-hose cabinets. Mechanical and electrical upgrades are also planned.

Some interior features will stay including black marble accents, travertine-tile stairways and glazed wall tiles. The removal of some historic features, such as the buildings' original plywood stamped with the words, "Made in Occupied Japan," signify the end of an era just as the installation of a modern top-of-the-line security system signifies the dawn of a new one.