Masonry Magazine April 2009 Page. 37
Masonry Restoration
OBLOK-LOK
A HOHMANN & BARNARD COMPANY
SETTING THE STANDARD OF EXCELLENCE
IN THE MASONRY INDUSTRY
tie could be cut, the stone removed, and a load test conducted. That little puff of white powder translated into a reduction of the pull-out capacity of the travertine from 900 lbf to 400 lbf. If a safety factor of four is applied, then the design strength of the connection between the stone and the concrete back-up became 100lbf, which on a 52-story building in a hurricane zone, is a little too close for comfort. Clearly, another solution was necessary, one which would not have a hugely negative impact cost-wise, since the contract had already been awarded based on the original design.
A torque-activated mechanical anchor was modified to enable it to expand within the body of the 30-mm thick travertine stone, while enabling it sufficiently below the surface of the stone to enable a patch to be applied to complete the repair. A series of tests was conducted with this anchor in both the travertine and the poured concrete back-up. The results showed a pull-out capacity in the travertine of about 1,500 lbf, and in excess of 2,500 lbf in the concrete back-up. Work then commenced installing this new anchor system. Only two lengths of anchor were used on the whole building with any variance in the cavity between the stone veneer and the structural back-up be accommodated by over-drilling into the concrete and setting the anchor deeper. Bore-scope analysis showed positive engagement of the anchors in both the travertine and concrete back-up.
A complete line of economical and custom repair solutions including:
• Spira-Lok Helical Wall Tie Systems
Torq-Lok Mechanical Repair Anchors
• Panel-Lok Thin Panel Veneer Anchors
Patch-Lok for Concrete Repair
• Spira-Bar for Crack Stitching
• Site Services for Testing
• Technical Support
Hohmann and Barnard bere scope
Hurricane Katrina swept through New Orleans in August 2005 and quadrupled the scope of work as the protocol changed to ensure that all veneer panels that appeared loose were anchored as an emergency repair. Due to the instability of the travertine panels and the glass, the entire building had to be roof rigged. This entailed the utilization of a custom engineered and installed tower scaffolding system in order to make all stage moves from the top of the building. Naturally, the additional cost of this work caught the attention of the insurance companies, and they brought in their peer review engineers to review the work being done. The anchor system passed with flying colors.
In addition, all of the travertine panels had to be removed from the tower penthouse due to storm damage. A new engineered system was developed and 1,128 pieces of new stone were installed and secured using a mechanical torque activated anchor in the CMU back-up. The panel itself was sandwiched between a recessed wide flanged nut, and a stainless steel toggle on the back of the stone. This effectively transferred both tensile and compressive live wind loads through the anchor into the structural back-up. This will also ensure that the stone panels will remain secure during future hurricanes, and that means peace of mind.
The consultant for the project was Stone & Glazing Consulting, the restoration contractor was American Restoration Inc, and the anchor systems were supplied by Blok-Lok Limited, a Hohmann & Barnard company. IMAS
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CONSERVE
PRESERVE
BLOK-LOK
A HOHMANN & BARNARD COMPANY
30 MILLWICK DRIVE, TORONTO, ONTARIO MIL 1Y3, CANADA
T. 416-749-1010 F. 416-749-1017 USA 800-561-3026
www.blok-lok.com sales@blok-lok.com
READER SERVICE #120
April 2009
MASONRY 35