Retrofits Can Make Buildings Blast Resistant

Monday, July 29th, 2013
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Ronan Point Explosion
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Motivated by the collapse of Ronan Point in London in 1968, where a gas explosion on the 18th floor triggered a progressive collapse, Cintec began developing strengthening systems to reinforce masonry walls in order to resist accidental gas explosions, vehicle impacts and earthquakes.

With the world on high alert more than ever, existing buildings can now benefit from new engineering solutions and technology.

Many cost-effective building protection measures have little to do with the actual building, focusing instead on the space surrounding it. Wherever possible, ‘stand-off’ or ‘set-back’ is without doubt the most effective technique to employ, but in urban environments this may be impossible or impracticable to achieve.

In addition, many of these structures, particularly those in urban areas where there are high concentrations of historic or prestigious buildings, are built using traditional masonry. A solution which respects the existing fabric is essential.

With one retrofitting solution, after an initial inspection, the building’s structure is modeled in 3D to assess the behavioral probability and the risk inherent to the structure in order to determine the best reinforcement pattern. At the site, the Reinforcing Anchor System, fashioned out of a steel bar enclosed in a mesh fabric sleeve, is inserted into the structure which will be subject to retrofits.

A specially developed, non-polymer cement-like grout is then injected into the sleeve under low pressure. The grout fuses with the mesh, expands and shapes itself around the steel to fit the space. Using state-of-the-art dry or low-volume wet diamond drilling techniques reduces or even eliminates water damage associated with conventional concrete wet drilling.

The high stresses within the steel core of the anchor are distributed through the grout to the masonry surface. The diameter of the hole and the corresponding sock are carefully selected so that the stresses at the surface of the sock are matched to the shear stress of the parent masonry.

In this way, weak or friable masonry substrates can be successfully reinforced to resist the high loads and pressures associated with an explosive event. The approach, appealingly, leaves no evidence of structural invasion. The anchors can be installed without the need to remove internal or external finishes, preserving architectural, historical, and commercial details.

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