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## Another Type of Steel Bracing Cable Another type of steel bracing cable that is susceptible to damage from fire during a building's construction are the tensioning cables that are found in post-tensioned concrete. They provide the tensile strength to literally squeeze concrete tightly enough to...

## Another Type of Steel Bracing Cable Another type of steel bracing cable that is susceptible to damage from fire during a building's construction are the tensioning cables that are found in post-tensioned concrete. They provide the tensile strength to literally squeeze concrete tightly enough to hold itself up. The high-strength steel cables are laid in the form of about-to-be poured floors, wrapped in a plastic coating that will keep the wet concrete from sticking to the steel itself. The ends of the steel cables project out past the end of the concrete forms (fig. 19-16). After the concrete is poured around it and allowed to begin to harden, the cables are tensioned by pulling on the exposed ends with hydraulic jacks exerting thousands of pounds of pressure. The cables in turn pull inward on the concrete, squeezing it tighter together, giving it rigidity. If a fire occurs while the exposed steel is unprotected during the jacking phase, a process that can take several weeks, the cables should be expected to fail, which in turn could cause total catastrophic collapse of the concrete floor. When the concrete has reached the correct hardness, the cables will be secured in permanent position with clamps that nestle into the concrete. After this process has been completed, the excess steel cable will be cut off and the place where the cables go into the concrete will be packed with more concrete, providing protection to the cables, making them much less vulnerable to fire.