Post-Installed Reinforcing in Fire Conditions
Post-Installed Rebar Design for Development Length Fire Exposure
Figure 5 below shows the effects of temperature on the HIT-FP 700R adhesive when exposed to a fire condition when used for development of rebar for either ACI or CSA code provisions. After determining the equivalent bond stress for the ambient temperature, τ equiv, as noted in Section 2.1 of this document, then calculate the bond stress in the fire exposure condition, τ fire( θ) using the equations from Figure 5. The development length in the fire exposure condition, l d, fire, will then be as follows:
l
d, fire = τ equiv τ fire( θ)
⋅ l d
The final development length used would be the maximum of l d, or l d, fire. See Section 2 of this document for more information on the design in fire exposure conditions.
Figure 5. Hilti HIT-FP 700 R bond stress vs. temperature of post-installed rebar applications, short term loads and sustained loads, not-including seismic
HIT-FP 700 R Standard Cure Time
Figure 6. Hilti HIT-FP 700 R adhesive cure and working time( approximate) Where:
• t work is the time after installation that the bar should not be tampered with.
• t assembly is the time after installation that it is permitted to begin to assemble formwork, tie rebar, or pour concrete.( Concrete must be braced or shored until t cure is reached).
• t cure is the time when the adhesive has fully cured and is rated for in-service loads.
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