Post-Installed Reinforcing in Fire Conditions 2024
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, t equiv
, as noted in Section 2.1 of this document, then calculate the bond stress in the fire exposure condition, t 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 = t equiv
∙ l d t fire( θ)
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 standard adhesive cure and working time( approximate)
Where: ø [° C ] ø [° F ] t work t assembly t cure
• t work is the time after installation that the bar should not be tampered with.
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5... 10 11... 15 16... 20 21... 30 31... 39 40
41... 50 51... 59 60... 68 69... 86 87... 103 104
≥ + 5 ° C / 41 ° F
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50 min 40 min 35 min 20 min 15 min 12 min |
36 h 30 h 24 h 12 h 6 h 3 h |
28 days 21 days 17 days 7 days 5 days 4 days |
• 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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September 2024 |
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13 |