What is the burn rule associated with Heavy Timber Arch?

What is the burn rule associated with Heavy Timber Arch?

• A. 15 minutes
• B. 20 minutes
• C. 25 minutes
• D. 30 minutes

Answer: (B)

Heavy timber arches are massive wooden members that can throw off a lot of heat but resist burning for a time due to the large cross-section and char layer that forms on the surface. The burn rule used for this kind of construction sets a practical benchmark around twenty minutes of continuous fire exposure. After roughly this period, the remaining uncharred wood may reach a point where its structural capacity is significantly compromised, increasing the risk of collapse if the area isn’t cooled or controlled. This time guide helps decision-makers prioritize safety: limit interior operations around that window, bolster defense, or reposition crews to safer areas while water is applied and ventilation is managed. Times like fifteen minutes are generally too short for large heavy timber members to reach critical weakness, while longer intervals such as twenty-five or thirty minutes tend to underrepresent the collapse risk in sustained fire conditions.

Heavy timber arches are massive wooden members that can throw off a lot of heat but resist burning for a time due to the large cross-section and char layer that forms on the surface. The burn rule used for this kind of construction sets a practical benchmark around twenty minutes of continuous fire exposure. After roughly this period, the remaining uncharred wood may reach a point where its structural capacity is significantly compromised, increasing the risk of collapse if the area isn’t cooled or controlled. This time guide helps decision-makers prioritize safety: limit interior operations around that window, bolster defense, or reposition crews to safer areas while water is applied and ventilation is managed. Times like fifteen minutes are generally too short for large heavy timber members to reach critical weakness, while longer intervals such as twenty-five or thirty minutes tend to underrepresent the collapse risk in sustained fire conditions.