In wood trusses, which component is the weakest point that warps and fails quickly when exposed to heat?

In wood trusses, which component is the weakest point that warps and fails quickly when exposed to heat?

• A. Gusset plate
• B. Bottom chord
• C. Nails
• D. Webs

Answer: (A)

The key idea is that the connection between wood members in a truss is the weak link under fire. The gusset plate is the metal connector that clamps the web members to the top and bottom chords, tying multiple members into a single load path. When exposed to heat, metal loses strength and stiffness and can warp or pull away from the wood, compromising several joints at once. Because this plate holds the connections for multiple members, its failure removes the primary load path and leads to rapid loss of integrity and potential collapse. The bottom chord, webs, and nails are all wood or individual fasteners; they can burn or loosen, but they don’t typically cause the immediate, system-wide loss of support that a compromised gusset plate does. That makes the gusset plate the critical weak point in a fire.

The key idea is that the connection between wood members in a truss is the weak link under fire. The gusset plate is the metal connector that clamps the web members to the top and bottom chords, tying multiple members into a single load path. When exposed to heat, metal loses strength and stiffness and can warp or pull away from the wood, compromising several joints at once. Because this plate holds the connections for multiple members, its failure removes the primary load path and leads to rapid loss of integrity and potential collapse. The bottom chord, webs, and nails are all wood or individual fasteners; they can burn or loosen, but they don’t typically cause the immediate, system-wide loss of support that a compromised gusset plate does. That makes the gusset plate the critical weak point in a fire.