It does raise some interesting quesitons. I am curious what the mode of failure is for an engineered floor joist (e.g., TJI) during a fire. Could it be the thin web fails first either by burning through or losing strength due to high temperatures? Or could it be the glues used to connect the flanges to the web fail at high temperature? Either way the flanges are left uselessly flopping around.

Remember how the World Trade Center towers collapsed - the heat from burning jet fuel lowered the bending strength of the steel floor trusses allowing them to bend and pull away from their end supports at the exterior walls. They then pancaked all the way to the ground.