Posted by cvengr on August 15, 2003 at 22:12:21:
In Reply to: Re: Safe building structures posted by cvengr on August 15, 2003 at 21:59:39:
If your intent is to note that steel melts due to fire, you may want to review some metallurgy. Steel will begin to loose its strength long before it melts. Depending on the steel employed, and its loading, (its stresses) and its strain rate, steel remains solid and begins to yield before catastrophic failure. Steel will generally fail in complex loading situations at joints when welds fail and force distributions throughout the structure are dynamically changed. Most of these failures occur in the austenitic range depending on type of steel used or in a ferritic cycling at elevated temperatures below the austenitic temperatures. Again still half the temp required to melt the steel (change from solid to liquid).
When you see a cold piece of steel bent from its original shape after a fire, the deformation was due to plastic deformation of the solid steel. If it melted, you will see a puddle of slag and steel beneath the fired area. (Like one sees old lead plumbing fittings or roof flashing melted on the ground after a fire.)
Wood, will burn and loose mass prior to failure, frequently without any warning of strength loss although slightly better than concrete or glass. Cross sectional area generally related to shear strength and as it is lost from burning the surface area and fuel required to burned to volume ratios change, leaving little warning of failure.
Concrete fails catastrophically, although reinforcing steel may help to buffer complete severing of members prior to catastrophic failure.
Glass, tends to fail catastrophically, although polycarbonates, laminated materials, and acrylics have differing properties.
Types & Styles
Library Places Building Photos Free 3D Models Archiplanet