Once you have achieved a level of success with lighting, cutting, and troubleshooting your torch, it may be time to move on to some new challenges, such as making relief cuts, combining torch cuts with heavy rigging, and performing “hot work” in a confined space.
Discussed here will be using a torch to slow controlled release forces such as tension and compression; doing hot work in a confined space; cutting from a man basket; creating connections in steel with a torch for the purpose of attaching rigging, shackles, and wire rope; and limiting heat transfer and fire spread.
Material Behavior/Load Path
Knowledge of how a metal is going to react to our tools is key. Grinding metal (dust) is different than cutting (chips) it. Steel is ductile (can be deformed), and iron is very brittle (will shatter when struck). Steel can be torch cut (kindling temp = 1,800°F); aluminum just melts. Understanding these differences and using them to your advantage, identifying brittle and ductile behavior, will aid you in any rescue/forcible entry assignments. These considerations are essential for performing a patient- based rescue.
1 Assume the cable is highly loaded. Like cutting a compressed object, we want a slow failure. Ideally, you cut the cable one strand at a time. Use a small sized torch tip, 00 or even a 000. (Photos by author.)
2 Making a secure connection to a steel building component can be tricky. Using a torch, we can create an opening to accept a sling or shackle and make a positive connection to stabilize the steel or move it.
3 Cut out enough steel to insert the rigging. Because of the sharp edge left from a torch cut, attach a shackle to the beam first, then add the sling to it.
Size up the load path of the work piece. Understand that when you create an opening or remove a load-bearing member, the remaining structure must continue to carry the load. You may need to add shoring/cribbing before the cut. It is likely that any object you need to cut will be loaded in several directions at once, located in different areas of the object. For example, a horizontal beam supported on its ends will be under tension on the bottom edge of itself and compression as it sags downward on the top edge.
Not unlike cutting a fallen tree with a chainsaw, at some point the saw bar gets pinched from the compressive forces in the upper part of the tree trunk. Then, as you continue downward, the trunk splits open from the tension along the bottom portion, pulling the cut apart. In this example, vertically support the log on both sides of the cut to limit the compressive forces pinching the bar.
Have a structural engineer help with sizing up these types of situations. This input will greatly increase your chances of success and the safety of everyone.
Compression
During a fire or tornado/hurri- cane or other impacts on a building, structural components will be placed outside of their normal loading. Beams can be overloaded by shifting loads and become bent and twisted. Structural parts meant to be horizontal may be vertical. It may be very difficult to determine if the steel you need to remove is predominantly in compression, tension, or both. Significant crushing stresses can lead to instabilities such as buckling or racking over sideways.
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