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One-Story Hybrid Construction

Tue, 25 Jan 2011|

Paul Dasbach discusses firefighting hazards and concerns at a commercial buidling that is part ordinary construction but with a storage space of steel truss construction.

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Transcript

[BLANK_AUDIO] [Music][Noise]. Hello and welcome to Fire Engineering's training minutes. My name is Paul Dansbach and in this section we're gonna talk about a building that most dire departments will have in their jurisdiction. The subject of today's training minutes section is a one story building of ordinary construction. Well, actually it's gonna be hybrid construction, and you'll understand why as we get into the video. The front part of the building which is the customer area of the building has a wood raftered roof, and exterior masonry walls. The back part of the building which is primarily used as a storage space for mercantile occupancy has a steel frame. Truss. We're gonna go inside and take a look at the features of that truss and some of the construction features of the building. Okay we're inside and we're gonna take a look at some of the conditions of the structure and some of the features of the structure that are going to be concerns to the fire service. First thing we notice is that we have a wide open floor area. Again, the lack of interior columns tells us that the building is a truss. This space, the space created by the truss roof portion of the building is approximately 60 feet by 75 feet wide. As you will notice, looking up towards the trusses. The trusses are a steel frame truss. The top cord and the bottom cord of the steel frame truss are parallel. From the exterior of the structure that's going to give the appearance that this building has a flat roof when in fact the structure of the roof is a steel frame truss. In one of our previous videos, we were in a structure that was vacant, and that was obvious by the wide, open floor areas and the absence of stock and material. This building is an occupied structure, and the stock and material is what creates the fire load. A fire in this occupancy will effect the trusses almost immediately. The steel will begin to absorb the heat and be heated. As the steel is heated, as the fire continues, once the steel reaches it's yield point, trusses will begin to fail. As we observe from the exterior of the building, the building has an overhead garage door. The size of the building 60 feet by 75 feet, may lend itself to interior firefighting. Well, at least firefighting from the overhead door. Incident command must make the decision based upon the location and the extent of the fire as to whether or not to commit fire fighting resources into the building or into the collapse zone. Application of a heavy caliber hose stream with good reach and penetration is possible. We have no ceiling in this occupancy that's going to obstruct the hose streams. And hose streams can be directed up to into the truss space, cool the steel and prevent failure if the trusses. As we look across the building built in, we notice a storage loft is built into one of these trusses. This storage loft is open an accessible to the floor below. This will allow application of a hose stream from the floor below or from the open overhead door. A stairway from another part of the building also provides access to the storage loft. Crews must make the decision. What is the most efficient way of applying a stream to a fire in a storage loft. To where you apply this frame to the floor below. Where we have direct access because there are no construction features, walls or ceilings obstructing that trust loft. Or do we attempt to stretch the line up a narrow stairway and place the line in service from the trust loft? We're gonna take a look at that narrow stairway, and then you can decide for yourself which is the most efficient and safe way to apply [UNKNOWN] As we discussed, there's a stairway that leads up to the storage lot in the truss area. This is the stairway. The stairway's accessible from another part of the building. The stairway is narrow, and will require the crew to make a 90 degree turn to access and apply the hose stream up into the truss loft. That stretch is gonna be a difficult stretch, using a two and a half inch hose line. Once the crew reaches the top of the stairway, they're gonna need to make a 90 degree left hand turn. To operate the hose stream up into the storage loft. Again, you're gonna need to make the decision which is the easier, safer, and more efficient hose stretch? Stretching up a narrow stairway, having to turn the line, or applying the hose stream from down below. On the floor area. Up on the roof we notice there are some skylights. The skylights provide an opportunity for some quick ventilation. Removal of the skylights will relieve the heat and products of combustion from inside the structure. Another feature of the roof is that the roof is basically flat. Remember, we described the steel trusses as a parallel court. The absence of a peak or bow on this roof may lead firefighters to believe that this is not a truss roof. Prior knowledge, pre-planning, and building intelligence. Will help provide firefighter with the necessary information to understand the building within their jurisdiction. In this session of training minute, we looked at a building that contained a steel frame truss roof. The top chord and the bottom chord are parallel giving the appearance that the roof may in fact be a flat roof of wood joists. Be aware that there are many different types and forms of trusses out there. All forms of trusses create some significant and unique firefighting challenges and hazards. Firefighters must recognize all buildings and structures that contain truss roofs, and fight the fires in a safe and efficient manner. Thanks for watching this session of Fire Engineering's training methods.

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