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Pedestal Buildings

Thu, 14 Nov 2013|

Paul Dansbach examines the features of "pedestal" buildings: structures whose bottom floors are poured concrete and whose upper floors are lightweight truss construction.

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Transcript

[MUSIC] Welcome to fire engineering training minutes. My name is Paul Dansbach. In today's session we're gonna talk about a pedestal or a platform type building. A pedestal or platform type building is a building in which the first story of the building is poured, reinforced concrete. The first floor forms the death work. For the wood framed stories, located on top of the pedestal or the platform. the building behind us, you see the story of the building is a, poured reinforce concrete. Above that, is three or four stories of wood frame. The wood frame construction utilizes parallel cord, lightweight floor trusses for the floor system and we utilize peak roof trusses for the roof system. We'll go inside and take a look at some of these construction features. << The first floor of a pedestal or a platform type building. It's typically utilized for building utility and primarily for parking spaces. We're in the area of the building that when the building is completed will be the elevator lobby. Look at the construction features around us. Behind us is a concrete block wall. This wall is a poured reinforced concrete wall. The openings will beef the elevator doors. You can see by the nature of this construction, the concrete block walls, the poured concrete floor, the poured concrete walls, provide a tremendous fire barrier. The weak spots in that fire barrier will obviously be any openings such as the elevator doors. And other utility penetrations. We'll take a look at some of those utility penetrations next. We're out on what will be the parking deck of the first floor when the building is completed. I wanna draw your attention up above to the utilities. PVC drain waste and vent line is being prepared. To run through the concrete slab. Remember, the concrete slab is a poured, reinforced concrete slab that offers a tremendous fire barrier, except when holes are penetrated through the slab to run utilities. As you will note, adequate openings are made for drain, waste, and vent lines for the plumbing. Those openings, once the pipe is installed, must be properly fire stopped to form an effective barrier to prevent vertical extension through the floor slab. We're now on an upper floor of the building. We look up and we see truss floors. The floor system, with the exception of. The pedestal, which forms the second floor. So the third floor, fourth floor, and the fifth floor are all parallel cord, lightweight wood trusses. Some of the fire problems associated with the trusses are poor service-to-mass ratio, number two. If we were building this building with standard dimensional building. It would be a two by ten and a two by ten, 16 inches on center. That would leave a 14 and a half inch space for the fire to run from one end of the [INAUDIBLE] to the other end of the [INAUDIBLE]. When trusses are employed in the building, once the fire gets past the interior finish, or if the fire originates in the truss space, the fire has unrestricted access to the entire floor area created by the trusses. Next we're gonna take a look at one of the roof trusses. We're up on the top floor of the building. When we look up we see a voltage ceiling. When we look up we can identify the roof structure. The roof structure is a peaked roof truss that's installed on a slope. Clearly the outline of the truss is present amongst the insulation. All of the fire problems associated with lightweight parallel wood floor trusses and peaked roof trusses are present in this building. To review, trusses, any form of truss and especially parallel cord floor trusses and peaked roof trusses are prone to early collapse. Firefighters must be aware of the construction features of the buildings in their response area. The key to safe fire ground operation at these buildings is early identification of trusses and appropriate strategy that employs proper tactics that ensures the safety of their members. And part of that is insuring that the members are not operating above or below trusses that are involved in fire. Thank you for watching this session of Fire Engineering's Training Minutes.

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