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Lightweight Wood Frame Construction

Mon, 24 May 2010|

Paul Dansbach points out some of the hazards firefighters face in lightweight wood frame buildings.

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Transcript

I'll Paul dance back and welcome to -- engineering training minutes. In today's session we're gonna look at the construction materials and techniques used to construct a lightweight wood frame building. The building our in -- being constructed as a three story hotel. The construction this building and -- lightweight Paulo court would trusses for the -- system. And light weight peaked roof trusses. Some of the fire problems and collapse footprint associated with a lightweight parallel -- trusses. Are the result of the worst servers -- mass ratio. As a result of the open web truss construction. Another problem associated with this particular type of -- Isabel possibly. Develop custom plate acts as the heat -- Conducts the heat into the fibers of the woods allowing the gossip -- to release and the connection will therefore how part. As you can throw the trust based upon us we also noticed when -- -- -- installed along the bottom quarter of trust. We have a very large. Wide open combustible void space for the fire to expand and grow in intensity. Fires that do extend up into the combustible void space often result in a large area of a floor collapsed. As a result of the trust's exposure to a far. It should be noted in this particular building. The combustible void space created by the trusses is being protected -- automatic. Fire sprinkler protection. This will not communication in every building that firefighters are all for quite a fire in that it's constructed with -- will -- would trust. The problem this field possibly connectors is that isn't -- similar material -- the would. On the fire conditions the steel reacts differently from the fire -- deal. Conduct that he into the fibers of the -- starting to -- a lumber invested quite a while also have a tendency to work as a result. Of its exports in the heat and pull out of the walk. As in most building construction. Features the connections are often the weak spot in the structural system. Especially when exposed to fire in this case that is very true of them -- definitely. There are several areas of the building where firefighters might expect to find a fire separation or fire barrier. Of the concealed spaces to separate the concealed spaces into smaller areas. One such area is the wall that separates the Carter from the dwelling unit or from the hotel room. The contractor in the construction this building has decided. We stole the drywall on the ceiling and the walls of the Carter about two foot down from the ceiling to maintain the integrity of this fire -- The wall behind me is a wood -- wall that's -- non -- partition. Non bearing meaning that it does not support of war or the roof above it merely supports itself. If we look -- we see the roof trusses. The roof trusses wrong from the Carter wall which is a very wall. To the exterior wall which is a -- wall. We say -- what we mean that those walls -- the walls that support the weight of the roof trusses. If we look at the roof -- and the dimension created through the distance between the roof -- between the top and the bottom quarter. The roof -- have a dimension of between three and a half to four feet between the top and bottom quarter of the trusses. The floor trusses conversely have a direction of about one inches between the top and bottom word on the roof trusses. As we look at this roof -- And we look up towards the peak of the roof -- we noticed that our distance between the top and bottom -- increases to about eight feet. The large volume of combustible void space created by. The distance between the top and bottom quarter of the trusses is an area -- -- can grow -- intensity. We can the trusses and result in a large area of collapse. When firefighters -- -- fire in a lightweight wood frame building under construction. -- should anticipate rapid fire development. And early collapse of the building as a result of the -- being immediately exposed. -- -- far. Another hazard if firefighters may face in the building on the construction. Is the elevator shaft in this building we have to elevators in a single shot. The -- may result in rapid fire development and vertical -- extension. As well as representing -- hazard for the barriers the temporary barriers not be in place. During a fire incident. One of unique construction features of this type of wood frame building is that the -- systems are almost three. Independent -- systems if we look into the hotel room. We've seen lightweight -- trusses those lightweight -- -- bear on the exterior wall and on the car to wall. From the Carter wall. Across the ceiling of the Carter for the -- -- -- on the opposite side is dimensional lumber it's that you play. Once we go into the hotel room on the other side of the Carter we have another lightweight parallel -- would trust. What this means for the firefighter is that if the floor. In one unit becomes one -- And -- off and starts to weaken the firefighters evacuate that -- across the Carter. On another floor system and going to the hotel room on the opposite side of the Carter there -- one full -- system away. From the floor that's in danger of collapse. Firefighters should be aware of the hazards associated. With parallel -- lightweight floor trusses. And -- lightweight roof trusses thank you for watching this session a fire engineering training that.

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