Thread: What to study

  1. #1
    Wittmer
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    Default What to study

    Hey guys,
    I will be appying to take the Chicago test in the next week or so. What sort of material should I expect on the test, and how in depth will it be? I heard of an FDNY Lieutenant's test that asked what the expansion ratio of a 20ft steel beam at 1600 degrees was. That seems a bit ridiculous to me.
    Also, are there any sample exams for tests like this online?
    Thanks alot,
    Kevin

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    I heard of an FDNY Lieutenant's test that asked what the expansion ratio of a 20ft steel beam at 1600 degrees was. That seems a bit ridiculous to me.

    Why is that ridiculous for a LTs exam? You should know that material if you plan on leading men into a burning building.

    P.S.-I believe the ratio is about 9 1/2" per 100 feet, so roughly 2".
    Proud East Coast Traditionalist.

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    I heard of an FDNY Lieutenant's test that asked what the expansion ratio of a 20ft steel beam at 1600 degrees was. That seems a bit ridiculous to me.



    Why is that ridiculous for a LTs exam? You should know that material if you plan on leading men into a burning building.

    P.S.-I believe the ratio is about 9 1/2" per 100 feet, so roughly 2".
    Damn... you beat me to it!

    To answer Wittmer...

    A 2" elongation of structural steel ( which begins at approximately 1100 degrees Farenheit might be just enough to intiate a wall collapse... and knowing that info matters as to if your company is in the building or outside of the building. A wall collapse can bring down the floors, trapping your personnel, or bury your people in a ton of rubble. You also have to know the types of wall and interior collapses and how to recognize the signs of impending collapse.

    To much information to know? Not if you are going to be a company officer!

    Everybody goes home!
    ‎"The education of a firefighter and the continued education of a firefighter is what makes "real" firefighters. Continuous skill development is the core of progressive firefighting. We learn by doing and doing it again and again, both on the training ground and the fireground."
    Lt. Ray McCormack, FDNY

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    Why are concerned about what is on an FDNY lieutenants test when you are going to take the Chicago entry level test?
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    The question you pose has several answers - all of them correct.

    The equation you should know is:

    E = a X L X (T2 - T1)
    Where:
    E = Expansion Length or Elongation (the units will be the same as L)
    a = Linear Coefficient of Thermal Expansion (for most types of steel a = 0.0000066)
    T2 = Final Steel Temperature (F)
    T1 = Initial Steel Temperature (F)

    The “expansion ratio” could be defined as “a”. For example, steel will expand 0.0000066 feet per foot length per Fahrenheit degree.

    To find the “expansion” of a 20 ft steel beam at 1600 F use the above equation. You have to assume an initial temperature if one is not provided in the problem. If you use 70 F, then the equation becomes”
    E = (0.0000066) X (20 ft) X (1600 F - 70 F)
    E = 0.202 ft
    E = 2.42 inches

    The significance of thermal expansion lies in the construction of the steel beam and its points of connection. Some are made so that the beam will slide as it expands (i.e., expansion joints in bridges). Some are fixed (i.e., welded to a column or bolted to a wall, referred to as “constrained“). When fixed connections are used, the expansion will result in (1) the steel beam bending if the wall is strong enough to resist the steel beam expansion, or (2) the wall will be pushed out if the wall cannot resist the expansion of the steel beam, or (3) a combination of both.

    The problem is compounded by:
    1) the effect of the vertical and lateral loads on the beam,
    2) the Linear Coefficient of Thermal Expansion increases with temperature from approximately 0.0000060 at 32 F to approximately 0.0000083 at 1300 F,
    3) cold formed steel and hot rolled steel have different values,
    4) Values for the Linear Coefficient of Thermal Expansion will vary, albeit slightly, depending on the source of the information,
    5) structural properties of the steel and resisting elements (I.e., wall) such as the modulus of elasticity,
    6) etc. etc. (It’s never easy)

  6. #6
    Wittmer
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    Guys-
    You've jump on me and overlooked the point of my post.
    I am not belittling the value of education and common knowledge in the fire service. I think it is important to know the chemistry and physics of a fire, and the effect of heat on structural components. I do think it is overboard memorize expansion ratios and whatnot for use on a fire scene. They are likely to be inaccurate to the level you are concerned without probing for temperatures along different areas of different components of the building. Would you also need to remember the ratings and behavior of different types bolts and fasteners under heat? What is more important to understand is the theory behind fire and structural collapse so you can worry less about specific numbers, but rather the larger picture of the fire scene. I am not as ignorant as you probably thought from my question. I am very much into learning about what I do. I've taken plenty of classes at the academy above FF1 and I am also working towards a degree in engineering.
    I guess it was a bad example to use an FDNY Lt's test question to ask about an entry level CFD test, but it was fresh in my mind and one of the only things I've heard about testing.

    Back to the point of my question - Should I expect firefighting material on the test, or is it more common knowledge and reasoning/logic skills?
    I'd appreciate input from anyone with experience in the testing process.

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    wittmer, it's not going to be a fire related exam, there are no pre-requisites to apply for the city. It will be a general aptitude test.
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