Roof Support Systems Overview
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Questions and Answers

What effect does fire have on traditional wood joisted roofs?

  • They emit smoke before any structural failure.
  • They become structurally stronger.
  • They retain their strength throughout the burn.
  • They may become soft or 'spongy' before failing. (correct)
  • What is a significant risk associated with plywood or oriented strand board used for roof sheathing?

  • They provide superior support compared to wood joists.
  • They can fail quickly without prior warning. (correct)
  • They are resistant to heat damage.
  • They are immune to structural failure under fire.
  • What characteristic of plywood I-beams increases their susceptibility to failure in a fire?

  • Thin web portion. (correct)
  • Thick outer layers.
  • Open web design.
  • Heavy construction material.
  • Which structure is often used in modern construction to support flat roofs?

    <p>Box beams and I-beams.</p> Signup and view all the answers

    What is a warning sign that a roof is weakening under fire conditions?

    <p>Any indication of advanced or heavy fire development.</p> Signup and view all the answers

    What feature of truss joists contributes to their early failure during a fire?

    <p>Open web design.</p> Signup and view all the answers

    What does deflection or vibration under the weight of firefighters indicate?

    <p>Lightweight roof construction</p> Signup and view all the answers

    How should firefighters respond to deflection or vibration during their operations?

    <p>View lightweight construction cautiously</p> Signup and view all the answers

    Which of the following is NOT a factor to consider when assessing roof safety during firefighting?

    <p>Color of the roof material</p> Signup and view all the answers

    What is the main purpose of assessing deflection or vibration in a roof during firefighting operations?

    <p>To assess roof construction type</p> Signup and view all the answers

    What type of educational method is mentioned for this lesson?

    <p>Lecture and discussion</p> Signup and view all the answers

    What is a significant risk associated with unprotected lightweight open-web joists in a fire?

    <p>They can be expected to fail quickly.</p> Signup and view all the answers

    Under what condition can fireproofing be omitted from roof supports in Type I construction?

    <p>When the roof is located more than 20 feet above the floor.</p> Signup and view all the answers

    What design consideration is unique to flat roofs compared to floors?

    <p>They typically deflect or vibrate when walked upon.</p> Signup and view all the answers

    How does the open web design of truss joists impact fire spread?

    <p>It permits rapid fire spread in directions perpendicular to the joists.</p> Signup and view all the answers

    Which of the following is true about the structural fireproofing requirements for roof supports?

    <p>Omission of fireproofing is allowed under specific conditions.</p> Signup and view all the answers

    What is a necessary design feature for modern flat roofs?

    <p>They must be able to safely support at least a few workers.</p> Signup and view all the answers

    What material is NOT mentioned as a support option for flat roofs?

    <p>Concrete slabs</p> Signup and view all the answers

    What is the main function of wood joists in flat roof systems?

    <p>To support the roof deck</p> Signup and view all the answers

    Which type of beams may be used alongside wood joists for roof support?

    <p>Solid or laminated beams</p> Signup and view all the answers

    Load-bearing walls are crucial for what aspect of flat roof support?

    <p>They support the ends of the wood joists.</p> Signup and view all the answers

    How do wood joists function in relation to roof decks?

    <p>They act like beams that support the roof deck.</p> Signup and view all the answers

    Study Notes

    Roof Support Systems

    • Traditional wooden joisted roofs utilize solid wood joists that lose strength gradually when exposed to fire.
    • Roofs can become soft or "spongy" prior to complete failure, particularly with wood plank decks.
    • Softening signs should not be the only indicators of risk; plywood or OSB sheathing may fail suddenly without warning.
    • Firefighters should treat advanced fire conditions as signs of potential roof weakening.
    • WARNING: Roof support systems can fail without notice under fire conditions.

    Box Beams and I-Beams

    • Modern roofs often employ box beams and I-beams made from plywood and wood truss joists.
    • These beams generally offer sufficient strength but have vulnerabilities in their thinner components, especially during a fire.
    • Plywood I-beams' thin web portions and lightweight truss joists can fail early when exposed to fire.

    Open Web Truss Joists

    • Open web truss joists allow fire to spread rapidly in directions perpendicular to the joists, increasing risk.
    • Unprotected lightweight open-web joists are expected to fail quickly if caught in a fire.
    • CAUTION: Any material used in lightweight open-web joists is at significant risk during fire conditions.

    Fireproofing Requirements

    • Certain types of buildings (Type I) allow for fireproofing omissions on roof supports under specific conditions.
    • Roof supports located more than 20 feet above the floor in assembly occupancies may have unprotected steel supports.
    • Buildings can feature unprotected supports even when the main structure is fire-resistive.

    Flat Roof Design

    • Flat roofs are designed for lighter loads compared to floors, often leading to visible deflection or vibration under weight.
    • Such designs must still support a minimal number of personnel for maintenance safety.
    • Deflection and vibration should be interpreted as signs of lightweight construction rather than premised immediate failure.

    General Roof Support

    • Flat roofs can be supported using open-web steel joists and steel beams.
    • Basic flat roof systems may use ordinary wood joists resting on load-bearing walls, acting like beams for the roof deck.
    • Solid or laminated beams and columns can be utilized to reinforce the wood roof joists.

    Study Materials

    • Textbook Chapters cover material properties, structural systems, and collapse summaries.
    • Evaluation includes quizzes and tests based on chapter content and visual presentations.

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    Description

    This quiz examines the principles of traditional wood joisted roofs, focusing on how the structural integrity of wood joists is affected by fire. Participants will learn about the indicators of failure, such as softening and sagging, and the properties of materials used for roof sheathing. Gain a deeper understanding of how to assess the safety of wood roof structures in fire conditions.

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