Bldg Construction Chapter 02


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Bldg Construction Chapter 02

  1. 1. Building ConstructionRelated to the Fire Service Chapter 2 — Structural Fire Resistance and Building Classifications
  2. 2. Learning Objective 1 Define fire resistance. Building Construction 2–2
  3. 3. Fire Resistance• Function of the properties of all materials used; includes combustibility, thermal conductivity, chemical composition, density, and dimensions• Ability of a structural assembly to maintain load-bearing and structural integrity under fire conditions (Continued) Building Construction 2–3
  4. 4. Fire Resistance• Ability of walls, partitions, and ceilings to act as a fire barrier• Fire resistance rating – Expressed in hours and fractions of hours – Incorporated into construction classifications and building codes Building Construction 2–4
  5. 5. Learning Objective 2 Discuss methods of determining fire resistance and the limitations of each method. Building Construction 2–5
  6. 6. Determination of FireResistance• Conducting standard fire resistance testing in a laboratory• Performing analytical calculations to determine the resistance to a standard fire test exposure• Employing analytical structural fire engineering design methods based on real fire exposure characteristics Building Construction 2–6
  7. 7. Fire Resistance Test Method• Laboratory test is most commonly used method• Component subject to heat of a standard fire in test furnace• Primary points of failure for test• Fire resistance ratings expressed in standard intervals (Continued) Building Construction 2–7
  8. 8. Fire Resistance Test Method• Factors impacting fire resistance ratings from standard test• Standard fire test evaluates ability of structural assemblies to carry a structural load and act as a fire barrier• Information NOT provided by test• Assemblies may be penetrated (Continued) Building Construction 2–8
  9. 9. Fire Resistance Test Method Building Construction 2–9
  10. 10. Learning Objective 3 Identify fire testing organizations and discuss the significance of fire test results. Building Construction 2–10
  11. 11. Fire Testing Organizations• Testing for fire resistance ratings is beyond capability of local fire and building departments• Several laboratories are equipped to conduct testing• Some organizations use furnaces primarily for research and product development Building Construction 2–11
  12. 12. Fire Test Results• Published by testing laboratories• Deviation from materials or dimensions specified alters test results Building Construction 2–12
  13. 13. Learning Objective 4 Recognize the role of analysis in determining fire resistance. Building Construction 2–13
  14. 14. Analytical Calculation ofFire Resistance• Mathematical equations have been developed to predict behavior of materials under test conditions• ASCE/SFPE 29 provides methods for calculating fire resistance ratings• Limited to use with certain materials Building Construction 2–14
  15. 15. Analytical Design UsingReal Fire Exposures• NFPA® 251 test – Most commonly used – May be too severe or not severe enough• Ratings determined analytically using a different time-temperature curve must be interpreted cautiously Building Construction 2–15
  16. 16. Noncombustible Materials• Building codes contain explicit criteria for determining combustible material• Incapable of supporting combustion under normal circumstances• Most common test for determining combustibility – ASTM E 136 Building Construction 2–16
  17. 17. Learning Objective 5 Discuss the basic building classifications as they relate to fire resistance. Building Construction 2–17
  18. 18. Classifications• Type I, Fire-Resistive• Type II, Noncombustible or protected noncombustible• Type III, Exterior protected• Type IV, Heavy timber• Type V, Wood frame (Continued) Building Construction 2–18
  19. 19. Classifications• In building codes, based on materials used in construction and hourly fire resistance ratings required for structural components Building Construction 2–19
  20. 20. NFPA ® 220• Details requirements for each classification and subclassification• Designated by three-digit number code – 1st – Fire resistance rating in hours of exterior bearing walls – 2nd – Fire resistance rating of structural frames or columns and girders supporting loads greater than one floor – 3rd – Fire resistance rating of floor construction Building Construction 2–20
  21. 21. International Building Code ®(IBC ® )• Similar to NFPA® 220• Requirements for individual structural members differ• Building codes use construction types and occupancy in conjunction with sprinkler systems and separations to establish limits on heights and areas of buildings Building Construction 2–21
  22. 22. Type I Construction• Structural members are noncombustible construction with a specified fire resistance Courtesy of McKinney (TX) Fire Department• Combustible material typically permitted in certain components• Most common methods of construction Building Construction 2–22
  23. 23. Type II Construction• Noncombustible – Can be either protected or unprotected• IBC® divides into two subclassifications• Material other than steel can be used• Building codes allow combustible material similar to that in Type I (Continued) Building Construction 2–23
  24. 24. Type II Construction• Unprotected, noncombustible building cannot be expected to provide structural stability under fire conditions• Point at which unprotected members will fail depends on several factors• Protected, noncombustible structural fire protection is similar to Type I Building Construction 2–24
  25. 25. Type III Construction• “Ordinary construction”• Exterior walls frequently masonry, but can be any noncombustible material with required fire resistance• Interior members – Partially or wholly combustible – Protected or unprotected (Continued) Building Construction 2–25
  26. 26. Type III Construction• IBC® divides into two subclassifications• When fire resistance is required, most common is plaster (older) or gypsum board (newer)• Wood dimensions permitted to be smaller than Type IV• Fundamental fire concern – Concealed spaces Building Construction 2–26
  27. 27. Type IV Construction• “Mill construction”• Difference from Type III• Used in older factories, mills, and warehouses• Primary fire hazard – Massive amount of fuel Courtesy of McKinney (TX) Fire Department from large structural members Building Construction 2–27
  28. 28. Type V Construction• All structural components may be combustible• Two subclassifications• Differences from Type III• Threat to adjacent structures if heavily involved in fire Building Construction 2–28
  29. 29. Mixed Construction• Some buildings are allowed a mixed construction type• May result in special challenges for emergency responders Building Construction 2–29
  30. 30. Learning Objective 6 Discuss the concept of fire load and its impact on building construction types. Building Construction 2–30
  31. 31. Fire Load• Maximum heat released if all available fuel in a building was consumed• Product of weight of combustibles multiplied by their heat of combustion• Expressed in lb/sq ft (kg/sq m)• Varies depending on heat of combustion of fuel Building Construction 2–31
  32. 32. Fire Load and ConstructionType• Buildings with combustible structural components have greater fire load than Type I and II• Fire load does not translate into equivalent structural load Building Construction 2–32
  33. 33. Learning Objective 7 Explain occupancy classifications as they relate to fire risks. Building Construction 2–33
  34. 34. Occupancy Classifications• Assign building occupancies into groups with broadly similar fire risks Building Construction 2–34
  35. 35. IBC ® Classifications• Group A – Assembly • Group I – Institutional• Group B – Business • Group M – Mercantile• Group E – Education • Group R – Residential• Group F – Factories • Group S – Storage• Group H – High • Group U – Utility and Hazard Misc. Building Construction 2–35
  36. 36. International Building Code ®• Considerable variation of hazards within groups, so further divided to describe occupancy groups with more similar characteristics• Total of 26 subgroups• Separate provision for one- and two- family dwellings not more than three stories high Building Construction 2–36
  37. 37. NFPA ® Classifications• Assembly • Residential• Educational • Residential board• Day care and care• Health care • Mercantile• Ambulatory health • Business care • Industrial• Detention and • Storage correctional Building Construction 2–37
  38. 38. Mixed Occupancies• Buildings may contain more than one occupancy classification• Codes require fire-resistive separations between various occupancies• Requirements depend on local code• Reduction in occupancy separation may be permitted if building is sprinklered Building Construction 2–38
  39. 39. Change of Occupancy• Frequently occurs• Can create problems• May require expensive renovations that owner not willing to pay Building Construction 2–39
  40. 40. Summary• Fire behavior in buildings is determined largely by construction materials and structural fire resistance.• Structural fire resistance is determined most often through laboratory testing. (Continued) Building Construction 2–40
  41. 41. Summary• Building codes classify construction into types based on construction material, structural fire resistance, and occupancy.• Occupancies within individual occupancy groups present roughly similar fire risk factors. Building Construction 2–41
  42. 42. Review Questions 1. What is fire resistance? 2. What is the value of standard fire tests? 3. What is a noncombustible material? 4. What considerations do firefighters need to take into account when they encounter dropped (Continued) ceilings? Building Construction 2–42
  43. 43. Review Questions 5. What are the major occupancy classifications contained in the International Building Code® (IBC®)? Building Construction 2–43