1. 9 Noncombustible Construction Page 197

2. Objectives (1 of 2)‏ Understand the difference between noncombustible and fire-resistive construction Identify the different types of steel building components and their characteristics 9 2

3. Objectives (2 of 2)‏ Describe different types of steel structural systems Describe the hazards of a metal deck roof fire Understand the hazards of high fire loads in unprotected steel structures and ways to improve the situation 9 3

4. Introduction Noncombustible and fire resistive construction Differ in the level of fire resistance assigned to the structural frame, walls, floors, and roof Noncombustible construction has little fire resistance Fire resistive construction has moderate to heavy fire resistance 9 4

5. Noncombustible Construction Allowable area and height is much less than fire resistive construction Maximum height is 12 stories Fire resistive can have unlimited height Fire-resistive construction can use steel for its framing system 9 5

7. Steel Modulus of elasticity about 29 million pounds per square inch (psi)‏ High tensile strength and shear strength Strong but lightweight members have little inherent fire resistance 9 7

8. Fire Characteristics of Steel Substantial elongation Above 1300°F, steel members may fail Cold-drawn steel will fail at about 800°F Steel transmits heat readily 9 8

10. Unwarranted Assumptions False belief in steel’s “fireproofness” Need to set priorities Heat absorbed by contents or structural elements is the most important heat Heat being evolved from contents that are burning is of secondary importance Heat leaving the structure—let it go 9 10

11. Water on Hot Steel Water is the fire department’s heat removal medium Myth: Water should not be thrown on heated steel Cooling effect of water draws steel back to its original dimensions 9

12. Definitions: Steel Construction Members (1 of 3)‏ Angles Bars Box columns Box girders Channels 9 12

13. Definitions: Steel Construction Members (2 of 3)‏ I-beams Plates Purlins Rolled or built-up members Spandrel girders 9 13

14. Definitions: Steel Construction Members (3 of 3)‏ Tees Tubes Weight Wide-flange shapes Zees 9 14

15. Steel as a Construction Material (1 of 2)‏ Makes it possible to erect tall buildings Has consistency in structural characteristics Can be connected to other structural elements Used for fire escapes 9 15

17. Steel as a Construction Material (2 of 2)‏ Provides the tensile strength that concrete lacks Used in concrete flooring systems Used to repair failures in concrete buildings 9 17

18. Steel Buildings Used in peaked roofs Bar joists span the main trusses to support a flat roof Steel is almost universally unprotected. Buildings often can only be classified as noncombustible 9 18

19. Protected Noncombustible Sprinklered Construction Found occasionally Major structural elements have fire resistance Building itself is not fire resistive 9 19

20. Rigid Frames Column is narrow at the base and tapers to its widest point at the top Girder is also tapered Wide haunch resists the outward thrust of the roof Clear spans of about 100 feet 9

21. Steel-Framed Buildings Many are prefabricated Butler Company is a prominent manufacturer 9 21

23. Huge Spans Span collapses can be sudden and tragic Adjacent bents are tied together Tying the steel units together creates dependencies between torsional or eccentric loads The higher the resistance to wind load, the more likely a progressive collapse 9 23

24. Developing Wide-Span Trusses Designs may push the limits of steel Hasty field changes or errors in construction can have catastrophic consequences 9 24

25. Deep Parallel-Chord Trusses Floor beams in hospitals Interstitial space Such voids should not be used for storage or maintenance Automatic sprinklers should be required 9 25

26. Heavy Parallel-Chord Trusses Have been used as transfer beams Often hidden in partition walls 9 26

28. Trussed Arches Arch of a steel arch bridge is often a truss Is a compression structure 9 28

29. Walls of Steel-Framed Buildings Wall composition varies Metals, cement-asbestos board, masonry, concrete, and reinforced plastics found Wall insulation and coatings also factors 9 29

30. Cement-Asbestos Board Noncombustible and is often used for friable construction Friable construction is used where an explosion is a possibility Will break away readily and relieve pressure 9 30

31. Glass-Fiber Reinforced Plastics Noncombustible Resinous binder most often used with it is flammable 9 31

32. Aluminum Noncombustible, but has a low melting point Has little mass per unit of area, so it disintegrates rapidly in a fire 9 32

33. Precast Prestressed Concrete Panels Usually erected in large sections Collapse is hazardous to fire fighters 9 33

34. Masonry Walls Often used for walls for unprotected steel- framed buildings Made of concrete block or a composite Usually only curtain walls Important to analyze the effect of the expansion of the steel frame on the wall 9 34

35. Galvanized Steel Walls Used when heat conservation is not important Asphalt asbestos protected metal (AAPM)‏ Robertson Protected Metal (RPM) is one proprietary name 9 35

37. Metal Panels Prefabricated metal panels in a sandwich construction Plastics are often used with metal panels Insulation, vapor seal, or adhesive in the panels may be combustible 9 37

38. Polyurethane Insulating Panels Protected by gypsum board and stainless- steel sheathing If a cutting torch is later used, a smoky, destructive fire may result 9 38

39. Aluminum Sandwich Panels Can be made with foamed polyurethane Some are listed by Underwriters Laboratories (UL) Inc. for low flame spread ratings Smoke-developed ratings may be quite high 9 39

41. Failure of the Closure of the Wall Panel to the Floor Slab Design of panel walls Method of installation Degradation of insulation Expansion of metal under fire conditions 9 41

42. High-Rise Framing Steel once stood unchallenged as a method for high-rise buildings Concrete now is finding more use 9 42

43. Builders’ Hesitation Brick, stone, and terra cotta added to framed buildings Goal was to reduce the apparent or perceived height of the building Didn’t openly discuss use of steel-frames 9 43

44. Tilt-Slab Hazards Walls braced with tormentors or braces until the roof secured If the roof is being lost in the fire, beware of wall collapse If heavy smoke is present, the sprinklers are not controlling the fire 9 44

45. Steel-Framed Buildings Under Construction Wind forces must be resisted, because the building is not fully connected Braces may not be properly installed 9 45

47. Plastic Design in Steel Construction Connections are built to transfer loads beyond the column Beams are lighter and columns are smaller than they would be otherwise The lighter the steel, the less fire resistance 9 47

48. More on the Fire Characteristics of Steel Conducts heat Elongates as temperature increases Loses strength at high temperatures 9 48

49. Steel Conducts Heat Steel transmits heat Tin ceilings can transmit fire The conductivity of steel can be a factor in spreading fires 9 49

51. Ships Practice of using ships as buildings is growing Ships have steel walls known as bulkheads Welding operations are performed without concern for heat transmission 9 51