This document discusses fire-resistant construction methods, focusing on concrete structures. It describes different types of concrete construction including cast-in-place, precast, reinforced, and prestressed concrete. It also discusses the use of concrete in floors, beams, columns, and other structural elements. Fire risks during construction are highlighted.

1. 10 Fire-Resistive Construction

2. Objectives (1 of 2)‏ Recall the difference between noncombustible and fire-resistive construction Describe different types of concrete structural systems Describe the two types of prestressing 10

3. Objectives (2 of 2)‏ Contrast precast and site-cast concrete Describe the hazards of formwork Describe the methods of fireproofing steel and of ensuring a level fire resistance in concrete Detail how compartmentation works to prevent the spread of fire 10

4. Introduction Fire-resistive construction Considered to be the best Most resistant to collapse and does not contribute fuel to a fire Is given the largest permissible area and heights 10

5. Concrete Cementatious material produced by a chemical reaction Cures indefinitely; low temperatures retard the curing of concrete Weak in tensile strength and has poor shear resistance 10

6. Concrete Structures Pre-World War II Suitable only for structures in which aesthetics played little part Built of steel frames and fireproofed with concrete Cinder blocks use cinders as the aggregate Concrete blocks use other materials for aggregate 10

7. Underwriters Blocks Concrete blocks produced under Underwriters Laboratories’ classification Manufacturer’s certificate gives the type and number of units delivered to a specific job Blocks must meet fire resistance standards 10

8. Today’s Variety of Concrete Structures Use variety of building construction elements Steel-framed buildings now often have cast-in-place concrete floors Precast concrete and prefabricated metal wall panels and decorative brick veneer are common 10

9. Steel vs. Concrete Framing Designer preferences Some design in steel Others prefer concrete Some buildings concrete-framed and steel-framed mixed together 10

10. Fire Department Problems Problems with concrete construction Collapse during construction with no fire Fire during construction Fire in completed, occupied buildings 10

11. Types of Concrete Construction Cast-in-place Plain, reinforced, and post-tensioned concrete Precast Plain, reinforced, and pretension concrete 10

12. Concrete Definitions (1 of 5)‏ Aggregate Cast-in-place concrete Casting Chairs Composite and combination columns 10

13. Concrete Definitions (2 of 5)‏ Composite construction Continuous casting Continuous slipforming Drop panels Flat plate structural system (or continuous beam)‏ 10

14. Concrete Definitions (3 of 5)‏ Footings Lally columns Lift slab Monolithic construction Mushroom caps 10

15. Concrete Definitions (4 of 5)‏ One-way structural system Plain concrete Pretensioning and post-tensioning Precast concrete Reinforced concrete Reinforcing bars or rods 10

16. Concrete Definitions (5 of 5)‏ Slipforming Spalling Temperature rods Two-way structural system 10

17. Concrete Structural Elements Columns Beams (including t-beams) and girders Concrete floors 10

18. Virtue of Columns High compressive strength and low cost Columns are of reinforced concrete Steel reinforcing rods carry some of the compressive load The compressive strength of steel is many times that of concrete 10

19. Increasing Column Sizes Unsatisfactory in modern construction The useable area would vary from floor to floor Overcome by increasing the size of the reinforcing steel as the loads increase 10

20. Reinforcing Rods Long with a relatively thin diameter Ends of rods are connected Ties or hoops join the rods in a column Ties cut the long slender column into a number of relatively short columns 10

21. Beams and Girding (1 of 3) ‏ Plain concrete beam Strong in compression, weak in shear No tensile strength When a beam is loaded, it deflects Deflection brings compression in the top of the beam and tension in the bottom of the beam 10

22. Beams and Girding (2 of 3)‏ Cantilever beam Tension is in the top of the beam Reinforcing rods are in the top of the beam 10

23. Beams and Girding (3 of 3)‏ Continuous beam Supported at more than two points Tension in the top of the beam in the area over the tops of the columns Tension in the bottom of the beams between columns 10

24. T-Beams There is neither tension nor compression in the beam Has the neutral plane coincide with the bottom of the wide, thin floor slab Double T’s are floor slab and beam combinations with two beams 10

25. Concrete Floors First used for leveling brick and tile arch floors Early floors built of individual beams supporting a floor slab Hollow tiles lightened concrete floors 10

26. Waffle Concrete Closely spaced beams are set at right angles to one another Unnecessary concrete is formed out 10

27. Lighter Construction Floor may be just a flat plate This gives a smooth surface Easily finished 10

28. Left-In-Place Form Occurs when concrete floors are cast onto corrugated steel The steel provides necessary tensile strength If the bond fails, the floor section may fail 10

29. Precast T-Beam Units Additional concrete is often cast-in-place on top of the units Entire unit becomes an integral beam-and-floor element Cylindrical openings can be cast lengthwise through the units to remove unnecessary weight 10

30. Older Building Codes Concrete floor can be in ordinary construction Case example: Concrete topping over wood beams concealed the destruction of the beams by fire. Four fire fighters died 10

31. One-Hour-Rated Designs of Wood Floors Lightweight concrete topping as much as 1 to 1 1/2 inches thick Thickness retards the passage of heat through the floor National Fire Protection Association (NFPA) 251 (American Society of Testing and Materials (ASTM) E119) fire resistance standard 10

32. Cast-In-Place Concrete Floor Can be a hazard during construction A slot is left in the wall at the point where the floor is to be cast If a windstorm occurs during the time that the slot is open, a collapse may result 10

33. Concrete Floors in Steel Buildings May be precast or cast-in-place May be only load-bearing or provide structural stability 10

34. Concrete Floors in Cast-In-Place, Concrete-Framed Buildings Cast integrally with columns Provide a monolithic rigid-framed building May be pinned May be connected as a monolithic unit 10

35. When Slabs Are Laid Down A space is left between them Protruding bars of one slab extend past the ends of the protruding bars of the other slab The sections are joined by a wet joint 10

36. Concrete Floors in Precast, Pinned Concrete Buildings May not contribute to the building’s structural stability Precast columns are often built with haunches or shelves Steel plates imbedded in the concrete may be welded together 10

37. Prestressed Concrete Recently developed Engineered stresses placed in architectural and structural concrete Analogy: A row of books side by side, before and after being threaded together with wire 10

38. Special High-Strength, Cold-Drawn Steel Cables Similar to those used for suspension bridges These or alloy steel bars are commonly used in prestressed concrete Known as tendons, but also called strands or cables 10

39. High-Tensile-Strength Wire Ordinarily used for prestressing More sensitive to high temperatures than structural steel Complete loss of prestress at 800°F 10

40. Two Methods of Prestressing (1 of 2)‏ Pretensioning Done in a plant High-tensile-strength steel strands are stretched between the ends of a form After processing, stretched strands draw back, thus compressing the concrete 10

41. Two Methods of Prestressing (2 of 2)‏ Post-tensioning Done on the job site High-tensile-steel strand wires are positioned in the forms After processing, steel tendons are stretched and anchored at the ends of the unit 10

42. Bridge Girders Some are tensioned enough to make shipment possible, then post-tensioned after being placed Cement paste might be forced into the space between the tendon and the concrete to provide a bond 10

43. Reinforced Masonry Widely used to resist earthquakes Unsuitable for multistory buildings in which large clear spans are required Apartment houses and motels are well adapted to this method 10

44. Ordinary Brick Bearing-Wall Buildings (1 of 2)‏ Walls must increase in thickness as the building’s height increases. Limit is generally about 6 stories Recent years, possible to 20 or more stories 10

45. Ordinary Brick Bearing-Wall Buildings (2 of 2)‏ Construction methods allow higher buildings Two wythes of brick are built The width of one brick is left between them Reinforcing rods are placed vertically Concrete is poured into the void 10

46. Special Cases (1 of 2)‏ Low-rise buildings Recent designs have eliminated reinforced concrete in the wall High compressive-strength bricks and special mortar are used instead Masonry wall-bearing building can be several stories high 10

47. Special Cases (2 of 2) ‏ Concrete block Has become popular for some resorts With outside open-air stairways and balconies, life safety is achieved 10

48. Collapse Under Construction Concrete structures under construction sometimes collapse Fire department rescues construction workers Fire officers should be well informed on the legal position of the fire department 10

49. Ordering the Removal of a Dangerous Structure Power given to the building commissioner Fire department has no right to demolish such a structure. 10

50. Lawsuits Common today Owner, architect, general contractor, subcontractors, and victims attempt to determine financial responsibility After collapses, some of those involved may try to cover up their actions 10

51. An Industry Warning Experts have warned of the collapse hazard of concrete structures Design engineers should use construction loads as governing loads in structures 10

52. Problems of Falsework Falsework Temporary structure to support concrete work in the course of construction Can represent 60% of the cost of a concrete structure 10

53. Concrete Formwork Designed without the extra strength calculated into a building to compensate for deterioration Built at the lowest possible cost Formwork failures can occur, but it is surprising is that they are relatively rare 10

54. Falsework for Walls or Columns Must have adequate strength to resist the pressure of heavy fluid concrete As concrete sets, pressure is reduced due to internal friction Setting of concrete is temperature dependent 10

55. Reshoring Concrete Concrete requires time to cure Formwork is then removed Reshoring is putting shores back in place to help carry the load Reshoring means concrete is not yet set 10

56. Collapses of Floors (1 of 2)‏ Many involve formwork supporting newly cast or high bay floors Proper cross-bracing can help prevent this 10

57. Collapses of Floors (2 of 2)‏ Formwork can also be a problem Often rests on the ground Mudsills are the planks on which the shores rest If mud is involved, bearing may be inadequate 10

58. A Widely Believed Fallacy “Reinforced concrete which has set hard to the touch usually has developed enough strength to be self-supporting, though it may not be capable of handling superimposed loads.” 10

59. Skyline Towers Collapse Skyline Towers collapsed in Arlington, Virginia, 1973 Collapse proved the fallacy Shoring had been removed from the topmost floor The floor collapsed, and the collapse was progressive 10

60. Lessons from Skyline Towers Removal of shoring by laborers is no different than removal by fire Any concrete formwork failure presents the likelihood for catastrophic collapse Few concrete buildings can withstand the collapse of one floor onto another 10

61. Hazards of Post-Tensioning (1 of 2)‏ Hydraulic jacks are used to tension the tendons or jack the cables No bond between the tendons and the concrete 10

62. Hazards of Post-Tensioning (2 of 2)‏ Weight of concrete transfers to columns only when tensioning is complete Case example: The Skyline Towers garage was made of post-tensioned concrete. Poor sheer resistance led to collapse 10

63. Collapse of Reinforced Masonry Used widely in construction Workers might overload a floor portion Case example: In Pittsburgh, Pennsylvania an excess load caused the partial collapse of several stories of precast floors 10

64. Collapse of Precast Concrete Precast concrete buildings under construction are unstable Temporary bracing holds units in place Wooden temporary shoring might also be used Case example: Montgomery County Maryland. Three-story garage collapsed due to oversized washer 10

65. Lift-slab Collapses (1 of 3)‏ Lift-slab construction Ground floor slab is cast first Bond breakers are used between the slabs Slabs are raised to the columns Each floor is temporarily connected to the columns 10

66. Lift-Slab Collapses (2 of 3)‏ Case example: L’Ambience Plaza concrete building under construction in Connecticut was due to the failure of a single connection 10

67. Lift-Slab Collapses (3 of 3)‏ When do the accidents occur? While the slabs are being lifted or while no lifting is being done Case example: In California, a roof slab was lifted to columns three inches out of plumb. As an attempt was made to pull the slab back into place, it collapsed 10

68. Fire Problems of Concrete Buildings Under Construction Concrete buildings under construction can present serious fire problems Fire in formwork can easily result in major collapse Little reserve strength in formwork Little understanding of potential hazard 10

69. Potential Fires at a Construction Site Fires at a construction site Causes include welding, cutting, and plumbers’ torches; temporary electrical lines; and arson Fuels are readily available Glass-fiber formwork is also combustible 10

70. Hazard of Heating Burning of scrap wood in steel barrels or the use kerosene heaters are hazards Liquefied petroleum gas (LPG) is also dangerous 10

71. Codes for LPG (1 of 2)‏ Store gas away from any open flames. Case example: 1963, LPG explosion at the Indianapolis Coliseum; caused when a leaking gas-fired cooker cylinder exploded and gas reached heater flame 10

72. Codes for LPG (2 of 2)‏ Install excess flow valves. Case example: In one city, gas stored and piped with plastic tubes at ground level; hazard should line break 10

73. Hazards of Post-Tensioned Concrete (1 of 2)‏ Catastrophic fire collapse potential Include bridges and parking garages Falsework fire could cause the sudden collapse of an entire concrete floor slab After tensioning, the ends of tendons are left exposed 10

74. Hazards of Post-Tensioned Concrete (2 of 2)‏ Hanging tendons can fail at about 800°F Excess tendons are rolled up and attached to a wooden rack. Rolled-up tendons are heat collectors Failure of tendons will cause the collapse of that part of the structure 10

75. Protection of Tendons Insist on fireproofing tendon anchors immediately after tensioning is completed Insist on temporary protection for incrementally tensioned tendons 10

76. A Total Collapse: Case Example A post-tensioned building under construction in Cleveland, Ohio, suffered a falsework fire After a second fire, the entire 18-story building collapsed 10

77. Precast Buildings (2 of 2)‏ Pose unique hazards while being constructed Construction involves erection of precast concrete units. 10

78. Precast Buildings (2 of 2)‏ Temporary bracing or support is used; it can collapse Columns can be braced with wood rather than by telescoping tubular steel braces; wood is flammable Cold-drawn steel cables often provide diagonal bracing in precast buildings; these fail at 800° F 10

79. Cantilevered Platforms Used by cranes delivering materials to buildings under construction Are braced by wooden shores that would fail in a fire 10

80. Tower Cranes Supported on the building’s structural frame Weight of the crane may be distributed over several floors by falsework A fire involving this falsework can bring down the crane 10

81. Falsework on a Completed Floor Should be investigated May be supporting a patch over a hole May be supporting a heavy load such as the crane 10

82. Falsework: Case Example Formwork for concrete placement burned on the 23 rd to 25 th floors of a high-rise Operator was trapped in his cab He was protected with a heavy-caliber stream from a nearby roof until rescued 10

83. Fire Problems in Finished Buildings Concrete construction Thought to be truly fireproof Later, it was learned that concrete, like any other noncombustible material, can be destroyed by fire 10

84. Characteristics of Concrete Inherently noncombustible Some people confuse noncombustibility with fire resistance Neither is synonymous with fire safety 10

85. Safety of Concrete Construction: Case Example Reinforced concrete Joelma building in Sao Paulo, Brazil, burned in 1974 Resulted in179 deaths. The structure had minor damage. 10

86. Fireproofing (Insulating) Steel Has a fire resistance rating if the protection system previously passed a standard fire test No such thing as a truly fireproof building Fireproofed steel is protected steel 10

87. Types of Fireproofing (1 of 2)‏ Individual fireproofing provides protection for each piece of steel Methods include encasement and intumescent coating Membrane fireproofing does not protect individual members 10

88. Types of Fireproofing (2 of 2)‏ One method uses a rated floor-ceiling assembly Underwriters Laboratories can test a roof and ceiling assembly NFPA 251 (ASTM E119) standard fire test 10

89. Hazards of Floor–ceiling Assemblies Can present a serious menace to the safety of fire fighters Assemblies need to be assembled exactly as performed in the laboratory 10

90. Ceiling System At the mercy of those have reason to remove ceiling tiles Access to utilities and additional storage space are two reasons to remove tiles 10

91. Legal Provisions None require membrane protection be maintained Replacement acoustical tile may be combustible All penetrations of the ceiling must be rated as part of the ceiling system 10

92. Term “Fire-rated” Used quite often in the fire protection and building construction fields Nonspecific and meaningless No part of a listed fire-resistance system stands by itself 10

93. Integrity of a Ceiling System Most are unaware of its significance Alterations compromise integrity Tiles are replaced haphazardly Holes are cut through tiles Displays are hung from the metal grid Testing doesn’t include superimposed loads 10

94. Laboratory Fire Tests Conducted under a slight negative pressure to remove smoke and fumes Fires generate positive pressure, and lay-in ceiling tiles may be easily displaced by fire pressures 10

95. Addition of Insulation Might not be part of the specifications of the listed ceiling assembly Wrong insulation causes heat to be held in the channels supporting the tiles A membrane protection system must be perfect 10

96. Cockloft Occurs between the ceiling and floor Allows for rapid fire spread Case example: Fire starting in one room traveled across a hallway above the ceiling; it came down through the tile ceiling of another room to ignite books 10

97. Firestopping Some code provisions provide for this Use of plenum space for various services makes it probable that the firestopping will conform only to the definition of legal firestopping 10

98. Deep, Long-span Trusses In some buildings, used to provide clear floor areas This creates plenum spaces several feet in height Sometimes voids are called “interstitial spaces” Using such space as storage places fire load next to unprotected steel 10

99. Fire Resistance of Floor-Ceiling Assemblies Not all are intended to be fire resistive A steel bar-joist floor with concrete topping and flame-spread-rated tiles below may appear to be fire resistive, but it is not 10

100. Missing Tiles Does not necessarily mean that a fire resistance system has been violated The building may be of noncombustible construction In such a case, ceiling tiles are at the option of the owner 10

101. Concrete Construction Building Some concrete assemblies have suspended tiles incorporated Most of the time, the suspended ceiling is installed to provide a hidden void for utilities 10

102. Fireproofing and Building Codes Fireproofing Applied to meet the standards required by the local building code Further, building department will indicate which systems tested at which laboratories are acceptable. 10

103. Efficiency of Fireproofing Depends on the competence of the subcontractor Also depends on the building department staff and on the fire department inspectors 10

104. Encasement Methods Terra cotta tile Early method for encasement Case example: The cast-iron columns of the Parker Building in New York City were protected with three-inch terra cotta tiles, but still burned and failed 10

105. Errors in Encasement Leaving the bottom web of beams unprotected Skewbacks, which are tiles shaped to fit around steel, corrects this error Skewbacks, however, often are removed for other reasons 10

106. Limitations of Encasement Method Fireproofing that is easily removed is a hazard Case example: A contractor removed the fireproofing protection from a major column. About a hundred cylinders of propane gas were stored adjacent to the column 10

107. Concrete Encasement Concrete became quite popular as a protective covering for steel Wood falsework provides a high fuel load Has been involved in a number of serious construction fires 10

108. Fireproofing of Steel and Concrete Beams Fireproofing is integral; accomplished by a specified mix of concrete in a specified thickness Some concrete is necessary for fireproofing 10

109. Disadvantage of Concrete Its weight Fireproofing is often a tempting target for cutting back Case example: Builders replace concrete with wire laths covered with cement plaster or gypsum, both of which are lighter 10

110. Sprayed-on Fireproofing Sprayed concrete spalls badly when exposed to fire Other sprayed-on fireproofing can pass laboratory tests, but questions exist about their reliability in the field 10

111. Issues with Sprayed-on Material (1 of 2) Importance not understood by other trades Case example: A building with fireproofing stripped from the columns by plasterers 10

112. Issues with Sprayed-on Material (2 of 2) Case example: A state office building in California had poorly applied fireproofing material If properly applied, can be very effective Case example: First Interstate Bank of Los Angeles 10

113. Asbestos Fiber Fireproofing Serious health hazard in its use Difficult to sell a building with asbestos fireproofing Asbestos is being removed from existing buildings 10

114. Signs of Trouble Deteriorated concrete Spalling that exposes reinforcing rods Cracks in concrete 10

115. Parking Garages When salt is used to melt snow and ice, corrosion is prevalent Damage is often difficult to determine 10

116. Calcium Chloride Added to concrete Has caused problems Preventive measures include sealing the concrete, providing adequate drainage, and flushing surfaces with fresh water in the spring 10

117. Concrete Rehabilitation Includes removal and replacement Installation of cathodic protection Using additional steel beams 10

118. Unprotected Steel (1 of 4)‏ Concrete structures Often repaired with steel Steel cables fail even below 800°F 10

119. Unprotected Steel (2 of 4)‏ Fire fighters’ role Should watch what is being done to buildings Almost none of what is done to a building after it is completed benefits the fire suppression effort 10

120. Unprotected Steel (3 of 4)‏ Case example: Fire fighter student saw structural problem with mall roof: owner did not want building department to know of problem 10

121. Unprotected Steel (4 of 4)‏ Steel designed into the structure Proper degree of fireproofing is usually specified If it is not designed into a structure, it is usually unprotected 10

122. Ceiling Finish and Voids Concrete construction has no inherent voids Finish stages of the building can create voids 10

123. Waffle Slab Concrete Imitation plastic waffle concrete is often suspended below the structural slab Problem: Combustible tile with a high fire-hazard rating is often used for ceilings Interconnected voids make it possible for the tile to burn on both sides 10

124. Suspended Ceilings When installed as part of initial construction, more likely to have satisfactory fire hazard characteristics Tile usually as safe as the law requires 10

125. Combustible Tile Need not be suspended to create a serious hazard Flammable adhesive create problems Installing new ceilings below old combustible tile ceilings presents a serious hazard Case example: John Sevier Retirement Center fire 10

126. Combustible Voids Can be created in a variety of ways Case example: A wooden suspended ceiling installed in an otherwise concrete construction. Sprinklers are below the ceiling. Fire could burn unchecked in the void 10

127. Modern Office Building Has huge communications and other utility requirements As much as one third of the height from floor to ceiling may be in-ceiling or under-floor voids 10

128. Noncombustible Voids Combustible thermal or electrical insulation and combustible plastic service piping may be in ceiling void Hung ceilings are generally not required for the structural integrity of the building 10

129. The Integrity of Floors In fire-resistive buildings Floor will be a barrier to the extension of fire More codes are requiring sprinkler protection Compartmentation is rarely achieved 10

130. Building Use Requires floor be penetrated Often, such penetrations compromise the integrity of the floor 10

131. Enclosures Around Ducts May be inadequate Can permit transmission of fire and/or smoke to other floors Poke-throughs are holes provided to draw utility services up to a floor from the void below 10

132. Penetrations of Floors for Services Are increasing Floor may be unable to resist the passage of fire adequately. Suspended ceiling hopefully will develop the necessary fire resistance Owner is not free to modify the ceiling 10

133. Concrete Floors Require expansion joints Case examples: Steel expansion joints transmitted fire from floor to floor in a huge postal building; molten aluminum expansion joints extended fire at McCormick place Concrete shrinks and creates cracks, which allows fire to pass 10

134. Imitation Materials Imitation concrete panels Commonly used, particularly on the exterior of buildings Fasteners that hold the panels on the building are made of plastic If the plastic burns or melts, the panels will drop off the building 10

135. Energy Conservation Has brought about the use of exterior insulation and finish systems (EIFS) Buildings can be finished in this manner when constructed or modified later Case example: Fort Worth, Texas Courthouse 10

136. Concrete’s Behavior in Fires Concrete in fire-resistive construction Resists compressive stresses Protects the tensile strength of steel from fire The concrete provides time to extinguish a fire 10

137. Impact Loads Will damage concrete When spoiling has reached reinforcing steel, shoring should be done Concrete floors may give no clue to the distress on the other side 10

138. Cutting Tensioned Concrete (1 of 2)‏ Fire tactics Can include cutting through a concrete floor for accessibility Hole cutter can cut a hole in conventional reinforced concrete and reinforcing rods 10

139. Cutting Tensioned Concrete (2 of 2)‏ Tensioned concrete structures Steel cables are under tremendous tension Cutting tension cables creates a potential whip 10

140. Precast Concrete (1 of 2) Cast-in-place, monolithic concrete buildings Resistant to collapse The loss of a column does not necessarily cause collapse. Load will be redistributed 10

141. Precast Concrete (2 of 2)‏ Precast concrete buildings Individual columns, floors, girders, and wall panels are pinned by connectors No protective covering is provided for the connectors Fire load must be severe to cause failure 10

142. Explosions in a Precast, Pinned building Such buildings have none of the redundancies of a rigid-framed monolithic concrete building Case example: Ronan Point collapse, which involved a 24-story apartment building 10

143. Concrete Trusses Not common Exist in the Tampa, Florida, and Dallas/Fort Worth, Texas, airports Exist in the American Airlines hanger at Dallas/Fort Worth 10

144. Fires in Concrete Buildings: Case Example 1 Los Angeles Central Library Fire in 1986 Loss was immense 200,000 books and numerous periodical collections were destroyed The book stacks provided an estimated 93 pounds per square foot (psf) of fuel 10

145. Fires in Concrete Buildings: Case Example 2 High-rise apartment building in Dallas, Texas $340,000 in damage Utility and vent pipes had been punched through the ceilings 10

146. Fires in Concrete Buildings: Case Example 3 Military Records Center near St. Louis, Missouri Severely damaged in a fire in 1973 The incredible fire load included over 21 million military personnel files in cardboard boxes on metal shelves 10

147. Know Your Buildings When building rate is high, difficult for fire departments to keep pace Slowdowns present an opportunity to get current on the hazards of specific buildings “Experience keeps a dear school, but fools will learn in no other.” 10

148. Summary ( 1 of 2)‏ Concrete is a cementatious material produced by a chemical reaction There are two basic types of in-concrete construction: cast-in-place concrete and precast concrete Prestressing places engineered stresses in architectural and structural concrete 10

149. Summary ( 2 of 2)‏ Concrete buildings under construction can present serious fire problems The concrete in fire-resistive construction serves two purposes—it resists compressive stresses and protects the tensile strength of steel from fire 10