Ch 10 Fire-Resistive Construction

10 Fire-Resistive

Construction

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

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

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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

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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

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

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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

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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

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Steel vs. Concrete Framing

• Designer preferences

• Some design in steel

• Others prefer concrete

• Some buildings concrete-framed and steel-framed mixed together

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Fire Department Problems

• Problems with concrete construction

• Collapse during construction with no fire

• Fire during construction

• Fire in completed, occupied buildings

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Types of Concrete Construction

• Cast-in-place

• Plain, reinforced, and post-tensioned concrete

• Precast

• Plain, reinforced, and pretension concrete

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Concrete Definitions (1 of 5)

• Aggregate

• Cast-in-place concrete

• Casting

• Chairs

• Composite and combination columns

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• Composite construction

• Continuous casting

• Continuous slipforming

• Drop panels

• Flat plate structural system (or continuous beam)

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• Footings

• Lally columns

• Lift slab

• Monolithic construction

• Mushroom caps

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• One-way structural system

• Plain concrete

• Pretensioning and post-tensioning

• Precast concrete

• Reinforced concrete

• Reinforcing bars or rods

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• Slipforming

• Spalling

• Temperature rods

• Two-way structural system

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Concrete Structural Elements

• Columns

• Beams (including t-beams) and girders

• Concrete floors

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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

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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

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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

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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

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• Cantilever beam

• Tension is in the top of the beam

• Reinforcing rods are in the top of the beam

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• 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

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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

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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

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Waffle Concrete

• Closely spaced beams are set at right angles to one another

• Unnecessary concrete is formed out

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Lighter Construction

• Floor may be just a flat plate

• This gives a smooth surface

• Easily finished

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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

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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

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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

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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

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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

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Concrete Floors in Steel Buildings

• May be precast or cast-in-place

• May be only load-bearing or provide structural stability

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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

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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

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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

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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

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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

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High-Tensile-Strength Wire

• Ordinarily used for prestressing

• More sensitive to high temperatures than structural steel

• Complete loss of prestress at 800°F

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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

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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

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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

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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

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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

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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

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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

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Special Cases (2 of 2)

• Concrete block

• Has become popular for some resorts

• With outside open-air stairways and balconies, life safety is achieved

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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

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Ordering the Removal of a Dangerous Structure

• Power given to the building commissioner

• Fire department has no right to demolish such a structure.

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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

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An Industry Warning

• Experts have warned of the collapse hazard of concrete structures

• Design engineers should use construction loads as governing loads in structures

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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

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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

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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

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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

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Collapses of Floors (1 of 2)

• Many involve formwork supporting newly cast or high bay floors

• Proper cross-bracing can help prevent this

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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

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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.”

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Hazard of Heating

• Burning of scrap wood in steel barrels or the use kerosene heaters are hazards

• Liquefied petroleum gas (LPG) is also dangerous

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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

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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

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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

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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

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Protection of Tendons

• Insist on fireproofing tendon anchors immediately after tensioning is completed

• Insist on temporary protection for incrementally tensioned tendons

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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

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Precast Buildings (2 of 2)• Pose unique hazards while being

constructed

• Construction involves erection of precast concrete units.

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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

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Cantilevered Platforms

• Used by cranes delivering materials to buildings under construction

• Are braced by wooden shores that would fail in a fire

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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

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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

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Falsework: Case Example

• Formwork for concrete placement burned on the 23rd to 25th 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

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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

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Characteristics of Concrete

• Inherently noncombustible

• Some people confuse noncombustibility with fire resistance

• Neither is synonymous with fire safety

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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.

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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.

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Efficiency of Fireproofing

• Depends on the competence of the subcontractor

• Also depends on the building department staff and on the fire department inspectors

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Asbestos Fiber Fireproofing

• Serious health hazard in its use

• Difficult to sell a building with asbestos fireproofing

• Asbestos is being removed from existing buildings

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Signs of Trouble

• Deteriorated concrete

• Spalling that exposes reinforcing rods

• Cracks in concrete

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Parking Garages

• When salt is used to melt snow and ice, corrosion is prevalent

• Damage is often difficult to determine

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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

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Concrete Rehabilitation

• Includes removal and replacement

• Installation of cathodic protection

• Using additional steel beams

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Unprotected Steel (1 of 4)

• Concrete structures

• Often repaired with steel

• Steel cables fail even below 800°F

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• 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

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• Case example: Fire fighter student saw structural problem with mall roof: owner did not want building department to know of problem

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• Steel designed into the structure

• Proper degree of fireproofing is usually specified

• If it is not designed into a structure, it is usually unprotected

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Ceiling Finish and Voids

• Concrete construction has no inherent voids

• Finish stages of the building can create voids

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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

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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

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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

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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

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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

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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

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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

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Building Use

• Requires floor be penetrated

• Often, such penetrations compromise the integrity of the floor

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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

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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

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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

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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

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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

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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

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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

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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

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Cutting Tensioned Concrete (2 of 2)

• Tensioned concrete structures

• Steel cables are under tremendous tension

• Cutting tension cables creates a potential whip

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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

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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

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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

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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

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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

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• High-rise apartment building in Dallas, Texas

• $340,000 in damage

• Utility and vent pipes had been punched through the ceilings

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• 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

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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.”

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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

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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

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Ch 10 Fire-Resistive Construction

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Transcript of Ch 10 Fire-Resistive Construction