Tieng Anh Trong Xay Dung

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Section 9 - Building Construction

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BUILDING CONSTRUCTION

INTRODUCTION

The most important reason for understanding building construction is safety.Firefighters should be able to identify the types of building construction, associatedterminology, and type of roof, to know when it is no longer safe to remain in or onthe building. Firefighters must be familiar with the basics of building construction

and how a fire in a particular building can affect its structural integrity. Knowingcommon building construction terminology will allow firefighters to understandand interpret building construction experts who may be called to a structure fire.Firefighters must also have an understanding of the major roof types and be awareof their associated strengths and weaknesses. When attacking a fire, this knowledgewill make it easier to avoid serious injury or fatalities due to the hazards intrinsicto a particular roof type.

Buildings may collapse for a variety of reasons including stress, poor construction,or deterioration. Firefighters should be aware of the potential and imminentindicators of building collapse. They should be able to inspect a building and

identify those indicators which may lead to building collapse, both under normalconditions and during fire suppression operations. These indicators, in some cases,may be avoided or alleviated. Firefighters must know what to do under thesecircumstances and when it is no longer safe to remain in, on, or near the building.An example might include the steady build-up of the water level when fighting aninternal structure fire. It may be possible to reduce the amount of water on the floor by either knocking out the lower windows at floor level or by drilling holes in thefloor.

Another important aspect of building construction that firefighters must be con-

cerned with is building classifications and the basic differences between each type.Since buildings vary in type, design, and construction methods each will have itsown unique fire problems and hazards. Therefore, firefighters who are familiarwith the type of building classification and associated collapse hazards will do a better job of containing the structure fire and they will be safer firefighters.




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OBJECTIVES

• Identify and describe common terms utilized in wood frame construc-

tion.

• Recognize and describe various types of walls found in typical build-ing construction.

• Identify major types of roof styles and associated roof coverings.

• Identify design causes of structural collapse and some major warningsigns of potential structural collapse during fire operations.

• Describe the indications of imminent building collapse which might be noted during an emergency. These may include:

a. Ankle-deep water on the floors b. Holes in the floorc. Sagging floorsd. Sliding sheets of plastere. Rising plaster dustf. Steel beams exposed to intense heat and fireg. Spongy floors and roof h. Burned-out trusses

• Identify the five major types of building construction and the collapsehazards of each.

• Identify the structural features which may influence fire spread andsafety, which would include:

a. Fire walls, doors, windows, shutters, partitions, stops b. Curtain boardsc. Venting devices (smoke and heat)d. Fire exits and escapes

e. Fire and smoke dampers

• Identify in high-rise construction the two different types of framework for high-rise construction.

• Identify construction methods used in tilt-up construction.




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TERMINOLOGY

The following dwelling cutaway, overviews examples of construction terminologyand techniques that are useful in developing a basic knowledge of construction

fundamentals.




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Definitions of Wall Types

Bearing Wall: A bearing wall is capable of supporting a vertical load, such as a flooror a roof, in addition to its own weight.

Non-bearing Wall: This wall is not designed to support a vertical load.

Exterior Wall: An exterior wall separates the interior from the exterior of a building.Such a wall is usually exposed to the outside, though not always. It forms the extentor boundary of the building.

Interior Wall: This wall will be wholly within a building and will not be exposedto weather.

Party Wall: A party wall usually separates two buildings of distinct ownership andlies on the lot dividing line between the two properties. This wall can be either

bearing or non-bearing.

Fire Wall: This type of wall is erected to prevent the spread of fire. It must havesufficient fire resistance to withstand the effects of the most severe fire that couldoccur in the building. As well, it must provide a complete barrier to the spread of fire. Any openings in this type of wall must be properly protected.

One-Hour Wall: This is a term often used in the fire service. There are 83 differentways to construct a typical one-hour wall as described in Chapter 43, Table 43-A, of the Uniform Building Code. A typical one-hour wall will be non-bearing and will

consist of either:

• 2"x4" wood studs, 16 inches centered, with both sides covered by onelayer of 5/

8" type “X” gypsum wallboard.

• 3 1/4" “Tin Can” metal studs, 24 inches centered, with both sides

covered by one layer of 5/8" type “X” gypsum.

Partition: This is an interior wall, one story or less in height, which separates twoareas. A partition can be either bearing or non-bearing.

Fire Partition: This is a partition that will inhibit the spread of fire but does notqualify as a fire wall.

Curtain Wall: A curtain wall is an exterior, non-bearing wall more than one storyin height. It is usually supported by the structural frame.

Panel Wall: This is an exterior wall one story in height. In a multistory building,panel walls must be supported at each floor level.




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Parapet Wall: This is defined as the portion of wall that extends above the roof of a building.

Shear Wall: This type of wall is erected to assist in resisting the force of wind. It is built within the building and usually is part of some required enclosure, such as an

elevator or stair shaft. This is a bearing wall.

Veneer Wall: This is an exterior wall created to improve the appearance of a building. It is constructed from a variety of materials including marble, brick, stone,or steel. The most common veneered wall is brick on a wood frame. These wallsare unsupported and are only as strong as the underlying wall. During a fire, thesewalls can become very unsafe.

Basic Roof TypesThe following roof types summarize the majority of different types of roofs foundwithin the city of San Diego and surrounding areas. There are several others, but in

general they are a variation of these types. Each type will be covered in detail furtheron within this section.




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Description: “A” frame configuration. Conventional or ordinary constructionconsists of a ridge board, rafters from the ridge board down to and across the outsidewalls (studs). Ridge and rafters are usually 2x6 inches or larger. Rafters are usually

16 inches to 24 inches “on center”. Additional support is provided by collar beamsand ceiling joists. The roof is constructed in semi-flat to steep pitches.

Strengths: Ridge board, rafters (if 2x6 inches or larger) and the area where rafters

cross the outside walls.

Hazards: Older gables may use 2x4 inch rafters. Newer roofs use 3/8 or 1/

2inch

plywood as a decking instead of 1x4 inch or 1x6 inch stripping. Plywood will burnand fail at a faster rate, offers little resistance to fire, and is difficult to remove forventilation purposes.




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Description: Similar to gable roof, but no “A” frame configuration. Ends of roof terminate in “hip” configuration. Conventional or ordinary construction consists of ridge pole (board), hip rafters from the ridge pole down to and across the corners

at the outside walls. Valley rafters are utilized where two roof lines are joinedtogether. Ridge and rafters are usually 2x6 inches or larger. Rafters are usually 16to 24 inches “on center”. Various degrees of pitch are utilized.

HIP ROOF

Strengths: Ridge pole, valley rafters, hip rafters, and the area where rafters cross theoutside walls.

Hazards: Similar to gable roofs, utilization of 2x4 inch rafters and 3/8 or 1/

2 inch

plywood as a decking. Roofs with a steep pitch will require roof ladders to conductventilation operations. If the roof is finished with tile, it becomes slippery when wet

and offers little footing when dry.




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CORRUGATED ROOF

Description: Fast and inexpensive to erect whether large or small. Corrugationsconsist of steel, aluminum, or fiberglass over a wood or metal substructure.

Corrugated steel is often utilized, usually 18 to 20 gauge thickness. (About thethickness of an American car fender, .0475".)

Strengths: Ridge and area where roof crosses the outside bearing walls.

Hazards: Corrugations may be steel, aluminum, or fiberglass. Expect rapid failureof these materials when exposed to heat or fire. Some buildings utilize plastic orfiberglass panels in the roof as skylights. Personnel should consider this roof extremely hazardous for ventilation operations.




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Description: Steel or wood substructure covered by corrugated metal “RobertsonDecking”; an air-entrained mixture of sand, cement, and occasionally pea gravel is

pumped on top of the corrugated metal decking and wire mesh to a thickness of about 3 to 4 inches. Composition roofing material is utilized as a final layer.

Strengths: Lightweight concrete surfaces offer a strong, hard surface. Structurallysound and resilient to fire.

Hazards: Difficult to penetrate with chain-saw or rotary saw with a masonry blade.Use a rotary saw with carbide-tipped wood blade to cut ventilation holes.




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SAWTOOTH ROOF

Description: Constructed in commercial buildings to yield additional light andventilation. Constructed with rafters of 2x8 inches or larger, and utilizes wood and/

or metal supports for bracing to provide additional strength. Vertical portion isusually “wired” glass with opening panes. Sloping portion is covered with 1x6 inchsheathing or plywood and composition roofing material.

Strengths: Substructure constructed from adequate (2x8 inch, 2x10 inch, etc.)lumber. Easy to ventilate-open the hinged panes of glass. Consider the area whererafters cross or are tied into the vertical walls as strong areas.

Hazards: Newer sawtooth roofs are covered with 1/2 inch plywood. Plywood

decking provides little resistance to fire.




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BRIDGE TRUSS ROOF

Description: Wooden truss members constructed from 2x12 inch lumber with

sloping ends. Usually a heavy grade of construction. Metal tie rods may be usedvertically for additional support. Joists are 2x6 inch and 2x8 inch and covered with1x6 inch sheathing and composition roofing material.

Strengths: Well-constructed. Consider the perimeter of the building (where trussesand the roof are anchored to outside bearing wall) and the bridge truss members asstrong areas.

Hazards: Dependent on the size of lumber utilized and span of trusses. Trusses arein “tension” and “compression” and will fail under severe fire conditions. If metaltie rods are used, early failure of rods will affect the stability of the trusses.




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BOWSTRING ARCH ROOFDescription: Arch roof with tie rods and turnbuckles offering lateral support. Tierods with turnbuckles are used below each arch member to support the exterior

walls. Tie rods may pass through the exterior wall to an outside plate facilitatingidentification. Tension is maintained by turnbuckles. Top chords or arch membersmay utilize laminated 2x12’s or larger. 2x10 inch rafters are covered by 1x6 inchsheathing and composition roofing material.

Strengths: This roof utilizes a good size of lumber and 1x6 inch sheathing as the roof decking. Consider the perimeter of the building and the bowstring arch membersas strong areas.

Hazards: The main hazard is early failure of metal tie rods and turnbuckles. Tierods (tension) provide lateral support to the walls and keep the arches (compres-sion) from pushing the exterior walls outward, and prevent collapse of the building.




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RIBBED (TRUSSED) ARCHED ROOF

Description: Usually large size (2x12, 2x14 inch) of wooden members utilized toconstruct truss arch. Some arches have multiple laminated beams to form one arch.Rafters (2x10 inch or larger) are covered with 1x6 inch sheathing and compositionroofing material.

Strengths: Most roofs of this type are well-constructed. Consider the perimeter of

the building and the trussed arch members as strong areas.

Hazards: Determined by size of lumber and span of arches. Most roofs of this typeare well-constructed.




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LAMELLA ROOF (SUMMERBELL)

Description: Egg-crated, geometric, or diamond-patterned roof. This roof iscommonly known as a “Summerbell Roof”, however, it is lamella roof constructiondeveloped by the Summerbell Company. Constructed from 2x12 inch woodframing, steel plates, and bolts at junctions of framing. Roof decking is 1x6 inchsheathing and composition roofing material. Arch roof is supported by exterior“buttresses”, or internally by tie rods and turnbuckles.

Strengths: Good construction utilizing solid construction techniques and lumber.Consider the perimeter of the building as a strong area.

Hazards: Possible total roof collapse if fire removes more than 20% of roof structure.Collapse may occur from the “domino effect.”




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CONVENTIONAL FLAT ROOF

Description: Wood joists (or rafters) of various sizes laid across the outside wallsor outside walls to interior walls or structural supports. Joists may also besuspended by metal hangers. Joists are covered with 1x6 inch sheathing or plywoodand composition roofing material. Very common roof.

Strengths: Dependent on the size of the joists and type of decking utilized.Consider the perimeter of the building as a strong area.

Hazards: Degree of hazard presented by joist is based on span, size of joist, “on-center spacing,” and if the joist is suspended by metal hangers. Roofs covered withplywood instead of sheathing present a problem. Plywood may be found in 3/

8 to

5/8 inch thickness. Plywood offers little structural integrity under fire conditions

and is difficult to remove for ventilation purposes. Also, plywood may be burnedout from the underside and not show signs of weakness from the top of the roof.




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Basic Roof CoveringsDuring firefighting and roof ventilation procedures there are a number of roof coverings that will be encountered. It is important for firefighters to familiarizethemselves with the different materials used, and the strengths and hazards of each.In this way the proper method of ventilation can be used in an expedient and safemanner.

Shake shingles: (Wood and Composite) Wood shingles or shakes are split piecesof red cedar wood used for roofing or siding. They are usually attached to 1x6 inchskip sheeting. Newer wooden shakes are now treated with fire retardent. Compos-ite or shake substitutes are made to simulate wood shake shingles, but in fact aremade of a variety of non-combustible materials.

Strengths: Composite shakes are non-combustible. Walking on rafters offers mostsupport.

Hazards: Wood shakes are combustible. Skip sheeting offers little support whenweighted.

Asphalt composition shingles: This shingle consists of a fiberglass mat that isimpregnated with asphalt. Plywood is placed over rafters and felt is placed on topof the plywood. Finally, the shingle is stapled or nailed over the felt.

Strengths: Walking on the rafters, valley rafters or ridgepole offers the best support.

Hazards: This material will melt and burn.

Heavy felt: This is asphalt-impregnated felt which comes in rolls. A hot mopprocedure of tar is placed over plywood and the felt rolled over it. This material isused predominately on flat roofs.

Strengths: Walking on joists and over exterior walls.

Hazards: This material will melt and burn. Since this is typically used on flat roofs,firefighters will encounter lightweight construction methods on more recent homes.Under heavy fire conditions, this type of roof can fail quickly.

Tile: These can be made from a variety of materials. They consist of:

• Slate• Clay• Concrete• Lightweight concrete

The last three can be either Spanish style or flat style. Tile roofs are heavy andusually supported by metal gusset plate trusses. The tiles are nailed to plywoodand are easily removed by hand.




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Strengths: The overlap area offers most support. The tiles are non-combustible.

Hazards: Stability of roof is masked. Tiles can be extremely slippery when wet.When ventilating, tiles must be removed and can slide off the roof and cause injury.

Ridge caps must be removed before a roof ladder can safely be hooked over theridge board. If trusses are exposed to fire the roof will collapse rapidly.

Metal: Steel roofing is a Class I (non-combustible) lightweight roofing material thatcomes in 4' x 15" panels. The roofing panels have the look of tile or can resemble thetraditonal wood shake roof. This type of roofing material prevents embers fromigniting roofs during wind-driven fires. As building codes in the wildland/urbaninterface become stricter, this type of roofing material has become more prevalentin California.

Steel roofing can be installed directly over an existing wood shake roof. This makes

it easy and less expensive to install. The panels are placed on a 2' x 2' batten and 1' x 4'counterbatten grid system. To strengthen the roof, the panels are staggered like brick work and nailed horizontally. One indication of this type of roofing is theoversized metal trim, of 4' to 6', found on the fascia boards and the end caps. Anotherindication is the steel roofing panels will not break when struck by a sledge or axe.Sounding and/or walking on the roof should be done at the bottom of the panelswhere the battens are located. Avoid areas that feel hot and sticky underfoot.

For more information review training video entitled "Stone-Coated Steel Roofs",available at video library at headquarters.

Strengths: Strongest part of roof is at the bottom of the panels where the battens arelocated. Panels are non-combustible.

Hazards: Two problems have surfaced in four Southern California cities whenfighting fires in structures with steel roofs. The first problem is rapid and undetec-ted fire spread under the new roof. The method of applying steel roofs over existingcombustible roofs creates a space (approximately 4") between the old and the newroof. This 4 inches of hidden space provides an avenue for the fire to spread rapidlyand to move undetected through the entire length of the roof. Once the original,combustible roof is burning, the entire new roof must be removed to ensure

complete extinguishment.

The second problem encountered is firefighter unfamiliarity with this type of roofing material. This lack of awareness has made roof removal difficult and timeconsuming due to improper tool selection and improper location of cuts. SeeVENTILATION section for information on steel roof ventilation.




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LIGHTWEIGHT CONSTRUCTION METHODS

Lightweight building and roof construction is currently very popular with archi-tects and building contractors across the country. Considering the present cost of labor, equipment, and building materials, it is not economically feasible to con-struct buildings the same as 50 years ago. Ease of installation and utilization of lightweight building materials have become the standard during the last 25 years.Heavy timber, laminated beams, and 1x6 inch sheeting have been replaced by 2x4’sand 1/

2 inch plywood regardless of building size. New style buildings with their

characteristic concrete tilt-up walls, false fascias, and flat roofs are other indicationsthat lightweight construction may be present. As a result of architects' reducing thesize of what there is to burn, today’s fire departments are losing one of their mostvaluable fireground factors-TIME.

This section will focus on the five major types of lightweight roof construction:

1. Panelized2. Metal gusset plate trusses3. Open web construction4. Wooden “I” beams5. Steel roofing

NOTE: This type of construction may also be utilized in floors , walls, etc.

PANELIZED ROOF SYSTEM




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Description: This roof can be found on structures constructed of wood, masonry,or concrete tilt-up slabs. This roof consists of four major components:

1. Laminated beams

2. Purlins3. 2x4 inch joists4. 1/

2 or 5/

8 inch plywood decking

Panelized roofs do not have a space between the ceiling and underside of the roof occupied by the familiar trussed joist construction. The roof is usually constructed by laminating beams of various sizes (6x36 inches are common). The beams aresupported at their ends by pilaster or posts and additional posts may be supportingthe beam along the span. The beams will be spaced from 12 to 40 feet apart and may be bolted together to create lengths well in excess of 100 feet.

Wooden purlins are installed with metal hangers on 8 foot centers. The commonsize of a purlin is 4x12 inches with the length depending on the spacing between beams. Joists measuring 2x4 inches x 8 feet are installed with metal hangers on 2 footcenters between the purlins and run parallel to the beams.Sheets ofplywood (4 x 8 feetx1/

2 inch) are nailed over this framework. The plywood is then covered with

composition roofing material. A three-layer insulation paper is stapled to theunderside of the roof between the beams and purlins. This paper offers littleprotection to the 2x4 inch joists and 1/

2 inch sheets of plywood. Insulation paper

consists of tar- impregnated kraft paper covered on either side by thin aluminumfoil.

Strengths: The strengths of this roof are beams, purlins, perimeter of building(where roof ties into the exterior walls).

Hazards: Span supports for beams of 4 inch hollow steel pipe may be found. Expectweakening and/or collapse of these supports with failure of large portions of theroof under heavy fire conditions. When the insulation paper is subjected to fire, thefoil will peel away from the middle layer of tar-impregnated paper. This paper willthen begin to give off flammable gases which build up between the insulation paperand plywood decking.

When ignition temperature is reached, the gases will flash resulting in heavy charto the wood and burning insulation dropping to the floor below. Fire is then ableto expose the 2x4 inch joists and 1/

2 inch plywood decking which offer little

resistance to fire.

When walking across a panelized roof, utilize the beams or purlins. Any othersection of this roof is comprised of 2x4’s and 1/

2 inch plywood which will rapidly

fail when exposed to fire.




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METAL GUSSSET PLATECONSTRUCTION

Description: Rough carpentry wood trusses used in commercial and residentialapplications utilize 2x4’s held together by metal gusset plate connectors (Seeillustration). This truss system is enjoying widespread use in roof, floor, roughwindow, and rough door openings. Trusses for roofs are constructed in a widevariety of forms. Regardless of form, these trusses share common features: bottom chords, and webbing (supports between the top and bottom chords are

referred to as “webbing”). The trusses are held together by metal gusset plateconnectors. Metal gusset plate connectors vary in size, thickness, and depth of penetration; however, 18 gauge steel plates with prongs that produce 3/

8 inch

penetration are common and used in a wide variety of applications.

Utilizing 2x4’s, spans of up to 55 feet will be found. A point of interest with thistype of construction (also open web construction and wooden “I” beams) is the




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fact that trusses are supported at their outside edges only (unless used as acantilever truss). Interior partition walls do not support the truss at any point alongthe bottom chord. Eighteen gauge “roof truss clips” may be found at variouschords. These clips are nailed to the bottom chord and to the top plate of the interiorwall. Roof truss clips provide some lateral stability for partition walls. In this

configuration, interior partition walls could be classified as “free standing.”

Common on-center spacing for this construction is 2 feet and may be covered with1/

2 inch plywood. Used in floor and roof systems.

Strengths: Consider the area where the trusses cross or are tied into the outside bearing walls as strong areas.

Hazards: Extensive use of 2x4 inch trusses with metal gusset plate connectorsequals short burning time and early failure and collapse. These trusses are undertension and compression and, when the bottom chord or webbing fails, either from

connector plates that have pulled out or from deep char, the truss will fail. Whenthe metal connector plates and surrounding wood are exposed to fire, the plates willfail in a short period of time by pulling out of the wood. The bottom chord of thetruss has replaced the 2x6 inch or larger ceiling joist of conventional construction.Coupled with the fact that these bottom chords do not rest on the interior wallswhich offer additional support, expect total collapse of portions or the entire roof in a short period of time. As in other truss-type construction, depth of cuts forventilation purposes are critical.

An additional hazard is identification of the construction of the roof you are about

to ventilate. A simple flat roof may be constructed from different types of joists ortrusses, yet there is a wide range of strength factors inherent in different types of construction.

OPEN WEB CONSTRUCTION(TRUSSED JOIST CONSTRUCTION)




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Description: Open web construction consists of bottom and top parallel woodensupporting beams called chords which are cross-connected by steel tube webmembers. The top chord (supported) and under-load offer a bridging effect causingthe top chord member to be in compression and the bottom chord member(unsupported) to be in tension. Open web construction is prefabricated at the

factory before installation with either parallel chords laid on edge or with flat-laidchords. The steel tube web members are prefabricated from 1 to 2 inch cold rolledsteel tubing with the ends pressed flat into a semicircular shape and a hole punchedthrough each end. These flattened ends are then inserted into slots in the chords.Steel pins (up to 1 inch) are then driven through the flat ends of the web memberscompleting the assembly. When the prefabricated joists are installed, top chordmembers are secured to the top of bearing walls with bottom chord membersremaining unsupported away from the wall. Spans to 70 feet are possible using asingle 2x4 or two 2x3’s as top and bottom chord members. 2x4’s exceeding lengthsof 20 feet are made possible by joining different lengths of 2x4’s in a glued mitered“finger joint”. Normal on-center spacing is 2 feet. Used in floor and roof systems.

Strengths: Consider the perimeter of the building where the roof ties into theexterior wall as a strong area.

Hazards: The hazards of this roof are many. Basically, this roof is constructed of 2x4’s or 2x3’s under tension and compression and 1/

2 inch plywood decking. These

components offer minimum resistance to fire. Some construction leaves the chordsexposed to the interior of the structure which increases the exposure hazard andallows larger areas of the roof to be exposed to fire. Expect to find a lack of fire stopsin this construction. Due to the size of the lumber and chord members in tension andcompression, expect rapid failure of this construction. When 2x4’s are laid flat as

chords (11

/2 inch thick) with1

/2 inch plywood decking, firefighters only have to cut2 inches deep (when cutting for ventilation purposes) to cut through the chordmembers. This may cause partial roof failure of the area supported by the severedchords.




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Shown are typical bearing conditions one might encounter with truss construction.Note how some extend well past the bearing wall. If a fire were to burn through thetruss on the inside, the remainder of the truss could topple over. Beware of thissituation!

Truss joists are lighter in weight than most other systems. This feature cuts erectioncosts, speeds construction and makes possible the use of less costly footings,foundations and bearing walls. For these reasons truss construction is very popularin commercial areas. A truss may span up to 25 feet in most floor systems and upto 40 feet in many roofs. Multiple spans are possible up to 70 feet total length.

WOODEN "I" BEAM

Description: Consists of three main components:

1. Top chord2. Bottom chord

3. 3/8 inch plywood stem

The stem is joined to the top and bottom chords by a continuous glued edge joint.Two by fours are used as chords, but 2x3 inch chords are very common. Some chordsmay resemble plywood because of laminations. However, the laminations (tradename of Micro Lam) or veneers run horizontally in the chords. Micro Lam differsfrom plywood where every other veneer is 90O to the preceding veneer. The MicroLam veneers are stronger than solid sawn lumber. In the 2x3 inch configuration,spans of up to 40 feet will be found. Until adequately braced and the plywood




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decking is nailed down, this construction is very unstable. Common on centerspacing for this construction is 2 feet. Half-inch plywood is utilized for the decking.Used in floor and roof systems.

Strengths: Consider the perimeter of the building where the roof ties into the

exterior walls as a strong area.

Hazards: What there is to burn consists of a 3/8 inch plywood stem and 2x3 or 2x4

inch chords. It will take little time for the 3/8 inch plywood to burn, weaken and

cause collapse of the chords and the roof. Buildings will be found with open andunprotected chords. Common practice is to run heating and air conditioningducting of various sizes through the stems which removes a good percentage of thestem and gives fire horizontal access to adjacent “I” beams. As with otherlightweight roofs, depth of cuts for ventilation purposes is critical.

COLLAPSE HAZARDS OF THE FIVE STANDARD TYPES OFBUILDING CONSTRUCTION

Type I, Fire-Resistive ConstructionThere are two basic types of fire-resistive construction: reinforced concrete build-ings and structural steel buildings. Both are designed to resist fire which burns outan entire floor without spreading flames to other floors or collapsing the structure.

However, during serious fires a collapse danger does exist with both types of construction. In reinforced concrete buildings, heated concrete ceilings collapse ontop of firefighters; in steel skeleton buildings, heated concrete floors buckleupward. Both of these structural failures are caused by spalling, the rapidexpansion of heated moisture inside the concrete. Small amounts of moisture,normally trapped inside concrete, expand when heated by fire and create an internalpressure within the concrete. This pressure can cause heavy sections of concrete tocrack away from a ceiling and collapse down onto fire operations or on top of afirefighter. This type of collapse occurs in a building without a suspended ceiling,where the concrete ceiling above the fire is directly exposed to flames below. In steelskeleton construction, the under side of each floor is not concrete; each floor consistsof light-gauge corrugated steel sheet which supports several inches of concrete floorabove it. Heat from a fire reaching the under-side of the corrugated steel isconducted through the concrete floor directly above. The moisture in the concreteabove the steel is heated, and the internal pressure develops in the concrete above.Consequently, the expanding concrete buckles upward suddenly 6 to 12 inches.

Type II, Non-Combustible/Limited CombustibleThere are three basic types of non-combustible buildings: The metal-frame struc-ture covered by metal exterior walls, the metal-frame structure enclosed by concrete




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block, non-bearing exterior walls; the concrete block bearing walls supporting ametal roof structure. On all three types, the steel roof support system may be eitherone of the following: a system of solid steel girders and beams, lightweight open-web bar joist, or a combination of both. The collapse danger to a firefighter from anon-combustible building is roof cave-in from the unprotected steel open-web bar

joist. The main disadvantage of the open-web bar joists is its susceptibility todamage by a fire in the combustible contents inside the building. Tests have shownthat unprotected lightweight open-web bar joist can fail when exposed to fire forfive to ten minutes. This possibility makes it extremely dangerous for a firefighterto operate on a roof supported by steel open-web bar joists which are being heated by flames. The open-web bar joist is the main structural hazard of non-combustibleconstruction.

Type III, Ordinary ConstructionThe ordinary constructed building called “brick-and-joist” has exterior walls of masonry with wood floors and roof. This construction method was used to build

many of the public, commercial, and multiple dwellings throughout the country.The structural hazard of an ordinary constructed building is the parapet wall, theportion of the masonry wall that extends above the roof line. The collapse dangerof the parapet wall is one of the reasons why the area directly in front of a fire building is so dangerous, and why firefighters are urged either to move inside thedoorway or away from the front of the building altogether.

There are several design features relating to ordinary construction which warrantclose observation. These include efflorescence, parging, and spreaders. Efflores-cence results when large amounts of soluble salts are used in mortar and excessive

water penetrates the masonry. Efflorescence appears as a white powdery substanceon the wall and indicates weakened mortar. Parging is the plastering over of amasonry wall with concrete. It is frequently a cosmetic fix for an unattractive,deteriorated wall. A wall out of alignment is always a sign of danger. Spreaders areintended to spread the load among one or more structural members and arefrequently used to support a wall in trouble. They are often indicated on the outsideof a wall by a circle, star, channel, or other device; arranged in a pattern they usuallyserve a decorative purpose. When placed at random, these spreaders provideadditional strength to the wall.

Type IV, Heavy Timber Construction

Falling masonry walls which crash to the ground and spray bouncing chunks of bricks and mortar along the street or pavement are the structural hazards of heavytimber buildings. This type of construction does not collapse during the earlystages of a fire when interior firefighting is taking place. However, after severalhours, its floors will collapse and the free-standing walls will fall into the street andon to the roofs of lower buildings nearby. Consequently, withdrawing to protectexposures is the strategy used at a fire involving heavy timber construction whenthe initial attack fails.




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Type V, Wood-Frame ConstructionThe structural hazard of a wood frame building is the combustible bearing wallconstructed of 2x4 inch wood studs. A wood frame building is a bearing wallstructure. The two side walls are usually bearing (that is, supporting a load otherthan their own weight); the front and rear walls are usually non-bearing. The

structural supports of the side bearing walls are only 2x4 inches in size and roof joists also 2x10 inches. Firefighters should know that wood-frame buildings usesmaller structural members to support larger structural members, and the weaklink in this design is smaller structural supports, the 2x4 inch bearing walls. Failureof a bearing wall will trigger simultaneous failure of the floors and roof.

1. TOP PLATES 8. SILL 2. KICKER BLOCK 9. TRIMMER 3. HEADER 10. SOLE PLATE 4. STUD 11. SUBFLOORING 5. TRIMMER 12. FLOOR JOIST 6. FIRE BLOCKING 13. HERRINGBONE BRIDGING 7. DIAGONAL BRACING 14. CRIPPLE STUDS




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STRUCTURAL COLLAPSE

There are many causes of structural collapse in buildings. Failure can result fromarchitectural faults in the original construction, the age of the building, slip-shodrepairs, and heavily-laden floors. Firefighters must be able to identify the indica-tions of potential and imminent collapse for the safety of both themselves and othersat an incident.

Design Faults in ConstructionThe potentially worst faults in building construction are unprotected vertical shaftsand openings. This includes stair shafts, vents, pipe chases, and atriums. Theseopen shafts are dangerous because they may allow a fire to expose other floors of the building, and in the case of vents a chimney effect can result, fueling the fire.

Combustion products can sweep up from the original fire and involve other areasof the building. This fault is responsible for the greatest loss of life not only becausepeople can be overcome by smoke but also because exits from the building aremade inaccessible.

Large, unprotected floor areas are also responsible for building collapse under fireconditions. Floors without physical barriers can become completely engulfed byfire. Because there is nothing to stop the progress of fire, a draft effect is createdmoving the fire across the floor. When a floor becomes enveloped in flame,firefighters find it difficult to fight the fire due to intense heat. Firefighting underthese circumstances is accomplished through halls, doors, and windows and in thecase of very large floors, the fire will be extremely difficult to contain because thefire hose stream cannot reach the center of the floor.

Building collapse can result from the high temperatures which unprotected metalstructures may endure during a fire. Steel is used frequently in building construc-tion for reasons of strength, elasticity, and cost. The problem arises when the metalis subjected to temperatures of over 1,000 degrees. The steel will expand andpossibly disrupt other structural components. Under even higher temperatures,the metal can give way completely. Firefighters should be aware that whencomparing steel and wood, where the structural members are of equal strength, a

wooden support will resist fire much better than steel. Large wooden members will burn slowly and resist fire for longer periods of time than unprotected steel, whichhas a poor record of withstanding fire.

Other faults pointing to the possible collapse of buildings are alterations of structural supports, bracing old supports with steel rods (i.e., look for “stars” on theoutside of the building), steel angle iron used to reinforce the three walls, andoverly-laden floors. Such alterations eliminate, or cheaply substitute, structuralsupports to gain more usable room or to save money.




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Indicators of Possible CollapseDuring fire operations, firefighters may observe events which could lead to collapseof the structure. For example, lack of water drainage on the floor greatly increasesthe risk of collapse. Two inches of water on a floor 40x80 feet will add more than 15tons of weight to the floor. Note- a 250 gpm nozzle can deliver one ton of water per

minute.

The following list of events should serve as warnings of imminent building collapseand firefighters observing any of these during fire operations must leave the building and report conditions to the company officer.

• Ankle-deep water on the floor• A large fire which has been out of control for more than 20 minutes• Steel beams that have been exposed to extreme heat and fire• Excessive water buildup• Sagging or bulging floors and walls

• Rising dust, indicating movement of the building, floor, or roof • Holes in the floor• Cracks in the walls, floors, or roof • Smoke and/or water leaking through the walls• Burned out trusses or I-beams• Sliding sheets of plaster• Walls or columns out of plumb (square)• Interior explosions, rumblings, noises, or heavy gusts of smoke• Spalling• Interior collapse

BUILDING INTERIORS

There are three principal elements which determine the fire resistance of a building:the fire resistance of the building itself, contents or processes within the building,and the characteristics of the interior finish of the building. The interior finishesinclude but are not limited to: wood, plywood, plywood paneling, plaster, gypsum

wallboard, fibrous ceiling tiles, plastics, and a variety of wall coverings. Surfacecoatings may also exist such as paint, varnish, and acoustic spray which will add tofire characteristics. Interior finishes can affect a fire in four ways:

1. They may influence the rate at which the fire build-up reaches “flashover”.

2. They can contribute to fire extension by allowing the flame to spreadover its surface.




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3. They may add to the intensity of the fire by contributing additionalfuel.

4. They can add toxic gas and smoke which will contribute to life and

property hazards.

Once a fire has gained some headway, the upper portion (ceiling) will becomeextremely hot as the gases fill it. If this area becomes hot enough, the gases mayignite. This is commonly referred to as “flashover”. Thermal radiation emanatesfrom the combustion, heating the materials in the area rapidly. When the combus-

tible materials have become heated to their ignition temperatures, simultaneousignition will occur. An interior finish which absorbs and holds heat would be morepreferable because it would inhibit flashover for a longer period of time.

A term referred to as “flameover” can occur if material is combustible. Flameoveris defined as the rapid spread of fire over one or more surfaces. For example, acombustible surface may allow the fire to spread over it rapidly permitting it toreach other material. If the finished material is of a combustible nature it will notinhibit the fire and it will only serve to fuel it.

Many burning interiors are dangerous not only because of the heat factor but also

due to the smoke and toxic gases they release. In fact, fire tests have shown a greaterthreat to life because of toxicity and smoke inhalation. Firefighters must alwayswear SCBAs when fighting interior fires so they are not overwhelmed by toxic gasor smoke.




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TILT-UP CONSTRUCTION

Tilt-up construction, or tilt slab as it is sometimes called, is constructed by casting

wall panels on the ground along the outside perimeters of a building. When thepanels are cured, they are tilted up into place and tied together. The individual wallpanels (load-bearing or non-load bearing) are usually pinned together by connec-tors. The fire resistance of the completed structure is dependent upon the protectionafforded to the connectors. Connectors are set into the precast element, and matingconnectors are provided on the structures to which it is to be attached. Bolts and nutsmay be used, or the connections may be welded. The recess provided for the joistsis then dry- packed with a stiff mortar. Often no protective covering is provided forthe connectors; it maynot even be required.Once the walls arestanding, the buildercarefully braces thewalls with tormen-tors or braces. This isrequired for stabilityuntil the roof is inplace and tied in, thusstabilizing the build-ing. The roof may beof any type construc-

tion. If the roof ismade of wood and isinvolved in fire it may simply burn away, leaving the concrete panels free standingas a vertical cantilever. If this occurs, beware of the possibility of the wallscollapsing. Other hazards involve concrete which may spall from the bottom of T- beams exposing the tendons to their failure temperature, or if steel is used it mayelongate. This elongation may push the walls down. Consequently, when dealingwith tilt-up construction and a building heavily involved in fire, great care must betaken to ensure proper placement of personnel and equipment.

HIGH-RISE CONSTRUCTION

The construction industry today uses two different types of framework for high-risestructures: structural steel, and reinforced concrete. Buildings with a reinforcedconcrete framework are made either by connecting large sections of concrete called




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“precast”, which includes plain concrete, reinforced concrete and pre-tensionedconcrete, or by building one monolithic structure of reinforced concrete called “cast-in-place”. Cast-in-place concrete includes plain concrete, reinforced concrete, andpost-tensioned concrete. By this method, tons of concrete are poured into woodenforms, creating a solid reinforced concrete skeleton structure of floors and support-

ing columns. A cast-in-place concrete building is built on the site, floor by floor.Steel reinforcing rods and wires are strategically placed inside wood forms, whichact as molds to shape the poured concrete into floors and columns. Whencompleted, the cast-in-place structure is one solid, concrete structure reinforced bysteel. The hardened concrete provides the compressive strength to the structure,and the steel reinforcement supplies the tensile strength to the concrete. After eachfloor is poured and hardened, the form work and the supporting shoring aredisassembled and rebuilt to receive the concrete for the next higher floor. Thisprocess is repeated for each additional floor.

In some so-called “fast-track” construction projects, one concrete floor is pouredevery 48 hours. Although it takes approximately 27 days for concrete to reach itsmaximum strength, the high-rise building construction process cannot wait thatlong for each floor to harden. After 48 hours, a concrete floor, depending upon thetype of concrete and the temperature, can have sufficient strength to enable thewood formwork below to be removed and reconstructed above. Even though theformwork is removed, bracing remains below the freshly poured concrete floors forsupport, and portable steel jacks or timber columns will continue to support severalfloors below.

Construction engineers state that within 24 hours of pouring, the entire concrete

floor can collapse on firefighters if the wood formwork below has been destroyed by fire. At this time it is most dangerous for a fire to occur in the formwork; however,even the concrete floors in place for 48 hours or more, without the formwork below,can collapse in small sections if they are heated by a scrap lumber fire. Conse-quently, the fire department faces problems with concrete construction in threedistinct areas: collapse during construction with no fire, fire during construction,and fire in a completed, occupied building.

When structural steel is used in high-rise construction, fireproofing is often appliedto meet the standards required by the local building codes. While there is no suchthing as a truly fireproof building, the term has survived as the designation of the

system by which steel is insulated. Fireproofing of steel is classified as individualor membrane.

Individual fireproofing provides protection for each piece of steel. In one method,steel is encased in a structure. Concrete, terra cotta, metal lath and plaster, brick andgypsum board are materials commonly used. This method is called encasement. Inanother method, fireproofing is directly applied to the steel, usually by spraying.Materials are asbestos fiber (no longer used), an intumescent coating containing




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non-combustible fibers which smell and char when exposed to flame, andcementatious coatings.

Membrane fireproofing does not protect individual members. In one method, wirelath and cement plaster are used. In another method, the fireproofing of the floor isaccomplished by a rated floor-ceiling assembly. The efficiency of fireproofingdepends first on the competence of the subcontractor and the willingness of the builder to demand quality work. It further depends on the building departmentstaff who inspect the original installation to determine that fireproofing and fireprotection are not compromised. This is particularly important in the case of spray-on fireproofing and membrane-floor and ceiling assemblies. Finally, it is a seriouserror to consider all high-rise buildings as a single problem. There are fire-significant construction differences among high-rises. The particular buildingswithin San Diego must be studied in detail to determine the particular potentialmodes of building failure.

STRUCTURAL FEATURES WHICH INFLUENCE FIRE SPREAD

In a study carried out by the NFPA, it was found that inferior construction,unprotected openings, large open areas, and inoperative fire doors were majordeterminants in the amount of damage done to a structure and its interior in fireconditions. These features were found to contribute to the spread of fire. Further-more, it was determined that the speed of flame spread over a substance is directlyinfluenced by the amount of flammable vapors released by combustible materials

when they are heated, their texture, and thickness. The following structural featureswill help limit the spread of fire if they are constructed properly (i.e., they do notviolate the building code). For more information on these features and other less-common ones, refer to the current Uniform Building Code.

Fire WallsFire walls are typically constructed of concrete, structural clay tiles, or some otherstructurally sound and non-combustible material and must have a fire-resistiverating of at least one hour.

Fire walls must be able to remain intact if and when there is collapse on either side.A fire wall will be continuous from the foundation to a parapet above the roof lineof the building. The height of the parapet portion is dictated to be at least 30 inchesabove the roof line. In addition, these walls must have a minimum thicknessdictated by the type of construction (refer to Chapter 43, Table 43-A of the UniformBuilding Code). All fire walls must have parapets, wing walls, be attached to thefoundation, and have fire- resistive ratings as required by location, type of construc-tion, and occupancy. Openings in fire walls must conform to the requirements of the building.




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Some of the code violations firefighters may encounter when dealing with fire wallsinclude: inferior construction materials, lack of thickness in the wall, no parapets,and openings that are not correctly constructed, inoperative, or blocked open.Firefighters should always inspect fire walls during pre-fire planning and inspec-tions to determine aspects of construction and imperfections which may create

hazards during a fire.

Fire PartitionsFire partitions are installed as a impedence to fire spread, but are not considered afire wall. They are constructed of non-combustible or protected combustiblematerials and are attached or supported by structural components having a fire-resistant rating equal to or better than the fire partition (usually one to two hours).As with fire walls, openings must conform to the requirements set forth to provideadequate fire protection. The fire resistance of a fire partition will be governed bythe type of construction used in the building.

Openings in Fire Walls and PartitionsThere are six different classifications for fire-protective openings. Depending uponthe type of building construction and the hazards which may be present, openingsmust provide protection equal to or greater than the wall or partition.

Three-Hour Protection:

These openings are often given a class rating of “A” and must provide threehours of fire protection equally on both sides. These enclosures cannotcontain any glass and are located in walls that separate buildings or separate

buildings into fire areas.

One-to 1 1/2-Hour Protection:

These enclosures protect openings into vertical shafts (e.g., stairwells andelevator shafts) and are often classified with a rating of “C”. As well, one to1 1/

2 hour protection must be provided in exterior wall openings. Exterior

wall openings are often referred to as Class “D” openings.

45-Minute Protection:

These enclosures must provide 3/4 of an hour protection against fires. Theopenings they protect are usually located in corridors and room partitions,generally considered Class “C” and in exterior walls that are subject to lightor moderate exposure to fire (Class “E” and “F”).




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Fire DoorsTypically, fire doors are used for the protection of both vertical and horizontalopenings. Fire doors can be horizontal or vertical sliding, single or doubleswinging, or overhead rolling. Any of these door types may or may not be

counterbalanced. Often, fire doors are either self-closing or automated. Self-closingdoors will return to a closed position after opening. Automated doors may remainopen after opening them, but will close when heat or smoke actuates the closingmechanism. Fire doors must not be locked though they may be latched. In addition,these doors should never be blocked, wedged or in a state that would prevent themfrom closing. Automatic closing doors must be kept in proper working order at all

times.

If fire doors contain glass, it must be at least 1/4 inch thick and must be safety

protected with wire. Fire doors can be considered safe if they contain a current labelfrom the “Underwriters Laboratories” or “Factory Mutual Laboratories” as evi-dence of testing. For more information refer to NFPA Standard # 80.




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Fire Windows and Fire ShuttersFor these types of enclosures to be effective in containing fire spread, they must beproperly maintained and serviced. Often these openings are associated withexterior wall openings (Class “E” and “F”) with labels stating “Inspected FireWindow for Light Exposures”. Fire windows must be constructed of wired glass,1

/4 inch or greater in thickness.

There are locations where fire windows are covered by shutters (i.e., at three-quarter, one-, and 1 1/

2 hour openings). The shutters must carry a rating equal to

or greater than the wall opening they are protecting. These fire shutters must eitherremain closed or must close automatically under fire conditions. Once closed, fireshutters must remain secure to be considered effective in reducing fire spread. Of the different types of fire shutters, the automatic rolling shutters installed overwindows on the interior side of the building are considered the most useful andpractical.

Curtain Boards (Draft Curtains)Curtain boards are most generally found in large open areas of buildings. Theirmajor purpose is to direct fire and smoke into a pre-designed area for rapidventilation. At the same time, they are designed to prohibit flame and smoke spreadin other directions. This is especially useful in sprinklered buildings to avoid waterdamage in unaffected areas, as the operation of the sprinklers can be localized to thefire area. For these fire-resistive structures to be considered effective they cannot bespaced more than 250 feet apart for low and moderately heated occupancies. In buildings that are subject to high heat sources, curtain boards must not be spacedany further than 100 feet apart. The depth of a curtain board must be a minimum of

six feet but in some cases (under severe fire hazards) may be doubled or as close as8 feet from the floor.

Ventilation DevicesThese systems are designed to complement other fire safe-guards and are notreplacements for fire protection devices. Vents are very useful in smoke and heatdissipation, especially in buildings where vapors and dusts are highly combus-tible. For a venting system to be considered effective, it should be free of any humanelement. Rather, it should be automatic using fusible links, hinged dampers, andcounterweights that are heat reactive. Types of vents include: monitor controlled,continuous gravity, unit type, sawtooth roof skylights, and exterior wall openings.

Monitors usually make use of fusible links which are effective from as low as 165°Fto 212 ° F or higher, if so required. The fusible links operate vent doors that may beglass, metal panels, or louvered when heat containment is not a factor.

Continuous gravity vents are narrow slot openings which are attached to weatherhoods on the roof. Many will have movable shutters which will open automaticallyin the event of a fire. This style of vent is most common in buildings where high heatproduction is of concern.




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Unit-type vents are lightweight metal frames or housings with built-in shutters thatopen in the event of high heat or fire (e.g., fusible links). This type of structure ismost commonly associated with curtain boards.

Sawtooth roof skylights are sashes of glass usually non-wired which can be openedto form a vent. Often this style of venting device must be operated manually andis influenced by wind direction and force.

Exterior wall openings are most effective in structures where heat and smoke do nothave to travel more than 60 feet. They are usually characterized by louvered, openvents but can also remain closed and automatically open in the event of fire.

Fire Exits and EscapesBuildings and structures must have appropriate fire escapes and exits in accor-dance with the location, size, occupancy, type of construction, and fire protection

available. Fire escapes and exits must be correctly marked, lighted in reducedvisibility areas, and indicate the most accessible route to safety. Furthermore, theycannot be obstructed in any way that would prohibit the swift evacuation of theoccupants. These exits cannot be locked while the building is occupied and mustremain open from the direction of occupant departure. The width of the exit mustnot be less than 28 inches, large enough for a single file line of people to escapefreely. For more information on fire escapes and exits firefighters should refer toNFPA 101, the Life Safety Code, and Uniform Building Code, Appendix III (d).

Fire and Smoke Dampers

These are used to restrict fire and smoke to the involved area and away fromunaffected areas. Fire and smoke dampers operate much like venting devices butin the opposite manner: instead of allowing smoke to dissipate these devices willclose under fire conditions. Like automatic vents, many are controlled by fusiblelinks, heat actuating switches, and in some cases, smoke detectors.

Fire dampers are generally automated and once closed, will remain closed untilmanually opened. These devices are required in a number of circumstances whichinclude:

• Where a duct passes through a fire-protected wall or partition or roof

• At fresh air intakes• At branches in the main duct• Vertical ducts passing through fire-resistive floors• When ducts have openings installed in a fire-resistive ceiling

There are other circumstances where fire dampers will be required and a numberof exceptions pertaining to particular situations. For more information on firedampers, firefighters should refer to NFPA 90A, 90B & 91.




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Smoke dampers are commonly required in air conditioning systems and areintended to interrupt the flow of air or smoke through the system when the airconditioner is shut down.

Fire Stops

Fire stops are utilized to prevent fire spread within the hollow walls, floors, andother internally open areas within a building or structure. They are usually piecesof wood (2x4 inch) placed between wall studs, partitions, ceiling planks, etc., to cutoff any draft within the hollow areas. When fire stops are not used it's probable thata fire could rage through the structure, burning unexposed internal areas before itis ever discovered. The minimum fire stopping would include isolation of allhollow walls at the floors and ceilings, isolation of the ceilings at the walls andcurtain boards. For more information on fire stopping refer to NFPA 101 (6-13).

Fire LoadsA comprehensive understanding of building construction requires basic knowl-

edge of the concept of loads and how they are applied. There are several types of loads: designed loads are those the building architect anticipated and planned for;and conversely, undesigned loads are unanticipated. Undesigned loads can beconcentrated or applied to a relatively small area, or equally distributed over alarger surface. These loads can be further subdivided into dead and live loads.Adead loadis the weight of the building and any part of a structure which is permanentlyattached to it ( dead loads may also be considered static, as they are relativelyunchanging). A live load is not built in and can be categorized as an impact load (if it is in motion when applied). A suspended load is held in place by attachment to

a building component above it. Any load can change in nature when portions of the building fail. For example, a large printing press permanently attached to the thirdfloor would be considered a dead load; should the floor fail, the falling press would become an impact load upon those floors beneath it.

Loads are applied in three ways: an axial load passes through the center of mass of the supporting element perpendicular to the cross section; an eccentric load is oneperpendicular to the cross section of the supporting element that does not passthrough the center of mass; a torsional load is one parallel to the cross section of thesupporting member which does not pass through the long axis. These loads areapplied through three forces: compression tends to push or squeeze a material

together; tension tends to pull materials apart; and shear tends to break material bycausing its molecules to slide past one another.

Building materials are also classified as brittle (weak in tension and shear and tendto break without bending), or ductile ( tend to deform before breaking).




REFERENCES

Building Construction for the Fire Service, Francis L. Brannigan, NFPA, Quincy,Massachusetts 1993.

Collapse of Burning Buildings, Vincent Dunn, New York, 1988.

Fire Protection Handbook, NFPA, Quincy, Massachusetts, 1981

Ventilation Methods and Techniques, John Mittendorf, Los Angeles, 1988

Uniform Building Code (UBC), Western Fire Chiefs, 1982

Documents

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