Building Construction

The 3 model codes are in the process of developing a single code package called the International Building Code (IBC). Included in this package is the International Fire Code (IFC). The IBC/IFC will be promulgated by the International Code Counsel (ICC): • Uniform Building Code (UBC), published by the International Counsel of Building Officials (ICBO)…Includes the Uniform Fire Code (UFC) • Standard Building Code, published by Southern Building Code Congress International…includes the Standard Fire Prevention Code. • BOCA, National Building Code…Includes the BOCA National Fire Prevention Code.The design process involves compromises & a prioritization of objectives. Cost is always a major concern and frequently necessitates a reduction of plans. The final design always involves a balancing of what is desired, what is needed, and what is practical. Fast tracking – the design & construction phases overlap to reduce total construction time. Inspection – involves the verification that the proper materials & construction techniques are used Testing – performed on certain materials, systems, and components such as concrete, fire pumps, and emergency generators.The usual role of the Fire Inspector is to ensure proper installation & operation of fire protection systems. Chapter 3: Building Classifications To the FF, the most significant building characteristic is how the building can be expected to behave under fire conditions. Fire resistance – a collective property of materials & assemblies…the ability of a structural assembly to maintain its load bearing ability under fire conditions. The properties of the materials include: • Combustibility • Thermal conductivity • Chemical composition • Density • DimensionsFire resistance rating – the quantitatively evaluated fire resistance of the structural components. The rating is determined by test procedures simulating fire conditions & is expressed in hours. Fire resistance for structural elements such as: • Beams • Columns • Walls & partitions • Floor & ceiling assemblies • Roof & ceiling assemblies It is necessary to erect assemblies in the field exactly as they are tested in the laboratories so that the ratings are obtained. To determine fire-resistance ratings, the component is subject to the heat of a fire in a test furnace.The procedure is described in NFPA 251, Standard Methods of Fire Tests of Building Construction & Materials (also American Society for Testing & Materials [ASTM] E-119). When a structural specimen is tested, the test is conducted until either the specimen fails or the specified endurance for which the specimen is being tested is reached. Best known testing laboratory is UL, Fire Resistance Directory. Fire-resistance ratings are expressed in certain standard intervals: • 20 min. • 45 min. • 1 hr • 2hr • 3 hr • 4hrFire resistance ratings for floor & ceiling assemblies are rated by both: • Restrained assemblies – affect the extent that an assembly may expand or rotate at its ends when exposed to high temperatures. • Unrestrained assemblies Fire testing has been going on for years. In recent years, mathematical equations have been used to predict the behavior of materials at high temperatures. Building codes usually make use of fire-resistance ratings based on the standard test. Computer models can deal with more realistic fire behavior of materials than the traditional standard time & temperature test procedure.Noncombustible material – in the form in which it is used and under the conditions anticipated, will not ignite, burn, support combustion, or release flammable vapors when subjected to fire or heat. The most commonly used test for determining combustibility is ASTM E 136, Standard Test Methods for Behavior of Materials in a Vertical Tube Furnace at 750? C. NFPA 220, Standard on Types of Building Construction, have 3-digit code designations: • 1st digit – rating of exterior bearing walls • 2nd digit – rating of structural frames or columns and girders that support loads of more than one floor. 3rd digit – rating of floor construction. Most codes will not allow a wood-frame school to be more than One-story in height. occupancy classifications. They are as follows: National Fire Protection Association (NFPA 101 Life Safety Code & NFPA 220 Standard on Types of Building Construction). & the International Code Council (ICC) National Fire Protection Association The five types of building construction are: Type I – the least combustible building type and considered to be “fire-resistive”. The two most common methods of constructing Type I buildings are by using reinforced concrete or a protected steel frame.The structural members (walls, floors, columns, beams, and roof) are constructed of non-combustible or limited combustible materials that have a specified fire resistance.. These non-combustible materials are defined by the building code that is adopted. The primary fuel load is composed of the contents of the structure. • Bearing walls, columns, & beams a fire-resistance rating of 3-4 hrs • Floor construction 2-3 hrs • Floor construction 1-2 hrs • Partitions usually 1-2 hrs Type II – is similar to type I in construction. Theses buildings are considered “non-combustible or limited combustible” construction.The structural members are allowed to be at a lower fire rating than type I buildings. Type II Construction can be either protected or unprotected. In unprotected construction, the major components are noncombustible but have no fire resistance. Unprotected steel is the most common characteristic in unprotected, noncombustible construction the sub classifications: 222 & 111, have structural components with one or two fire-resistance ratings; 000 have no fire-resistant requirements. Roofs are often flat, built-up types that may contain combustible felt.The primary fuel load is composed of the contents of the structure. Type III – is also known as “ordinary construction”. The exterior bearing walls are constructed of “non-combustible or limited combustible” construction normally masonry. The interior structural members (walls, columns, floors, beams, and roofs) are constructed of wood or some other combustible material. Combustible interior materials are protected by insulating materials such as plaster or gypsum board. The adopted building code specifies the fire rating required for these materials.A fire concern is the spreading of smoke/fire through concealed spaces. Type IV – is referred to as “heavy timber” construction. The exterior walls are constructed to the same specifications as type III (normally masonry), but the interior structural members (arches, columns, floors, beams, and roofs) are constructed of solid or laminated wood without concealed spaces. The primary fire hazard is the massive amount of fuel presented by the large structural members in addition to the buildings contents. Building codes will require a minimum dimension on all columns and beams (usually at least 8”).Type V- is the most combustible type of construction. It is also referred to as “wood-frame construction”. The exterior walls, bearing walls, floors, roofs, and supports are constructed of wood or some other approved combustible. The materials used are the same as those approved for type IV, but are allowed to be in smaller dimensions. There are more voids & channels than found in type III. Some Type V buildings have a brick veneer, but are reliant upon the wood framing for structural support. Brick veneer adds little fire resistance, except for a possible reduction in communication between buildings.Free standing structures usually up to 6-stories in height. • Requires 1-hr fire-resistance rating for all structural elements. Normally accomplished by covering with plaster or fire-rated gypsum board. • May have non-rated structural elements International Code Council (ICC) Type I – the least combustible building type. Characterized by the use of steel, iron, concrete, or masonry structural elements: • Type IA o 3-hr resistance rating to structural frame & load bearing walls o 2-hr resistance rating of floors o 1 ? hr resistance rating of the roof • Type IB 2-hr resistance rating to structural frame & load bearing walls o 2-hr resistance rating of floors o 1-hr resistance rating of the roof Type II – often referred to as a “1-hr building”. The structural members are allowed to be at a lower fire rating than type I buildings • Type IIA – similar to Type I in structural elements being steel, concrete, or masonry. 2-hr fire resistance on floors. • Type IIB – Requires approved noncombustible materials, but the materials may have no assigned fire-resistance rating. Type III – Exterior bearing walls must have a 2-hr fire resistance rating. Type IIIA – requires materials with a 1-hr fire resistance throughout the structure. • Type IIIB – Lacks 1-hr fire-resistance rating Type IV – exterior walls constructed of noncombustible materials, while the interior building elements are constructed of solid or laminate wood having no concealed spaces • Exterior walls – may have fire retardant treated wood framing with 2-hr fire resistance rating or less. • Wooden columns – Requires min. 8” dimensioned lumber • Floor framing – requires sawn or glued-laminated timber of at least 6” nominal depth & not less than 10” depth. Roof framing – wood-frame or glued laminated arches. Minimum of 6” nominal width & 8” nominal depth for the first half of its length…then no less than 6” nominal dimension for the top half of its length. • Roofs – no concealed spaces Type V – structural, exterior, and interior walls constructed of any material permitted by code. • Type VA – requires 1-hr fire-resistance rating for all structural elements except nonbearing interior walls & partitions. • Type VB – May have non-rated structural elements Chapter 4: Structural PrinciplesThe magnitude of forces acting on a building is the most critical aspect of engineering design, and the ability to evaluate these forces is what distinguishes a casual knowledge of buildings from a professional knowledge. Load – any effect which a structure must be designed to resist: • Gravity • Wind o Direct pressure – impact of wind on a surface (primary effect considered) o Drag – fluid effect of wind as it moves along a surface o Negative pressure – suction effect produced on downwind side o Secondary effects Rocking – due to variations in wind velocity ? Vibration – due to harmonics of building ? Clean-off effect – moving air blowing objects off building • Earthquakes – create lateral shaking forces that are the most damaging • Soil pressure o Active pressure – pressure exerted against the foundation o Passive pressure – force of foundation against the soil Live load – any load not fixed or permanent • Contents • Snow • Rain Dead load – weight of any permanent part of a building • Roofs • Floor slabs/decks • Interior/exterior walls • Stair systems • Columns Permanent equipment (elevators, HVAC, pumps) Concentrated load – applied at one point or over a small area. *Water has a density of 62. 4 pounds per cubic foot Static load – steady or applied gradually (dead load of a building, snow load & many live loads. Dynamic loads – involve motion…wind, moving vehicles, earthquakes, vibrations, & falling objects. Differ from static loads in that they deliver energy in addition to weight. Structural Equilibrium & Reactions: Equilibrium – the support provided by a structure is equal to the applied loads. Reactions – forces that resist the applied loads.Exterior loads can create different kinds of interior forces in materials: • Tension – pulls apart • Compression – squeeze (concrete has good compressive strength but little tensile strength). Exterior bearing walls • Shear – slide one plane past an adjacent plane Stress – a measurement of force intensity and is expressed as force units divided by the area over which the force is applied. Exterior loads are classified as: ? Axial ? Eccentric ? Torsional Structural Components: • Beam – a structural member that can carry loads perpendicular to its longitudinal dimension.Primary design is their ability to resist bending from the applied loads. • Column – designed to support an axial compressive load • Arches – curved structure in which the interior stresses are primarily compressive. Arches develop inclined reactions in their supports. • Cables – flexible & are tension stresses • Trusses – framed structural units made of groups of triangles in one plane. A true truss is only made up of straight members. 22 – 70 ft • Space frames – 3-dimensional truss structures Chapter 6: FoundationsAll buildings settle to some extent due to the compaction of the soil: • Uniform settlement • Differential settlement o Downward/settlement o Upward/heaving o Lateral displacement/outward Foundation Types: • Shallow – transfers weight of the building to the soil at the base of the building. Typically use footings to transmit load to the soil o Wall footing – continuous strip of concrete that supports a wall o Column footing – square pad that supports a column o Grillage footing – consists of layers of beams placed at right angles to each other & usually encased in concrete. Deep – penetrate the soil directly under a building to reach soil at a greater depth that can support weight of building. A high-rise building requires a foundation that extends 100 ft or more. o Piles – driven into the ground & develop their load carrying ability through friction with the surrounding soil or by being driven into contact with rock or a load-bearing soil layer (timber, steel, or precast concrete) o Piers (caissons) – shaft is drilled or dug out and filled with concrete. ? Straight shaft ? Conical footing (bellied pier) • Mat foundation – a thick slab beneath the entire area of a building.A mat may be several feet thick. • Floating foundation – used where soil strength is low…The volume of earth excavated is equal to the weight of the building, minimizing settlement. Underpinning – the process of strengthening an existing foundation. Shoring – refers to temporary supports. May be necessary to support a structure until underpinning can be put into place. Chapter 7: Structural Systems From FF viewpoint, materials & basic structural systems are related. Type I – reinforced concrete or protective steel framing are found Type II – use of unprotected steel can be found Reinforcing Concrete: Ordinary – steel bars are placed in the formwork, and wet concrete is placed in the framework around the bars. o Stirrups – vertical reinforcing steel bars o Vertical & diagonal bars in concrete resist tension • Prestressed – a compressive force is applied by preloading steel bars before a load is applied. Forces are slightly higher than what is actually needed for support. o Pretensioned reinforcing – when the concrete has hardened sufficiently, the force applied to steel strands is released. o Posttensioned reinforcing – steel strands are placed in formwork & covered with grease or in plastic tubing.After the concrete has cured, the strands are then tensioned. Cutting through the steel is dangerous because it is not bonded to the concrete. Concrete Structures: • Cast-in-place – uses slump test to determine moisture content o Flat-slab concrete frame – slab (6-12” thick) is supported by concrete columns ? Drop panels/mushroom capitals – support heavy live loads ? Flat plate system – supports lighter loads & drop panels are not used o Slab & beam – concrete slab supported by concrete beams o Waffle construction Precast Concrete – have more in common with steel-framed buildings than with cast-in-place concrete buildings. Can produce slabs, beams, columns, & wall panels. Does not have continuity of cast-in place type. A corbel is a ledge that projects out from the column & supports the beam. o Solid slab – 30’ spans o Hollow-core o Single & double tee slabs – spans up to 120’ Concrete structural systems can have fire-resistance ratings from 1 to 4 hrs. Structural lightweight concrete has a lower density than ordinary concrete & has lower thermal conductivity. It is a better insulator against heat of fire than ordinary concrete.Steel Framed Structures: • Beam & Girder Frames o Rigid frame – rigidity between beam & column so there is no angle change between the two as loads are applied (Bolted & welded). Vertical members may be rigidly connected to foundation. o Simple frame – primarily designed to support vertical force & some angular change could occur if diagonal bracing were not provided (bolted) o Semi-rigid – not completely rigid but enough to provide diagonal support to structure. When rigid connections are not used, lateral stability for a frame must be provided through the use of diagonal bracing or shear panels. Steel Trusses – can carry loads across greater spans more economically than can steel beams. Used frequently in 3-dimensional space frames. o Open web joist – round bars used for diagonal members are called bar joists o Joist girder – heavy steel trusses used to take the place of steel beams as part of the primary structural frame. • Rigid Frame with inclined roof– Used for spans from 40 to 200’. Top is called the crown & points where the inclined members intersect the vertical members are called the knees. Steel Arches – used to support roofs on buildings where large unobstructed floors are needed (>300’). o Girder arch – solid arch similar to a beam o Trussed arch – uses truss shapes • Steel Suspension systems – steel rods or cables to support roofs providing unobstructed areas w/o reducing vertical clearance at sides of building. • Steel Columns – uses a “slenderness ratio” compares the unbraced length of a column to the shape and area of its cross-section (determines the load that can be safely supported w/o buckling). Square columns & flat stock has fewer tendencies to buckle than tubular type. rotational ends often allow for buckling) Masonry Structures: Traditional masonry structure consists of exterior load-bearing walls that support the floor & roof. These load-bearing buildings can be as tall as 20-stories. Fire rated masonry units can have fire-resistance rating of 2 to 4 hrs. Rule of thumb: bearing wall has header course every 6th course w/ ends of brick facing out. • Nonreinforced walls – stability is from weight of masonry & bonding between adjacent wythes. Usually limited to a max. height of 6-stories o Course – side by side horizontal layer Wythe – horizontal courses laid on top of each other in a vertical layer (supplies strength & stability to a wall) o Stretcher course – bricks placed end to end o Soldier course – bricks placed vertically on end • Reinforced walls – use vertical steel rods & cement grout in center cavity • Lintels – support masonry in V-type pattern…not entire weight of wall • Parapets – prone to collapse • Interior structural framing of masonry buildings – masonry buildings w/ heavy timber interior framing are referred to as mill buildings. o Beam pockets Pilaster – used to increase thickness at the point where a beam transmits a large load to a masonry wall o Fire cut – wood joist/beam slightly angled to allow a beam to fall freely away from a wall w/o acting as a lever against the masonry & do not preclude the collapse of a masonry wall o Masonry walls usually collapse as a result of collapse of the interior framing. Wood Structures: Not economical in buildings over 3-stories • Heavy Timber – columns not less than 8×8”; & beams not less than 6×10”. Similar to steel construction • Post & Beam – posts are 4×4” or 6×6”; posts are spaced 4 to 12’.Less fire hazard do to exposed surface that does not have any combustible voids. • Light Wood Framing – most popular 2”- nominal lumber o Balloon frame – less shrinkage than platform type o Platform frame Chapter 8: Floors & Ceilings: Floor Systems: • Concrete Floors – can be either cast-in-place or precast. It is possible for a concrete floor slab to be supported by either steel beams or trusses. In theses cases, the fire resistance of the floor depends on the fireproofing of the supporting steel. • Tile Arch Floors – this masonry style is not used in modern floor support systems.System uses a tile arch system in combination with steel beams. • Steel Supported Floors o Open web joists – uses lightweight concrete (2” min thickness) supported by corrugated steel decking. The steel decking is supported by web joists. The open web joist can also support precast concrete panels or wood decking. ? Standard span (depth 8 to 30”; spans to 60’) ? Long span ? Deep long span o Steel beam & light gauge steel joints – Steel beams support lightweight cold-rolled floor joists. These joists can be used to support metal deck or wood panel flooring systems.Joist are 6 to 12” in depth & spaced 16 to 48” apart. • Wood Supported Floors – typically have combustible voids. Wood flooring is often covered over by concrete & other materials such as terrazzo and quarry tile. At times no consideration is given to the additional loads imposed on the floor supports. This masonry adds absolutely nothing to the strength of the floor because no steel reinforcement is used. Sudden failure of wood-supported concrete floors has killed many FF. o The most substantial wood floors are found in masonry heavy timber buildings Type IV (floor decking min 3” thick; floor decking is supported by 6×10” beams).Typically no void spaces are permitted. o Bridging – wood/metal diagonal braces or solid blocking is used to distribute concentrated loads between adjacent joists, to increase floor stiffness. o Laminated beams are used in floor support systems. They exhibit a fire behavior similar to that of solid lumber. o Hangers & connectors – take the place of toenailing • Floor coverings – flammability is measured by the level of radiant heat. NFPA uses the critical radiant heat flux test. Higher critical radiant heat flux indicates a lower flammability. o Class I – 0. 43 Btu per ft? er second (lower flammability) o Class II – 0. 19 Btu per ft? per second Ceilings: materials are never rated independently. A ceiling is always rated as part of a floor & ceiling assembly. • Plaster • Gypsum board • Mineral tile • Interstitial space – used in hospitals/laboratories. Allows enough height for walking above a ceiling to facilitate maintenance of equipment. Typically spaces are low in combustibles & automatic sprinklers are not present. Chapter 9: Walls Various types of walls are provided in the design of buildings for purposes other than structural support.Walls constructed for any purpose affect the course of fire in a building. Fire Walls: Erected to limit the maximum spread of fire. It acts as an absolute barrier to a fire under conditions of a total burnout on either side. Not popular with designers due to costs & interference of free movement. Building codes typically allow elimination of fire walls when equipped with automatic sprinklers. Typically constructed of masonry or other fire-resistive materials (concrete block). Usually require a fire resistance rating of 4 hrs. Fire walls must extend beyond walls & roofs to protect exposures (18–36”). • Construction Freestanding – self-supporting & independent of the building frame. Usually found in buildings of wood-frame or masonry construction. Must be able to resist a lateral load of at least 5 pounds per sq ft (NFPA 221) o Tied walls – erected at a column line in a building of steel-frame or concrete-frame construction. • Openings o Doors – must be automatic or self-closing fire doors. If a 4 hr wall is needed then there must be 2 doors with a 3-hr rating on each side. Two doors are required in case one fails to close under fire conditions. o Ducts – if penetrating a fire wall they must be equipped with fire dampers. Special design considerations – in industrial conveyer situations fire walls may need to be penetrated. Solution may be a fire-resistive enclosure around the conveyer in combination with a water spray. Party Walls: a wall that lies on a lot line between two buildings and is common to both buildings. They are almost always load-bearing. Not uncommon for walls to be breached by owners. Fire Partitions: Interior walls used to subdivide a floor or area of a building but do not qualify as fire walls. They are usually erected from one floor to the underside of the floor above.They are frequently used in corridors & occupancy separations. They are also used to create areas of refuge in health care facilities. Fire-resistive partitions create “compartmentalization” of areas. This only provides passive fire-protection. • Construction – material chosen depends on the required fire-resistance & construction type of building. Fire rated glazing can be used for partitions where visibility is needed & a fire rating is required. Enclosure & Shaft Walls: Used to enclose vertical openings, such as stairwells, elevator shafts, & pipe chases, which extend from floor to floor in a building.Required to have a fire-resistance of 1 or 2 hrs. Curtain Walls (cladding): When the main structural frame is the support for a building curtain walls, that only enclose the building, are used. Designed to separate interior from exterior environment. They are used in steel frame & concrete frame structures. Frequently constructed using a combination of glass & steel, stainless steel, or aluminum. They may also be constructed with materials such as lightweight concrete, plastic, fiberglass, and other metal core panels. Because they are not load-bearing, it lacks fire resistance of a more massive load bearing wall.It is not uncommon for buildings to be constructed with curtain walls that are noncombustible but have no fire resistance. Curtain walls are supported at the edge of the floor assembly. Chapter 10: Roofs General points regarding all roofs: • Usually weaker than floors • Many have concealed spaces • Over time, loads may be added to roofs they weren’t designed for • They are subject to wear & deterioration Architectural Styles: • Flat roofs – easiest for FF to work on. Inverted roof is a flat roof with a framework above the main joists to support decking. • Pitched Gable o Hip o Gambrel – slopes in 2-directions with a break in the slope on each side o Butterfly – slopes in 2-directions; 2 shed roofs that meet at lower eaves o Monitor – provides light & ventilation; vertical side normally has glass called a clerestory. o Sawtooth – found on industrial buildings; maximizes natural light & ventilation. o • Curved – most frequently supported by arches & bowstring trusses. A dome roof produces forces similar to those of an arch. That is, horizontal thrusts exist at the base, and compressive forces exist at the top. Lamella arch – constructed from short pieces of wood beveled & bolted together in a diagonal pattern using a special plate (lamella washer). o Geodesic dome – created using spherical triangulation. That is, triangles are arranged in 3-dimensions to form a nearly perfect spherical surface. Roof Supporting System: It is not uncommon for modern roof to deflect or vibrate under the weight of personnel that walk on them…Does not necessarily indicate imminent failure of the roof. • Flat roof • Raftered roof – basic design results in an outward thrust against the buildings walls.Rafters are almost always wood. A ridge beam supports the rafters when an exposed ceiling w/o joists is desired. • Trusses – “monoplane” trusses have all members in the same plane (2×4” or 2×6”; 2-4’ apart). Typical of lightweight trusses. Heavy wood trusses are up to 5-members in thickness & can be spaced 8’ or more apart. • Bowstring • Wood & steel trusses – fink & pratt styles are the most common types used for pitched roofs. • Arches – may be constructed from masonry, concrete, laminated wood, or steel. The behavior of the roof is determined by the material used for the arch.Some arched roofs use a steel tie rod between the two ends of the arch to resist outward thrust. • Rigid frames – can be constructed of concrete, laminated wood, or steel. This type of roof cannot be identified from the outside due to the peaked contour. Inside it can be identified because the frame typically is not concealed. • Rain Roof – a second roof constructed over a damaged/deteriorated original roof Roof Decks: can be constructed of plywood, wood planks, corrugated steel, precast gypsum or concrete planks, poured gypsum, poured concrete (also serves as the supporting members), and cement planks containing wood fiber.Decking made of corrugated steel in combination with concrete is called composite decking. Roof Coverings: The water resistant barrier • Flat roof coverings o Vapor barrier o Thermal insulation o Roofing membrane – actual waterproof material. ? Built-up – tar or asphalt saturated roofing felt (4-layers common) ? Elastomeric-plastomeric membranes – single-layer very thin; attached by adhesives, gravel ballast, mechanical fasteners, or torched. ? Fluid-applied membranes – used on curved roofs in liquid form and permitted to cool in place. o Drainage layer Wear course – protects from mechanical abrasion • Pitched Roof Coverings o Shingles & tiles ? Wood shingles (thin) & shakes (thick) ? Asphalt shingles ? Slate ? Clay tile Fire Ratings of Roof Coverings: NFPA 256, Standard Methods of Fire Tests of Roof Coverings. The number of times a roof covering is tested depends on the material being tested. Classified as: • Class A – effective against severe fire exposure • Class B – effective against moderate fire exposure • Class C – effective against light fire exposure Roof Openings: • Penthouses (bulk-head) – small structures erected on the main roof of a building.Used for elevator machinery, mechanical equipment, or additional living space. • Roof hatches – usually placed over a stairway • Skylights – building codes require wired glass or tempered glass in skylights. Some modern buildings use plastic domes. • Smoke & heat vents – typically found on roofs of industrial & warehouse buildings. Some are designed to open automatically (fusible link) or manually. Plastic domes are designed to soften & fall when exposed to fire. Curtain boards are also used in conjunction with smoke & heat vents. Smoke detection devices are sometimes used to operate vents.Roof vents are not as effective in sprinkled buildings (loss of buoyancy in smoke). Chapter 13: Building Services & Subsystems Some of the most important fire & life safety features built into a structure include compartmentalization & fire resistance. Many services & subsystems penetrate the built-in compartmentalization. Elevators: Have developed into one of the safest & most reliable modes of transportation: ASTME/ANSI A17. 1, Safety Code for Elevators, published by the American Society of Mechanical Engineers. Types are classified by their use: • Passenger • Freight Service elevators – a passenger elevator designed to carry freight Most common power sources electric & hydraulic: • Hydraulic –fluid forced under pressure into a cylinder containing a piston or ram. Hydraulic elevators do NOT have brakes. The piston/ram must be long enough to reach the highest floor (upper limit is usually 6-stories). Most hydraulic elevators have a machine room near the elevator pit. • Electric – either drum or traction devices o Drum – used in older styles where cable is wound the drum. Normally use counter weights to reduce lifting effort of drum.The size of the drum will limit height of building use (still may be found in freight elevators) o Traction – The most common type in buildings over 6-stories high…very fast & has no height limitations. Hoist cables attached to the elevator car run up & over the drive pulley at the top of the hoistway and then down the back wall of the hoistway. The cables do not wind around the drive pulley – they merely pass over it. With the aid of compensating cables, the weight of the elevator car & the counterweights offset each other so the drive motor only has to lift the weight of the passengers.Drive motors can be either AC or DC & have as much as a 500-volt power supply. Traction elevators have a braking system that operates both during normal operation & malfunctions. System uses a brake drum located on the shaft of the drive motor. In a power failure electromagnet releases brake shoes against the drum. ? AC motors aid directly in stopping the car at the correct floor ? DC motors do not aid in stopping the car…the motor stops the car & the brakes are applied to hold the car in place. Safety Devices: Terminal switch – cuts power before very top or bottom limits of hoistway is reached • Buffers – large springs at the pit…cannot safely stop free-falling car • Speed reducing switch – slows car when speed is exceeded • Overspeed switch – backs up speed reducing switch • Car safety – tapered steel jaws that wedge against guide rails to stop free fall Elevator Cars: • Safety plank…sits on the platform • Crosshead • Uprights…connect the main structural members together. Elevator Hoistways: A vertical shaft in which the elevator car travels & includes the elevator pit.The pit extends from the lowest floor landing to the bottom of hoistway. Codes require venting at the top of practically every modern hoistway. Hoistway enclosures are usually required to be a fire-rated assembly with a 1 or 2 hr rating. No wiring, duct work, or piping should be run within the hoistway unless required for the elevator itself. Types: • Single – one elevator car • Multiple – more than one car…no more than four. Cars are normally NOT separated by a wall or partition • Blind – used for express elevators that serve upper floors of tall buildings.There are no entrances to the shaft on floors between the main entrance & the lowest floor served. However access doors are provided for rescue purposes on every three floors. Elevator Doors: Include both car doors & hoistway doors. Passenger cars are powered by an electric motor on top of the elevator car. • Passenger o Single slide – not found on high-speed elevators o Two-speed – two panels on located behind the other o Center opening – two panels move away from each other when opening, most common type of passenger elevator door • Freight Vertical Bi-part – two panels move vertically… bottom/top • Access Panels – either hinged through the top of the car or hinged/removable panels on the sides of the car. o Top exit – provided on all electric traction elevators. May or may not be on hydraulic. All can be opened from the outside & all open outward. Some have electrical interlocks that will not allow movement when panel is open. o Side exit – used in multiple hoistways where cars are equipped with side exits to allow lateral transfer from a stalled car to a functioning car next to it. Hoistway Doors – except for freight elevators, are dependent upon the car doors for their power. Have typical fire-resistance rating of 1 ? hrs. The doors are also equipped with locks that prevent doors from opening when an elevator car is not at the landing. Emergency Use of Elevators: • Phase I Operations – opens the doors and keeps them open when the car reaches the recall floor. • Phase II Operations – designed to let FF use the elevators by overriding the recall feature. Doors are required to be operated from within the car. Moving Stairs: Should not be used during emergency operations, should be stopped & used as stairs.Move in one direction 90 to 120’ per minute. Steps are linked together by a step chain. The driving machinery is located under the access plate at the upper landing. Vertical openings are protected in the same manner as other vertical openings, or: • Sprinkler draft curtain with an 18” deep draft stop & automatic sprinklers • Vertical opening protection by a rolling shutter at the top of the escalator Stairs: Stairs that connect no more than 2-levels & are not required to be part of the means of egress are called access or convenience stairs.The riser height & tread widths are to be within 3/8” in difference within the entire flight • Straight run – extend in a straight line for their entire length. Landings may be found as a break up. • Return stairs – have an intermediate landing between floors & reverse direction at that point. • Scissor stairs – two separate stairs constructed in a common shaft. Old scissor stairs use straight runs which return to every other floor. Newer design allows ingress & egress from each stair at each landing & used to provide additional exit capacity. • Circular stairs – minimum run width of 10”.The small radius is not to be less than twice the width of the stairway • Folding stairs – attic access…springs can fail under fire conditions • Spiral stairs – normally residential applications Protected Stairs: enclosed with fire-rated construction (usually 1-2 hr rating). Generally serve more than two-stories and are part of a required means of egress. Constructed of non-combustible or limited-combustible materials. The stair enclosures are required to be isolated from the rest of the building. Only penetrations allowed for: • Light • Fire protection • Environmental controlExterior Stairs: may be either open to the air or enclosed. Enclosed exterior stairs must comply with requirements similar to those of interior enclosed stairs. Fire Escapes: Codes have not permitted fire escapes in new construction for decades. Lowest flight may consist of a swinging stair section. They are usually anchored to the building & are not supported at ground level. Smokeproof Stair Enclosures: Used in stairs serving high-rise buildings. • Active smoke control – uses mechanical ventilation that is activated by automatic smoke/heat detection equipment. The stairwell is pressurized to keep the smoke out.A properly installed system will allow for FF operations & occupant escape simultaneously. Mechanical ventilation should keep smoke out even if a door is open to a fire floor. • Passive smoke control – uses natural ventilation through an opening to the outside air: o Vestibule o Balcony o Smoke shaft Unprotected Stairs: can be used as part of an exit system in 2-story buildings (access or convenience stairs) Utility Chases & Vertical Shafts: utility chase is a term generally applied to the vertical pathways in a building that contain building services: • Plumbing • Electrical raceways Telecommunication • Data cables • HVAC It is normally not possible to provide any fire barriers along the length of the shaft. Vertical shaft enclosures are built with fire-rated construction methods but contain combustible materials. • Pipe chases – typically require non-combustible or fire-resistive construction. Some buildings don’t have pipe chases but rather use mechanical rooms on each floor stacked one above another. • Refuse chutes – creates a frequent fire response. Required to be constructed of noncombustible material with rated doors. The chute is typically surrounded by a fire rated enclosure. Linen chutes • Grease ducts HVAC Systems: have a potential to significantly impact any fire event. Corridors are still occasionally used as plenums through use of transoms…dangerous practice. HVAC ducts commonly penetrate fire-rated assemblies & require smoke/fire dampers. Most large HVAC systems (2,000 CFM +) must provide an automatic system shutdown with a smoke detection device. Large commercial furnaces must also be enclosed with fire-rated construction. • Smoke damper – actuated by smoke detector and automatic alarm systems • Fire damper – uses spring loaded shutter held open by a fusible link.Electrical Equipment: High voltage is defined as operating at 600 volts or higher. • Transformers o Air-cooled o Oil-filled – older units contain PCBs & must be labeled • Emergency power supplies – generators, batteries or combinations of both. Usually required in the following: o Correctional/detention o Health care facilities o Covered malls o Buildings with atriums o Buildings required to have a smoke management system must have backup generators Lead acid batteries – commonly used storage batteries. Contain sulfuric acid and pose an inhalation and skin contact hazard.Metallic lead is a toxic heavy metal. Document during pre-incident planning. Chapter 14: Underground Facilities & Other Considerations Underground usually describes below grade installations that are deeper than ordinary basements. Codes may group underground buildings with windowless buildings. Defined by some codes as one in which the lowest level is 30’ below the main exit that serves that level. • Parking facilities • Subway stations • Storage facilities Ventilating heat & smoke is the biggest single problem in controlling fires in underground buildings.Firefighting can be extremely difficult when a facility is 100’ or more below grade. Below grade evacuation is more difficult than high-rise buildings due to greater exertion & potential for stairwell being filled with smoke. The maximum available fire-resistant protection is typically four hours. Codes require automatic sprinkler protection & a smoke exhaust system. Atriums: vertical opening usually extending through several floors of a building. Atriums differ from other vertical openings in their size (create interior courtyards), but pose same potential for communication of heat & smoke.It is possible for an atrium to extend only part way through a building or extend more than 30-stories. Typically require: • Sprinklers • Enclosed with one-hour rated construction or a combination glass/sprinklers. • One-hour enclosure is typically eliminated for up to 3-stories • Can be enclosed if a smoke exhaust system is present The exhaust system used to be determined by the size of the atrium and the size of the enclosed floors connected to the atrium. Current codes base exhaust capacity on the height of the atrium above the top balcony serving the exit system & magnitude of the expected fire.Covered Shopping Malls: The mall is technically the covered pedestrian way. Distinguished by other commercial buildings with multiple tenants by the width of the covered mall (min. 20-30’ in width). Can be described as a business district of a medium-sized city under one roof. Protection of openings by fire walls & fire doors may be waived from protection from large anchor stores & smaller stores. Current codes require malls to be fully sprinklered. Individual stores usually require one-hour fire-resistive separations. One problem is the front of the stores is open, separated by only a security gate or sliding glass door.This causes potential for communication of heat/smoke into the mall area. Another problem is the potential for long hose lays from front entrance. Codes now require FD hose outlets: • In stairs • At major entrances • At entrances from the mall with corridors & passageways Another problem is the transient nature of businesses. Potential construction hazards that may shut off a sprinkler system during renovation. Explosive Venting of Buildings: explosion is an event that produces a rapid release of high-pressure gas. They can be physical events (boiler explosion) or a chemical reaction.Explosion exerts an internal force on the structural components of the building, which most buildings are not designed to withstand. The occurrence of an explosion is a complex process that involves several variables: • Ratio of fuel & air • Chemical nature of material involved • Presence of inert materials • Ignition source Internal explosions are not something typically taken into account when designing a building. Types of explosions involving combustion: • Detonations – explosion in which combustion proceeds at a speed greater than the speed of sound. Impart greater impact on structural members than deflagrations. Deflagrations – combustion proceeds at a speed less than the speed of sound. Buildings can be designed to minimize damage of deflagrations. Maximum pressure may be as high as 10 times the atmospheric pressure. Explosion venting is designed to quickly relieve pressure before it causes excessive damage. Explosion vents include: ? Louvered openings ? Hangar-type doors ? Wall panels ? Windows roof vents Vents must operate quickly and be light-weight (reduced-diameter bolt & hinges). No simple rule exists with respect to the required size of explosion vents (requires an engineering analysis).Venting limits structural damage, but does NOT provide protection of personnel within a building. Air-Supported Structures: Buildings supported by means of relatively small interior pressure. The interior pressure is maintained by fans. Membranes are made of non-combustible materials. Normal entrance/exits are through air locks to reduce leakage. There are several limitations to these structures: • Interior pressure can only be slightly higher than outside or will be uncomfortable • Vulnerable to high winds • Conventional ventilation is not possible Rack Warehousing:Storage racks can vary from two or three tiers with a total height of 12 ft to 80 ft. Storage is highly efficient, but results in a very high-density of storage. The racks are frequently arranged in narrow aisles & makes FF access very difficult. The racks are normally arranged back-to-back which causes two problems: 1. penetration of water from overhead sprinklers is obstructed by the intervening tiers of storage 2. flue spaces may be created that permit vertical communication of fire through racks The design of automatic sprinklers for rack storage is very specialized.Storage racks are constructed of unprotected steel, causing a collapse potential under fire conditions. Chapter 15: Building Fire Protection Systems These systems are not necessarily an inherent part of a building. However, fire protection systems are a significant part of a building & affect the overall fire behavior of a building. Motivations to install systems are: • code requirements • *insurance requirements • general fire protection • marketability • *management interest in economic survival of business * The greatest stimulus for the installation of the systems.Typically, codes will permit buildings to be constructed with greater areas w/o fire walls or eliminate fire walls all together when they are equipped with automatic sprinklers. Codes also will allow a reduction in fire-resistive requirements and an increase in flame-spread ratings with sprinklers. Building codes will either specifically require certain fire protection systems or permit “tradeoffs” of building code requirements when a fire protection system, usually sprinklers, is provided. Typical occupancies requiring sprinklers: • Schools • Nursing homes/hospitals • High-rises • Covered malls Buildings with atriums Automatic sprinklers & standpipes are required for high-rises. Automatic sprinklers, standpipes, & fire alarms are required for a high-rise hospital. Design of Fire Protection Systems: The refinement of fire system design has meant that fire protection systems, especially automatic sprinkler systems, vary from building to building. In residential systems, sprinklers are not installed in all places. Building Smoke Management Systems: Smoke management is the general category that includes all methods that may be used to lessen the impact of smoke on building occupants or FF.In addressing smoke movement in a building the following terms are encountered: • Smoke management – all methods that may be used to lessen the impact of smoke on FF & occupants o Barriers o Smoke vents o Compartmentation o Pressurization o Smoke shafts • Smoke control – used to describe systems that use mechanical fans to direct the flow of smoke. o Smoke exhaust fan o Entire HVAC system Building ventilation systems – HVAC can recirculate air to reduce amount of air to be cooled or heated. This can cause a problem when smoke is introduced into the system.To prevent this, the system can be switched from normal operating mode to fire mode. This is done either automatically or manually. • Automatic smoke control – accomplished by the use of smoke detectors located on various floors of a building corresponding to the areas served by the HVAC system. When smoke is detected, the HVAC system controls are signaled to switch to fire mode. Automatic transfer can also be initiated by sprinkler flow switches & heat detectors. Dampers can be either open or closed to redirect the flow of air & exhaust smoke.Continuing to supply air to the non-fire floors creates a “pressure sandwich” of higher air on floors above & below the fire floor. • Manual smoke control – advantages to these controls are the elimination of system disruption due to false alarms and more specific system control. When a system has both automatic & manual capability, manual control should take priority. Disadvantage is it’s slower than automatic operation. The activation of a smoke control system should NOT be by means of a pull station. Some systems are controlled by a dedicated control panel in a control room or a Firefighter’s smoke control station (FSCS).The FSCS should have complete system monitoring & control capability…FSCS has the highest priority of system operation. Smoke Control System Design: Buildings can be designed with either dedicated or non-dedicated smoke control systems. • Dedicated – provided for only the purpose of smoke control. Separate from HVAC system. Advantage of simplicity, but costly & usually neglected in maintenance. • Non-dedicated – uses all or a portion of the Normal HVAC system for smoke control. More of a complex system, but cheaper & usually better maintained. System alteration may interfere with smoke control functions.Chapter 16: Buildings under Construction Very little attention is paid to the fire protection needs during the actual period of construction. Frequent site visits by first-due companies are necessary to keep FF familiar with a project. Access to construction sites can cause a problem due to fences, barricades, & excavations. Emergency vehicle access up to the actual building can be very difficult. Fires frequently occur in the upper floors of high-rise construction projects. It may be necessary to use a construction elevator to gain access to upper floors.A construction elevator is a temporary elevator erected to the outside of a building and is removed upon completion of the project. It is common practice to disconnect the power to these elevators after hours. Material hoists should NEVER be used to transport personnel. Fire Hazards at Construction Sites: • Temporary electrical wiring • Heating – frequently left unattended. Propane tanks are susceptible to mechanical damage (100-lb tanks + extra cylinders can be present). Kerosene tanks for heaters are susceptible to sparks from welding and exposure fires that may occur in debris.Fire prevention codes usually require a fire watch provided during and after welding or cutting with torches. Person on fire watch should be given a fire extinguisher & have no other duties…not uncommon to have fire watch omitted due to economic measures. • Combustible debris Fire protection: • Temporary – on long duration projects, some level of fire protection must be provided. Temporary fire protection is usually standpipes & outlets. The most effective method is to make use of permanent fire protection system as it is installed.This may require that 2 standpipe risers be available so that one can be maintained in service while the contractor extends the other. • Fire Extinguishers – if trained can be useful at construction sites. Theft of extinguishers can be a problem…barrels of water w/ buckets can sometimes be submitted. Hazards of Remodeling & Renovation: These buildings can introduce unusual hazards. In some respects, the remodeling of a building can be more hazardous than new construction operations. This is because the remodeling may take place in one portion of a building while the remainder of the building remains occupied.If a portion of a sprinkler system has been shut off for remodeling, the verification of restoration of the system being turned back on. Demolition of Buildings: fires are common on these sites. Scrap metal including fire protection piping may be stripped from the building. The removal of scrap metal w/ torches is common fire causes. The building itself is structurally unstable during the operation. Exterior FF tactics from a safe distance are the best course of action for fighting these fires. Renovation: Includes small projects such as replacing bathroom fixtures, or it can consist of extensive structural or architectural alterations.

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