Chap 2 Constructive Terms Of Building Design Flashcards
Passive fire protection is
- The fire containment provided by a structure( partition walls with spray on fire retarding and fire resistive construction)
- Often fails and cannot be depended on stop fire spread
Active fire protection is
Fire protection provided by automatic sprinklers and firefighters hose
Cold formed steel beam is
A sheet steel c-beam used in lightweight steel floor construction
Convenience stair
Opening in a floor slab for a stair between floors
Sometimes called access stair
Corner safe areas
Four flanking areas around a burning building
Demising wall
A partition wall that extends from floor slab to floor slab above
Fire resistive rating is
A relative rating to indicate in hours how long a wall , floor ceiling beam or column will sustain performance during a fire
Fluted metal steel deck
Sometimes called a corrugated metal deck
Wavy piece of sheet steel deck used to support concrete floor.
Frame tube construction
1 building structure with hollow tubular exterior (perimeter columns )bearing walls
2. WTC towers WERE FRAME TUBE CONSTRUCTION whose exterior hollow bearing walls varied from 4” thickness near bottom or only 1/4 “ thickness near top
Gravity load
Combination of live and dead load
Purlin
A timber laid horizontally and perpendicular to support the common rafters of the roof
I beam
Wood or steel
Consists of center called a web section and top and bottom flanges
Wood I beams has a web section of glue and wood shavings connecting the top and bottom flanges which are made of 2x2 wood sections
Laminated beams
It’s glued or layered composition beam
Laminated wood chips are used in lightweight I-beams. And layers bent wood is used in timber chord truss construction
Bridge truss
A perpendicular truss used in steel bar truss floor systems to provide lateral stability
Hat truss
A means of load distribution connecting core columns and perimeter columns
Used on top floor of WTC towers
Multilevel floor collapse
A floor failure that causes one or more floors below and one or more enclosing walls to collapse
Global collapse
A total collapse of building
Progressive collapse
The initial structural failure spreads from structural element to structural element resulting in a collapse of the entire structure or a disproportionately large part of it
Interstitial space
Also known as a plenum space
Concealed space btwn floors used to contain large mechanical and electrical equipment
Can be up to 8 feet high
Can contain a walkway for access for maintenance, repairs and renovations
Sprayed Fire-Resistive material (S.F.R.M)
- Insulation or fluffy sprayed on fire-retarding used to protect steel from the heat of the fire
- Must cover the steel entirely
3: must be proper thickness or density - Must adhere to the steel and not flake off when exposed to air movement in the HVAC plenum. Area
Timber
Wood larger than 2x4 thickness
Arch
1 curved masonry piece used as a support over an open space
2. The removal or destruction of any part of an arch will cause the entire arch to collapse
Beam
A horizontal structural member subject to compression tension and sheer
3 ways a beam can be supported are
Cantilever
Simple support
Continuous support
Cantilever support of a beam
Beams supported at one end only
Least stable
Simple support beam is
Beam supported at both ends
More stable than cantilever
Continuous beams are
Supported at both ends and at the center
Most stable
Joists are
A piece of lumber used as a floor or roof beam
Terms joist beam rafter are used interchangeably
Restrained beam end
Welded, nailed bolted or cemented end of the floor or roof beam
Restrained beam end will not collapse as readily as an unrestrained beam end at fires
Example: a wood beam cemented into cavity of brick wall
Unrestrained beam end
A beam resting on a support held in place only by gravity
Collapse at fires more readily than a restrained or fixed beam end
Examples : fire cut beam ,beam resting on corbel ledge ,beam resting on girder
Fire cut beam
1 gravity supported beam end designed to release itself from masonry wall during a collapse
- The end of the beam where it rests within the cavity of the masonry wall is cut on a angle
- An unintended indirect advantage of fire cut beam is the safety of FF operating outside the building near the enclosed walls . A floor collapse will not topple the walls outward in top of them
- The disadvantage to ff operating inside of fire cut beam is early floor collapse
Ballon frame construction
- Exterior walls have studs that extend continuously from the foundation sill to the top plate near then attic
- Fire , smoke and heat can spread from the cellar area or intermediate floors to the attic space in the concealed space between the exterior walls
- If a non- bearing wall fails the continuous studs will cause the wall to fall straight out in one section at a 90 degree angle
- If bearing wall falls it can cause collapse of floors it supports
Braced frame construction
Also called Post and girt
1. Vertical timbers called posts reinforce each of the 4 corners of the structure
2. Horizontal timbers called girts reinforce each floor level
3. The posts and girts are connected by mortise and tenon joints
4. This type usually fails inward outward type collapse where:
A. Top part of the wall collapses inward on top of the pancaked floors
B. The bottom part of the wall collapse outward on street
Mortise is
Structural member used in braced frame wooden construction
It’s a hole cut in timber that receives the tenon
Mortise opening reduces the thickness of the timber and reduces the load carrying capability of the timber at this point
When braced frame construction fails it often fails at the mortise and tenon connection
Tenon
- A projecting reduced portion of the timber designed to be inserted into the mortise hole of another timber
- because of it’s reduced size the tenon connection is the weakest portion of the reduced timber
Platform construction
Has one completed level of 2x4 inch wood enclosing walls raised and nailed together
The floor beams and floor deck for the next level are constructed on top of these walls
The next level of 2x4 wood enclosing walls are constructed on top of the first completed level
From a fire protection point of view , platform construction is superior to ballon and braced frame construction because there are no concealed wall voids extending for more than one floor level
Curtain fall collapse of an exterior masonry wall
- Exterior masonry wall drops like a falling curtain and drops straight downward
- This often occurs to brick veneer , brick cavity or masonry backed stone wall
- Can occur from the use of master stream striking a masonry veneer wall at close range
Inward / outward collapse of an exterior wall
- The exterior walls breaks apart horizontally
- The top part of the wall collapses inward back on top of the structure
- The bottom part of the wall collapses outward onto the street
- Wooden braced frame buildings collapse in this manner
- timber truss roof collapses can cause a 2nd collapse of the front or rear wall in This manner
90 degree angle collapse of the exterior wall.
The wall falls straight out as a monolithic piece at a 90 degree
The top of the falling wall stricken the ground a distance from the base of the wall that is equal to the height of the falling section
3. Chunks of brick or steel lintels may bounce or roll out beyond this distance
Lean -to floor collapse
A floor collapse in which one end of the floor beam remains partially supported by the bearing wall
The other end of the floor beam collapses onto the floor below and is either supported (“supported lean to collapse”) or unsupported (“unsupported lean to collapse )
Pancake floor collapse
The collapse of the floor sectio down upon the floor below in a flat pancake style
Pancake collapse occurs when the floor beams pull loose or collapse at both ends
Tent floor collapse
A floor collapse in the shape of a tent where an interior partition wall or interior wall holds up the center of the fallen floor
v-shape collapse
The collapse of a floor at the center of the floor beams
Both ends of the floor section remain partially supported or rest up agonist the outer bearing walls
Lean over building collapse
A type of wood frame building collapse where the building collapse to one side
It will be Indicated by the structure starting to tilt to one side
Secondary collapse
The collapse of portions of a burning taller structure onto a smaller structure causing the collapse of the smaller building
According to Dunn a load transmitted ____ through a structural member is least likely to collapse
Axiallly
According to Dunn which loads can cause collapse during fire
FLID
FIRE
LIVE
IMPACT
DEAD
Dunns Hierarchy of building elements form greatest to least
- Bearing wall
- Column )
- Girder
- Beams floor and roof
- Decks
3 common Types of stress on structural members are
Compression
Tension
Shear
All of the following according to DUNN are considered primary structural members
Bearing walls Columns Girders Ridge pols Hip rafters Headers Trimmer floor beams
The most unstable wall a ff will encounter is
A ornamental facade parapet wall is often a free standing decorative wall which frequently collapses during fire
According to DUNN Structural collapse during a fire is directly portioned too
Fire load
The greater the fire load the greater the possibility of structural collapse
