Flashcards in Ch. 9 Steel Construction Deck (86):
BEHAVIOR of steel under fire conditions depends on: (2)
-the MASS of steel
-degree of RESISTANCE
PROTECTION of steel depends on: (4)
-INTEGRITY of installation
Steel is basically an alloy of:
Iron and carbon
*structural steel less than 3/10 of 1% carbon*
-cast iron = 3-4% carbon
Composition of steel can be altered:
Molybdenum - strength
Vanadium - strength/toughness
Manganese - resistance to abrasion
Lower carbon content of steel results in material that is ____ rather than _____.
-ductile = enables steel to be rolled into variety of shapes
**Rolling ingots at 2,200F between rollers**
The _____ of steel also allows it to be rolled in the cold state. Known as CRS.
CRS can be used for _______ partitions or _______ walls.
Interior non-load bearing
Steels with _____ yield points have _____ ductility.
Very common steel, A36, has yield point of ______.
*yield point reached-pronounced deformation*
Breaks at "Ultimate Stress"
Steel possesses 2 inherent disadvantages:
Tendency to RUST (exposed to air and moisture)
Loss of STRENGTH (exposed to heat)
Steel protected by rust: (3)
Coating (zinc and aluminum)
Produced using ingredients that resist rust (stainless)
To the fire service, ______________ is its most significant characteristic.
Deterioration of the strength of steel at elevated temperatures
Fire typically encountered by firefighters do NOT ___________. However, they DO create enough heat to ____________, resulting in _________.
Create temperatures hot enough to MELT steel
Greatly weaken steel
At 1,000F, yield point of steel has dropped from 36,000 psi to _______. At 1,200F, it has dropped to ______.
Because temperatures in excess of _______ are regularly encountered in fire, failure of unprotected steel, to a greater or lesser degree, _________.
Can be anticipated
Density of steel
490 lbs per cu. ft.
Unprotected steel; members such as ____ and ____ can be expected to fail EARLY
BC 20 ft beam heated from 70-1,000F will elongate _____
*HOT 100 ft @1000F = 9 1/2 in. lengthwise*
Heating of steel _____ occur in a uniform manner
Both yielding and thermal expansion take place simultaneously; however the tendency for steel to _____, and therefore ______ is the MORE SIGNIFICANT concern in most fire situations.
Bend or buckle
Cast iron tends to fail by _______________. (Columns and staircases)
Fracturing from impact loading
Cast Iron; Firefighter need to be concerned with _____________. It may be a failure of _________.
The way the cast iron fronts are ATTACHED to the structures.
These attachment points
Steel shapes can be used to construct a frame of:
Large horizontal member used to support joists and beams at their isolated points along their length.
Because steel is _____ but very _____, it is not efficient to use it in the form of _____________ as is done with wood or concrete.
Solid slabs or panels
Connections are ________.
Connection of a beam to a column not only _____ but also ________.
Transfers the load
Determines the rigidity of the basic structure
Beam and GIRDER frames can be classified as: (3)
Beam and Girder Frame;
Not completely rigid: enough rigidity for some diagonal support
Shear panels or diagonal bracing
Shear panels-reinforced walls
Beam and Girder Frame;
Support a vertical force
Degree of angular change CAN OCCUR if no diagonal bracing
Supported by masonry wall
Also examples of simply supported
Beam and Girder frame;
Connections resist bending forces
No change in angle
Two commonly encountered applications of the basic steel truss are the:
Open web joist (Lightweight steel truss).
Joist girder (Heavy steel truss-take place of beams)
*steel truss-opens her web, find the girder*
Open web TRUSS constructed entirely of steel, with steel bars used as the web members (round bar used)
-Closely spaced configurations
-Supported on masonry wall
Steel trusses frequently used in _______, in which case they are known as _________ because __________.
Three-dimensional space frames
They resemble greek letter Delta
Open web joist
Depths up to ____
Spans up to ____
6 ft, 144 ft.
Less than 2 ft, 40 ft
Open web joist made of:
2 bars. OR
Open Web Joists.
Diagonals members made from:
Flat bars welded to top/bottom OR
Continuous round bar bent back and forth *bar joist*
Gable roof rigid-frame structures must be ___________ to prevent deflections in the direction _______ to the plane of the frame sections.
Gable roof rigid frame - diagonal bracing accomplished by:
Diagonal cross-members: in the plane of the roof AND
In the vertical plane of the walls
Steel rigid frames (with inclined Gabled roofs) usually are used for spans:
Top of a rigid frame is the ____ and the points where inclined members intersect the vertical members are known as the _____.
*rigid with no rotation*
_________ used to support roofs on buildings where large unobstructed floors are needed, includes gymnasiums and convention halls.
Steel arches can be constructed to span distances _______.
In excess of 300 feet
Two types of steel arches:
_______ constructed as a solid arch that may be built up from angles and webs with a cross section similar to that of a beam.
Girder arch (SOLID)
____ is built using truss shapes. May have ______, which allows for slight movement between the two halves due to _____ or _____.
Settling or temperature change
Drawing steel through a die to produce wire greatly _________ the strength of steel. It is possible to produce wire for use in bridge cables with strengths as high as ________ psi.
Cables: such slender shapes are subject to _______ and therefore limited to the support of ________ forces.
Possibility of buckling is _______ with steel columns than with columns made of other materials.
-because of small cross-section compared to length
Most common cross-sections of columns are: (3)
Possibility of buckling in an individual column is a function of: (3)
Method by which its supported at top and bottom
_______ is a number that compares the unbraced length of a column to the shape and area of its cross-section. The higher the numerical value, the ________ likely it is that buckling will occur.
*womens size increases, she is going to buckle*
Columns used for structural support should NOT have a slenderness ratio greater than _____.
P. 270 Steel structures
Two factors that affect possible failure:
Mass of the steel members
Type of structural connection
Steel connections, both in case of rigid, with beam and girder and heavy trusses, use ______, which _________ the connection, _______ the steel mass and _______ it's possibility of failure.
Large beam and girder frame made of repeating sections, adjacent sections tend to be mutually supporting. Provides _____.
Degree of redundancy
Steel column encased in _______ of concrete with a siliceous aggregate would have a fire resistance of ______.
*increases weight and cost*
Most commonly used insulating materials are ______, _____, and _______. Some of these insulating materials are applied by spraying and are known collectively as __________________.
Spray-applied Fire Resistant Materials (SFRMs)
Gypsum can be used as an insulating material either in the form of ________ or _________.
Two types of gypsum board:
Type X (additives)
Gypsum consists of approx. _________ water.
Gypsum can be used to protect both _____ and _______, providing fire resistance ratings from _________. Gypsum board is used in ___________ to attain higher fire resistance ratings.
Spray-applied Fire-Resistive Materials (SFRMs) are _____ and _______. The most commonly used SFRMs are _____ or ______ such as ____ and _____.
Mineral fiber or expanded aggregate coatings
SFRMs - Degree of fire resistance depends not only on: (2)
But also thickness
Applied fireproofing can vary from ____ to _____ to produce a fire resistive rating of __________.
7/8-1 7/8 inches
SFRMs - relatively soft and easily dislodged, not suitable for exterior use
Low-density mineral fiber materials
SFRMs - densities greater than 20 lb/cu. ft., can endure conditions of limited weather exposure and higher humidities such as parking facilities
SFRMs - use magnesium oxychloride have densities ranging from 40-80 lb/cu. ft.
SFRMs cementitious - densities of _______
15-50 lb/cu. ft.
Intumescent coatings will __________ when exposed to the heat of a fire. An intumescent coating will _____________ when heated, and will expand ________ it's original volume.
Undergo a chemical reaction
Char, foam AND expand
15 to 30 times
Intumescent coating applied thickness of ________, which is _____ than the thickness of spray applied materials. Because they have appearance of paint, ______ to visually establish fire-resistive coating has been applied.
.03 - .4 inches
VERY COMMONLY used method of protecting steel floor or roof assembly is ____________.
The most common method is to use ______ in a __________ suspended by ______.
FREQUENTLY used in systems that make use of __________.
Use of membrane ceiling can provide a floor and ceiling assembly or a ceiling and roof assembly with a fire rating of ______.
Open web joists
1 to 3 hours
Ceiling materials are _______ rated independently. A ceiling is always rated as part of a ___________ assembly, so it is not accurate to speak of the fire resistance of a ceiling alone.
Floor and ceiling
_______ is one of the two methods of providing fire-resistive construction, such as Type ___, ____ and _____. The other method is ________.
IA, IB, IIA
Examples of permit reductions:
Eliminating fire-resistance of roof construction if ceiling is MORE THAN 20 ft above floor.
Reduction of required fire resistance when an automatic sprinkler system
Basic properties of steel (4)
STRONGEST of bldg material
NON-ROTTING, resists aging, dimensionally stable
Relatively INEXPENSIVE (strength/forms enable to be used in smaller quantities)
Speed at which unprotected steel fails depends on (5)
INTENSITY of fire
Type of CONNECTIONS
Type of STEEL
Beams and columns connected by (2)
Bolting or welding
*riveting not practical today*
Suspension systems can provide large unobstructed areas similar to arches without ________________.
The reduction in vertical clearance at the sides of the building
Slenderness ratio can be modified by the manner:
In which the ends are attached to the rest of the structure
Very common floor design in steel frame bldgs uses a lightweight concrete with a minimum thickness of ______ supported by corrugated steel decking.
Corrugated steel, in turn, is supported by ___________.
Joists supported by _____ or ______.
Open-web steel joists.
Steel beams or masonry wall
Where floor loads or spans dictate, _____ are used to support flooring instead of lighter open-web joists. _________ are also sometimes used.
Light gauge steel joists
Steel joists produced with depths of _______ and can be spaced ______ apart.
6 to 12 in.
16 to 48 inches apart
In gabled rigid-frames structures, the ______ between the roof and wall will be the strongest/last part to fail.