Chapter 9 Steel Construction Flashcards
Steel beams and trusses have largely replaced __________ in commercial structures
Wood beams and trusses
Steel framing is used in both types of buildings
Fire-resistive
Non fire resistive
The primary two metals alloyed in steel is
Iron and carbon
Structural steel has less than what percent of carbon
Less than three tenths of one percent
Cast iron has a higher carbon content of
3 to 4%
Higher carbon content in cast iron makes it
Hard but brittle
One disadvantage of steel is the tendency to _______ when exposed to air and moisture
Rust
Molybdenum
Strength
Vanadium
Strength and toughness
Manganese
Resistance of steel to abrasion
Substance or mixture composed of two or more metals
Alloy
An alloy of iron and Carbon
Steel
The lower carbon content of steel compared to cast iron results in a material That is
Ductile rather than brittle
Ductility of steel also allows it to be shaped by
Rolling as opposed to molding
Repeated passing ingots of steel heated to 2,200 degrees between large rollers until intended shape is achieved
The rolling process
One common structural steel is
ASTM A36 includes manganese carbon and silicon
The stress exerted on steel against the resulting deformation known as
Strain
Yield point stress is reached
Approx 36,000 psi
Steel undergoes pronounced deformation finally the steel breaks at the
Ultimate stress
Steel alloys with higher yield points have less
Ductility
Cold rolling occurs at temperatures above
Recrystallization temperature
Steel expands as it is
Heated
The amount of expansion for slender members such as beams and columns can be determined can be determined through a property known as
Linear coefficient of thermal expansion
Steel is a good conductor of heat because it’s a heavy material having a density of around
490 pounds per cubic feet
Bar joist or slender trusses can be expected to fail early when exposed to an
Intense enough fire
Steel structural members that are not protected against exposure to heat
Unprotected steel
Fire can create temps in excess of 1200 degrees witch is hot enough to
Weaken steel to its
Yield point
Yielding and thermal expansion take place
Simultaneously
Theoretical minimum amount required to raise the temp of the beam to
1,000 degrees
The usual way to protect steel from the heat of a fire is to add an
Insulation material
Fireproofing on steel beams can vary from __________ and to produce a fire resistive rating of ________
7/8 - 1 7/8 inches
1-4 hours
Low density fiber materials are not suitable for
Exterior use
Cementitious materials have densities ranging from
15-50 lb ft
Process that heats a substance to a high temperature but below the melting of fusing point causing loss of moisture, reduction or oxidation and decomposition of carbonates and other compounds
Calcined
Process of driving free and chemically bound water out of gypsum
Calcination
Gypsum board is available as
Regular or type X
Regular gypsum board has no special
Additives to enhance its fire resistance
Type X gypsum board contains additives to
Increase its fire resistance
Gypsum includes _________ entrapped water
Approx 20 %
Gypsum can be used to protect both _________ and ________ providing rating from 1-4 hours, gypsum board is used in multiple layers to Syrian higher fire resistance ratings
Column and beams
Intumescent coating will char, foam , and expand ________ its original volume
15-30 times it’s original weight
Intumescent coatings are applied as paint in thicknesses of
0.03 to 0.4 inches
A commonly used method of protecting a steel floor or roof assembly is
Membrane ceiling
______ panels are also used for membrane ceilings
Gypsum
Membrane ceiling can provide a fire rating
1-3 hours
The basic method by which steel is used in the design of building is the construction of
Structural framework that supports the floors , roof , and exterior walls
The connection of a beam to a column transfers the
Loads between members
Connections determine the ______ of the basic structure
Rigidity
Beam and girder steel frames can be classified as
Rigid , simple, semi rigid
Beams and columns in steel frame buildings are connected by
Bolting and welding ,
Riveting was used in the first half of the 20th century
Connections between the beams and columns in a ___________ system are designed to resist the bending forces resulting from the supported loads and lateral forces
Rigid frame system
The joints in a ________ are designed to primarily to support a vertical force
Simple frame system
The connections of ___________ are not completely rigid but posses enough rigidity to provide some diagonal support to the structure
Semi rigid frame
_________ trusses provide a structural member that can carry loads across greater spans than beams can
Steel
Steel trusses are frequently used in three dimensional space frames know as
Delta trusses , because the cross section resemble the Greek letter delta
Two commonly encounter applications of the basic steel truss are
Joist girder
Open web joist
Joist girder are _________ used to take the place of steel beams as part of the primary structural frame
Heavy steel trusses
Open web trusses are massed produced and available in depths of _________ and span up to _______
6 ft
144 ft
Most often found depths less than 2 ft and spans of 40 ft
Open web truss is know as
Bar joist
