11 STEEL FRAME CONSTRUCTION
HISTORY
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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HISTORY
Metals In Pre-Modern Building
Construction
• Greek and Roman bronze
cramps used to join blocks of
stone
• Renaissance wrought iron
chains and rods used to
counter thrusts in arches and
vaults
• Steel produced in quantities
too small for use in building
construction
– Making steel was labor
intensive
– Limited uses, for weapons
(e.g., Damascus steel swords),
cutlery, other specialties
• Right: Iron tie rods and
cramps in masonry
construction, Pantheon, Paris,
1789
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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HISTORY
1750 +
• Growth in use of cast iron
for framing in industrial
buildings and other
structures
• Coalbrookdale Bridge,
1779 (top right)
– First all-metal structure
– Cast iron
• Right: Crystal Palace,
1851 (bottom right)
– cast iron and glass
• Eiffel Tower, 1889
– cast iron
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HISTORY
1850 +
• Starting in 1850's, steel
becomes increasingly plentiful
with the development of large
scale steel making methods
such as the Bessemer process.
• After the U.S. Civil War,
excess steel making capacity
sets the stage for the first use of
steel in buildings in this
country.
• Home Insurance Company
Building, 1885, William Le
Baron Jenny (right)
– First tall building supported
entirely by a fire-protected metal
frame (cast iron and steel)
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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HISTORY
Modern
• Steel is one of three commonly
used noncombustible structural
materials. (Concrete and
masonry are the others.)
• Suitable for construction of
buildings of all sizes, from
single family residences to the
tallest skyscrapers.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
11 STEEL FRAME CONSTRUCTION
THE MATERIAL
STEEL
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Greater proportions of
carbon generally increase
the hardness and
brittleness of the resulting
iron alloy.
• Cast iron
– Typically 2% – 4% carbon
– Strong in compression,
but less so in tension
– Brittle (prone to sudden
failure)
• Wrought iron
– Little or no carbon
– Strong in tension, but
weaker in compression
– Malleable (easily shaped)
and relatively soft
• Steel
– Less than 2% carbon
– Strong in both tension and
compression
– Ductile (not prone to
sudden failure)
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Mild steel (low carbon steel)
• The commonly used alloy
for structural steel
members
• Not more than 0.3%
carbon
• Small amounts of other
alloys, such as nickel,
chromium, molybdenum,
manganese, vanadium,
and silicon improve
strength, toughness, and
other qualities
• Reasonably strong, highly
ductile, and easily welded
• Equally strong in tension
and compression
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THE MATERIAL STEEL
Making Cast Iron
• Iron ore, oxides of iron
extracted from the ground, is
combined with coke (carbon
derived from coal) and
limestone in a large blast
furnace.
• Hot air forced through the
furnace burns the coke.
Chemical reactions with the
combustion products remove
oxygen from the ore, leaving
elemental iron, but with a
relatively high carbon content.
• The limestone combines with
impurities and is drawn off as
waste slag.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Steelmaking
• In a traditional steel mill, iron ore is the raw
ingredient. First, it is processed into molten iron
in a blast furnace, followed by conversion to
steel in a second operation.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Steelmaking: Basic Oxygen Process
• Scrap metal and molten iron are
charged into the furnace.
• Pure oxygen is injected into the
mixture, oxidizing the carbon and
other impurities. Large amounts of
heat are generated—no external fuel
or energy source is required.
• Impurities combine with the flux,
and float on top of the molten
metal.
• The mixture is sampled, and
ingredients and the process are
adjusted as needed.
• Molten steel and slag are separately
poured off. Additional alloying
elements may be added to the steel.
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THE MATERIAL STEEL
Steelmaking: Mini-Mill
• In the North America today, most steel is made from
recycled steel scrap in "mini-mills" using electric arc
furnaces. Steel carp is converted directly to new steel,
bypassing the need to make iron from ore.
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THE MATERIAL STEEL
Steelmaking: Electric Arc Furnace
• Scrap metal is charged into the
furnace.
• Electrodes are lowered into the
scrap. An electric current flows
through the electrodes creating an
arc that melts the metal. Large
amounts of externally supplied
energy are required.
• Oxygen is injected to oxidize
impurities and enhance heating.
Flux is added to draw off impurities.
• Once the charge is fully melted,
additional scrap may be added.
• The mixture is sampled, and
ingredients and the process are
adjusted as needed.
• Molten steel and slag are separately
poured off. Additional alloying
elements may be added to the steel.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Electric Arc Furnace
• Right: Molten steel
being tapped from an
electric arc furnace into
a vessel called a "ladle"
• Note the geared
mechanism under the
furnace for controlling
furnace tipping.
• The upper ends of two
electrodes are just visible
at the top of the furnace.
• Next, the steel may
move on to secondary
steelmaking steps or
proceed directly to
casting.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Steel Making
• Mini-mills
– Less expensive to build than
traditional mills
– Produce higher-quality steel at less
cost than traditional mills
– Use less energy than traditional mills
(In a traditional steel mill, the basic
oxygen furnace does not require an
external source of energy, but the
blast furnace does.)
– Recycled content : 90% +
– In North America, virtually all hotrolled structural steel shapes are
manufactured from recycled steel in
mini-mills.
• Traditional mills
– Recycled content: 25% - 35%
– Primary products are flat-rolled
stock, including steel decking and
other sheet products used in
building construction
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Steelmaking: Casting
• As the molten steel begins
to solidify, it is cast into a
variety of shapes, ranging
from plain rectangles or
rounds to more complex
cross sections, such as
beam blanks, that
approximate the shape of
finished beam products.
• Right: In the continuous
casting process, casting
begins once the outer shell
of the steel mass has
solidified, while the inner
portion is still molten.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Production of Structural Shapes
• Structural shapes are produced
in a rolling mill. Prior to rolling,
the beam blanks are reheated to
the necessary temperature.
• Blanks then pass through a series
of rollers in which they are
progressively deformed into the
desired final shape.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Production of Structural
Shapes
• Wide-Flange (W-Shape) :
The most commonly
used shape for beams and
columns; Not an "I-beam"!
• Channels, angles, tees:
For trusses, lighter weight
framing, and other
miscellaneous uses
• American Standard:
Traditional I-beam with a
shape that is less
structurally efficient than
a contemporary wideflange of the same weight
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Wide-Flange Shapes
• Example designation:
W10 x 30
– W: Wide-flange shape
– 10: Nominally 10 inches
deep
– 30: 30 pounds per lineal
foot
• By varying roller sizes and
spacings, a variety of shapes
and weights can be
produced, all nominally 10"
in depth:
–
–
–
–
The unshaded portions of the diagrams illustrate
how a variety of weights of beams can be
rolled from the same set of rollers by opening
up the space between the rollers.
W10 x 9: 9.87" x 2.69"
W10 x 30: 10.47" x 5.81"
W10 x 33: 9.71" x 9.73"
W10 x 112: 11.36" x 10.42"
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Wide-Flange Shapes
• Generally, taller, more
narrow profiles are best
suited for use as
horizontally spanning
elements (beams, girders,
etc.)
• Profiles more square in
proportion are better
suited for use as vertical
columns.
• Size designations are
nominal, but not
necessarily an accurate
indication of actual depth.
– A W14 x 285 is 44" tall!
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Manual of Steel Construction Shape Data
• Left page
provides
dimensional data.
• Right page
provides
structural
properties,
relating to the
strength and
stiffness of the
shape.
• Note that within
groups of shapes,
dimension T, the
depth between
top and bottom
flanges, does not
vary. These
shapes are rolled
from the same
sets of rollers,
with only the
spacings of the
rollers changing.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Other Shape Designations:
• S18 x 70
– American Standard beam
– 18" nominal depth
– 70 pounds per foot
• MC10 x 33.6
– Miscellaneous channel
– 10" nominal depth
– 33.6 pounds per foot
• C6 x 13
– American Standard
channel
– 6" nominal depth
– 13 pounds per foot
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THE MATERIAL STEEL
Other Shape Designations:
• L4 x 3 x 3/8
– Angle
– 4" x 3" nominal leg lengths
– 3/8" leg thickness
• WT13.5 x 47
– Structural tee cut from a W
shape
– 13.5" nominal depth
– 47 pounds per foot
– (This example shape was
produced by cutting a
W27x94 in half
lengthwise.)
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Steel Alloys
• Traditional mild steel
– ASTM A36
– Minimum 36 ksi (36,000 lb
per sq. in.) yield strength
• Contemporary high-
strength, low alloy steels
– ASTM A992: W shapes
– ASTM A572: other shapes
– Produced economically in
mini-mills
– Minimum yield strength 50
to 65 ksi
• Use of stronger steel
allows savings in weight
and reductions in the size
of structural elements,
reducing overall costs.
ASTM A992 steel columns lay stacked in a fabricator yard.
Note the holes predrilled for connections that will be
completed in the field.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
More Steel Alloys
• Weathering steel ASTM
A588
– Surface rust adheres to base
metal, limiting further rusting
– Mostly used in highway and
bridge structures, eliminating
the need for a protective
coating
– Right: 365-ft span highway
arch bridge made principally
of weathering steel
– Cor-Ten steel (a proprietary
trade name for weathering
steel)
• Stainless steel ASTM A240,
A276
– Added nickel and chromium
– Forms self-protecting oxide
layer that provides long
lasting protection against
corrosion
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
By adjusting the chemistry,
alloying, and forming
processes of steel, a
multitude of different steel
types with varying physical
properties can be made.
• Example: ASTM A913 steel
– High-strength, low-alloy, steel
that has been modified by
thermal processes after
rolling to impart a
particularly desirable
combination of strength,
weldability, and toughness
characteristics
– Especially suited for welded,
heavy weight members and
for use in structures in areas
of high seismic risk
– Right: Welding two heavy
A913 steel column sections
end-to-end
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Cold-Worked (ColdFormed) Steel
• Deforming steel in its
cold state causes
realignment of the steel
crystals and increases its
strength.
• Examples:
– Corrugated steel decking,
rolled from steel sheet
(right)
– Steel studs and joists
(Chapter 12)
– High-strength wire for
concrete prestressing
strands (Chapter 13)
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Hollow Structural Sections
(HSS)
• Hollow square,
rectangular, round, and
elliptical shapes
• Made by cold- or hotforming steel strip (sheet)
and welding longitudinally
• Example designation:
HSS 8 x 8 x ½
– Hollow structural section
– 8" x 8" nominal size
– ½" wall thickness
• HSS shapes are used for
trusses, structurally
efficient column sections,
and where the simple
outside profile is
desirable.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Open-Web Steel Joists
(OWSJ)
• Lightweight trusses,
manufactured in standard
configurations
• Made from both hot- and coldformed components
• Depths range from 8 in. to 6 ft
• Traditionally spaced 2 to 10 ft
on center; more recently, wider
spacings are being used for
greater economy
• Right: Note the deeper joists for
the two floor levels, which carry
greater loads than the more
shallow roof joists above.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Open-Web Steel Joists
(OWSJ)
• Designations
•
•
•
•
K series: spans up to 60 ft
LH series: spans up to 96 ft
DLH: spans up to 144 ft (roofs
only)
JG: joist girders
• Example 18K3
•
•
•
18-in. deep
K series joist
Size 3 members (larger
numbers correspond to
heavier members)
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Joining Steel Members:
Riveting
• White-hot fastener is
inserted through holes in
members to be fastened.
• Fastener is hammered to
produce a head on the
plain end.
• As the metal cools, it
contracts, and strongly
clamps the steel
members.
• Mostly found in historical
structures. Not used in
modern building
construction.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Joining Steel Members:
Bolting
• Carbon steel bolts
– Relatively low strength
– Limited use; for fastening
light framing elements or
temporary connections
– Also called common, or
unfinished bolts
• High-strength bolts
– Stronger than common
bolts
– Used for fastening primary
structural members
Fundamentals of Building Construction, Materials & Methods, 5th Edition
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THE MATERIAL STEEL
Joining Steel Members: Bolting
• Bearing-type connection (left)
– Body of bolt resists movement
between connected members by
bearing directly against sides of bolt
holes.
– Bolt is stressed in shear.
– Connection will experience some
slippage before reaching full
strength.
• Slip-critical connection (right)
– Bolt is tensioned to such an extent
that movement between members is
resisted by friction between the
adjoining "faying" surfaces of the
members themselves.
– Bolt is stressed in tension.
– Under normal loads, no slippage
occurs.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Joining Steel Members: SlipCritical Connections
• Required for joints that
experience load reversals,
for joints with oversize or
slotted holes, and where
minor slippage would be
detrimental to the
structure (such as columnto-column splices in very
tall buildings).
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Joining Steel Members: In
slip-critical connections,
adequate bolt tension must
be assured.
• Turn-of-nut method: Nut is
tightened some additional
fraction of a turn after
achieving a snug condition.
Bolt tension is verified by
checking selected fastener
tightness with a torque
wrench.
• Load indicator washers
(right): When bolt is
adequately tightened,
protrusions on the washer
are flattened. Bolt tension
is verified by inserting a
gauge between bolt head
and washer.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Joining Steel Members: SlipCritical Connections
• Tension control bolt
(right): When bolt is
adequately tightened, the
splined end snaps off. Bolt
tension is verified by
visually inspecting for
splines.
• An additional advantage of
this bolt type is that a
second worker is not
required to hold the bolt
head on the opposite side
of the connection during
tightening.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Joining Steel Members:
Welding
• The joining surfaces of
steel members are
heated to a molten state,
additional molten metal
is added, and the
members are fully fused.
• After welding is
complete, two members
can be joined as if they
are one monolithic
element.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.
THE MATERIAL STEEL
Joining Steel Members:
Welding
• Fillet welds are relatively
easy to make, as little
preparation of the joint is
required.
• Groove welds require
properly shaped and
spaced joints.
• Puddle welds are used to
fasten metal decking to
structural steel members.
• Welds that are critical to
the stability of the structure
can be inspected using a
variety of techniques to
ensure their soundness and
freedom from hidden
flaws.
Fundamentals of Building Construction, Materials & Methods, 5th Edition
Copyright © 2009 J. Iano. All rights reserved.