Chapter 11 Steel Frame Construction

Fundamentals of Building Construction, Materials & Methods, 6th Edition
Copyright © 2013 J. Iano. All rights reserved.
11 STEEL FRAME CONSTRUCTION
STEEL FRAME
CONSTRUCTION

History
What is Steel?
Steel is an alloy of purified iron and trace
amounts of carbon (less than 2%) and
usually a few other elements, used as a
structural and fabricating material.

History
Metals In Pre-Modern Building
Construction
Greek and Roman
bronze crimps were
used to join blocks
of stone.
Renaissance
wrought iron chains
and rods were used
to counter outward
thrusts in arches
and vaults.

History
Making steel in the
pre-industrial age
was labor-intensive.
The use of steel
was limited
primarily to
weapons (such as
Damascus steel
swords), cutlery,
and other
specialties.
Metals In Pre-Modern Building
Construction

History
1750 and later
Growth in use of cast
iron framing in
industrial buildings
and other structures.
Right: Coalbrookdale
Bridge, over the River
Severn in Shropshire,
England England,
1779; this is the first
all-metal architectural
structure.

History
1750 and later
Cast Iron: iron that
has been melted and
poured (cast) into a
mold, to set.
Cast iron is strong in
resisting
compression, forces
that seek to compress
or crush.

The Material Steel
Cast Iron
Cast iron contains 2% –
4% carbon. It is
strong in resisting
compression, but less
strong in resisting
tension. Cast iron is
brittle – it snaps under
extreme stress and is
vulnerable to sudden
failure.

History
1750 and later
Wrought Iron: iron
that has been heated
in a forge and
hammered into shape.
Wrought iron is strong
in resisting tension,
forces that seek to pull
an object apart.

The Material Steel
Wrought Iron
Wrought iron has very
little carbon content. It
is strong in resisting
tension, but weaker in
resisting compression.
It is malleable (easily
shaped) and relatively
soft.

History
1851
Crystal Palace,
London, 1851: the
world’s first building
made from pre-
manufactured
components (cast
iron beams and
columns) and plate
glass panels, built in
Hyde Park to house
the Great Exhibition
of 1851.

History
1851
Eiffel Tower, Paris,
1889: Lattice tower
constructed of
wrought iron
components, built as
the entrance to the
1889 World’s Fair.

History
Late 19th Century
With the development of the
Bessemer Process in 1856,
the production of steel
became relatively
inexpensive, and steel
became increasingly
plentiful.
After the U.S. Civil War,
increased steel-making
capacity set the stage for
the first use of steel in U.S.
buildings.

History
Home Insurance
Company Building,
Chicago, 1885, by
William Le Baron Jenny.
This was the first tall
building supported
entirely by a fire-
protected cast iron and
steel structural frame.
Late 19th Century

History
Steel’s weakness is
extreme heat – steel
building structure must
be entirely enclosed in
fireproof cladding or
similar material.
Late 19th Century

History
20th Century
Steel is a commonly-
used noncombustible
structural material. Steel
is strong in resisting both
compression and tension,
and is suitable for
buildings of all sizes,
from single family
residences to the tallest
skyscrapers.

THE MATERIAL
STEEL

The Material Steel
Carbon Content in Iron Alloys
Greater proportions of carbon
generally increase the hardness and
brittleness of the iron alloy.

The Material Steel
Steel
Contains less than 2%
carbon. It is strong in
both tension and
compression. Steel is
ductile – it bends
under extreme stress
and is not prone to
sudden failure.
(Reliance Building under
construction, Chicago, 1895)

The Material Steel
Mild Steel (Low carbon steel)
This is the most
common alloy for
modern structural steel.
It contains no more than
0.3% carbon.
Small amounts of added
other metals improve
strength, toughness,
and can give it other
qualities.

The Material Steel
Mild Steel (Low carbon steel)
Steel is
reasonably
strong,
highly
ductile, and
easily
welded.

The Material Steel
Making Molten Iron
Iron ore (oxides of iron
extracted from the
ground) is combined with
both coke (carbon derived
from burning coal in the
absence of air) and
limestone in a large blast
furnace.
Hot air forced through the
furnace burns the coke.

The Material Steel
Making Molten Iron
As the furnace burns the
coke, chemical reactions
remove oxygen from the
ore, leaving elemental iron
that is imparted with a
relatively high carbon
content.
The limestone combines
with extracted impurities
and is then drawn off as
waste slag.

The Material Steel
Steelmaking
In a traditional steel mill, iron ore, limestone, and
coke are the raw ingredients.

The Material Steel
Steelmaking
First, the ore is processed into molten iron in a
blast furnace.

The Material Steel
Steelmaking
Then it is converted to steel in a second operation,
known as the basic oxygen process.

The Material Steel
Basic Oxygen Process
Scrap metal and molten iron
are charged into the furnace.
Pure oxygen is injected into the
mixture through a hollow
‘lance’, burning off the carbon
and other impurities.
Large amounts of heat are
generated—no external fuel or
energy source is required.

The Material Steel
Basic Oxygen Process
Impurities combine with the
flux, and float on top of the
molten metal.
The mixture is sampled, and
ingredient quantities are
adjusted as needed.
Molten steel and slag are
separately poured off.
Additional alloying elements
may be added to the steel.

https://www.youtube.com/watch?v=9l7JqonyoKA

The Material Steel
Mini-Mills
In the North America today, most steel is made from
recycled steel scrap in "mini-mills" using electric arc
furnaces. Steel scrap is converted directly to new
steel, bypassing the need to make iron from ore.

The Material Steel
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.
In this process, large
amounts of externally
supplied energy are required.

The Material Steel
Oxygen is injected to burn
off impurities and enhance
heating. Added flux draws
off impurities.
Once the charge is fully
melted, additional scrap may
be added.

The Material Steel
As in the basic oxygen
process, 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.

The Material Steel
Molten steel being tapped
from an electric arc
furnace into a vessel
called a ‘ladle.’
The geared mechanism
under the furnace is for
controlling furnace
tipping.

The Material Steel
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.

The Material Steel
Mini-Mills
Mini-mills are less expensive
to build than traditional steel
mills.
They produce higher-quality
steel at a lower cost and use
less energy.
Recycled content: 90%+
In North America, virtually all
hot-rolled structural steel
shapes are made from
recycled steel in mini-mills.

The Material Steel
Traditional Mills
Recycled content: 25% -
35%
Primary products are flat-
rolled stock, such as steel
decking and other steel sheet
products.

The Material Steel
Casting
In the continuous
casting process,
casting begins
once the outer
shell of the steel
mass has
solidified, while
the inner portion
is still molten.

The Material Steel
Casting
As the molten steel
begins to cool, it is cast
into shapes ranging
from plain rectangles or
rounds to more complex
cross sections, such as
beam blanks (right),
long continuous forms
that approximate the
shape of finished beam
products.

The Material Steel
Rolling Mill
Structural shapes are produced in a rolling
mill. Prior to rolling, the beam blanks are
reheated back to the temperature necessary to
make them malleable.

The Material Steel
Rolling Mill
Reheated beam blanks pass
through a series of rollers and
are progressively deformed into
the desired final shape.

The Material Steel
Structural Shapes
Wide-Flange
(W-Shape): This is the
most commonly used
shape for beams and
columns – it is not an
I-beam.
Channels, angles,
tees: Forms used for
trusses, lighter weight
framing, and creating
other, more-complex
shapes.

The Material Steel
Structural Shapes
American
Standard: The
traditional I-beam.
Its shape is less
structurally-efficient
than a wide-flange
and is rarely used
anymore.

The Material Steel
Shape Designation
W10 x 30
W: Wide-flange shape
10: Nominally 10
inches deep
30: 30 pounds per
lineal foot

The Material Steel
Shape Designation
By varying roller sizes
and spacings, various
weights can be
produced, all nominally
10" in depth:
W10 x 12: 3.96"wide x 9.87"deep
W10 x 30: 5.81"w x 10.5"d
W10 x 39: 7.99"w x 9.92"d
W10 x 112: 10.4"w x 11.4"d

The Material Steel
Shape Designation
The unshaded portions
of the diagrams
illustrate how a variety
of weights of beams
can be rolled from the
same set of rollers by
increasing the space
between the rollers.

The Material Steel
Shape Designation
Size
designations
are nominal, a
very
approximate
indication of
actual depth.
A W14 x 873 is 23.6" deep!

The Material Steel
Wide Flange Shapes
Taller, more narrow
profiles are best for
horizontally-
spanning elements,
such as beams and
girders.

The Material Steel
Wide Flange Shapes
Profiles more square
in shape are better
suited for use as
vertical columns.

The Material Steel
AISC Steel Construction Manual
Left page:
Dimensional
data
Right page:
Shape
properties
related to
structural
stiffness and
strength
calculations.

The Material Steel
Within groups of
shapes, T, the depth
in-between top and
bottom flanges,
does not vary.
These shapes are
rolled from the
same sets of rollers,
with only the
spacing of the pair
of rollers changing.

The Material Steel
Other Shape Designations
S: American
Standard beam
(“I-beam”)
MC:
Miscellaneous
channel
C: American
Standard
channel

The Material Steel
L: Angle
L4x3x3/8: 4"x3"
nominal legs
with 3/8"
thickness

The Material Steel
WT: T-shape cut
from a W-shape
WT13.5x47:
13.5"d x 47lb/ft.
(Produced by
cutting a W27x94
lengthwise in
half.)

The Material Steel
Hollow Structural Sections (HSS)
Hollow square,
rectangular, round,
and elliptical shapes.
Made by cold- or
hot-forming steel
strip (sheet) and
then welding
longitudinally.

The Material Steel
Hollow Structural Sections (HSS)
HSS shapes are used
for trusses,
structurally efficient
column sections, and
where the simple
external profile is
desirable.
Example designation:
HSS 8 x 8 x ½
8"x8"x½" steel thickness

The Material Steel
ASTM A36 Mild Steel
Traditional structural
steel. The yield
strength (the stress, at
which, it permanently
deforms) is 36,000
pounds per square inch
36 ksi (kilopounds per
square inch).
A36 steel is now used
primarily for accessory
steel angles, channels,
etc.

The Material Steel
High-Strength, Low Alloy Steels
ASTM A992: W shapes
ASTM A572: other
shapes
This steel is produced
economically in mini-
mills from scrap steel.
Yield strength is 50 to
65 ksi. ASTM A992 steel columns lay
stacked in a fabricator yard. Note
the holes predrilled for connections
that will be completed in the field.

The Material Steel
High-Strength, Low Alloy Steels
Use of stronger steel alloys permits
savings in weight and reductions in the
size of structural elements, reducing the
overall cost of a building project.

The Material Steel
Weathering Steel
In weathering steel,
surface oxidation (an
extremely thin coating of
rust) adheres to base
metal, inhibiting further
corrosion.
Weathering steel is
mostly used in highway
and bridge structures,
eliminating the need for
any protective coating.
(Often called Cor-Ten steel, a US
Steel trade name.)

The Material Steel
Stainless Steel
Steel with added
nickel and
chromium.
Stainless steel also
forms a thin self-
protecting oxide
layer that provides
long lasting
protection against
corrosion.

The Material Steel
Cold-Formed Steel
Deforming steel in its cold
state causes a realignment of
the steel crystals and
increases its strength.
Corrugated steel decking for
supporting floor and roof
slabs (right)

The Material Steel
Open-Web Steel Joists (OWSJ)
Lightweight pre-
manufactured trusses
are made from both
hot- and cold-formed
components.
Truss depths range
from 8 inches up to 6
feet.

The Material Steel
Open-Web Steel Joists (OWSJ)
Traditionally spaced 2
to 10 feet on center.
Wider spacing is used
for greater economy.
Right: Floor joists are
deeper; roof joists,
which carry less load,
are less deep.

The Material Steel
Large-span Joists
K series: spans up
to 60 feet.
LH series: spans
up to 96 feet.
DLH: spans up to
144 feet (used in
roofs only).
JG: joist girders
(girders are simply
large beams).

JOINING
STEEL
MEMBERS

Joining Steel Members
Riveting
A white-hot fastener is
inserted through aligned
holes in members to be
fastened.
The end of the fastener is
hammered to produce a
second head on the plain
end.

Riveting
As the metal cools, it
contracts, and tightly
clamps the steel
members.
Riveting is mostly
found in historic
structures; it’s rarely
used in modern
construction.

Bolting
Carbon steel bolts
• Relatively low strength
• Limited uses, such as
fastening together light
framing elements or
holding temporary
connections
• Carbon steel bolts are
also called common, or
unfinished bolts

Bolting
High-strength bolts
• Stronger than
common bolts
• Used for fastening
primary structural
members

Bearing-type connection
The body of the bolt resists movement between
connected members by bearing directly against
sides of bolt holes (left illustration).
The bolt is stressed in shear (two opposite
forces, offset from
each other).
The connection will
slip slightly, before
reaching full
strength.

Slip-critical connection
Bolt is tensioned to such an extent that
movement in the joint is resisted by friction
between the adjoining "faying" surfaces of the
members themselves (right illustration).
Bolt is very highly
stressed, but in
tension (force
Pulling at either end
On the bolt).
No slippage.

Slip-critical connection
Slip-critical connections are required where
joints experience load reversals, in highly
stressed joints, or where slippage would be
detrimental (such as column splices in
tall buildings).

Bolt Tensioning Methods
With slip-critical connections,
proper bolt tension must be
assured.
Turn-of-nut method: Nut is
tightened some additional
fraction of a turn after
achieving a snug condition.
Bolts on right tightened 1/3
turn past snug.

Load Indicator Washers: When
bolt is adequately tensioned,
protrusions on the washer are
flattened. Bolt tension is
verified by inserting a gauge
between bolt head and washer.

Some load
indicator
washers squirt
dye when
adequate
tension is
achieved,
making
inspection
easier.

Tension Control Bolt: When bolt is
adequately tightened, the splined
end snaps off. Bolt tension is
verified by visually inspecting for
splines.
(Tension control bolts also allow for
tightening if the contractor can only
access one side of the bolt.)

Welding
Steel surfaces to be
joined are super
heated to a molten
state. Additional
adhering molten metal
is added from the
electrode.
In the finished welded
joint, members are
fully fused.

Welding
Fillet welds: Easy to
make; little joint
preparation is required.
Groove welds: Require
properly shaped and
spaced joints.
Puddle welds: Fasten
metal decking to
structural members.

Welding
Welds critical to
structural stability
may be inspected
and tested
(ultrasonic testing or
magnetic testing) to
ensure their
soundness and
freedom from hidden
flaws.

DETAILS OF
STEEL FRAMING

Details of Steel Framing
Framed Connection
Angles, plates, or tees
connect the web of a beam to
side of column.
Angles are usually joined to
the beam in the fabricator's
shop.
The beam/angle assembly is
then bolted to the column in
the field.

Shear Connections
When a weight is
distributed equally along a
beam (like when it’s
supporting a floor slab),
the beam/column
connection only needs to
be designed to resist shear
forces (two opposite forces
offset from each other) –
the downward weight of
the floor and the upward
support of the column.

Shear Connections
Shear connections transfer
gravity loads from a beam
to columns.

Shear Connections
Shear tabs are
welded to a column
in the shop, then
bolted to beam in
the field.
Beams are cut
short, slightly, to
allow for deviations
in column positions
and to ease
installation.

Moment Connections
When a heavy weight is
concentrated in a single
point on a beam, the
beam/column connection
needs to be designed to
resist a bending moment
(the tendency for the beam
to rotate upward at the
column jointure and break
apart from it.)

Moment Connections
Moment connections transfer
both gravity loads (shear)
and rotating forces (bending
moment) to the column.
Both the beam flanges and
the web are joined to the
column. The column is
reinforced to resist bending
forces imparted from the
beam; the beam is
restrained from even the
smallest of rotations.

Moment Connections
A pair of beam-column
moment connections. Full
penetration welds join the
top and bottom beam
flanges to the column.
Column reinforcing plates
are added to the column
to give it additional
rigidity.

Moment Connections
This connection creates a
continuous beam condition
that can fully transmit
bending forces, allowing
the cantilever on the right.
A shear connection would
not work here.

Stabilizing the Building Frame
The rectangular geometry
of the building frame must
be made stable against
lateral forces (wind and
seismic activity) in a
variety of ways:
• Diagonal bracing
• Moment-resisting frame
• Shear walls

Braced Frame
Diagonal Bracing (top)
creates stable, triangular
geometry in a building
frame.
It can be constructed
utilizing shear connections
between beams and
columns, allowing for a
small amount of rotation
between the two.

Braced Frame
Eccentric Bracing (bottom)
allows the frame to deform
slightly in the gap between
diagonals during extreme
seismic events, absorbing
some of the dynamic energy
of the earthquake.

Moment-Resisting Frame
Some or all of the
beam-column
connections are
moment connections
capable of resisting
rotations between the
members, making the
frame rigid.
Moment-Resisting Frame

Shear Walls
Rigid vertical walls or
core structures resist
lateral forces, while the
remainder of the frame
relies on shear
connections.
Usually the core is made
of concrete, or
occasionally, heavy steel
plate.
Shear Walls

Methods can also
be combined:
Here, we see
inverted ‘vee’
diagonal bracing
along with beam-
to-column
moment
connections.

These are buckling-
resistant braces,
designed to deform
in a controlled
manner during an
earthquake,
absorbing the
seismic energy.

This is the beginning of a heavily reinforced concrete
core that will contain vertical services and act as
stabilizing shear walls. Lateral forces (wind and
seismic activity) are greatest at the base of the
building and diminish toward the top.

More Connections
When connecting a
beam to a column web,
access is more difficult.
A seated connection,
shown here, relies on a
seat angle bolted below
the beam and a similar
stabilizing angle at the
top.

More Connections
Bolted beam web
and welded flanges.
The shear tab here
is deep enough to
position the bolts
clear of the column
flanges for easy
access.

More Connections
The end plate is
welded to the beam in
the shop and then
bolted to the column in
the field.
This connection is
capable of transferring
some, but not all, of
the rotating force
(bending moment) of
the beam.

More Connections
Partial bending
moment
resistance is
achieved,
without
welding, in the
field.

More Connections
This is a framed
beam-girder
connection: the
beams’ top flanges
are coped (cut
away), to allow the
tops of the beams
and the top of the
girder to be flush
with each other.

More Connections
Bolted column or splice. Splices
are typically located at waist
height, to avoid interference
with beam-column connections
at the floor; column splices are
conveniently accessible to
workers standing on the floor
deck.
These bolts are slip-critical
connections.

More Connections
Where outer dimensions
of connected column
sections vary, shims or
filler plates are inserted to
make up the difference.

More Connections
Welded column splice: the bolted
connector plate holds the
columns in alignment prior to
welding. Later, the column
flanges are welded with partial
penetration welds. The hole in
the plate provides an attachment
point for the lifting line during
positioning.

More Connections
Where inner dimensions of spliced
columns differ, a butt plate or
bearing plate is added to the
connection.
The plate is thick enough to
transfer the full bearing loads
from the upper column section
down to the lower one.

THE
CONSTRUCTION
PROCESS

The Construction Process
Steel Framing Plan
The framing plan
shows sizes and
locations of steel
members.

Steel Framing Plan
W30 girder-column
connection: Beam
to column flange.
W27 beam-column
connection: Beam
to column web.
W18 to W30
connection: Coped
beam-girder.

Steel Fabricator
The fabricator
prepares the
various steel
members and
delivers them
to the
construction
site.

Steel Fabricator
Traditionally, the
fabricator prepares
shop drawings
showing the
configuration of each
steel member.
The drawings are
then reviewed by
architect and the
structural engineer.

Steel Fabricator
The fabricator also
shares responsibility
for the design of the
steel connections,
based on more
general requirements
provided by the
structural engineer.

Steel Fabricator
Workers cut to
length, cope, drill,
punch, weld, and
add tabs, angles,
plates, and other
accessories to the
steel members, as
indicated on the
approved shop
drawings.

Steel Fabricator
A welder in the
fabricator’s shop,
welding deep,
full-penetration
groove welds to
join two heavy
A913 steel
column sections
end-to-end.

Steel Fabricator
Fabricated
members are
stacked, using
overhead crane,
and await
transport to the
construction
site.

Steel Fabricator
Steel members are
individually labeled
to correspond to
information on the
erection drawings,
so that each piece
can be assembled
in the proper
location once
delivered to the
construction site.

Steel Fabricator
More recently, using
Building Information
Modeling (BIM) systems,
steel fabrication
information and details
can be developed by the
structural engineer in
the building model, as
an alternative to relying
on fabricator shop
drawings.

The Erector
Assembles steel
members that have
been delivered to the
construction site.
The erector may or
may not be same
entity as fabricator.
Construction workers
are known as
ironworkers.

As the
frame is
erected,
temporary
cables with
turnbuckle
s are used
to plumb
up (make
vertical)
the frame.
The Erector

Steel Decking
Corrugated steel
decking laid over the
framing is the most
common floor and
roof decking
material.
The decking is
puddle welded to the
framing members
below.

Steel Decking
Steel decking comes
in a variety of profiles
and depths, to suit
different load and
span conditions.
Top: Relatively
shallow roof
decking.

Steel Decking
Composite floor
decking. Deformations
in the metal allow a
structural bond to form
between the deck and
the concrete poured
over it, increasing the
strength of the
composite floor
assembly.

Shear Studs
Welded to the tops of
beams, shear studs
penetrate through the
metal decking. Once
the concrete is
poured, the beams,
decking, and concrete
cohesively act
together as a form of
composite
construction.

Concrete Fill
Concrete is placed
over the metal
decking to complete
the structural floor
or roof deck.
A grid of welded
wire reinforcing
within the concrete
increases resistance
to cracking.

Other Decking Materials
Precast concrete
planks can be
placed over steel
structural
members (right).
Other
lightweight
board or plank
materials may
be used for roof
decks.

FIRE PROTECTION
OF STEEL
FRAMING

Fire Protection
Fireproofing
Above roughly
500 - 600
degrees
Fahrenheit, steel
rapidly looses
strength.
Fireproofing acts
as insulation,
protecting steel
from the heat of
fire.

Fire Protection
Fireproofing
• Concrete
• Plaster
• Gypsum Board
• Spray-applied
insulation
• Loose insulation
within column
cover

Fire Protection
Fireproofing
US Steel corporate
headquarters
building, in
Pittsburgh, used
water-filled
columns as
fireproofing!

Fire Protection
Fireproofing
Not shown:
• Insulation blankets
• Intumescent
Coatings: thin,
coatings that
expand to create a
thick insulating
layer when
exposed to the
heat of fire.

Fire Protection
Spray-Applied Fire-Resistive
Material (SFRM)
Spray-applied
material is a
common
means of
fireproofing
steel
structural
components.

Fire Protection
Material (SFRM)
Spray-
applied
fireproofing
being applied
to framing in
a steel high-
rise
structure.

Fire Protection
Material (SFRM)
Diagonal bracing,
which resists
wind loads and
earthquake (but
not gravity
loads) is, in fact,
not required to
be fire-protected.

Chapter 11 Steel Frame Construction

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Chapter 11 Steel Frame Construction