Chapter11_2x

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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

D
ETAILS OF
S
TEEL
F
RAMING

11 S
TEEL
F
RAME
C
ONSTRUCTION

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Example Beam
-
To
-
Column
Connection: Framed
Shear Connection


Framed Connection:
Angles, plates, or tees
connect web of beam to
side of column (right)


Angles are bolted to beam
in the fabricator's shop.


Beam/angle assembly is
bolted to the column in
the field.

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ETAILS OF
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


Shear Connection:

Transfers
gravity loads from beam to
columns. But the connection
is not sufficiently rigid to
transfer bending forces
between the two members.


In an engineering analysis, this
connection is modeled as if it
is free to rotate. In fact, the
connection is sufficiently
flexible to allow small rotations
between the beam and column
such that bending forces in the
beam do not impart bending
forces into the column.


Also called an
AISC Simple
Connection.

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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


This pair of lightweight
beam
-
column shear
connections rely on
shear
tabs

welded to the column
in the fabricator's shop
and bolted to the beam
webs in the field.


The beams are purposely
cut slightly short to make
it easier to swing them
into position between the
columns and to allow for
minor deviations in
column locations.

D
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S
TEEL
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Example Beam
-
To
-
Column:
Moment Connection


Web of beam is connected to
column with bolted angles.


Top and bottom flanges of
beam are field
-
welded to
column with full penetration
welds.


Column is reinforced with
plates to carry bending forces
from beam flanges into
column.


This connection transfers
gravity loads
and

bending
forces between the members.


Beam is restrained from even
small rotations, termed
AISC
Fully Restrained.

D
ETAILS OF
S
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


The "dog bone" cut in the
beam creates a zone of
weakness away from the
connection itself.


Under extreme stress during a
seismic event, this weakened
area of the beam will deform
plastically, protecting the
welded joint, which is more
brittle, from failure.


Lower photograph:

A similar
connection just erected. A
single bolt holds the beam
temporarily in place. The top
and bottom flanges will be
welded to the column. In lieu
of bolted angles as above, the
beam web is connected with a
welded shear tab.

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ETAILS OF
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RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


A pair of beam
-
column
moment connections.
Note the full penetration
welds at the top and
bottom flanges, and the
reinforcing plates in the
column.

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ETAILS OF
S
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F
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


Second view of the
connection in the
previous slide.


This connection results in
a continuous beam
condition that can fully
transmit bending forces
through the column,
allowing the beam to
cantilever on the right.
(The posts at the corner
are temporary supports.)

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Stabilizing the Building
Frame


The rectangular geometry
of the building frame
must be made stable
against lateral forces by
one of three methods:

-
diagonal bracing

-
moment
-
resisting frame

-
and shear walls

D
ETAILS OF
S
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F
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Stabilizing the Building
Frame:
Diagonal Bracing


Diagonal bracing creates
stable, triangular geometry
within the frame.


A diagonally braced
frame can be constructed
with shear connections
that are free to rotate.


Eccentric bracing,

a
variation on diagonal
bracing, allows a plastic
hinge condition to
develop during extreme
seismic events, absorbing
the dynamic energy of the
earthquake.

D
ETAILS OF
S
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F
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Stabilizing the Building
Frame:
Moment
-
Resisting
Frame


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

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Moment
-
Resisting Frame

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Stabilizing the Building
Frame:
Shear Walls


Shear walls,
most often

made of concrete, can
stabilize a structural frame
constructed with shear
connections that are free to
rotate.


Shear walls in tall buildings
sometimes also incorporate
heavy steel plate.


The different stabilizing
methods are frequently
used in combination in a
single structure.


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Shear Walls

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Stabilizing the Building Frame


Inverted vee diagonal
bracing in a steel building
frame.


These
buckling
-
resistant
braces

are specially
designed to deform
plastically in a controlled
manner during an extreme
seismic event and protect
the building from the
energy of the earthquake.


The beam
-
to
-
column
connections are also
moment connections.

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Stabilizing the Building Frame


The beginnings of a concrete core tower that will contain vertical building
services and that will also act as shear walls, stabilizing the building frame.


Note the large quantities of steel reinforcing. Stresses from lateral forces are
greatest at the base of the stabilizing system and decrease toward the top.


To judge scale, note the broom and shovel leaning at the base of the right
wall.

D
ETAILS OF
S
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F
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

More Beam Connections


When connecting a beam to
the column web, access to the
connection is more
constrained than when
connecting to column flanges.


Top:
A
seated connection
relies on a
seat angle
below the
beam and stabilizing angle at
top. The angle connections are
not stiff enough to transfer
bending forces, and this is a
shear connection.


Bottom:
Moment connection
with bolted web and welded
flanges. The shear tab is deep
enough to position the bolts
clear of the column flanges for
easy access.

D
ETAILS OF
S
TEEL
F
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

More Beam Connections


An
end plate connection
.
The plate is welded to the
beam in the shop and
bolted to the column in the
field.


This connection is
sufficiently rigid to transfer
some (but not all) bending
forces between the beam
and column and is termed
semi
-
rigid

or
AISC Partially
-
Restrained.

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

More Beam Connections


Framed beam
-
girder
connection


Note the
coping
of the
upper flanges of the beams
so that the tops of the
beams can be made level
with the top of the girder.

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Column Connections


Left:
A bolted column
-
column connection, or
splice
. Column connections
are frequently located at
roughly waist height, to
avoid interference with
beam
-
column connections
and so that connections are
conveniently accessible to
workers standing on the
floor deck.


Right:
Where outer
dimensions of connected
column sections vary,
shim
or
filler plates

are inserted
in the connection to make
up the difference.

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


A bolted column splice with
plates shop
-
welded to the
ends of both column
sections

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

More Column Connections


Left:

A 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
erection.


Right:
A
butt plate
or
bearing
plate
is inserted in the
connection where inside
dimensions of the column
sections differ. The plate is
thick enough to transfer the
loads from the upper column
section to the lower one.

D
ETAILS OF
S
TEEL
F
RAMING

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


The beam
-
column
connection is a shear
connection relying on a
shear tab welded to the
column in the fabricator's
shop and bolted to the
beam web in the field.


The HSS column splice
relies on a lightweight plate,
shop
-
welded to the lower
column section and field
-
welded to the upper section.


Just to the right of the
column is a welded OWSJ
-
beam connection with a
light reinforcing plate
underneath the beam
flange.

D
ETAILS OF
S
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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

T
HE
C
ONSTRUCTION
P
ROCESS

11 S
TEEL
F
RAME
C
ONSTRUCTION

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Steel Framing Plan


Shows sizes and locations of
structural steel members
(dimensions have been
omitted from the plan at
right)


The W30 girder
-
column
connection is a beam to
column flange connection.


The W27 beam
-
column
connection is beam to
column web connection.


The W18 to W30
connection is a coped
beam
-
girder connection.

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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

The Fabricator


The steel
fabricator
is
responsible for
providing each
needed piece of
structural steel to
the construction
site.


Traditionally, the
fabricator
prepares
shop
drawings
showing
the dimensions of
each piece of steel
required for the
job.

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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


The shop drawings
are reviewed by the
architect and
structural engineer
before the
fabricator begins
work.


The fabricator
frequently is also
responsible for
determining the
details of the steel
connections
themselves, based
on more general
connection load
requirements
provided by the
structural engineer.

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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

The Fabricator


More recently, with
building
information modeling (BIM)

systems, steel fabrication
information and details may
be developed by the
structural engineer in the
building model as an
alternative to relying on
fabricator shop drawings.


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Fundamentals of Building Construction, Materials & Methods, 5
th

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Copyright © 2009 J. Iano. All rights reserved.

The Fabricator


In the fabricator's shop,
each piece of steel is cut to
length, coped, drilled,
punched, welded, shaped
and provided with tabs,
angles, plates and other
accessories as indicated on
the shop drawings.


Fabrication operations are
performed by a
combination of automated
equipment and skilled
workers.


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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

The Fabricator


Fabricated steel members
are stacked in the
fabricator's yard using an
overhead crane, awaiting
transportation to the
construction site.


Note the identifying labels
on each piece of steel.



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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

The 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.

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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

The Erector


The
erector
is
responsible for erection
of steel once delivered
to the construction site.


The erector may or may
not be the same entity as
the fabricator.


The erector's workers
are called
ironworkers
.

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th

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Copyright © 2009 J. Iano. All rights reserved.

The Erector


As the frame is erected, temporary cables with turnbuckles are used to
plumb up
(make vertical) the frame.

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th

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Copyright © 2009 J. Iano. All rights reserved.

Floor and Roof Decking


Corrugated steel decking
laid over the steel
framing is the most
common floor and roof
decking material.


The decking is puddle
welded to the framing
members below.

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Fundamentals of Building Construction, Materials & Methods, 5
th

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Copyright © 2009 J. Iano. All rights reserved.

Floor and Roof Decking


Steel decking comes in a
variety of profiles and depths
to suit different load and
span conditions.


Top:

Relatively shallow
roof
decking
.


S
econd from bottom:

Composite floor decking
with deformations that allow
a structural bond to develop
between the metal deck and
the concrete poured over it,
to increase the strength of
the deck/concrete floor
assembly.

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th

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Copyright © 2009 J. Iano. All rights reserved.

Floor and Roof Decking


Shear studs

may be
welded to tops of beams,
projecting through the
metal decking. Once
concrete is poured, the
beams and concrete act
together structurally as
another form of
composite construction.

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th

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Floor and Roof Decking


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 the
floor's resistance to
cracking.

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th

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Copyright © 2009 J. Iano. All rights reserved.

Floor and Roof Decking


Other materials, such as
the precast concrete
hollow core planks shown
here, can also be used to
create the floor and roof
decks.

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Copyright © 2009 J. Iano. All rights reserved.

F
IREPROOFING
OF
S
TEEL
F
RAMING

11 S
TEEL
F
RAME
C
ONSTRUCTION

Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.

Steel Strength and
Temperature


Above roughly 500 or 600
degrees F, steel rapidly
looses strength.


Fireproofing

acts as
insulation, protecting steel
from the heat of fire and
the survival of the
building structure.

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th

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Copyright © 2009 J. Iano. All rights reserved.

Fireproofing materials


Concrete


Plaster


Gypsum wallboard


Spray
-
applied insulation


Loose insulation within
sheet metal column cover


Water
-
filled columns
(e.g., U.S. Steel Building,
Pittsburgh)


Not shown:


Insulation blankets


Intumescent Coatings:
Thin, paint
-
like coatings
that expand to create a
thicker, insulating layer
when exposed to the heat
of fire

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th

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Copyright © 2009 J. Iano. All rights reserved.

Spray
-
Applied Fire
-
Resistive
Material (SFRM)


The most common
fireproofing


The level of protection
required for various parts
of the structure is
determined by the
building code and relates
to the size of the building
and its occupancies.


To achieve an equal level
of protection, lighter steel
members require more
insulation than heavier
members, since lighter
member heat up more
quickly.


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Fundamentals of Building Construction, Materials & Methods, 5
th

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Copyright © 2009 J. Iano. All rights reserved.

Spray
-
Applied Fire
-
Resistive Material (SFRM)


Spray
-
applied fireproofing has been applied to the first two levels of
framing in this steel high rise structure.


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Fundamentals of Building Construction, Materials & Methods, 5
th

Edition

Copyright © 2009 J. Iano. All rights reserved.


Cross
-
bracing, which
resists wind and
earthquake

but not
gravity

loads, is not
normally required to
be fire
-
protected.

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