1_building_const_4.ppt

BUILDING
CONSTRUCTION
IV
STRUCTURAL STEEL
CONSTRUCTION

4. STRUCTURAL STEEL CONSTRUCTION
4.1 STRUCTURAL STEEL FLOOR FRAMING
SYSTEMS
Structural steel girders, beams, and columns are used to construct
a skeleton frame for structures ranging in size from one-story to
skyscrapers. Because structural steel is difficult to work with on
site, it is normally cut, shaped, and drilled in a fabrication shop
according to design specifications; this can result in relatively fast,
precise construction of a structural frame. Structural steel may be
left exposed in unprotected non-combustible construction, but
because steel can lose strength rapidly in a fire, fire-rated
assemblies or coatings are required to qualify as fire-resistive
construction.
4.0
4.1
Structural Steel
Construction
Structural Steel Floor
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Open-Web Steel Joists
Metal Decking
Steel Trusses & Rigid
Frames
Structural Steel Framing
Systems
Steel Welding

4.1.1 ONE-WAY BEAM SYSTEM
4.0
4.1
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.1.2 TWO-WAY BEAM SYSTEM
4.0
4.1
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.0
4.1
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.1.3 THREE-WAY BEAM SYSTEM
4.0
4.1
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.2 STEEL COLUMNS &
CONNECTIONS
4.2.1 TYPES OF STEEL
COLUMNS
Steel columns are of the
following types:
a. Struts of one or two angles.
These are used for
compression members in roof
trusses, light towers, and lattice
girders. The two angles of a
double struts are riveted
together by rivets driven
through washers placed
between the two angles at
intervals of 4 to 6 ft.
b. Starred angles of two or four
connected by batten plate
spaced at intervals of 3 to 4ft.
These are used to support the
light loads.
c. Latticed
Columns made
up of channels
or angles
connected by
lattice bars are
often used
where light loads
are to be
supported on
long columns.
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

d. Rolled H-columns. These
are obtainable with depths
ranging from 6” to 16” and are
now commonly used instead
of built-up columns in steel
skeleton construction.
e. Built-up Columns. These
are usually of H-shaped
section formed by a
combination of plates and
angles although box columns
with two or more webs are not
uncommonly used in heavy
building frames.
f. Top Chord sections of heavy
trusses are usually
unsymmetrical and are made
of two rolled or built-up
channel sections and a cover
plate. The open (bottom) side
of the section is latticed.
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

g. Columns for bents are
sometimes made up of a pair of
channels and an I – beam with
batten plates at intervals of 3 to
4 ft. connecting the flanges of
the channels. Columns made of
four angles and a web-plate are
commonly used in mill building
bents.
h. Battened columns are those
in which two component parts of
the column are connected only
by batten plates. They are
decidedly inferior to latticed
columns and should be avoided
if a continuous plate or latticing
can be used instead.
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.2.2 LALLY COLUMNS
These are columns made up of a
cylindrical steel pipe shell filled
with 1:1-1/2:3 Portland cement
concrete. The standard type of
lally column is reinforced with
only the steel pipe shell. Special
types of columns are obtainable
with additional reinforcement
consisting of steel pipe,
reinforcing bars or structural steel
shapes. The light weight column
is 4” in outside diameter with a
shell thickness of 0.134”, while
the heavy-weight columns are
from 3-1/2 to 12-3/4 inches in
outside diameter with shell
thicknesses of 0.216 to 0.375
inches.
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.2.3 COMPOSITE COLUMNS
These are columns in which a concrete core is further reinforced with
a steel or cast-iron core designed to support a part of the load. Steel
cores may be structural H-sections or four angles, latticed or battened;
cast-iron cores are usually either solid shafts or hollow pipe sections.
The column may be further reinforced by vertical rods or bars placed
at the circumference and enclosed by spirals.
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.2.4 STEEL COLUMN CONNECTIONS
1. Column Bases
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

2. Column Splices
4.0
4.2
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.3 STEEL BEAMS &
CONNECTIONS
4.3.1 TYPES OF STEEL
BEAMS
Steel beams may be rolled in
the shape of the letter I (I-
beams), channel beams or
angles. Beams of T shape were
formerly used but have now
been restricted to minor uses.
The I-beam is the ideal type of
steel beam.
4.0
4.3
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

Girders may be built up of angles
and plates riveted together for
long spans and for unusual cases
of very heavy loading. Those are
of two types:
a. Plate Girders. A plate girder is a
beam composed of a wide plate,
known as a web, at the top and
bottom of which are riveted angles
and plates. The simplest type of
plate girder consists of a web and
four flange angles. If this does not
give sufficient flange area, cover
plates may be added. The web
may be frequently reinforced
against buckling by angles riveted
to its sides, known as stiffener
angles.
b. Box Girders. This is a built up
beam in which more than one web
plate is used.
4.0
4.3
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

Beams and girders may be
connected to columns by either
seated connections or framed
connections.
In a seated connection the
bottom flange of the beam rests
on and is field-riveted to an
angle shop-riveted to the flange
or web of the column. Another
angle is field-riveted to the
column and to the top flange of
the beam.
In a framed connection the web
of the beam or girder is
connected by angles or by
gusset-plates to the column. In
framed connections, angle seats
are usually shop-riveted to the
columns to hold the beam or
girder during erection.
4.0
4.3
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.3.2 STEEL BEAM CONNECTIONS
A.MOMENT CONNECTIONS
AISC Type 1 – also called Rigid Frame connections are able to hold
their original angle under loading by developing a specified resisting
moment, usually by means of plates welded or bolted to the beam
flanges and the supporting column.
4.0
4.3
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

B. SHEAR CONNECTIONS
AISC Type 2 – Simple Frame connections are made to resist only shear
and are free to rotate under gravity loads. Shear walls or diagonal
bracing is required for lateral stability of the structure.
4.0
4.3
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

C. SEMI-RIGID CONNECTIONS
AISC Type 3 – Semi-Rigid Frame connections assume beam and girder
connections possess a limited but known moment resisting capacity.
4.0
4.3
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.4 OPEN-WEB STEEL JOISTS
Open web joists are lightweight, shop fabricated steel members
having a trussed web. A K series joist has a web consisting of a single
bent bar, running in a zigzag pattern between the upper and lower
chords. The LH and DLH series joists have heavier web and chord
members and are for increased loads and spans.
4.0
4.4
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.5 METAL DECKING
Metal decking are corrugated steel panels used as a working platform
during construction and eventually as formwork for sitecast concrete
slab. The decking panels are secured with puddle-welds or shear
welded through the decking to the supporting steel joists or beams.
The panels are fastened to each other along their sides with screws,
weld, or button punching standing seams. If the deck is to serve as a
structural diaphragm and transfer lateral loads to shear walls, its
entire perimeter is welded to steel supports. In addition, more
stringent requirements to support and side lap fastening may apply.
There are three major types of metal decking:
4.0
4.5
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.5.1 FORM DECKING
serves as a permanent formwork for a reinforced concrete slab until the
slab can support itself and its live load.
4.0
4.5
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.5.2 COMPOSITE DECKING
serves as a tensile reinforcement for the concrete slab to which it is
bonded with embossed rib pattern. Composite action between the
concrete slab and the floor beams or joists can be achieved by welding
shear studs through the decking to the supporting beam below.
4.0
4.5
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.5.3 CELLULAR DECKING
manufactured by welding a corrugated sheet to a flat steel sheet,
forming a series of spaces or raceways for electrical and
communications wiring; special cutouts are available for floor outlets.
The decking may serve as an acoustic ceiling when the perforated cells
are filled with glass fiber.
4.0
4.5
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.6 STEEL TRUSSES & RIGID FRAMES
4.6.1 ROOF TRUSSES
TRUSSES. A truss is a structural framework composed of a series of
straight members so arranged and fastened together that external loads
applied to it will cause only direct stress in the members. The upper and
lower members of a truss are called the top chord and bottom chord
respectively. The members of the truss which are framed between and
join the top and bottom members are called web members.
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

When the external loads act downward and the truss is supported at
the ends, the top chord is always in compression and the lower chord
always in tension, similar to the upper and lower flanges of a beam.
The web-members are subjected to stresses of either tension or
compression. Web-members subjected to tensile stresses are called
tension web-members; those which are subjected to compression are
called compression web-members. In certain positions, a web-member
may be subjected to tension through the action of a load applied at
one point, and when applied at another point that load may produce
compression in the member so that at one time it will be subjected to
tension and at another time to compression. Such a member,
designed to resist either tension or compression, is called a
counterbrace. A member of a truss system which acts only for a
particular partial loading, and which has a zero stress when the truss
is completely loaded is called a counter.
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

When a truss is supported at its ends by columns, the truss together
with its columns, considered as a unit, is called a bent.
The intersection between two or more members of the truss is called
a joint or panel joint and the distance between two adjacent joints
along either the top or bottom chords is known as the panel or panel
length. The quadrangular space, crossed by an inclined web-member,
is also referred to as a panel. The axes of all members at each joint
should always meet in a common point.
The span of a roof truss is the distance between the centers of the
supports and its rise is the distance between the apex of the truss and
the line joining the points of support. The pitch of a roof truss is the
ratio of the rise to the span for a truss symmetrical about its center
line. The slope of an inclined member is the tangent of the angle of
inclination with the horizontal, usually specified in inches rise per 12”
run.
The portion of the roof between two adjacent trusses is called a bay.
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.6.2 TYPES OF TRUSSES
A. RELATIVE TO THE NUMBER AND ARRANGEMENT OF THE
MEMBERS COMPOSING THE TRUSS
1. Complete Frame. A complete structural frame, or truss, is one
which is made up of the minimum number of members required to
provide a complete system of triangles fixing the relative positions of
a given number of panel joints. If the number of panel points in the
given structure and n = the number of necessary members.
n = 2p – 3
2. Incomplete Frame. One in which the number of members is less
than that required by the equation given above.
3. Redundant Frame. A redundant frame is one which contains more
members than that required by the equation given above.
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

B. RELATIVE TO FORM
1. Triangular
2. Quadrangular
3. Crescent
4. Scissors
5. Arched
DOUBLE HOWE
WARREN
BOWSTRING
SCISSORS
CAMBERED
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

C. RELATIVE TO METHOD OF SUPPORT
1. Simple Truss. A truss supported at each end-point.
2. Overhanging end span. A truss supported at one end-joint and other
joint not an end-joint.
3. Cantilever span. A truss where the entire support is at one end only.
Panel Length
Truss Plate
Peak
Top Chord
Heel
Overhang Bottom Chord Length
Cantilever
Span (Out to Out of Bearings)
Web
Bottom Chord
Bearing Point Panel Point
Splice
Wedge Block
Continuous Lateral Brace
Slope
Pitch
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

D. RELATIVE TO ARRANGEMENT OF THE WEB-BRACING
SYSTEM
FINK
HOWE
PRATT
SCISSORS
SAWTOOTH
WARREN
PETTIT
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.6.3 RIGID FRAMES
Rigid frames consist of two columns and a beam or girder that are
rigidly connected at their joints. Applied loads produce axial, bending
and shear forces in all members of the frame since the rigid joints
restrain the ends of the members from rotating freely. In addition,
vertical loads cause a rigid frame to develop horizontal thrusts at its
base. A rigid frame is statically indeterminate and rigid only in its plane.
4.0
4.6
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.7 STRUCTURAL STEEL FRAMING SYSTEMS
4.7.1 ARRANGEMENT OF VERTICAL COMPONENTS
4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.7.2 STRENGTHENING THE FRAMING SYSTEM
The framing system can be stiffened against horizontal forces in the
following three (3) methods:
1. The structure is composed of rigid frames which may comprise
some hinged joints but there must be sufficient rigid joints to ensure
that none of the nodes of the frame is free to move sideways. The
members may be straight or curved and a variety of shapes may be
chosen for such framed structure.
4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

2. A bracing system which consists of a triangulated framework of
rolled sections will hold the joints together and further strengthen the
framework against lateral loads. The center lines of members
converging at a joint should intersect at one point. The joints
themselves are conventionally assumed to be hinged, so that the
members are either ties or struts, loaded purely in tension or
compression, respectively. However, the overall bracing effect of a
lattice system can be enhances by constructing it with tiff members
and rigid joints.
4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

3. Finally, shear walls in the form of more or less solid diaphragms,
usually of reinforced concrete, transmit the wind and earthquake
forces by shear and bending.
4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.7.3 The Ultimate Structures for Skyscrapers – THE TUBULAR
FRAME
The high-rise building conceived as a rigid tube ---
If a high-rise building is of suitably compact shape on plan (circular,
square, not too narrow a rectangle), the external columns can be
structurally merged with the external lattice bracing or with spandrel
girders so as to form a vast rigid tube. This stiffening system is
particularly effective and economical. This is due not only to the
optimum distribution of the bracing, but also more particularly to the co-
operation of all the columns and bracing or spandrel girders in the
external walls.
4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

The John Hancock Center, Chicago (architects:
Graham and Skidmore, Owings and Merrill)
employs the tube in its framing system. In this 335
m high 100-story building, all the horizontal forces
are transmitted through external bracing, whereby
a substantial saving has been achieved in
comparison with a bracing system located in the
interior. The external lattice members form a
distinctive architectural feature.
4.0
4.7
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.8 STEEL WELDING
Welding has become fully accepted as a means of joining steel
structural members in buildings because it has the inherent advantage
of fusing the metals to be joined, thereby simplifying connections and
fabricating operations.
4.8.1 DEFINITION OF FUSION WELDING (ELECTRIC ARC
WELDING)
The fusion welding process employs an electric arc, wherein energy in
the form of heat is supplied by establishing an arc between the base or
parent metal (the parts to be joined) and a metal electrode. As the arc is
formed, tremendous heat is concentrated at the point of welding.
Instantly, the materials are at melting-point temperature. The parent
metal melts in a small pool and additional metal supplied by the
electrode is transferred through the arc an deposited in the pool. As the
electrode continues along the joint, the molten metal left behind
solidifies to form the weld.
4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.8.2 COATED ELECTRODES
Most welding is done with coated electrodes. The function of the
coating is to form a gaseous shield, which protects the arc and
molten metal from contact with the air. Oxides and nitrides resulting
from contact with the air tend to produce brittle welds. The coating
also forms a slag-fuse shield, which floats above the molten metal,
protecting it from the atmosphere. The slag is easily removed after
the weld has cooled.
The size and strength of weld is determined by the length of its leg.
For an E60 electrode on A36 steel, the allowable stress may be
computed on the basis of 800 pounds per linear inch per 1/16 inch
of leg size.
For A36 steel or higher-strength steels up to Fy = 60 ksi, an E70
electrode should be used and the the allowable stress may be
computed on the basis of 930 pounds per linear inch per 1/16 inch
of leg size.
4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.8.3 TYPES OF WELD
FILLET WELD – is of approximately
triangular section joining two
surfaces approximately at right
angles to each other. The fillet weld
is the most common type of weld
used in structural work.
GROOVE WELD – is made by
depositing filler material in a groove
between two members to be joined.
The standard types of grooves are
square, V, bevel-U, and J. With
the exception of the square groove,
all grooves may be either single or
double.
PLUG or SLOT WELD – is made of a
circular hole (plug) or an elongated
hole (slot) in one member of a lap
joint, joining that member to the
portion of the surface of the other
member that is exposed through the
hole.
4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

4.8.4 WELD POSITIONS
There are four positions in welding. In order of economy, they are the
flat, horizontal, vertical, and overhead positions. Overhead welds, which
is the most difficult, should be avoided whenever possible.
4.8.5 WELD JOINTS
The three most common joints used in structural work are the butt, T,
and lap joints. Other types are the edge and corner joints. Fillet
welds are applicable to T, lap, and corner joints; groove welds are
applicable to all joints with the exception of lap joints.
4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

STANDARD WELDING SYMBOLS
4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

WELDING SYMBOLS – Examples of use
4.0
4.8
Structural Steel
Construction
Framing Systems
Steel Columns &
Connections
Steel Beams &
Connections
Metal Decking
Frames
Systems
Steel Welding

1_building_const_4.ppt

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