The document outlines various aspects of structural steel construction, including common steel shapes, framing systems, types of steel columns, and connections. It details the construction methods for skeletal frames, the types of metal decking, and the various truss types used in building design. Additionally, it highlights the importance of framing systems and the integration of different components for structural stability and efficiency.

1. BUILDING
CONSTRUCTION
III
UNIT III
STRUCTURAL STEEL
CONSTRUCTION
AR.PRADHYUMNA.U

2. STRUCTURAL STEEL CONSTRUCTION
STRUCTURAL STEEL SHAPES
The most common shapes of structural steel used in buildings are the American Standard
Steel Shapes such as:
1. Square Bars
2.
3. Round Bars
4. Plate Bars
5. Angle Bars
6. Channels – The standard channel has the shape of unsymmetrical balance consisting of
two flanges on one side. It requires lateral support to prevent its tendency to buckle.
Channels are generally used as parts of built-up sections for columns and are also
suitable for framing around floor openings, spandrels and lintels attributed to the absence
of flanges on the other side. The channel section is identified as C 15 x 20 which means
that the channel has a depth of 20 cm and weights 15 kg per meter length.
7. I-Beams – The use of a standard I-beam as a column is uneconomical because the whirl
or revolving action of the member about an axis through the centroid of the web is
comparatively small.

3. 7. Tee Beams
8. H-Columns
9. Wide Flanges – Wide Flange sections are designated as W 12 x 24 which mean that the
flange has a depth of 24 cm and weighs 12 kg per meter length. All wide flange sections are
generally with parallel face flange except those with 5% slope inside face produced by
Bethlehem Steel Company. Comparatively, wide flange sections are more efficient than
standard I-beams with respect to bending resistance.
10. Zees – The zee section is another structural form in a letter Z which is not frequently used in
building construction except for the fabrication of steel windows and other frames.

4. STRUCTURAL STEEL FRAMING
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.
The three major types of framing systems are the following:
One-Way Beam System – each pair of
external columns supports a long-spanning
beam or girders. This form of construction is
suitable for long, narrow buildings, especially
when a column-free space is desired. The
absence of columns in the interior is an
advantage in structures such as car parks, as
freedom from obstruction makes for greater
and safer maneuverability, besides allowing
the layout of the parking spaces to be altered
at any time.

8. Two-Way Beam System –
a two-layer system, where beams frame into girders, increases floor depth considerably and
provides more space for mechanical systems. Steel girders span the short axis of a building bay
thus contributing to the lateral stability of the structure.

9. Three-Way Beam System – is used when a large column-free space is required, where
long-spanning plate girders or trusses can be used to carry the primary beam, which
in turn support a layer of secondary beams.

11. STEEL COLUMNS AND CONNECTIONS
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.

12. 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.
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.

13. 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.
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.

14. In the design of steel columns the following should be taken into consideration: No part of a steel
column should be less than 1/4” thick. No material whether in a body of the column or used as a
lattice bar or stay plate, shall be of less thickness than 1/32 of its unsupported width, measured
between centers of rivets transversely, or 1/6 of the distance between center of rivets in the
direction of stress. Tie-plates are to have not less than 4 rivets and are to be spaced so that the
ratio of length to the least radius of gyration of the parts connected does not exceed 40, the
distance between nearest rivets of two stay plates in this case being considered as length. In
built-up columns the thickness of any outstanding member (for example, the outstanding legs of
angles) shall not be less than 1/12 of the width of the outstanding portion.
Base plates for steel column are usually made of steel plates and shapes. Cast-iron bases are
sometimes used for very heavy columns. Ribbed cases may also be used instead of plates and
when bolted to the columns, add greatly to the stability of the supporting members because of
their greater width.

15. 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.
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.

16. STEEL COLUMN CONNECTIONS

17. STEEL BEAMS AND CONNECTIONS
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. The horizontal portion is the web. Channels are sections of this shape: They vary
in depth from 3” to 15”, and in weight from 4.1lb. per ft. to 55lb. per ft.

18. 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.

19. 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.
STEEL BEAM
CONNECTIONS
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.

20. 2. 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.
3. Semi Rigid Connections – AISC Type 3 – Semi-Rigid Frame connections assume beam
and girder connections possess a limited but known moment resisting capacity.

21. 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.

22. 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:

23. Form Decking – serves as a
permanent formwork for a reinforced
concrete slab until the slab can
support itself and its live load.
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.
Cellular Decking – is
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.

24. STEEL TRUSSES AND RIGID FRAMES
ROOF 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.
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, design 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.

25. 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.

27. 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 in 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.

28. B. RELATIVE TO FORM
1. Triangular
2. Quadrangular
3. Crescent
4. Scissors
5. Arched

29. 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

30. D. RELATIVE TO ARRANGEMENT OF THE WEB-BRACING SYSTEM
1. Fink 5. Hammer-beam
2. Howe 6. Sawtooth
3. Pratt 7. Warren
4. Scissors 8. Pettit
FINK
HOWE
PRATT
SCISSORS
SAWTOOTH
WARREN
PETTIT

32. 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.

33. STRUCTURAL STEEL FRAMING SYSTEMS
ARRANGEMENT OF VERTICAL COMPONENTS

35. 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.

36. 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.

37. 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.

38. 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.

39. 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.

40. JOINING OF STEEL MEMBERS
Steel shapes can be joined in the building frame using any of the
following fastening methods:
RIVETING
A rivet is a short pin, of malleable metal such as iron, steel, or copper, with a head at one end; used
to unite two metal plates by passing it through a hole in both plates and then hammering down the
point to for a second head.
In structural riveting, a hot steel rivet with a formed head is inserted in holes through two members to
be joined; its head is then held with a hand hammer with a cup shaped depression, while a
pneumatic hammer drives a rivet set repeatedly against the other end to form a second head.
The rivet shrinks as it cools, drawing members tightly together.
Rivet set, rivet snap, settoing punch, snap – a tool for shaping the head of a rivet.

41. The types of rivet heads are:
• Countersunk, raised
• Countersunk, flat
• Button, coned neck
• Button, straight neck
• Pan, coned neck
• Pan, straight neck
The bolts commonly used in steel frame
construction falls into two general categories:
Carbon-steel bolts – or common bolts; are
similar to the ordinary machine bolts. Carbon
steel is steel having no specified minimum
content of alloying elements; minimum copper
content not exceeding 0.40%.
High-strength bolts – are bolts made of either
high-strength carbon steel or quenched and
tempered alloy steel; tempered meaning, heat
treated during manufacture to develop the
necessary strength. It is usually tightened
using pneumatic or electric impact wrench.
BOLTING

42. A major problem in high strength bolting or friction type connections is how
to verify the necessary tension has been achieved in all the bolts in a
connection.
There are several ways to achieve proper tightening:
Turn-of-nut method
Load indicator washer
Tension control bolts

43. 4.9.3 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.
A. 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.

44. 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.

46. C. 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.

48. D. 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.
E. 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.

49. STANDARD WELDING SYMBOLS

50. WELDING SYMBOLS – Examples of use

51. END