Structural Steel

Assemblies &
Connections
Built-up Sections
When rolled steel sections are inadequate to meet load and
span requirements, built-up sections are used.
These are made up of standard rolled shapes and combined
so that they are designed to act as a single structural unit in
resisting stresses.
These are members made up by a fabricator from two or
more standard sections.
Examples of common built-up sections are shown here, consisting
of sections for columns, beams, and girders, using combined
assemblies of plate and angular sections acting as flange and web
as well as stiffeners.
PLATE GIRDERS & BOX GIRDERS
Grillage Foundations
Before reinforced concrete was used
universally as a building material, it was
customary to employ steel grillage for
sizable foundations.
Grillage footings consist of one or more
tiers of steel beam sections, where
components of each layer are
perpendicular with the other layer.
Ample spaces between the components are
provided for proper placement of concrete
acting as protective cover and to help load
distribution.
Furthermore, separators or diaphragms hold
the components in position.
For very heavy structural loads, grillage
beams may be lighter and more economical
than steel columns with base plates on
concrete.
Column Base Plates
A column base plate spreads the column load over
its foundation in various dimensions in meters and
thickness in increment of 12mm.
Rolled steel bearing plates are placed in absolute
contact with the concrete foundation for proper
distribution of load; the underside maybe
straightened by pressing and planing, or the
undersurface contact is achieved by providing
cement grout.
Anchorage of column base to the reinforced concrete base
is made by passing embedded anchor bolts through holes
in the base plate, with stiffener plates and angles fastened
or welded to the column web and flanges.
Column Splices
Steel column splices are normally located 60 cm. or more above the
proposed floor levels for better column to column connection.
Generally, splices are made by fastening or welding splice plates 10mm
to 12mm thick to column flanges. The splices are not designed to resist
loads but only to hold the column sections in position.
Column splices usually present the following conditions:
a) Where the upper column differs with The lower section
in terms of width or depth, cover plates would be
sufficient;
b) If it is a bit smaller than the lower column, fewer filler
plates are inserted;
c) If the difference in width or depth is quite great, aside
from the additional filler plates, a horizontal plate is used
to attain Full bearing area against the lower column.
Beam/ Girder Bearing Plates
Beam bearing plates are
provided for any steel beam or
girder resting on masonry or
concrete abutment in order to
provide ample bearing area and
to seat the beam at its proper
elevation.
Thus, this affords a uniform beam load distribution to its
supports.
Sometimes, the bearing plate may not be mechanically secured
nor welded to the beam flange.
Seated Connections
A seated connection applies to a connection between a beam
or girder to a supporting column or pier, consisting of a shelf or
seat angle attached to the column flange, which provides
support to the beam or girder.
A top or clip angle is used only to hold the beam in position but
does not resist nor transfer beam loads to the column.
Framed Connections
A framed connection refers to a connection between a girder to a
smaller beam wherein the beams are directly placed on top of
the girder, or angles are attached to the web of the beams, which
can provide a flush-top connection – where the upper surfaces of
the top flanges of the beams are made at the same level, done by
cutting a portion of the upper flange (by coping or blocking such
connections).
Steel Separators
Separators or diaphragms are
used when two or more
structural sections are held to
give lateral support to the
compression flanges and provide
proper alignment; they are not
counted upon to transfer load
from one member to the other in
the event of unequal loading.
Four types of separators are used:
the pipe separators being the most commonly used for S-
sections and channels of shallow depth, angle separators,
plate and angle, and rod separators.
The maximum spacing of separators is often limited to
1.50m., and they should also be placed at the ends of the
structural sections.
PLATE 4. STEEL FOUNDATION & CONNECTION DETAILS
Building Framing
Systems
Framing is the process of connecting
building materials together to create a
structure.
Framing is a construction system.
• Studs, plates, headers, rafters, girders,
flooring and joists are all terms used to
identify different components in framing.
Steel Roof Framing Components:

• Bay – a regularly repeated spatial element defined

by supports in a building structure.
•Cross-bracing – any system of bracing in which the
diagonals intersect (x- bracing)
• Purlin – a horizontal member spanning from truss
to truss where roofing material is attached.
• Ridge – the horizontal line at the junction or
intersection of the upper edges of two sloping roof
surfaces.
• Sag rod – steel bar attached or secured to purlins at
centers or one-third of purlin span to provide lateral
support.
• Rigid frame – a framework usually
designed to carry both a lateral and
vertical load which is transverse to the
length of a framed structure.
• Span – the distance between any two consecutive
supports of a structural member.
• Girt – bracing element located in bays to provide
lateral support between adjacent main roof trusses,
rafters, or bents.
• Eaves – the lower edge of a sloping roof that part
which projects beyond the wall.
• Turnbuckle – a device for connecting and
tightening a wire, rod, or stay, consisting of a right
screw and a left screw which are coupled by means
of a link.
Steel Truss Components:
• Chords – principal members (top
and bottom)
• Gusset – a plate, usually triangular
or trapezoidal in shape, used to
connect two or more slender
members, to add strength to a
framework.
• Web members – king post, verticals, diagonals, horizontals (occasional)

• Panel – sections between adjacent truss joints along the chords

• Rise – height

• Span – length

• Truss joints – heel joint, center joint, peak joint, and intermediate joints
Types of trusses:
a. Triangular (pitched top
chords)
• Fink (standard or cambered)
• Pitched Howe
• Pitched Pratt
• Belgian
• Scissors
b. Parallel-chord (rafter/beam/ girder trusses)
• Warren
• Flat Howe
• Flat Pratt
c. Curvilinear
• Bowstring (continuous or
segmental top chord)
• Crescent ( concentric or
nonconcentric chord radii)

Note: The cambered Fink, Scissors,

and Crescent truss designs can
accommodate curved or domed
ceiling sections
Open-Web Steel Joists Applications:
a) floor joists;
b) decking;
c) purlins;
d) beams and struts
Small prefabricated steel Warren trusses, called
open-web joists, are commonly used to support
floor and roof surfaces.

They are economical, strong, lightweight, and

easily erected.
The open areas between the webs permit
installation of utilities such as electric conduits,
piping and ducting.

When used in combination with fire-proofing

materials, these joists can carry fire protection
ratings of four hours.
Open-web joists can be obtained with underslung or
square ends.
Some used for roof decking are designed with sloped
upper chords (standard pitch of 1/4” per foot) to
allow roof drainage.
For anchorage the methods most commonly used
are masonry anchors (bolts) embedded in concrete
or masonry, or welding for anchorage to structural
steel.
Temporary support to steel can be made by means of
a hairpin anchor bent around the supporting flange.
Bents/Rigid Frames
For each type of loading, there is a theoretically
ideal structural form – a form having only tensile
and compressive stresses without any bending
stress.
As indicated, the parabolic arch is the ideal form for
the usual uniformly distributed loading.
Galileo discovered the catenary as the shape of a
heavy chain or rope suspended between two
points, and is inversely,
therefore, the ideal form for a load distributed
along the curve itself.
The truss can be an ideal solution for concentrated
loads.
Although these forms also require the least amount
of material for each given structural condition,
they might not be the most desirable solution for
architectural or other reasons.
A rigid frame is a satisfactory answer to the problem
since it can offer a good compromise between the
ideal structural shape and the desired enclosed
space.
When well designed, a rigid frame appears both
functional and graceful.
Such framework can take on almost human
form: a combination of masculine muscle at the
knees and crown with feminine slender at the
legs and ribs (rafter).
The knees and crown of steel rigid frames are
strengthened by increasing the section depth
and plate or angular stiffeners/ bracing are
added to prevent buckling especially at the
web sections.
Rigid frames can be built in a variety of shapes; they
can be made of rolled steel beams of constant depth,
or fabricated from flat steel plates into I - shaped
sections of varying depths.
Configurations:
A. Rectangular
B. Sloping legs
C. Arched
D. Gabled
E. Mill bent
F. Continuous