Portal frames are low-rise structures comprising columns and horizontal or pitched rafters connected by moment-resisting connections. They provide clear unobstructed spans and are efficient for enclosing large volumes, making them useful for industrial, commercial, and agricultural buildings. Girder-slab systems combine a structural steel frame with prefabricated concrete girders and slabs for fast construction of mid-to-high rise buildings. Shell structures are thin curved concrete structures that function as both structure and enclosure through their strength and rigidity provided by their form. Common shell structures include folded plate, barrel vaults, and domes of revolution.

1. Large Span Structures

2. PORTAL FRAME
Portal frames are generally low-rise structures, comprising columns and
horizontal or pitched rafters, connected by moment-resisting connections.
Resistance to lateral and vertical actions is provided by the rigidity of the
connections and the bending stiffness of the members, which is increased by a
suitable haunch or deepening of the rafter sections.
This form of continuous frame structure is stable in its plane and provides a
clear span that is unobstructed by bracing.
They are very efficient for enclosing large volumes, therefore they are often
used for industrial, storage, retail and commercial applications as well as for
agricultural purposes.
Multi-bay portal frame during
construction
Cross-section showing a portal frame and its restraints
A portal frame building comprises a series of transverse
frames braced longitudinally. The primary steelwork consists of columns and
rafters, which form portal frames, and bracing. The end frame (gable frame)
can be either a portal frame or a braced arrangement of columns and rafters.
The light gauge secondary steelwork consists of side rails for walls
and purlins for the roof. The secondary steelwork supports the building
envelope, but also plays an important role in restraining the primary
steelwork.
The roof and wall cladding separate the enclosed space from the external
environment as well as providing thermal and acoustic insulation. The
structural role of the cladding is to transfer loads to secondary steelwork and
also to restrain the flange of the purlin or rail to which it is attached.
Anatomy Of A Typical Portal Frame

3. Principal Components Of A Portal
Framed Building
Fixed portal frame
All connection between frame memebres are rigid. Use
For small tomedium size frame where the moment
transfer to the foundation will not be excessive.
Two pin portal frame
Hinged are used at the base connection to eliminat
The tendency of the base rotate.Main use iswhere
Weak ground condition.
Three pin portal frame
This form of the frame has high hinged joint
at the base connection and the center of spanning
member.
The effect of the third hinge is to reduce the
Bendingmoment in the spaning member but
To increase deflection.
The rafter slope is 1:12
Types of Portal Framed Building

4. Mono-pitch Portal Frame
Where the span of a portal frame is large and there is no requirement to
provide a clear span, a propped portal frame can be used to reduce the rafter
size.
 A mono pitch portal frame is usually chosen for small spans. It is a simple
variation of the pitched roof portal frame, and tends to be used for smaller
buildings (up to 15 m span) leave height between 5 to 10m, roof pich between
5 to 10 degree and frame spacing between 6m to8m.
Propped portal frame
Propped span frame
Types Of Portal Frames

5. Purlin And Sheeting Rail
Purlin are fixed across rafter and sheeting rail across the column of single
storey frames to provide support and fixing for roof and wall sheeting and
insulation.
The spacing of the purlin and sheeting rail depends on the type of roof and
wall sheeting used.
The deeper the profile of sheeting the greater its safe span.
The greater the spacing of frames the greater the dead weight of sheeting
and imposed loads, and the deeper the section of purlin and rail necessary to
support the weight of roof and wall covering and loads from wind and snow.
Purlin
Sheeting Rail
ROOF LIGHTS

6. SPACE FRAME
Space frames are essentially three dimensional trusses able to span in two
directions. They may be flat for use as roofs, walls or inclined walls, or may be
curved to form continuous barrel type roof geometries.
Flat frames used as roofs sometimes have slight cambers to direct water to
appropriate roof outlets.
Depth: Span/40
Typical maximum length: 100 m
The space frame can be formed on either a flat or a curved surface. The
earliest form of space frame structure is single-layer grid. By adding
intermediate grids and including rigid connection to the joist and girder framing
system, the single-layer grid is formed.
The major characteristic of grid construction is the omnidirectional spread of
the load as opposed to the linear transfer of the load in an ordinary framing
system
Space Frame Structure ,Mumbai
Stansted Airport, London
Space Frame Structure
Frame Work Consisting Tubes And Connectors

7. .
Advantages Of Space Frame Structures
i. Light.
ii. Elegant & Economical.
iii. Carry load by three dimensional action.
iv. High Inherent Stiffness.
v. Easy to construct.
vi. Save Construction Time & Cost.
vii. Services (such as lighting and air conditioning) can be integrated with
space frames.
viii.Offer the architect unrestricted freedom in locating supports and planning
the subdivision of the covered space. Structural solution that provides
complete freedom in large span areas while providing strong resistance
and economic efficiency.
ix. Providing column-free space, aesthetic appearances and spectacular
qualities while offering flexibility and adaptability.
x. Satisfying the needs of an extremely diverse range of clients demands
from municipalities to aviation, from sport halls to shopping centers for
their own specific project needs.
xi. Best fit to any structures with their outstanding and elegant designings
while perfectly interfacing with any structures whether new or renovation
works.
Types of space frames
They are classified broadly in three categories
Skeleton (braced) frame work e.g. domes, barrel vaults, double and
multiplier grids, braced plates. They are more popular. They are innumerable
combinations and variation possible and follow regular geometric forms.
Stressed skin systems e.g. Stressed skin folded plates, stressed skin
domes and barrel vaults, pneumatic structures.
Suspended (cable or membrane) structures e.g. Cable roofs.

8. GIRDERS
Advantages
The Girder-Slab System in combination with a structural steel frame offers a
complete steel and concrete superstructure. It is ideal for use in mid to high-
rise residential structures such as hotels, student housing, apartments, senior
housing and condominiums.
The Girder-Slab System greatly improves construction operations and the
ability to meet critical deadlines. Unlike cast-in-place concrete structures, the
Girder-Slab System uses off site prefabricated components that are quickly
erected on site by one trade even in cold weather (Ironworkers).
A girder is a support beam used in construction. It is the main horizontal
support of a structure which supports smaller beams. Girders often have an I-
beam cross section for strength, but may also have a box shape, Z shape and
other forms.
Foundation Across Kanhan River, Nagpur
Girders are often held together by high
industrial strands. These strands are
made up of molten steel and their job
is to tie the girders into beams. The
girders, with the help of the strands,
can distribute the force and pressure
better.

9. Stiffeners Used For Further Support
At Complex Corners With Abnormal Roofing
Slopes
I-Girder
Sketch Of A Buiding With Girder Spanning
Girders In Metro Construction Girder In The Framework

10. SHELL STRUCTURES
A shell structure is a thin curved membrane or slab usually of reinforced
concrete that functions both as structure and covering.
The term “shell” is used to describe the structures which possess strenght and
rigidity due to its thin, natural and curved form such as shell of egg, a nut, human
skull, and shell of tortise.
Material
The material most suited for construction of shell structure.
is concrete because it is a highly plastic material when first mixed with water
that can take up any shape on centering or inside formwork. Small sections of
reinforcing bars can readily be bent to follow the curvature of shells.
Once the cement has set and the concerete has hardened the r.C.C membrane
or slab acts as a strong, rigid shell which serves as both structure and covering to
the building
A shell is a type of structural element which is characterized by its geometry,
being a three-dimensional solid whose thickness is very small when compared
with other dimensions, and in structural terms, by the stress resultants
calculated in the middle plane displaying components which are both coplanar
and normal to the surface. Essentially, a shell can be derived from a plate by
two means: by initially forming the middle surface as a singly or doubly
curved surface, and by applying loads which are coplanar to a
plate's plane which generate significant stresses.
Different Shell Structures

11. TYPES OF SHELL STRUCTURES
The distinguishing feature of the folded plate is the ease in forming plane
surfaces. A folded plate may be formed for about the same cost as a horizontal
slab and has much less steel and concrete for the same spans.
LOTUS TEMPLE, NEW DELHI INDIA
Folded plate shells
The principle components in a folded plate structure consist of :
1)the inclined plates
2)edge plates which must be used to stiffen the wide plates
3)stiffeners to carry the loads to the supports and to hold the plates in line
4)columns to support the structure in the air.

12. CYLINDRICAL BARREL VAULTS
Barrel vaults are perhaps the most useful of the shell structures because they
can span upt o 150 feet with a minimum of material. They are very efficient
structures because the use the arch form to reduce stresses and thicknesses in
the transverse direction.
DOMES OF REVOLUTION
A dome is a space structure covering a more or less square or circular area.
The best known example is the dome of revolution, and it is one of the earliest
of the shell structures. Excellent examples are still in existence that were built
in roman times.