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Framed buildings are building structures formed by the framed elements
usually in the form of columns and beams, as well as further strengthened as
necessary by the introduction of rigid floor membranes and external walls.
Common forms of framed building structure subdivided into 2 main types:
INSITU RC FRAME
RECTANGULAR FRAMED STRUCTURES
•A framed structure is a network of
beams and columns joined up to form the
skeleton framework of the building.
•The structural frame carries the total
load of the building and transfers it to the
•Cladding is fixed over the framework, or
infill panels are placed between its
members, to totally enclose the space
within the building.
•Framed structures are easily erected
from pre-made members.
•These members are easily connected
together in the correct sequence to form
the structural framework.
• Problems arise when large members are used and when the height of the
structure makes lifting difficult.
• In these situations a crane will be needed to lift the members into place.
• Rectangular frames are usually made from steel but they may also be
made from concrete.
• The multi-storey car park under construction is a concrete framed
• They are set a right angles to each other to provide support for the floors,
walls and roof
A STEEL FRAMED STRUCTURE IN COURSE OF ERECTION
Rectangular framed structures are
used for multi-storey buildings
or other similar buildings where a
multi-storey structure is required.
The floor space will incorporate a
large number of columns.
• Speedy construction due to simplicity in geometry – consist of only
columns and beams as the main structural elements
• Rigid and stable – able to resist tremendous vertical (dead load) and
lateral loads (wind)
• reduced dead load – absent of thick shear wall etc.
• Roofed over at an earlier stage – every floor slab being finished becomes an
cover to protect the lower floors from sun and rain
• offer large unobstructed floor areas – without obstacle between columns
• flexible utilization of space.
• Adaptable to almost any shape
• easily altered within limits of frame – regular or non-regular grid system is
very adaptable in spatial arrangement
• offsite preparation possible – especially for prefabricated construction
using precast concrete or structural steel elements
PRINCIPLES OF DESIGNING FRAME
As already indicated, the primary function of a skeleton frame is to carry
safely all the loads imposed on the building and this is must do without
deforming excessively under load as a whole or in its parts. In order to fulfill
this function efficiently it must provide in its design and construction adequate:
• STRENGTH AND STABILITY
These are ensured by the use of appropriate materials in suitable forms
applied with due regard to the manner in which a structure and its parts
behave under load.
• FIRE RESISTANCE
An adequate degree of fire resistance in the frame is essential in order that its
structural integrity may be maintained in the event of fire, either for the full
period of a total burn-out or for a long period at least long enough to permit
any occupants of the building to escape.
Columns and struts carry load primarily in compression along their length, and
are found in most building structures.
So, principles or criteria of column design can explain as:
• The strength of stocky columns is related to material strength.
• The strength of slender columns is limited by buckling.
• In practice steel columns have to allow for both buckling and material failure,
and for interaction between the two.
• The resistance of a cross-section to buckling is represented by its radius of
• End conditions influence buckling behaviour and are accounted for by using
an effective length.
• In practice columns are subject to a combination of compression and
• Because buckling resistance and actual stress are both related to the size of
the cross-section, iterative design procedures must be used.
he composite beam design is concerned with sizing the steel section. The philosophy of
designing composite beams is to utilize the implicit strength of the concrete slab. The
form and thickness of this will have been determined by its functional requirements as a
Design may be governed by any of the following criteria:
• Deflection - the stiffness of the beam will be chosen to minimize deformation.
• Vibration - the stiffness and mass are chosen to prevent unacceptable vibrations,
particularly in settings sensitive to vibrations.
• Bending failure by yielding - where the stress in the cross section exceeds the yield
• Bending failure by lateral torsion buckling - where a flange in compression tends to
buckle sideways or the entire cross-section buckles torsionally
• Shear failure - where the web fails. Slender webs will fail by buckling, rippling in a
phenomenon termed tension field action, but shear failure is also resisted by the
stiffness of the flanges
Moment Resisting Frames
EARTHQUAKE RESISTIVE FEATURES IN FRAME
1. SHEAR WALLS
• First used in 1940, may be described as
vertical, cantilevered beams, which resist
lateral wind and seismic loads acting on a
building transmitted to them by the floor
EFFECTS IN EARTHQUAKE
Building frame system
with Shear Walls
Typical arrangement of shear walls
• A simple building with shear walls at
its ends. Ground motion enters the
building and creates inertial forces
which move the floor diaphragms.
This movement is resisted by the
shear walls, and the forces are
transmitted back down to the
Shear wall: vertical analogy
as cantilever beams
2. MOMENT-RESISTING FRAMES
Moment-resisting frames are structures having the traditional beam-column
framing. They carry the gravity loads that are imposed on the floor system.
The floors also function as horizontal diaphragm elements that transfer
lateral forces to the girders and columns. In addition, the girders resist high
moments and shears at the ends of their lengths, which are, in turn,
transferred to the column system. As a result, columns and beams can
become quite large.
■ Moment-resisting frames can be
constructed ofsteel, concrete, or masonry.
■ Consist of beams and columns in which
bending of these members provides the
resistance to lateral forces.
■ There are two primary types of moment
frames, ordinary and special.
■ Special moment-resisting frames are
detailed to ensure ductile behavior of the
beam-to-column joints and are normally
used in zones of higher seismicity.
■ Steel moment-resisting frames have
been under intensive study and testing.
3. BRACED STRUCTURES
• Braced frames develop their resistance to
lateral forces by the bracing action of
diagonal members. The braces induce
forces in the associated beams and columns
so that all work together like a truss with all
members subjected to stresses that are
• Braced frames act in the same manner as
shear walls, though they may be of lower
resistance depending on their detailed
• Bracing generally takes the form of steel
rolled sections, circular bar sections, or
tubes; vibrating forces may cause it to
elongate or compress, in this case it loses
its effectiveness and permits large
deformations or collapse of the vertical
• Bracing can be used to stop buildings swaying
over. It helps buildings stand up to the sideways
forces that can occur during earthquakes or high
winds. Bracing members can work in tension or in
EFFECTS OF EARTHQUAKE
4. BRACED STRUCTURES