3. 1 Frame Action Of Column and Two-Way
Slab Systems
Concrete floors in tall buildings often
consist of a two-way floor system such as a
flat slab, or a waffle system.
Advantages
1. Optimum use of floor space
2. Relatively simple construction process
Disadvantages
1. Generally flexible structure and lateral
deflection govern the design process.
4. Effective Width of flat Slab.
The effective width of
flat slab can be used
to determine the
equivalent width of
slab.
The effective width
depends on
1. Column aspect ratios
2. Distance between
columns
3. Thickness of flat slab.
5. 2 Rigid Frame
Cast in Place Concrete Building has inherent
advantages of continuity at joints.
Beams framing directly into columns, can be
considered rigid with the columns.
Beams carry shear and bending moments
due to lateral loads often require additional
construction depth.
The design and detailing of joints where
beams and columns meet the special
attention is required.
7. Advantages
1. Rigid Frame systems for resisting lateral
and vertical loads have long been accepted
as a standard means of designing buildings.
because they make use of the stiffness in
the beams and columns that are required in
any case to carry the gravity loads.
Limitation
1. Rigid Frames are not Stiff as compared to
shear wall.
2. Excessive depth of girder required to make
the rigid frame economical.
11. Uses
When the Structure is of tube type and the adjacent
distance between two columns are 40ft then the
beam depth required is much more and this beam is
called haunch beams.
If the depth of haunch beam is more then 3 ft then
the posttensioning is used.
A haunch girder with more depth give the required
stiffness for lateral loads without having to increase
the floor to floor height.
This is achieved by making the mid section of the
girder flush with the floor system.
12. 4 Shear Walls
The elevator shafts, stairwells necessary for
access in a high rise must be protected by
fire walls, as demanded by fire safety
regulation.
It makes sense to exploit them in improving
the building rigidity.
With their highly resistance to shear stress,
are highly suitable for assuming the shear
forces that arise through lateral loads.
13. Classification of Shear Walls
Classification of Shear wall should be based
on following criteria.
1. Based On Shape
2. Based on dimension
3. Based on Opening
14. Based On Shape
1. Rectangular
2. Dumbled
3. Intersection of Two Shear Walls
15. Based on Dimension
h/ l < 1 Square shear wall
H / l > = 1 Slender Shear Wall
l
h
18. Coupled Shear Walls
When two or more shear walls are interconnected
by a system of beams or slabs, the total stiffness of
the system exceeds the summation of the individual
wall stiffnesses because, the connecting slab or
beam restrains the individual cantilever action by
forcing the system to work as composite unit.
used economically to resist lateral loads in building
upto about 40 stories.
However planer shear walls are only efficient lateral
carieers only in that planes hence it is necessary to
provide wals in two orthogonal directions.
20. 5 Shear Wall Frame Interaction
Most Popular System
Broad Range of Application and has been used for
10 – stories to as high as 50 stories or even taller
building.
21. Rigid Frame Shear Wall Interaction.
Using only shear walls to
respond to lateral loads is
impractival above about
500ft.
The lateral rigidity is gratly
improved by using not only
the shear wall system but
also the rigid frame to resist
lateral forces.
The total deflection of the
interacting shear wall and
rigid frame systems is
obtained by superimposing
the individual models of
deformation as shown in fig.
