BASICS OF STRUCTURAL ENGINEERING
PART -1
LEARN STRUCTURAL TIPS
v Force
A force is
an interaction that causes an affected object to be pushed or pulled in a
certain direction.
v Mass
A measure of how much matter is in an object.
Mass is commonly measured by how much something
weighs. But weight can change for different locations (such as on the moon)
while the mass stays the same.
Mass is measured in grams, kilograms and, tones
(Metric) or ounces and pounds (US units).
v Acceleration
Acceleration is the name we give to any
process where the velocity changes. Acceleration is
the rate of change of velocity with time.
An apple is falling down. It starts falling at 0
meters per second. At the end of the first second, the apple is moving at 9.8
meters per second. The apple has accelerated. At the end of the second, the
apple is moving down at 19.6 meters per second. The apple has accelerated again.
The role of acceleration in structural
engineering we will discuss in static and dynamic analysis of structures.
v Moment
Momet Nothing But the force multiplied by its
perpendicular distance and also, we can say that the Moment of a
force is a measure of its tendency to cause a body to rotate about a specific
point or axis. This is different from the tendency for a body to move, or
translate, in the direction of the force. In order for a moment to develop, the
force must act upon the body in such a manner that the body would begin to
twist.
Following
the above picture the Weight F is the force and D shows perpendicular distance
from the point of force and M is the moment so we can say that.
M=
F x D
v Stress
Before going to discuss the stress and strain we
need to understand the Tension and Compression forces and their behavior.
TENSION:
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Pulling
force
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Imagine
the force felt in your arms while you hang from a bar.
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A
structural element subjected to tension is elongated.
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COMPRESSION:
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Squeezing
force
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Imagine
the force felt in your arms while you stand on your hands.
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|
A
structural element subjected to compression is shortened.
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STRESS:
In simple words, stress is the internal
resistance offered by the body against externally applied load.Stress also defined as the force per unit area
that the force acts upon. As we know that Stress are either compressive or tensile,
the Structural materials are chosen by their ability to resist tensile or
compressive forces, depending upon the application. Most of the materials
are better at resisting one or the other. Like, concrete is strong in
compression and relatively weak in tension. Steel is equally strong in tension
and weak in compression.
As you can check the figure 1 and 2 Two persons
are doing exercise , don’t worry this not a gym class and I am not going to teach
you here how to build six pack , just I would like to explain that If your
hanging on a bar the tensile force will act on your arms that is mentioned as T
and if you walk on your hands the compression force will act on your arms that
is mentioned by C.
v Strain
When
an external force is applied on a body, there is some change occur in the
dimension of the body. The ratio of this change of dimension in the body to its
actual length is called strain
If you would like to understand clearly,
A Body consist of small molecules and particle’s, between which forces are
acting. These molecular forces resist the change in the form of the body which
external forces tend to produce. Is such an external force applied to the body
its particles will displaced and the mutual displacements continue until the equilibrium
established between the external and internal forces in such a case the body in
a state of strain.
Strain has no units because it is a ratio of lengths.
v Deflection
It Refers to the movement of a beam from its
original position due to the forces being applied to the member. Deflection,
also known as displacement, can occur from external applied loads or from the
weight of the structure itself. It can occur in beams, trusses, frames and
basically any other structure. To define deflection, let's take a simple
cantilevered beam with Load (P) acting at the end this force will cause the
beam to bend and deflect from its natural position the
is the deflection of
the beam.
It
measures the physical displacement of a member under a load.
v Shear force
Shear means the tangential force
acting along the cross section of the member, we need to understand the practically
to get the concept.
consider one wooden piece and cut
it along with the cross section the force generated along the cross-sectional
plane that force will come under the shear force.
Shear force and bending moment are
used to check the strength of beam. I.e. how much shear force or bending moment
beam can bear before permanent deformation.
v Bending moment
The bending moment defined as the
algebraic sum of all the moments either left or right of the section this what we
read but we need to understand it different ways to get complete picture on the
subject of bending moment …like A bending
moment is the reaction induced in a structural element when an
external force or moment is applied to the element causing the
element to bend. The most common or simplest structural element subjected
to bending moments is the beam.
When you bend a ruler, even though apply the
forces/moments at the ends of the ruler, bending occurs all along the ruler,
which indicates that there is a bending moment acting all along the ruler.
Hence bending moment is shown on a bending moment diagram.
The bending moment plays a major role in
designing the structures , once we apply the load on a member it
will tends to bend the member and steadily the bending stresses will generate along
the member after a certain duration the member will subject to large
deformations it leads to the deflection in the member and finally the member
get cracked and the life of the structure will becomes less.
The section of the member also
having importance in the system since the moment of resistance of the structure
directly related to the moment of inertia and moment of inertia consist of the
sections of the members since we use the rectangular sections for main structural
columns then circular if you calculate the moment of inertia of the rectangular
member it shows greater value than circular , if the moment of inertia less it
leads to reduce the section modulus and also reduce the moment of resistance of
the member usually we use the circular column for architectural appearance with
large diameters it leads to uneconomical. this relation we can find in Theory
of simple bending equation
v Axial force
Axial force is a general term, meaning,
"force along the axis".
Axial Force is
generally defined as the Force acting along the axis of the component /
assembly. For example, consider a cylindrical Building column/ Square column.
The column is a structural member of a building and it is designed to take
Axial Compression force. Similarly, the circular rod in the ceiling fan is
designed to take Axial Tension Force + Torque due to rotating fan.
Axial force can be
in Tension/ Compression as defined in the examples above.
If you understand
the load transfer from one element to other elements ,usually the dead and live
loads from the floors it will transfer to the beams and from the beam it will
distribute to the columns finally the reaction will reach to the foundation and
then it will transfer to the soil.
Units-KN
