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:	Pulling force
	Imagine the force felt in your arms while you hang from a bar.
	A structural element subjected to tension is elongated.
COMPRESSION:	Squeezing force
	Imagine the force felt in your arms while you stand on your hands.
	A structural element subjected to compression is shortened.

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