AHSANULLAH UNIVERSITY OF SCIENCE & TECHNOLOGY

Department of Civil Engineering

Prestress Concrete Design Sessional

CE 416

PRESENTED BY

MD. SHARIFUL ISLAM

STUDENT NO: 10.01.03.008

COURSE TEACHERS

Mr. Munshi Galib Muktadir

Ms. Sabreena Nasrin

PRESENTATION TOPIC :

AXIAL FORCE

PRESENTATION OUTLINE

-Definition

-Unit

-Scope

-Description

-Conclusion

A force applied parallel to the centerline of an

object.

Axial force evaluates the internal forces that

exist in a structure, often presented by the

characteristics of its dimensions.

COLUMN UNDER AXIAL FORCE F

Force F

Center line

Axial force is determined by width, effective

length, and load and is measured in kilo

pounds or kips (1,000 pounds of force).

SCOPE:

Compressive axial force (-ve)

Tensile axial force (+ve)

Compression members, such as columns, are mainly subjected to axial

forces. The principal stress in a compression member is therefore the

normal stress,

The failure of a short compression member resulting from the

compression axial force looks like,

DESCRIPTION

An axial force is any force that directly acts on the center

axis of an object. These forces are typically stretching

force or compression force, depending on direction.

A prime example of these forces can be seen on

columns within buildings. The column has an axis that

runs through the entire form from top to bottom. The

column is constantly compressed as it supports the roof of the structure.

One of the most important parts of examining axial forces is

the idea of a geometric center.

Geometric center:

This is a point within the boundaries of a solid object that is

the perfect center of the entire mass. It is basically the point at

which the mass of the object is the same in any opposing

direction.

Factors such as density and protruding arms could cause the

geometric center to exist on the surface or even outside of the

form.

Concentric:

when the force load is even across the form’s geometric center,

it is concentric.

Eccentric:

when the force load is uneven across the form’s geometric

center, it is eccentric.

In the column example, the axial force runs through the

geometric center of the form; this makes the force

concentric. A concentric force is stable at rest. When the

axis doesn’t pass through the geometric center, the shape

isn’t stable and the force is eccentric. This typically means

that the form is unable to withstand axial forces while at rest.

The compressed beam under axial force F stores

energy U of a value according to the formula

Now, the figure below shows a small segment along a beam element

subjected to simplified 2D forces ( axial force P, shearing force V, and

bending moment M):

In a general case 3 forces and 3 moments act on the segment.

Uniform axial stress = P/A (similar to truss elements)

Uniform shearing stress = V/A

The bending moment M causes a bending stress that varies linearly with

the vertical distance y from the neutral axis.

Bending stress (bending in y direction) = My/I

where I is the moment of inertia about the neutral axis.

The bending stress is the largest at the extreme fibers.

In this example, the largest compression occurs at the top fiber and the largest tension occurs at the extreme bottom fibers.

THANK YOU