In this post you will find information on:
- What we call the load.
- Types of loads
- Concentrated force (point load)
- Continuous load evenly distributed
- Continuous load unevenly distributed
- Bending Moment: Applied external moments.
In this article we will focus on static loads. As stated Wikipedia:
Static load - the action of forces with time-invariant values, directions and points of application relative to a given body.
What is important and worth emphasizing static loads are invariant over time. There are also dynamic loads, but we will deal with them in the next posts on dynamics.
Types of loads
We will focus on the basic loads that you may encounter in tasks in mechanics or strength of materials.
| All beam load diagram drawings used in the entry were generated in the Beam Calculator |
Concentrated force (point load)
Concentrated force is the most common type of load in the world of mechanics assignments. You can see an example of a concentrated force applied to a beam below.
A concentrated force is a vector with a specific direction, direction and value applied at the point of attachment, the application of the force.
| The SI unit of force is the Newton [N]. |
| The most commonly used symbols are F or P. |
Examples of concentrated force in the world around us are a person standing on a footbridge or bridge, a lamp standing on a table. In fact, none of the examples given presses on the ground at a single point, but on a specific surface. Nevertheless, we will adopt a certain simplification in the problems to be solved and reduce such loading elements to a point force. Due to the fact that the ratio of the area on which the object presses on the substrate to the area of the whole element is small.
Concentrated forces can be applied at an angle. Then it is good to decompose the force into two components: horizontal and vertical.
Continuous load evenly distributed
The next type of load we will discuss is continuous load. This type of load causes the most problems when solving tasks. Unlike a concentrated force, it acts over some length. Therefore, to calculate the resultant force from a continuous load, the value of the load must be multiplied by the length over which it acts.
As in the example above, the continuous load most often denoted by the lowercase letter "q" can be replaced by a concentrated force of Q=q*l
| The SI unit of continuous load is [N/m]. |
A real-life example when it comes to continuous load is snow on the roof, which is distributed over the entire surface. In this case, we cannot reduce to a concentrated force.
Continuous load unevenly distributed
Continuous unevenly distributed load is the next type we will analyze. The principle of operation is similar, with the difference, as the name suggests to us, that the load will not be uniform.
We can meet several cases of this load. We can have a load in the shape of a triangle or a trapezoid.
Bending Moment: Applied external moments.
Finally, we will discuss the concentrated moment. This is the result of reducing a pair of forces to a point. When writing equilibrium equations The concentrated moment is not taken into account in the calculation of the resultant forces on the horizontal and vertical directions. We take it into account only in the equations for moments.
| The unit of concentrated torque is [Nm]. |
| In the case of the moment, there is no need to multiply it by the distance |
You have just learned about the most commonly used types of loads. You will learn how to calculate their effects on a beam, frame or truss in the following posts.
P.S All beam load diagram drawings used in the entry were generated in the Beam calculator