Load Calculations | Types of Loads
Students find it difficult to understand the concept of loads although it is a very simple concept. We are going to write a series of articles on “Load Calculations” and help you all in understanding different types of loads that are to be considered for structural designing and also how to calculate them.
In this article, we will discuss different types of loads with examples.
In our next article, we will cover the following points:
- Design principle assumption and notation assumed
- Design Constant
- Assumptions regarding Design
- Loads on Beams
- Loads on slabs
An object is subject to mainly two types of forces:
- Live loads
- Dead loads
Basically, an object subject to any type of force which could be gravitational force (weight), pressure or anything affects the object is called a load.
This concept is used in Mechanical and structural engineering. Let’s take in terms of Structural Engineering. Whenever a structure is designed, these concepts are taken into consideration because real world objects are analyzed in order to design the structure. This is very important in terms of structural stability.
What are “Dead loads”?
As the name itself suggests, dead loads could be termed as self weight of the non-living objects. It could be the weight of the materials, equipments or any other components in the structure that will remain permanent throughout the life of the structure.
Dead load has to be considered in order to make the structural design accordingly. Dead loads vary from structure to structure. Every building is unique and has different considerations.
An additional load is considered in case additional forces build up in a structure in case of settlement or due to secondary effects of pre-stress construction or due to shrinkage of concrete.
For the calculations of dead loads, we could also consider,
- Machinery and other equipment
- Built-in partitions
- Finishes (POP – Plaster of Paris)
- Cladding (Use of various materials which increase the self weight of the structure) etc.
Basically, all the permanent loads are to be considered.
What are “Live loads”?
Unlike dead loads, live loads are variable. We could term them as probabilistic loads. Live load varies from time to time.
As the name suggests, live load is the load of human beings living in the building. Their movement is not fixed. The number of people at a time in a structure can also vary.
A person lives in a 4BHK apartment with his wife and two kids. If he happens to throw a party for 50 persons, the live load on the structure increases considerably for that period of time.
As soon as the guests leave, the number of persons reduces from 50 to 4.
So, here’s what I mean by variable force.
Let’s take another example:
Live load to be considered while designing a staircase:
- Pressure of the feet
- Wind load on the stair in case the staircase is located outside the house
Live load to be considered while designing the roof:
Movement of workers on the roof during construction, maintenance along with their materials and equipments
Also, if the owner of the house plans to make a terrace garden on the roof, that adds additional load to it.
For dwelling houses to a 10KN/m2. In any building project, slabs are assumed to be 100m thick from stiffness/deflection consideration.
Beams are taken separately and the self-weight is calculated and added separately on the frame. The net weight of the above load is multiplied by a load of 1.5 for concrete.