In the field of construction, the term “load” refers to any force or weight that is placed on a structure. There are two main categories of loads that engineers must consider when designing buildings, bridges, and other structures: dead load and live load.
Understanding the differences between these two types of loads is crucial for ensuring the safety and stability of structures.
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Side-by-side difference between dead load and live load
Definition
- Dead load refers to the weight of the structure itself and all the permanent fixtures attached to it, such as walls, roofs, floors, and columns.
- Live load refers to the weight of all the temporary or movable loads that a structure can carry, such as people, furniture, vehicles, and equipment.
Magnitude
- Dead load is a constant load that remains the same throughout the life of the structure. It is typically larger than the live load and accounts for the majority of the total load that a structure must support.
- Live load varies depending on the intended use of the structure and can fluctuate over time.
Duration
- Dead load is a permanent load that remains constant throughout the life of the structure.
- Live load is a temporary load that varies depending on the use of the structure.
Importance
- Dead load is crucial for determining the strength and stability of a structure, as it provides a foundation for all other loads that the structure must support.
- Live load is important for designing the structure to safely accommodate the intended use, and it is typically a key factor in determining the required size and strength of the structure.
Distribution
- Dead load is distributed uniformly throughout the structure and acts in a downward direction toward the ground.
- Live load is not distributed uniformly and can vary depending on the location and use of the structure. It can also act in different directions, such as horizontal or vertical.
Impact
- Dead load does not cause any impact on the structure, as it is a constant load that remains in place.
- Live load can cause an impact on the structure, especially if it is subjected to sudden changes or movements.
Design considerations
- Dead load is considered in the initial design of the structure, as it is a permanent and predictable load.
- Live load is considered during the design process, but it may require additional analysis to determine the most appropriate design parameters, especially for structures that will experience high or variable loads.
Safety factors
- Dead load is typically given a lower safety factor than live load, as it is a predictable and less variable load.
- Live load is given a higher safety factor than dead load, as it is a variable load that can fluctuate and may be difficult to predict accurately.
Code requirements
- IS: 875 PART 1 – DEAD LOADS — UNIT WEIGHTS OF BUILDING MATERIALS AND
- STORED MATERIALS for dead load
- IS: 875 PART 2 – IMPOSED LOADS for live load
Examples
- Dead load includes the weight of the foundation, walls, floors, roof, and any permanent fixtures, such as pipes, ducts, and electrical wiring.
- Live load includes the weight of people, furniture, equipment, vehicles, and any other temporary loads that a structure is designed to accommodate.
A quick comparison table between dead load and live load
| Aspect | Dead Load | Live Load |
| Nature of load | Permanent and constant | Temporary and variable |
| Source of load | Weight of structure | People, equipment, furniture |
| Duration of load | Long term | Short term |
| Magnitude of load | Typically greater than live load | Typically smaller than dead load |
| Distribution of load | Evenly distributed across the structure | Unevenly distributed depending on the location and intended use |
| Effect on structure | Causes deflection | Causes vibration, impact |
| Environmental factors | Dead load is typically not affected by environmental factors such as wind or earthquakes | Live load may be affected by environmental factors, which can increase or decrease the load |
| Calculation method | Weight of materials | Live load values are given in IS 875 Part 2 |
| Examples | Structural components | Furniture, people, vehicles |
