In this article, We explain the various load combinations are used in design of RCC Structure as well as Steel Structure. Also share the load combinations for Limit state of strength as well as limit state of serviceability.
So Read the article till the end, and if you get any knowledge from this article, please share with your friends. Let’s Start.
Table of Contents
What is Load Combination
Load Combination is define as a set of various loading condition that are acting together in structure which is used to ensure the required safety and economy in the design of a structure.
While, A load combination causing critical condition in structure such as maximum deformation and stress etc. known as a Critical Load Combination.
It is a set of such load cases which is likely to act together on structure such as dead load, live load and wind load or dead load, live load and earthquake load etc.
It is very high chance to not occurrence of earthquake and wind load on building simultaneously. That’s why in load combination, wind load and earthquake loads are not in same sets.
Load Combination as per IS 456 – 2015
Load combination as per is 456 for grouped in two categories, 1. Limit State of Collapse, 2. Limit State of Serviceability.
Also Read: Working Stress Method Vs Limit State Method of design
1. Load Combination for Limit State of Collapse
Limit State design Combination
- 1.5 (DL+LL)
Earthquake Load combinations for Design
- 1.5 (DL+EQX)
- 1.5 (DL-EQX)
- 1.5 (DL+EQZ)
- 1.5 (DL-EQZ)
- 1.2(DL+LL+EQX)
- 1.2(DL+LL-EQX)
- 1.2(DL+LL+EQZ)
- 1.2(DL+LL-EQZ)
- 0.9DL+1.5EQX
- 0.9DL-1.5EQX
- 0.9DL+1.5EQZ
- 0.9DL-1.5EQZ
Wind Load Combination for design
- 1.5(DL+WLX)
- 1.5(DL-WLX)
- 1.5(DL+WLZ)
- 1.5(DL-WLZ)
- 1.2(DL+LL+WLX)
- 1.2(DL+LL-WLX)
- 1.2(DL+LL+WLZ)
- 1.2(DL+LL-WLZ)
- 0.9DL+1.5WLX
- 0.9DL-1.5WLX
- 0.9DL+1.5WLZ
- 0.9DL-1.5WLZ
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2. Load Combination for Limit State of Serviceability
Limit state Serviceability Combination
- DL+LL
Earthquake Serviceability Combination
- DL+LL+EQX
- DL+LL-EQX
- DL+LL+EQZ
- DL+LL-EQ
- DL+EQX
- DL-EQX
- DL+EQZ
- DL-EQZ
Wind Load Serviceability Combination
- DL+WLX
- DL-WLX
- DL+WLZ
- DL-WLZ
- DL+LL+WLX
- DL+LL-WLX
- DL+LL+WLZ
- DL+LL-WLZ
3. Load Combination with Temperature Load
Design Combination With Temperature Load
- 1.5(DL+LL+TL)
Earthquake Load combinations with Temperature Load
- 1.0(DL + EQX + TL)
- 1.0(DL – EQX + TL)
- 1.0(DL + EQZ + TL)
- 1.0(DL – EQZ + TL)
- 1.0(DL + LL + EQX + TL)
- 1.0(DL + LL – EQX + TL)
- 1.0(DL + LL + EQZ + TL)
- 1.0(DL + LL – EQZ + TL)
Wind Load Combination with Temperature load
- 1.0(DL + WLX + TL)
- 1.0(DL – WLX + TL)
- 1.0(DL + WLZ + TL)
- 1.0(DL – WLZ + TL)
- 1.0(DL + LL + WLX + TL)
- 1.0(DL + LL – WLX + TL)
- 1.0(DL + LL + WLZ + TL)
- 1.0(DL + LL – WLZ + TL)
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Load Combinations As Per IS 1893 -2016
1. Load Combinations for Orthogonal Structural Element
When Lateral load resisting element are oriented along two mutually orthogonal horizontal directions, structure shall be designed for effects due to full design earthquake load in one horizontal direction at a time, and not in both directions simultaneously. That means the load combination are used as per IS456 criteria which is listed above.
2. Load Combinations for Non Orthogonal Structural Element
When lateral load resisting elements are not oriented along mutually orthogonal directions, Structure shall be designed for the simultaneous effect due to full design earthquake load in one horizontal direction plus 30% of design earthquake load along the other horizontal direction. Thus structure should be designed for the following sets of combinations of earthquake effects.
For above mentioned criteria, sets of load combination are listed below.
Earthquake load combinations for design
- 1.5(DL+EQX+0.3EQZ)
- 1.5(DL+EQX-0.3EQZ)
- 1.5(DL-EQX-0.3EQZ)
- 1.5(DL-EQX+0.3EQZ)
- 1.5(DL+EQZ+0.3EQX)
- 1.5(DL+EQZ-0.3EQX)
- 1.5(DL-EQZ-0.3EQX)
- 1.5(DL-EQZ+0.3EQX)
- 1.2(DL+LL+EQX+0.3EQZ)
- 1.2(DL+LL+EQX-0.3EQZ)
- 1.2(DL+LL-EQX-0.3EQZ)
- 1.2(DL+LL-EQX+0.3EQZ)
- 1.2(DL+LL+EQZ+0.3EQX)
- 1.2(DL+LL+EQZ-0.3EQX)
- 1.2(DL+LL-EQZ-0.3EQX)
- 1.2(DL+LL-EQZ+0.3EQX)
- 0.9DL+1.5(EQX+0.3EQZ)
- 0.9DL+1.5(EQX-0.3EQZ)
- 0.9DL-1.5(EQX+0.3EQZ)
- 0.9DL-1.5(EQX-0.3EQZ)
- 0.9DL+1.5(EQZ+0.3EQX)
- 0.9DL+1.5(EQZ-0.3EQX)
- 0.9DL-1.5(EQZ+0.3EQX)
- 0.9DL-1.5(EQZ-0.3EQX)
Also Check: How to Calculate Expansion Joint in Building
Earthquake Load Combinations for Serviceability checks
- DL+LL+EQX+0.3EQZ
- DL+LL+EQX-0.3EQZ
- DL+LL-EQX+0.3EQZ
- DL+LL-EQX-0.3EQZ
- DL+LL+EQZ+0.3EQX
- DL+LL+EQZ-0.3EQX
- DL+LL-EQZ+0.3EQX
- DL+LL-EQZ-0.3EQX
- DL+EQX+0.3EQZ
- DL+EQX-0.3EQZ
- DL-EQX+0.3EQZ
- DL-EQX-0.3EQZ
- DL+EQZ+0.3EQX
- DL+EQZ-0.3EQX
- DL-EQZ+0.3EQX
- DL-EQZ-0.3EQX
3. Three Directional Earthquake Load Combination
Indian Standard IS 1893 -2016 Suggested that if your structure followed any conditions which are listed below, It is necessary to consider vertical earthquake shaking in your structure design.
- Structure is located in Seismic Zone IV or V
- Structure has vertical or plan irregularities.
- Structure is rested on soft soil.
- Bridges.
- Structure has long spans.
- Structure has large horizontal overhangs of structural members or sub-systems.
The all Three dimensional load combinations are listed below.
Also Read: Ductile Detailing of Beam as per IS 13920-2016
Three dimensional earthquake load combination for design
- 1.5(DL+EQX+0.3EQZ+0.3EQY)
- 1.5(DL+EQX+0.3EQZ-0.3EQY)
- 1.5(DL+EQX-0.3EQZ+0.3EQY)
- 1.5(DL+EQX-0.3EQZ-0.3EQY)
- 1.5(DL-EQX-0.3EQZ-0.3EQY)
- 1.5(DL-EQX-0.3EQZ+0.3EQY)
- 1.5(DL-EQX+0.3EQZ-0.3EQY)
- 1.5(DL-EQX+0.3EQZ+0.3EQY)
- 1.5(DL+EQZ+0.3EQX+0.3EQY)
- 1.5(DL+EQZ+0.3EQX-0.3EQY)
- 1.5(DL+EQZ-0.3EQX+0.3EQY)
- 1.5(DL+EQZ-0.3EQX-0.3EQY)
- 1.5(DL-EQZ-0.3EQX-0.3EQY)
- 1.5(DL-EQZ-0.3EQX+0.3EQY)
- 1.5(DL-EQZ+0.3EQX-0.3EQY)
- 1.5(DL-EQZ+0.3EQX+0.3EQY)
- 1.2(DL+LL+EQX+0.3EQZ+0.3EQY)
- 1.2(DL+LL+EQX+0.3EQZ-0.3EQY)
- 1.2(DL+LL+EQX-0.3EQZ+0.3EQY)
- 1.2(DL+LL+EQX-0.3EQZ-0.3EQY)
- 1.2(DL+LL-EQX-0.3EQZ-0.3EQY)
- 1.2(DL+LL-EQX-0.3EQZ+0.3EQY)
- 1.2(DL+LL-EQX+0.3EQZ-0.3EQY)
- 1.2(DL+LL-EQX+0.3EQZ+0.3EQY)
- 1.2(DL+LL+EQZ+0.3EQX+0.3EQY)
- 1.2(DL+LL+EQZ+0.3EQX-0.3EQY)
- 1.2(DL+LL+EQZ-0.3EQX+0.3EQY)
- 1.2(DL+LL+EQZ-0.3EQX-0.3EQY)
- 1.2(DL+LL-EQZ-0.3EQX-0.3EQY)
- 1.2(DL+LL-EQZ-0.3EQX+0.3EQY)
- 1.2(DL+LL-EQZ+0.3EQX-0.3EQY)
- 1.2(DL+LL-EQZ+0.3EQX+0.3EQY)
- 0.9DL+1.5(EQX+0.3EQZ+0.3EQY)
- 0.9DL+1.5(EQX+0.3EQZ+0.3EQY)
- 0.9DL+1.5(EQX-0.3EQZ+0.3EQY)
- 0.9DL+1.5(EQX-0.3EQZ-0.3EQY)
- 0.9DL-1.5(EQX+0.3EQZ+0.3EQY)
- 0.9DL-1.5(EQX+0.3EQZ+0.3EQY)
- 0.9DL-1.5(EQX-0.3EQZ+0.3EQY)
- 0.9DL-1.5(EQX-0.3EQZ-0.3EQY)
- 0.9DL+1.5(EQZ+0.3EQX+0.3EQY)
- 0.9DL+1.5(EQZ+0.3EQX+0.3EQY)
- 0.9DL+1.5(EQZ-0.3EQX+0.3EQY)
- 0.9DL+1.5(EQZ-0.3EQX-0.3EQY)
- 0.9DL-1.5(EQZ+0.3EQX+0.3EQY)
- 0.9DL-1.5(EQZ+0.3EQX+0.3EQY)
- 0.9DL-1.5(EQZ-0.3EQX+0.3EQY)
- 0.9DL-1.5(EQZ-0.3EQX-0.3EQY)
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Three dimensional earthquake load combination for Serviceability check
- DL+LL+EQX+0.3EQZ+0.3EQY
- DL+LL+EQX+0.3EQZ-0.3EQY
- DL+LL+EQX-0.3EQZ+0.3EQY
- DL+LL+EQX-0.3EQZ-0.3EQY
- DL+LL-EQX-0.3EQZ-0.3EQY
- DL+LL-EQX-0.3EQZ+0.3EQY
- DL+LL-EQX+0.3EQZ-0.3EQY
- DL+LL-EQX+0.3EQZ+0.3EQY
- DL+LL+EQZ+0.3EQX+0.3EQY
- DL+LL+EQZ+0.3EQX-0.3EQY
- DL+LL+EQZ-0.3EQX+0.3EQY
- DL+LL+EQZ-0.3EQX-0.3EQY
- DL+LL-EQZ-0.3EQX-0.3EQY
- DL+LL-EQZ-0.3EQX+0.3EQY
- DL+LL-EQZ+0.3EQX-0.3EQY
- DL+LL-EQZ+0.3EQX+0.3EQY
- DL+EQX+0.3EQZ+0.3EQY
- DL+EQX+0.3EQZ-0.3EQY
- DL+EQX-0.3EQZ+0.3EQY
- DL+EQX-0.3EQZ-0.3EQY
- DL-EQX-0.3EQZ-0.3EQY
- DL-EQX-0.3EQZ+0.3EQY
- DL-EQX+0.3EQZ-0.3EQY
- DL-EQX+0.3EQZ+0.3EQY
- DL+EQZ+0.3EQX+0.3EQY
- DL+EQZ+0.3EQX-0.3EQY
- DL+EQZ-0.3EQX+0.3EQY
- DL+EQZ-0.3EQX-0.3EQY
- DL-EQZ-0.3EQX-0.3EQY
- DL-EQZ-0.3EQX+0.3EQY
- DL-EQZ+0.3EQX-0.3EQY
- DL-EQZ+0.3EQX+0.3EQY
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Load Combination Quiz
What are the load combinations for deflection check?
The Serviceability load combinations are used to check deflection of any structure. all serviceability load combination are listed above.