# What is Load Combination | Load Combination as per IS 456

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.

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 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

• 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

Do you know: How to Calculate different Types of load in building

### 2. Load Combination for Limit State of Serviceability

• 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

• DL+WLX
• DL-WLX
• DL+WLZ
• DL-WLZ
• DL+LL+WLX
• DL+LL-WLX
• DL+LL+WLZ
• DL+LL-WLZ

• 1.5(DL+LL+TL)

• 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)

• 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)

Do you Know: Earthquake Proof Masonry Construction Aspects

## 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 As per IS 456

This Quiz includes the question and answer related to Load Combination as per IS 456 & IS 1893

1 / 6

DL+LL+WL Combination for Limit State of Serviceability is

2 / 6

Earthquake Load Combination for Non Orthogonal Structures?

Where,

• EQX and EQY is Horizonal Earthquake Force
• EQZ is Vertical Earthquake Force

3 / 6

DL+WL Combination for Limit State of Collapse is

4 / 6

DL+IL+WL Combination for Limit State of Collapse is

5 / 6

1.5 (DL+LL) is a load combination of

6 / 6

Three Dimensional Earthquake Load Combination is Used in which cases?