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What are the load combinations used in building design as per IS 456-2000 and IS 1893-2016 code
The load combinations are mainly used in building design. The combination of two or more loads with suitable factor of safety namely 1.5, 1.2 or 0.9 is called as load combination. As per the gravity loads and as per the lateral loads the load combinations are varies. These combinations will helps to filter the maximum reinforcement values and maximum bending moments for the particular structures. The below specified loads are considered in the loads combination as per the IS 456-2000 code and IS 1893-2016 code.
Loads considered in combinations
As per the combinations the main loads are classified in to below types
- Dead load
- Live load
- Seismic load
- Wind load
Dead load in combinations
Dead load is comes under the gravity loading condition and it is the first load case in our combination. The self weight of the structural elements like beams, columns, slabs are considered initially, secondly the wall loads related to the external wall loads, internal wall loads and parapet walls are taken depending upon the density of brick work. The floors loads for marbles or tiles are considered and the water loads are calculated in the last stage under dead loads.
Live load in combination
The live load is also comes under the gravity load condition and it is the second load case in the combination as per IS code standards. The slab load is considered as live load in square meter load. For the residential buildings, commercial buildings, educational buildings the intensity of live load which is given in IS 875 code provisions.
Seismic load in load combination
Seismic load is the third type we need to consider under the lateral loading condition. The loads are acts to the building structures perpendicular to the gravity loads. The seismic load is taken as per the IS 1893-2016 code provisions. The seismic zones are classified in to four types in Indian region. Which are Zone II, Zone III, Zone IV and Zone V.
Zone II is low seismic zone, Zone III is moderate seismic zone, Zone IV is high seismic zone and lastly Zone V is critical zone. As per the IS 1893 code if we design in Zone V areas we have to focus the earth quake resistant building models like by providing bracings, shear walls, etc.
The load assignment for this type combination is considered in both X and Y direction condition namely EQx and EQy types. In X direction 2 cases are considered again with 1 and -1 factor, In Y direction again 2 cases are considered again with 1 and -1 factor.
Wind load in load combination
The wind load is the last load case considered as per the load combinations this type of load is also comes under the lateral loading condition which is acts perpendicular to the gravity force. The wind load analysis is calculated as per IS 875 part 3 code provisions. As per the IS 875 specifications the wind load on the building structure is considered if the building height is exceeds the 10m.
For example let us consider the building which is of G+2 building if we take 3m height for each floor the total height of the building is get as 9m which is less than 10m so no need to take wind load for this structure. Again in the same process if we take G+3 building structure with 3m each floor height total height of building is taken as 12m which is greater than 10m so we need to calculate the wind load values as per the code provisions.
Complete load combinations as per IS 456-2000 and IS1893-2016 code
The combinations of loads are classified in to 21 numbers which are shown in the below table.
|
S. No |
Loads Taken |
Combination of loads |
| 1 | Dead load, Live load | 1.5 (DL+LL) |
| 2 | Dead load, Live load and Seismic load | 1.2 (DL+LL+EQx) |
| 3 | Dead load, Live load and Seismic load | 1.2 (DL+LL-EQx) |
| 4 | Dead load, Live load and Seismic load | 1.2 (DL+LL+EQy) |
| 5 | Dead load, Live load and Seismic load | 1.2 (DL+LL-EQy) |
| 6 | Dead load, Seismic load | 1.5 (DL+EQx) |
| 7 | Dead load, Seismic load | 1.5 (DL-EQx) |
| 8 | Dead load, Seismic load | 1.5 (DL+EQy) |
| 9 | Dead load, Seismic load | 1.5 (DL-EQy) |
| 10 | Dead load, Live load and wind load | 1.2 (DL+LL+WLx) |
| 11 | Dead load, Live load and wind load | 1.2 (DL+LL-WLx) |
| 12 | Dead load, Live load and wind load | 1.2 (DL+LL+WLy) |
| 13 | Dead load, Live load and wind load | 1.2 (DL+LL-WLy) |
| 14 | Dead load, wind load | 1.5 (DL+WLx) |
| 15 | Dead load, wind load | 1.5 (DL-WLx) |
| 16 | Dead load, wind load | 1.5 (DL+WLy) |
| 17 | Dead load, wind load | 1.5 (DL-WLy) |
| 18 | Dead load, Seismic load | 0.9DL+1.5EQx |
| 19 | Dead load, Seismic load | 0.9DL-1.5EQx |
| 20 | Dead load, Seismic load | 0.9DL+1.5EQy |
| 21 | Dead load, Seismic load | 0.9DL-1.5EQy |
The complete detailed concepts of load combinations are explained in my YouTube Channel see below.
After defining these load case we need to define in Staad Pro or ETABS or SAP or other structural related software.
Conclusions of complete load combinations as per IS 456-2000 and IS 1893-2016 code
Well now the above explained concepts are related to the complete load combination as per IS 456 and IS 1893 code provisions. As per theses two code provisions it was classified in to 21 numbers related to the gravity loads and lateral loads under dead load, live load, seismic load and wind loads
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