Loads in Structure
At the time of structural analysis primary work is load allocation as per expected future operations. All countries have their own standards for load allocation, so does India. We use IS 875 for load combination and 1893 for earthquake load calculation. Loads are broadly divided into 3 categories based on directions9coordinates X,Y,Z). Loads are also classified differently as per their cause: –
- Live load
- Dead load
- Wind load
- Earthquake load
- Snow load
- Special loads like thermal load, flood load`
- Temperature load
Mostly loads act simultaneously which makes the analysis complicated. Load factors are decided as per the load combinations and cumulative load calculated multiplying load factor with actual load. A judicious combination of loads keeping in view the probability of their acting together. At the same time their disposition to other loads and severity of stresses or deformations caused by combination of various loads is necessary to ensure necessary safety and economy of the design. In absence of such recommendations basic combinations provided below can be used and whichever combination produces the most unfavourable effects in the structure may be adopted. Important observation is all loads will not attain their maximum value at the same time. Various load combinations with load factors:
- 5 DL + 1.5 LL
- 5 DL + 1.5 LL + WL/EL
- 2 DL + 1.2 LL + 1.2 WL/EL
- 5 DL + 1.5 WL/EL
- 9 DL + 1.5 WL/EL
Reference: – https://law.resource.org/pub/in/bis/S03/is.875.5.1987.pdf