1. What is the characteristic strength of materials?
The strength of materials below which not more than 5% of the test results are expected to fall is known as the characteristic strength of the material and it is denoted by fck.
2. What is limit state?
The acceptable limit for the safety and serviceability requirements before failure occurs is called limit state. This structure is so designed that it carry the loads with sufficient degree of safety and serviceability and structure will not become unfit for use for which it is to be designed.
3. Name the latest RCC and steel code.
Latest code for RCC is IS 456:2000 and for steel code is IS 800:2000.
4. What is cement concrete?
Cement concrete is a mixture of binding material (cement), fine aggregate (sand), coarse aggregate, water and admixture in proper proportion to achieve concrete of desired properties at fresh state and hardened state.
5. What are the types of limit state?
There are mainly two types of limit state, one is limit state of collapse and second is limit state of serviceability.
6. What is the maximum percentage of reinforcement in a column as per IS 456:2000?
As per IS 456:2000, maximum percentage of reinforcements in column is 6%.
7. What is the modulus of elasticity of steel as per IS 456:2000
Modulus of elasticity of steel is 2 x 105.
8. Why tensile strength of concrete is ignored while designing in limit state method?
As we know that the tensile strength of concrete is very much less as compared to its compressive strength and also the tensile strength of concrete does not contribute towards enhancement of moment of resistance of the section except providing bod between concrete and steel for developing tensile strain and thus stress in steel.
9. What are the limitations of working stress method?
The limitations of this method are:
- It assumes stress strain relation for concrete is constant, which is not true.
- It gives the impression that “factor of safety times the working load” is the failure load, which is not true. This is particularly so in case of indeterminate structures. In these structures there will be redistribution of forces as plastic hinges are formed at critical sections.
- And this method gives uneconomical sections.
10. What are the advantages of working stress method?
Advantages of this method are:
- It is simple.
- Reasonably reliable and,
- As the working stresses are low, the serviceability are automatically satisfied and there is no need to check them.
11. Explain Load Factor Method (LFM) or Ultimate Load Method (ULM)
In this method ultimate load is used as design load and the collapse criteria used for the design.
12. What is characteristic load in Limit state method?
Structures have to carry dead load and live loads. The maximum working load that the structure has to withstand and for which it is to be designed is called characteristic loads. As per the code the characteristic loads means the value of the load above which not more than 5% results are expected to fall.