Question

Ultimate load method of designing a RCC structure w.r.t. elastic theory method is: ____.

More economical

More costly

Equal in cost

Not comparable in costing

Answer ( Option A)

More economical

Solution

Mehods of designing an RCC structure:

There are 3 methods of design an RCC structure:

1. Working stress method:

• This was the traditional method of design.

• The method basically assumes that the structure behaves in a linear elastic manner.

• The actual stresses developed due to the actual working load.

• Stresses developed are kept within permissbible stress value.

• The factor of safety is applied to stress values only.

• The design usually results in relatively large sections of the structural members.

2. Ultimate load method:

• This method is sometimes also referred to as the Load factor method.

• In this method, the stress condition at the site of the impending collapse of the structure is analyzed and the nonlinear stress-strain curves of concrete and steel are made use of.

• The concept of modular ratio and its associated problems are avoided entirely in this method.

• This method is more economical than the working stress method.

3. Limit state method:

• A condition of the structure once achieved, the structure cannot perform its intended function satisfactorily in the future in terms of safety or serviceability.

• Condition of a structure, once achieved the structure cannot be used satisfactorily in future is called limit state condition.

• Limit state can be achieved due to Limit state of collapse and Limit state of serviceability.

• This method is based on the Ultimate Strength of the structure, satisfactory performance at the working stage, and satisfying the serviceability & durability requirements.