Pre-stressed Concrete is often preferred over conventional RCC for long-span bridges because
- AIt allows for a smaller cross-section and lighter self-weight.Correct
- BIt completely eliminates the need for high-strength steel.
- CIt is cheaper for small residential buildings.
- DIt does not require any specialized equipment for tensioning.
Solution
Concept
Pre-stressed Concrete Advantages
Formula
N/A
Step-by-step solution
1. Review the given question regarding why Pre-stressed Concrete is preferred over RCC for long-span bridges. 2. Understand that pre-stressing counteracts tensile stresses, allowing for thinner cross-sections and reduced self-weight. 3. Match this key advantage with the choices and select Option (a) as the correct choice.
Explanation
Pre-stressed concrete uses high-strength steel tendons that are stretched to put the concrete under compression before loads are applied. This counters tensile stresses from heavy loads, allowing engineers to design thinner, lighter beams that can span much longer distances without sagging or cracking compared to conventional RCC.
Shortcut
To remember the main advantage of Pre-stressed Concrete for long-span bridges, use the phrase "PSC = Slim & Span": - Slim & Light: Smaller cross-section and lighter self-weight due to pre-compression. - Long Span: Ideal for long bridges without sagging or excessive cracking compared to conventional RCC.
Common mistake
A common mistake is selecting option B by incorrectly assuming that pre-stressed concrete eliminates the need for high-strength steel; in reality, high-strength steel is essential for applying and maintaining pre-stressing forces. Another frequent mistake is selecting option D by overlooking that specialized tensioning equipment and jacks are strictly required during construction.
Correct answer: A) It allows for a smaller cross-section and lighter self-weight.