Prestressed concrete means 

Explanation:

Prestressed Concrete

Prestressed concrete is a form of concrete construction where compressive stresses are deliberately induced in the concrete before any external loads are applied. This is done to counteract the tensile stresses that will develop under service loads, thus improving the concrete's performance and durability.

Analyzing the Given Options

1. Option 1: "Compressive stress induced in concrete before bending." (Correct Answer)

   • In prestressed concrete, compressive stress is introduced in the concrete using prestressing techniques like pre-tensioning or post-tensioning.

   • This compressive stress counteracts the tensile stresses that occur when the concrete is subjected to external loads.

2. Option 2: "Compressive stress induced in steel before bending." (Incorrect Answer)

   • In prestressed concrete, compressive stress is not applied to steel. Instead, tensile stress is applied to steel tendons.

   • Steel tendons are stretched and anchored to induce compressive forces in the concrete.

3. Option 3: "Tensile stress induced in steel before bending." (Incorrect Answer)

   • Tensile stress is indeed applied to the steel tendons in prestressed concrete, but this is not the same as the compressive stress induced in concrete.

   • The question specifically asks about the stress in the concrete, not in the steel.

   • Therefore, this option is not correct in the context of the question.

4. Option 4: "Tensile stress induced in concrete before bending." (Incorrect Answer)

   • In prestressed concrete, compressive stress is induced in the concrete, not tensile stress.

   • Tensile stress is undesirable in concrete because it is weak in tension and prone to cracking under tensile loads.