Which elements are common examples of pre-tensioned concrete?

• A. Thin-walled steel plates
• B. Fiber-reinforced polymer slabs
• C. Double I shapes or certain floor slabs for large concrete buildings
• D. Simple timber beams

Answer: (D)

Pre-tensioned concrete uses steel tendons that are stretched before the concrete is cast, so once the concrete cures those tendons compress the member. That built-in compression gives higher strength and better crack control, which is especially valuable for long spans and heavy floors. The common examples are prestressed elements like double-I shaped beams or certain long-span floor slabs in large concrete buildings. Other options describe materials or systems that aren’t concrete prestressing—thin-walled steel plates are steel, fiber-reinforced polymer slabs are composites, and simple timber beams are wood. So the statement about double-I shapes or long floor slabs in large buildings best fits pre-tensioned concrete.