Final answer:
The assertion about pre-tensioning and post-tensioning in the question is false. Pre-tensioning happens before concrete is cured, whereas post-tensioning occurs after. These techniques are employed to counteract the tensile forces experienced by concrete structures.
Step-by-step explanation:
The statement provided is false. Pre-tensioning is a technique where the steel is stressed before the concrete has been poured and cured. In contrast, post-tensioning is a method where the steel tendons are stressed after the concrete has hardened or cured. The purpose of both methods is to apply a force that counteracts the tensile forces that will occur in service, thus enhancing the structural integrity of the concrete.
Tension is indeed the result of opposite forces pulling in parallel directions along the length of a connector, such as a string or a rope, and does tend to pull towards the center at the ends of the connector.
In order to calculate thermal stress on concrete blocks with no space for expansion, engineers use the initial and final temperatures, the thermal coefficient of expansion, and the Young's modulus of concrete. Designing components that can expand and contract prevents thermal stress, and in the context of concrete, steel is often used for reinforcement rods as its coefficient of linear expansion closely matches that of concrete. This harmony between materials helps to prevent stresses that might otherwise risk structural integrity.