The use of external post-tensioning tendons to increase load-carrying capacity is a well-known practice. In essence, tensile stresses in concrete resulting from additional loads can be limited or eliminated by compressive stresses induced by post-tensioning. This technique is primarily applied in bridges, where the increasing traffic and permissible life loads often require an increase in load capacity. External post-tensioning, as a method for enhancing the load-carrying capacity of structural elements, can also be successfully employed in buildings. Changes in building usage and evolving load standards may render the existing structural capacity insufficient. External post-tensioning tendons begin to exert their influence immediately after being tensioned, which is why the technology is often referred to as "active" strenghtening.
