Pattern of defect on post tensioned system in building application / Eafa Eada Mohamed Ali Piah

The A.C.I. Committee on Prestressed Concrete gives one of the descriptions of post tensioned concrete. ‘Prestressed Concrete is concrete in which there have been introduced internal forces of such magnitude and distribution that the forces resulting from given external loadings are counteracted to a desirable degree'. Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons. Post-tensioning applications include office and apartment buildings, parking structures, slabs-on-ground, bridges, sports stadiums, rock and soil anchors, and water-tanks. In many cases, post-tensioning allows construction that would otherwise be impossible due to either site constraints or architectural requirements. Buildings have to serve defined functions. Accordingly, they have to be equipped with various electrical, mechanical and sanitary installations and certain climatic and other environmental variables have to be maintained within given tolerances. Similar to a vertebrate's skeleton the structural frame of a building is just one essential component of a complex system and working on the design or construction of a building has a highly interdisciplinary character in any position. The post-tensioning of buildings can only be successful if this is recognized and a close cooperation with all relevant parties is established. Building frames have to resist gravity and lateral loads. Horizontal members (floor slabs, beams) account for the major part of the total costs. With increasing height the relative costs of vertical members (walls, columns) increase and extra costs are incurred for resisting the increased lateral loads (wind, seismic action).