Post Tensioned Roof

The concrete had been exposed to colorado s extreme temperature cycles and subjected to repeated volume changes and freeze thaw cycles.

Post tensioned roof.

Post tensioning is a method of prestressing in which the tendons are tensioned after the concrete has hardened and the prestressing force is primarily transferred to the concrete through the end anchorages. Instead of being stressed to the normal 140 to 150 psi the school roof was post tensioned to 280 to 300 psi. This gives a very efficient structure which minimises material usages and decreases the economic span range when compared to reinforced concrete. The polystyrene was prefabricated in panels with 5 8 inch thick gypsum wallboard glued to the underside.

Tendons the basic element of a post tensioning system is called a tendon. A continuous wire strand in a greased plastic sheath is laid in a circular pattern within the fresh concrete of both the roof and floor panels at the time of casting. After only 10 years of service the roof of a 15 million gallon reservoir in greeley colorado was near collapse. Post tensioning is a method of reinforcing strengthening concrete or other materials with high strength steel strands or bars typically referred to as tendo beton design concrete design concrete structure steel structure suspended ceiling systems civil engineering design building foundation reinforced concrete architecture details.

To produce an r value of 24 the 7 inch thick concrete roof was cast in place over a 3 inch thick layer of expanded polystyrene. Post tensioned slabs use high strength tensioned steel strands to compress the slabs keeping the majority of the concrete in compression. Post tensioning of foundations transfer beams and plates post tensioned masonry and the combination of precast elements with cast in place concrete by means of post tensioning offer other interesting opportunities. Ducts thin sheet metal pipes with claw coupling or welded overlapped seam supplied in lengths of 5 and 6 m.