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Plastic deformation theory

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 If a deformation of steel due to load returns in original state as a load deletes, it is said to linear and elastic behavior. However, when the load is reduced, the strain decreases along an almost unloading line CD which is parallel to the initially linear region of curve. When the load is again zero at the end of unloading, the strain is not zero ; there remains a residual strain AD. The irrecoverable strain AD is referred to as plastic strain while the recoverable strain CE is the elastic strain. The graph follows.

 The advantage of this method fellows.

 Other methods consider only elastic area and pre-camber according to design dead load.  but these methods very inconvenient and difficult. while our method considers plastic and elastic area so initially H-beam is cambered by pre-loading over elastic area. existing method makes use of a fixed support so very inconvenient, while our method chooses simple support, so this is very useful. this method can be applied simple and continuous preflex beam.

Process of manufacturing preflex composite beam using plastic deformation of rolled profile

 Most of all, a beam is connected by prestressed steel bar in both ends of beam and by plastic loading in both quarters of beam, plastic deformation appears. after beams are turned over, in same course, support is connected by PS bar. moreover  by loading in both quarters of beam, the beams are made straight then low casing concrete is placed and cured. finally by unloading low flange casing concrete is introduced prestress. this is method of manufacturing preflex composite beam.