METHODS OF ADVANCED CONSTRUCTION IN R.C.C PRESTRESSED CONCRETE CONCRETE BEAMS SLAB FRAMES

PRESTRESSED CONCRETE ORDINARY CONCRETE has poor tensile strength , the major portion of an ordinary

reinforced concrete beam plays little part in the flexural strength of the beam underload.

When reinforcement is stretched before or after the concrete is cast and the stretched reinforcement is anchored to the concrete it causes a compressive prestress in the concrete as it resists the tendency of the reinforcement to return to its original length .

This compressive prestress makes more economical use of the concrete by allowing all of the section of concrete to play some part in supporting load .

In prestressed concrete the whole or the part of concrete section is compressive before the load is applied ,so that when the load is applied the compressive prestress is reduced by flexural tension.

For the prestress to be maintained,the steel reinforcement must not suffer permanent elongation or creep under load.

High tensile wire is used in prestreesed concrete to maintain the prestress under load.

Under load, a pre stressed concrete member will bend or deflect and compressive and tensile stresses will be developed in opposite faces.

Concrete in parts of the member will therefore have to resist compressive stress induced by the pre stress as well as compressive stress developed during bending .for this reason high compressive strength concrete is used in pre stressed work to gain maximum advantage of the pre stress

A consequence of the need to use high strength concrete is that pre stressed members are generally smaller in section than comparable reinforced concrete ones.

Concrete beams and slab frames: A beam and slab floor is generally the most economic and therefore most usual form

of floor construction for reinforced concrete frames. When a reinforced concrete frame is cast monolithically with reinforced concrete

floors it is logical to design the slabs to span in both directions so that all the beams around a floor slab can bear part of the load

This two way span of floor slabs effects some reduction in the overall depth of floors as compared to a one way spanning floor slab construction.

The insitu cast reinforced concrete floor illustrated, combines main and secondary beams as a grid to provide the leas thickness of slab for economy in the mass of concrete in construction, and comparatively widely paced columns. This square grid

results in minimum thickness of floor slab and minimum depth of beams, and therefore the minimum dead weight of construction.

Because of the user requirements and circulation needs in a building which will increase the overall depth, weight and therefore cost of construction of a reinforced concrete frame.