Pretension member:
1. In pretensioned prestress concrete, steel is tensioned prior to that of concrete. It is released once the concrete is placed and hardened. The stresses are transferred all along the wire by means of bond.
2. Suitable for short span and precast products like sleepers, electric poles on mass production.
3. In pretensioning the cables are basically straight and horizontal. Placing them in curved or inclined position is difficult. However the wire’s can be kept with eccentrically. Since cables can not be aligned similar to B.M.D. structural advantages are less compare to that of post-tensioned.
4. Prestress losses are more compare to that of post-tensioned concrete.
Post-tensioned member:
1. Concreting is done first then wires are tensioned and anchored at ends. The stress transfer is by end bearing not by bond.
2. Suitable for long span bridges
3. The post tensioning cables can be aligned in any manner to suit the B.M.D due to external load system. Therefore it is more economical particularly for long span bridges. The curved or inclined cables can have vertical component at ends. These components will reduce the design shear force. Hence post-tensioned beams are superior to pretensioned beams both from flexural and shear resistances point.
4. Losses are less compare to pre-tensioned concrete
1. In pretensioned prestress concrete, steel is tensioned prior to that of concrete. It is released once the concrete is placed and hardened. The stresses are transferred all along the wire by means of bond.
2. Suitable for short span and precast products like sleepers, electric poles on mass production.
3. In pretensioning the cables are basically straight and horizontal. Placing them in curved or inclined position is difficult. However the wire’s can be kept with eccentrically. Since cables can not be aligned similar to B.M.D. structural advantages are less compare to that of post-tensioned.
4. Prestress losses are more compare to that of post-tensioned concrete.
Post-tensioned member:
1. Concreting is done first then wires are tensioned and anchored at ends. The stress transfer is by end bearing not by bond.
2. Suitable for long span bridges
3. The post tensioning cables can be aligned in any manner to suit the B.M.D due to external load system. Therefore it is more economical particularly for long span bridges. The curved or inclined cables can have vertical component at ends. These components will reduce the design shear force. Hence post-tensioned beams are superior to pretensioned beams both from flexural and shear resistances point.
4. Losses are less compare to pre-tensioned concrete
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