What are the different type of losses in prestress in pre tensioning and post tensioning?
What are the different type of losses in prestress in pre tensioning and post tensioning?
In a pre- tensioned member, the major components of prestress losses are those due to elastic, creep and shrinkage deformation of concrete and that due to relaxation of steel. In a post-tensioned member, additional losses due to friction take place.
What are the losses present in post tensioned member?
In post-tensioned members, losses occur during the stressing operation due to friction between the tendon and sheathing or duct, which is caused by the intended and unintended tendon curvature. There are also losses due to seating of the wedges or nuts as the jacking force is transferred into the anchorage device.
What is the difference between prestressed and post stressed concrete?
Prestressing simply means that the steel is stressed (pulled or tensioned) before the concrete has to support the service loads. Post–tensioned concrete means that the concrete is poured and then the tension is applied-but it is still stressed before the loads are applied so it is still prestressed.
What is the difference between prestressing and post tensioning?
1. Pretension is the technique in which we are imparting tension in strands before placing the concrete. Post tensioning is done by forming a duct in which strands are pulled (tensioned) after the concrete gains it’s full strength.
What are the losses in prestressing method?
The various reductions of the prestressing force are termed as the losses in prestress. The losses are broadly classified into two groups, immediate and time-dependent. The immediate losses occur during prestressing of the tendons and the transfer of prestress to the concrete member.
Which of the following losses of prestress occurs only in pre tensioning and not in post tensioning?
Loss due to Friction: The friction generated at the interface of concrete and steel during the stretching of a curved tendon in a post-tensioned member. The loss due to friction does not occur in pre-tensioned members because there is no concrete during the stretching of the tendons.
What is losses in post tensioning?
Post-tensioned: All forms of time-dependent losses occur, but the only immediate loss to occur is elastic deformation of concrete that too if tendons are stressed sequentially.
Why there are losses in prestressed?
Loss of prestress can be characterized as that due to instantaneous loss and time-dependent loss. Losses due to anchorage set, friction and elastic shortening are instantaneous. Losses due to creep, shrinkage and relaxation are time-dependent.
What are the losses in prestressed concrete?
Types of Losses in Prestress of Prestressed Concrete
- Loss due to Elastic Shortening.
- Loss due to Shrinkage of Concrete.
- Loss due to Creep of Concrete.
- Loss due to Creep in steel (Relaxation of steel)
- Loss due to Friction.
What are the types of prestressing?
There are four sources of prestressing force: Mechanical, hydraulic, electrical and chemical.
Which of the following losses occurs in post tensioning pre stressed concrete structures?
Which kind of loss is not applicable for post tension cases?