How many types of losses in prestress are observed in Pretensioned member? Explanation: The losses in prestress in pretensioned member are four types: Losses due to elastic deformation of concrete, Loss due to relaxation of stress in steel, Loss due to creep of concrete, Loss due to shrinkage of concrete, in pretensioned members, due to prestress present at the ends of the members the tendon
? Table: Types of Losses of Prestress
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What are the losses of prestress in post tensioned members?
What are the types of losses in pretensioned prestressed concrete? The prestress losses are defined as the loss of tensile stress in the prestress steel which acts on the concrete component ofthe prestressed concrete section. In pretensioned concrete, the four major sources of prestress losses are elastic shortening (ES), creep (CR), shrinkage (SH) and relaxation (RE).
How many types of losses in prestress are observed in Pretensioned member? – Related Questions
What is prestress loss?
This is called loss of prestress and may be caused by subsequent prestressing of various tendons (elastoplastic shortening of steel and concrete), creep of the concrete (viscoelastic shortening), shrinkage of the concrete (shortening due to initial strain), and relaxation of the steel (viscoelastic extension).
How are prestress losses calculated?
The prestress loss due to elastic shortening in pretensioned members is taken as the concrete stress at the centroid of the prestressing steel at transfer, f cgp, multiplied by the ratio of the modulus of elasticities of the prestressing steel and the concrete at transfer.
How can we prevent prestress loss?
The result shows that maximum 10% of prestress loss occurs at the continuous joint and the proposed block-out method can reduce the prestress loss ratio by maximum 5%, approximately.
This means that the block-out method can enhance the prestressing efficiency of continuous PSC girder bridges.
Which system of prestressing is widely used in India?
The Freyssinet anchorage system, which is widely used in Europe and India, consists of a cylinder with a conical interior through which the high-tensile wires pass and against the walls of which the wires are wedged by a conical plug lined longitudinally with grooves to house the wires.
When jacking is done in one end what is the maximum loss?
Jacking at one end only during prestressing induces a higher amount of frictional losses as compared to jacking at both ends although prestressing forces are the same. So, jacking at both ends (half the number of tendons at each) is generally preferable.
What are the sources of prestress?
There are four sources of prestressing force: Mechanical, hydraulic, electrical and chemical.
What are different methods of post tensioning?
Prestressing steel, such as strands, bars or wires, is used to impart compressive stresses to the concrete.
Pre-tensioning is a method of prestressing in which the tendons are tensioned before concrete is placed and the prestressing force is primarily transferred to the concrete through bond.
What is freyssinet?
Freyssinet System: Introduced by the French Engineer Freyssinet and it was the first method to be introduced. High strength steel wires of 5mm or 7mm diameter, about 12 in number are grouped into a cable with a helical spring inside.
What is the difference between RCC and PSC?
Advantages of prestressed concrete:
Which loss of following are immediate losses?
Immediate losses which occur before and during transfer: Anchorage set (slip) Elastic shortening. Friction loss due to length (wobble) and curvature effects.
What is Anchorage slip in prestressed concrete?
What is PSC beam?
Prestressed concrete is a system devised to provide sufficient precompression in the concrete beam by tensioned steel wires, cables, or rods that under working conditions the concrete has no tensile stresses or the tensile stresses are so low that no visible cracking occurs.
What is effective prestress?
The stress remaining in concrete due to prestressing after loss of prestress; includes the effect of the weight of the member, but excludes the effect of any superimposed load.
What is the difference between pre tensioning and post tensioning?
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 is partial loss in prestressing?
Prestressing a concrete member effectively applies a substantial axial force to the member that is in place for its entire service life. This reduction in force is referred to as partial prestress loss and is addressed as part of the design of a prestressed member.
Which loss of prestressing is time dependent loss?
The time-dependent losses are primarily made up of three components.
These are creep and shrinkage of the concrete, and relaxation of the prestressing steel after its application to the concrete.
Which type of prestressing is used in railway sleepers?
Mono-block sleepers: These are Beam-type single-piece prestressed concrete sleepers, and have roughly the same dimensions as timber sleepers.
The advantages of the twin-block sleeper over the mono-block sleeper are: well-defined bearing surfaces and also high lateral resistance in the ballast bed.
