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Properties of pre-tensioned tendons

In service Concrete Advanced in Design Defaults > Reinforcement and reinforcement design > Prestressing pre-tensioned can be used to define general properties and type of stressing of pre-tensioned tendons.

Type of stressing	See the figure below the table.
Anchorage set	Anchorage set at stressed end of tendon.
Initial stress	Specifies the initial stress at stressed end of tendon (before seating).
Stress during correcting	Defines the stress at stressed end of tendon. The amount of relaxation can be decreased by keeping the stress constant (so called correction of relaxation).
Duration of short-term relaxation	Specifies the time period between the end of correction of relaxation (if any) and time of anchoring.
Duration of keeping stress	The duration of keeping constant stress during correction of relaxation.
Anchorage length	The length of development of bond between the concrete and pre-tensioned tendon.
Length of prestressing units	Total length of wires or strands (between wedges); for pre-tensioned concrete it is equal to the length of stressing bed plus the length of abutments, see Fig. Pre-tensioned beam.
Distance between sections for output	Defines sections where results are given.
Length of stressing bed	self-explanatory
Shortening of stressing bed due to stressing of all prestressing units	self-explanatory
Coefficient of thermal expansion of stressing bed	self-explanatory
Temperature of prestressing units and stressing bed at stressing	self-explanatory
Temperature of prestressing units at the time when bond exists	self-explanatory
Temperature of stressing bed at the time when bond exists	self-explanatory

Pre-tensioned beam

$image\pretensioned_beam.gif$

Input of overhang

a) The user defines the real length of the tendon - this length includes also the overhang length (only prestressing losses are calculated on this real length of the tendon).

b) The user inputs the overhang-length on both ends. These overhang lengths are then subtracted from the total real length of the tendon. The length of the tendon used in the FEM calculation equals to the real length of the tendon decreased by the overhangs on both ends.

Example

Beam with length of 10.0 m, tendon with length of 11.0 m and overhangs 0,5 m on each end. → The tendon length for calculation of losses = 11.0 m; tendon length for FEM calculation = 10.0 m

Type of stressing

Type 1	$image\TypeOfStressing1.gif$
Type 2	$image\TypeOfStressing2.gif$
Type 3	$image\TypeOfStressing3.gif$
Type 4	$image\TypeOfStressing4.gif$
Type 5	$image\TypeOfStressing5.gif$

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