Prestressing Steel Properties
Description
Definition of the material properties for a section or beam is a three step process:
- Add the material type (concrete / reinforcing steel / etc.)
- Define a set of properties for that material type (proof strength etc.)
- Allocate the material properties defined in 1 and 2 to the relevant parts of the section or beam section component.
This form performs the second of these 3 stages for prestressing strand. As data is entered the program checks that values are within the expected range for steel. This check will highlight any values in error by a factor of 10 more. The displays for Ultimate Limit State and Serviceability Limit State are to the same scale, and are updated as the values in the fields are changed.
The data for relaxation is used only in the beam analysis parts of the program.
Relevant nationally determined parameters are displayed in this form, but these may only be edited in the Nationally Determined Parameters Form accessible through the NDP Values button.
Form Graphic
Field Help
0.1% Proof strength fp0.1k
Enter the proof strength of the prestress tendons. A warning will be issued if the value entered is unrealistic, but the value will not be rejected.
The properties of prestressing steel are defined by EN 1992-1-1: Clause 3.3.2-(1) as being defined in EN 10138. The default value was revised from 1600MPa to 1637MPa at version 6.60 of the program, based on the pending update to EN 10138-3.
fpk
EN 1992-1-1: Clause 3.3.6-(7) defines the default value of (fp0.1k / fpk) as 0.9. However, the content of this field is independent of fp0.1k.
εuk (inclined branch option only)
EN 1992-1-1: Clause 3.3.6-(7) defines the default value of εuk as 0.02 and the Design Strain Limit Factor (εud / εuk) as 0.9. From this is deduced the default value of 0.0222 for this field.
Modulus of Elasticity Ep
Enter the modulus of elasticity of the prestressing steel. The default value is 195 kN/mm2 from EN 1992-1-1: Clause 3.3.6-(3).
Relaxation loss after 1000 hours
The three classes of relaxation are defined in EN 1992-1-1: Clause 3.3.2-(4).
Relaxation class
The drop-down menu allows selection from the three classes of relaxation defined in EN 1992-1-1: Clause 3.3.2-(4). Selection of a class automatically sets the content of the relaxation loss field to the value from EN 1992-1-1: Clause 3.3.2-(6) that corresponds to the selected class.
Density
Enter the density of the Prestressing Steel.
The default 77kN/m3 is defined by EN 1992-1-1: Clause 3.3.5-(4).
Nationally Determined Parameters
The items under this heading cannot be edited in this form as they are Nationally Determined Parameters, and are present for information only. The values can however be edited on the NDP values form which can be accessed directly from the button on the right of this form.
Property name
The program will supply a reference name which provides an identifier to the material property set which is usually unique. This value may be edited to give a more readily recognisable name if required. 'INC' is appended to the name for the 'Inclined' case.'