Revision of Ver.7.4.1

Tendon Property

Define the tendon properties such as tendon area and instantaneous prestress losses.

From the Main Menu select Load > Prestress Loads > Tendon Property.

Select Static Loads > Prestress Loads > Tendon Property in the Menu tab of the Tree Menu.

 

To define new or additional tendon properties

Click in the Tendon Property dialog box and enter the following:

Add/Modify Tendon Property dialog box

 

Tendon Name: tendon name being defined

Tendon Type

Define the tendon type among Pre-Tension, Post-Tension and External.

Internal (Pre-Tension): Prestressing tendons prior to casting concrete, which transmits prestress through bonding between concrete and tendons

Internal (Post-Tension): Post-tensioning tendons through hardened concrete members ?tendons are gradually stressed and anchored to the members.

External: Tendons are placed external to concrete members and stressed.

Note 1
Depending on the Tendon Type (Pre-Tension, Post-Tension and External), the entry fields for variables related to tension losses in tendons and duct diameter are either activated or inactivated.

Note 2
If the tendon placement location is External, the tendon is displayed as a straight line in Display.

 

Material

Select the material properties of the tendon. Click to the right to add new or modify/delete previously defined tendon properties.

 

Total Tendon Area

Specify the total area of the tendon. You may either directly specify the cross-sectional area or click to enter the standard cross-sectional area and the number of strands for auto-calculation of the total area.

 
Classification
 

Tendon Type

12. 4

12. 7B

15. 2B

G15. 2

28. 6

Number of Strands

EA

12

12

12

19

1

Tendon Area

CM2

11.148

11.8452

16.644

26.353

5.324

Duct Diameter

CM

6.8

6.8

7.8

11.5

5

Wobble Friction Factor ¥ë

/m

0.004

0.004

0.004

0

0.004

Curvature Friction Factor ¥ì

/rad

0.3

0.3

0.3

0.3

0.3

Anchorage Slip

mm

11

12

11

5

5

Relaxation

%

5

5

5

1.5

2.5

Young's Modulus

N/mm2

200000

200000

200000

200000

200000

Yield Strength ¥òpy

N/mm2

1450

1600

1600

1600

1500

Tensile Strength ¥òpu

N/mm2

1700

1850

1850

1860

1800

 

Duct Diameter

When the Tendon Type is Post-Tension, input for the diameter of duct is required. Based on the tendon area, the duct diameter is automatically calculated, which is then referred to for duct diameter input.

 

Strand Diameter

When the Tendon Type is Pre-Tension, the diameter of strand should be entered. The program automatically calculates the diameter of strand corresponding to the specified Total Tendon Area. The diameter of the strand is used to compute Transfer Length.

 

Revision of Ver.7.4.1

Relaxation Coefficient: C

Select Magura or CEB-FIP for the method of applying relaxation. To ignore the steel relaxation, uncheck the box.

When Magura is selected

Select 10 or 45 for Relaxation Coefficient (C), which relates to the product. Relaxation coefficients of 10 and 45 may be used for general steel and low-relaxation steel respectively.  Losses due to steel relaxation are determined from the following equation:

where,  ,: initial stress,:  stress at time t after loading, : yield stress (0.1% Offset Yield Stress)C: Relaxation Coefficient (general steel: 10, low-relaxation steel: 45)

When CEB-FIP is selected

Enter the final loss ratio due to steel relaxation. Prestress loss due to steel relaxation is determined from the following equation:

where,: initial stress, : final loss ratio due to steel relaxation, : progress of steel relaxation at the last time step

 

The progress of steel relaxation with time is as follows:

Progress of relaxation (k)

Lapse

k=1/16 ln{ (t-to)/10+1 }

0 ¡Â (t-to) ¡Â 1000

k={ (t-to)/(0.5?0^6) }0.2

1000 ¡Â (t-to) ¡Â 0.5x106

k=1. 00

(t-to) ¡Ã 0.5 x106

where to: the timing of prestressing,  t: the time when tendon loss due to relaxation is evaluated

Revision of Ver.7.4.1

Note

For Relaxation Coefficient (C), 10 for general steel and 45 for low-relaxation steel may be entered. Check off the box to ignore Relaxation.

When JTG04 is selected

If the user selects JTG04 standard in the Material Data and selects JTG04 for Relaxation Coefficient in the Tendon Property, the Characteristic Value of Strength (fpk) is automatically entered as per the JTG04 code. If the user does not select JTG04 standard in the Material Data, the user can directly enter the Characteristic Value of Strength (fpk).

In case Steelbar540, Steelbar785 or Steelbar930 is selected in the Material Data, the Application of Overstress Reduction Factor is ignored.

When TB05 is selected

If the user selects TB05 standard in the Material Data and selects TB05 for Relaxation Coefficient in the Tendon Property, the Characteristic Value of Strength (fpk) and the Tendon Relaxation Coefficient (¥î) are automatically entered as per the TB05 code. If the user does not select TB05 standard in the Material Data, the user can directly enter the Characteristic Value of Strength (fpk) directly.

Note

Calculation of Tendon Relaxation Coefficient (¥î) and loss due to Relaxation Tendon Relaxation

 

Curvature Friction Factor

Calculation of Relaxation Coefficient ( )

If material = Wire1470, Wire1570, Wire1670, Wire1770, Wire1860

 If material = Strand1470, Strand1570, Strand1670, Strand1720, Strand1770, Strand1820, Strand1860

If material = PSB830

 

If material = PSB830 and Application of Overstress Reduction Factor is checked on

 Calculation of Prestress Loss

If  is greater than or equal to

 If  is less than  

where ,       : The loss of Prestressed Stress due to Tendon Relaxation

                                             : Tendon Relaxation Coefficient

                                          : Anchor Tendon Stress

                                         : Tendon Tension Strength Standard Value

to account for friction loss due to the curvature of tendons

 

Wobble Friction Factor

To account for straightness/length effect (imperfection in alignment along the length of tendon, regardless of straight or draped alignment)

 

Ultimate Strength

 

Yield Strength

 

External Cable Moment Magnifier

Enter the increase of effective prestress of external cable to be used for calculating failure-resisting moment. Entered stress increase will be used for PC design.

 

Anchorage Slip (Draw in)

Tendon slippage at the anchor

Begin: slippage at the beginning of tendon if tensioned here

End: slippage at the end of tendon if tensioned here

 

 Bond Type

Bonded: Section properties reflect the duct area after grouting

Unbonded: Section properties exclude the duct area.

 

To modify the previously entered tendon data

Select the tendon from the list in the Tendon Property dialog box and click to change any relevant data.

 

To delete the previously entered tendon data

Select the tendon from the list in the Tendon Property dialog box and click to eliminate any relevant data.