Tendon Property 





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







From the Main Menu select Load > Temp/Prestress > Tendon Property. 





To define new or additional tendon properties Click in the Tendon Property dialog box and enter the following:
Tendon Name: tendon name being defined
Tendon TypeDefine the tendon type among PreTension, PostTension and External. Internal (PreTension): Prestressing tendons prior to casting concrete, which transmits prestress through bonding between concrete and tendons Internal (PostTension): Posttensioning 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 Note 2


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 λ 
/m 
0.004 
0.004 
0.004 
0 
0.004 
Curvature Friction Factor μ 
/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 σpy 
N/mm2 
1450 
1600 
1600 
1600 
1500 
Tensile Strength σpu 
N/mm2 
1700 
1850 
1850 
1860 
1800 
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 lowrelaxation steel respectively. Losses due to steel relaxation are determined from the following equation:
where, 
where, 
: initial stress, 

: stress at time t after loading 


: yield stress (0.1% Offset Yield Stress) 


C: Relaxation Coefficient (general steel: 10, lowrelaxation steel: 45) 
When European is selected
The following expressions are applied for Class 1 (Ordinary), Class 2 (Low) and Class 3 (Hot rolled) to calculate relaxation loss with time.
∆σpr: Absolute value of the relaxation losses
σpi: Absolute value of the initial prestress for posttensioning and maximum tensile stress applied to the tendon minus the immediate losses occurred
t: Time after tensioning (in hours)
µ = σpi /fpk, where fpk is the characteristic value of the tensile strength of the prestressed steel.
ρ1000: Relaxation loss (in %), at 1000 hours after tensioning and at a mean temperature of 20°C
When CEBFIP(2010) is selected
Enter the loss ratio after 1000 hours steel relaxation by the percentage of initial prestress. Prestress loss due to steel relaxation is determined from the following equation:
where, 
: initial stress 


: loss ratio after 1000 hours due to steel relaxation 


: progress of steel relaxation at the last time step 


The progress of steel relaxation with time is as follows:
Time in hour 
1 
5 
20 
100 
200 
500 
1000 
Slow Development 
20 
35 
45 
65 
75 
85 
100 
Mean Development 
30 
45 
55 
70 
80 
90 
100 
Rapid Development 
40 
55 
65 
75 
85 
95 
100 
Following formula is applied:
where ρt: the relaxation after t hours, ρ1000: the relaxation after 1000 hours, k =log(ρ1000/ρ100)
When CEBFIP(1990) is selected
Enter the loss ratio after 1000 hours steel relaxation by the percentage of initial prestress. Prestress loss due to steel relaxation is determined from the following equation:
where, 
: initial stress 


: loss ratio after 1000 hours due to steel relaxation 


: progress of steel relaxation at the last time step 


The progress of steel relaxation with time is as follows:
Time in hour 
1 
5 
20 
100 
200 
500 
1000 
Relaxation losses at percentage of losses in 1000 hours 
25 
45 
55 
70 
80 
90 
100 
For an estimation of relaxation up to 30 years, the following formula is applied
where ρt: the relaxation after t hours, ρ1000: the relaxation after 1000 hours, k to be 0.1549
Note
The relaxation loss after 50 years is taken as three times the 1000 hour loss. The relaxation loss between 30 years and 50 years is linearly interpolated.
When CEBFIP(1978) 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{ (tto)/10+1 } 
0 ≤ (tto) ≤ 1000 
k={ (tto)/(0.5x106) }0.2 
1000 ≤ (tto) ≤ 0.5x106 
k=1. 00 
(tto) ≥ 0.5 x106 
where to: the timing of prestressing
t : the time when tendon loss due to relaxation is evaluated
When INDIA (IRC:182000) is selected
Relaxation loss at 1000 days is as follows (at 20 °C ± 2 °C ):
Initial Stress 
Relaxation loss for Normal relaxation steel (%) 
Relaxation loss for Low relaxation steel (%) 
0.5fp 
0 
0 
0.6fp 
2.5 
1.25 
0.7fp 
5.0 
2.5 
0.8fp 
9.0 
4.5 
Relaxation loss, in relation to time, is as follows:
Time (hour) 
1 
5 
20 
100 
200 
500 
1000 
Relaxation loss (%) 
15 
25 
35 
55 
65 
85 
100 
When INDIA (IRC:1122011) is selected
Relaxation loss at 1000 days is as follows (at 20 °C ± 2 °C ):
Initial Stress 
Relaxation loss for Normal relaxation steel (%) 
Relaxation loss for Low relaxation steel (%) 
0.5fp 
0 
0 
0.6fp 
2.5 
1.25 
0.7fp 
5.0 
2.5 
0.8fp 
9.0 
4.5 
Relaxation loss, in relation to time, is as follows:
Time (hour) 
1 
5 
20 
100 
200 
500 
1000 

Relaxation loss (%) 
Normal 
34  44  55  70  78  90  100 
Low 
37 
47 
57 
72 
79 
90 
100 
if the 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
iIf 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 (ξ) 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 (ξ) and loss due to Relaxation
Select the user defined relaxation function in hour/day and loss ratio due to steel relaxation relation.
Click [...] button to add/modify User Defined Relaxation Function.
to account for friction loss due to the curvature of tendons
To account for straightness/length effect (imperfection in alignment along the length of tendon, regardless of straight or draped alignment)
Enter the increase of effective prestress of external cable to be used for calculating failureresisting moment. Entered stress increase will be used for PC design.
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.
Revision of Civil 2015 (v1.1)
Q1. What are the considerations in the program regarding external tendons?