Please let me know where I can find the definitions for deflections and various times? Is the beam wt plus prestress included in the "At Transfer" deflecton. Does the "At Erection" deflection include the beam only plus prestress at the time the beam is erected? There is not value reported for long term dead? Is the dead load stress increment the short term deflection due to applied topping and SDL? Are the definitions in the example manual? I am designing with AASTHO.
Hi,
1) "Please let me know where I can find the definitions for deflections and various times?"
Description of deflection can be found in the design report:
“The deflections are calculated from integration of the curvatures along the
beam, using the parameters detailed below:
(Note that the reported values of deflections for live loadings are
exaggerated when these are derived from enveloped effects)
…
“
Age values are listed in the time-dependent losses section:
“ REFINED ESTIMATES OF TIME-DEPENDENT LOSSES - Article 5.9.5.4
Elastic modulus of prestressing steel: Ep = 2.85E4 KSI
Total effective tendon area: Aps = 7.3362 IN²
Elastic modulus of concrete at transfer: Eci = 4619.0 KSI
Percentage relative humidity: H = 70.0 %
Humidity factor for creep: khc = 1.56-0.008H = 1.0
Humidity factor for shrinkage: khs = 2.00-0.014H = 1.02
Age at the end of curing: tc = 3.0 day
Age at transfer: ti = 4.0 day
Age at in-situ casting: td = 60.0 day
Final age: tf = 120.0 day
…
“
“Age at transfer” and “Age at in-situ casting” values can be set on the “Pre-tensioned Beam section definition” form. “Age at the end of curing” and “Final age” values can be edited on the “Data for Shrinkage and Creep” form.
2) "Is the beam wt plus prestress included in the "At Transfer" deflecton?"
Yes, that’s right: precast self-weight + pre-stress.
3) "Does the "At Erection" deflection include the beam only plus prestress at the time the beam is erected?"
Deflection at beam erection includes transfer loads and beam erection load.
4) "There is not value reported for long term dead?"
Long-term Dead stresses are used to calculate Dead Stress increment therefore no separate values are displayed. See #5.
5) "Is the dead load stress increment the short term deflection due to applied topping and SDL?"
Dead Stress Increment = Long-term Dead – Transfer Stresses. Deflection from the Increment is calculated with effective elastic modulus.
6) "Are the definitions in the example manual?"
See #1.
Please, let me know if I managed to answer your questions.
Regards,
Karoly
