First assignment released digitally,
I am gladly presenting to you, especially for course's attendants, third assignment problems and bonus problems. This assignment was designed mainly to calculate losses in prestressing tendon, checking stresses, Magnel optimization curve, and its concept in order to get full comprehension in simple serviceability design.
Both of these problems can be downloaded through links below:
http://www.4shared.com/office/eCODoWOY/TUGAS_KECIL_3-12.html
and
http://www.4shared.com/office/Tnc77eW9/Pertanyaan_Bonus_Tugas_3.html
Password may be needed to be able to download it,
Password : prestress
Please feel free to discuss the problems in this blog or weekly assistance meeting on next Friday.
Good luck and try to do it by yourself.
Ariel A. Suselo
how long is the diameter of the strand?? must i assumed it??
ReplyDeleteThe diameter should be taken from jacking force (Pj) and its allowable stress (fpj). The stress in one strand should not bigger than its yield strength (0,85*fpu).
Deleteoww.. ok! thanks!
ReplyDeleteIs the area calculated by dividing Pj with fpj for 2 tendons or 1 tendon?? If it is for 2 tendon, should i calculate the Pj/tendon??
ReplyDeleteand what does symmetric double curvature mean?
DeleteThe area from your calculation should be considered for 2 tendons, but you need to calculate jacking force in each tendon to determine elastic shortening loss in sequential jacking.
DeleteSymmetric double curvature is defined as cable configuration which has two parabolic figure in one configuration and is mirrored at middle span.
The change in curvature or parabolic figure in located 4 meters from each supports (I think I forgot to put this information in the problems).
Update notification about "average prestressing stress after immediate loss"
ReplyDeleteThe idea to calculate average jacking stress or force after simulate friction, wobble, and wedge's slip is to use STRESS term. Using this term, we can easily solve the problem (especially for number A.2.d and A.2.e) without being confused with "one way" or "two way" jacking forces pulling process (either using Pj or Pj/2).
After we get the average stress, we can use it to calculate average force with total area of tendons.
Keep in right path...
i want to make number A5, deflection for short term especially.
ReplyDeletewill wear this equation:
d= wps'*a*L^2/(96*E*I)(3-2*(a/l)^2)
as write at Mr.Bambud's book
but i don't understand what l is, in (a/l)^2 ?
is the long of the structure (20m)?
The l in that equation is the same with L:20 m. The simplified equation need to be updated as follows:
Deleted:wps*a^2*L^2/(96*E*I)*(3-2*(a/L)^2)
It would be better if you can verify the simplified equation with applicable deflection equation such as moment area or conjugate beam method.
BTW, the equation is in page 29 :)
ReplyDeletethx
Assignment update
ReplyDelete1.Stress limits for magnel diagram are allowed to be extended according to ACI 318, include the compression stress limit after long term loss to taken 0.45 fc' (live load should be reduced to 19 kn/m) or 0.5 fc' (live load : 20 kn/m)
2.Concrete stress for creep calculation according to ACI should be calculated from beam selfweight stress reduced by 20% sidl stress. But for field application consideration, you may just calculate the beam selfweight stress.
3.The time considered for shrinkage calculation should be equal with relaxation calculation (720 hours or 30 days), but you may take concrete final setting time (28 days) because the hidration process has almost been done.
Keep being updated