Memorandum

TO:	All Design Section Staff
FROM:	J. Kapur
DATE:	July 17, 2002
SUBJECT:	Calculation of Shipping Losses in Prestressed Girders

Prestress losses at release, lifting, transportation, and erection of prestressed girders, and the final elastic and time dependent losses shall be as follows:

     Release – 1 day (lifting of girders from casting beds)----------computed losses

     1 month – 4 months (transportation and erection of girders)--75% of final losses

     After 4 months (final losses)---------------------------------------computed losses

 

Background

We have recently added trapezoidal open box beams (U-beams) to our precast girder inventory. The prestress losses for these sections are significantly less then the losses for our conventional I-beam sections.  The lump sum shipping loss of 35 KSI is not appropriate for the U-beams. In some cases, the 35 KSI shipping loss can exceed the computed final loss. To remedy this situation, while keeping the method of estimation simple, shipping losses will now be taken as a fraction of the final loss.

 Contact Rick Brice at 705-7174 or Bijan Khaleghi at 705-7181 for questions regarding this change.

 

JK:dsb