Precast/Prestressed Girder Help

Detensioning

A simulation of the strand-cutting operation occurring in the precast yard is given on the printout. It represents the state of stress in the top and bottom of the beam as each group of strands is cut or detensioned. Generally, this is important only to fabricators or consulting engineers designing straight patterns with debonded strands.

Information in the detensioning table is organized in rows and columns. The three leftmost columns give the group number, number of strands in that group, and elevation of the group at the end and middle of the beam. There will be (n+1) additional columns of stresses, corresponding to the length of shielding plus transfer distance, where "n" is the number of different shielding lengths present in the beam. If there is no shielding present, there will only be one stress column corresponding to the first transfer distance.

A pair of rows corresponds to each strand group. The stresses shown at a particular group are the algebraic sums of the full self-weight stress at the location under consideration plus the prestress resulting from the cutting of the group under consideration and all groups above it in the chart at the top (Ft) and bottom (Fb) of the beam.