Rapid, economical production of more than a thousand prestressed and post-tensioned box girders was crucial to the building of a public transportation system in Vancouver for the 1986 World's Fair. Since much of the system is elevated and in urban areas, precasting was chosen as a way to speed erection, lessen congestion on the job, cut costs and control quality. Tight tolerances were established, and the success of the precasting operation depended in large measure on the specialized forming system described in this article.
Working cooperatively with the precaster and system designers, the form supplier found that all needs could be met with only two form designs. One, basically straight for tangent portions of the track, has peak and sag curve capability and can be adjusted for ups and downs of the line. The other creates both horizontal and vertical curvature and superelevation necessary for banking the track. The pieces of equipment designed by the specialty forms contractor were so sophisticated and so adjustable that they can well be called forming machines, and not simply forms.