Civil Engineering Reference
In-Depth Information
Figure 15.47
GSZ Pearl River Delta Viaduct, PRC: general arrangement of box deck option
In order to allow a daily turn round, each mould would be serviced by a production
line, Figure 15.48. This consisted of a mould for the prefabrication of the bottom
slab of the box and three jigs for the preparation of reinforcing cages for the webs
and top slab of the box. Each production line would be serviced by a pair of gantry
cranes that handled the reinforcing cages, bottom slab and the core mould. It was
planned to install immediately four moulds together with their production lines, with
the provision for four more if it was necessary to accelerate the works.
The prefabricated bottom slab would be placed in the mould followed by the
prefabricated reinforcing cage which included the ducted post-tensioning tendons,
then concrete for the deck and the New Jersey parapet would be cast and steam
cured overnight. In the morning, when the concrete had reached a strength of at least
20 MPa, a fi rst stage of prestress would be applied by partially stressing some tendons
equipped with oversized anchor plates. The deck would be jacked up out of its mould,
rolled forwards on rails and parked. This would free the mould for the next cycle. 24
hours later, the prestress would be completed, and the deck moved to storage.
With several units a day moving over the viaduct, it was considered impractical to
carry out any sustained work on the decks once they had been erected. Consequently
all cast concrete was excluded from the deck erection cycle. As the viaduct alignment
included horizontal and vertical curves, the ends of some of the decks had to be angled
slightly. Other specialisations included decks adjacent to expansion joints, occasional
shorter spans and special parapet details. It was considered that if the units were to be
prefabricated in the order in which they were to be used, there would be too much risk
Figure 15.48
GSZ Pearl River Delta Viaduct, PRC: production line for prefabrication of one
box per day
