A Self-Learning Manual - Institution of Engineers Mauritius

A Self-Learning Manual
Mastering Different Fields of Civil Engineering Works (VC-Q&A Method) Vincent T. H. CHU
Fig. Warren Truss and Pratt Truss
19. What is the difference between dry joint and wet joint in precast
segmental bridges?
Dry joints have been properly used in the past in which the bridge
segments are formed by match casting. The prevalence in the past is due
to it lower cost and time for construction. There is no gluing material to seal
up the joint. As such, leakage through the joint into the box culvert occurs
from time to time and this may affect the durability of external
post-tensioning tendons. Moreover, owing to the effect of seismic,
temperature and creep, the joints are found to open under these conditions.
Spalling of top concrete slab at bridge joint was also reported.
Wet joint involves the use of epoxy glue at the mating precast segments.
After the application of epoxy glue, a temporary precompression pressure
of 0.3MPa is applied by stress bars at top, bottom and the sides of the
mating precast segments. The epoxy sets under the applied pressure. The
use of epoxy joints provides lubrication to help in the fit-up and alignment of
the mating segments and minimizes the effect of hard point contact
between segments.
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