Construction—North America—USA—Structural Repair Solutions
The San Antonio Y Interchange:
Permanent Repair with DYWIDAG Systems
The San Antonio Y Interchange in the center of San Antonio, Texas, USA, is a Y shaped interchange between US Highway 35 from
the northeast and US Highway 10 from the northwest that merge together moving south. The viaducts of this elevated intersection
were built in the 1980s utilizing precast concrete segmental type construction. The 755 sections were post-tensioned together
using longitudinal and transversal tendons, and the bridge has a total length of approximately 23km (14.3mi).
When the interchange was built, it was not
yet known how important it is to completely
grout the tendons, and at the time industry
standards did not place a strong emphasis
on this component of the construction.
As the grouting operations were not carried
out thoroughly, voids often occurred that
allowed moisture and oxygen to infiltrate the
system, thereby causing corrosion of the post-
tensioning strands. During a cursory evaluation
of the Y Interchange, the Owner, TXDOT,
found voids in some of the tendon ducts.
Furthermore, the ducts of many tendons were
damaged, and most anchors had no caps,
which are important for protecting the strand
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tails and act as an additional level of corrosion
protection.
DSI Construction USA was selected as the
subcontractor by the Owner and Contractor to
perform all of the remediation work associated
with this section of the elevated highways.
One of the biggest challenges was determining
the number of the originally installed tendons
that had to be repaired because an in-depth
evaluation and survey was not possible in
advance.
DSI engineered all test inspection and repair
protocols as part of their construction plan and
carried out the work through the use of bore
scopes to identify the condition of the strands
within the voided areas. In addition, when DSI
identified voids, specialized vacuum grouting
techniques were employed to measure the
void volumes and then fill the voids with grout.
Since the original construction of the Y
Interchange was done in several phases
and by different contractors, the tendons
had also been supplied by several different
Post-Tensioning companies, resulting in many
different anchorage types. DSI designed,
produced and installed custom caps for each
type of anchorage.