| Location:
Galveston, Texas
The Galveston
Causeway Bridge providing highway access from the Texas mainland to Galveston
Island is approximately 2 miles in length. Recent bridge inspections of
the southbound structure have noted corrosion-induced damage to the prestressed
I-beams. Corrosion has caused spalling of concrete on the beam bottom flange
and section loss, and, in some cases, fracture of the prestressing strands.
This corrosion damage is a concern because extensive damage can significantly
reduce the integrity and capacity of the structure.
The objective
of the nondestructive testing and corrosion evaluation was to determine
and assess the current conditions of the prestressed concrete I-beams.
WDP developed a testing protocol that called for the evaluation of select
beams within each investigated span. Different areas of the tested beams
were evaluated based on the level of visual damage. Areas with different
levels of visual damage were tested. This protocol allowed the entire bridge
to be reasonably evaluated without the necessity of testing a large number
of beams and spans.
The evaluation
and testing consisted of impact-echo testing along the beam bottom flange
in order to detect any hidden delaminations within the bottom flange. In
addition, a corrosion evaluation was conducted to assess the likelihood
and rate of active corrosion of the prestressing strands. The corrosion
evaluation consisted of measurement of half-cell corrosion potentials,
corrosion rate measurement, and chloride ion content testing.
The investigations
revealed that long-term chloride-induced corrosion had caused significant
damage to the prestressing strands and mild reinforcing steel in the bottom
flange of selected beams throughout the structure. However, nondestructive
evaluation of selected beams indicated that there was not extensive hidden
damage to the beam bottom flanges at that time.
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Client:
Texas Department of Transportation
Though some
beams exhibited high levels of damage and multiple strand failures in some
areas, there was no evidence of flexural cracking, large deflections, or
other indications that the beams had experienced a significant loss of
structural integrity.
WDP used the
results of the investigation and testing to make repair recommendations.
The repair solutions included the use of external post-tensioning to strengthen
damaged beams, long-term corrosion protection through the use of corrosion
inhibitors, and the replacement of chloride contaminated concrete.
Services
WDP used on this project included:
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