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Many bridge elements undergo enormous stress
throughout the imposing seasonal changes and loading conditions. Using
proactive measures, especially with prestressed bridges such as P/S box-beam
bridges, can alleviate this problem.
Although P/S concrete bridge members have provided
bridge owners with a consistent and durable product for nearly 45 years,
bridge engineers should closely monitor and note any localized or global
rust staining from the tendons in the P/S members found during bridge
inspection efforts. By noting such staining and taking steps to repair,
bridge owners may avoid accelerated corrosive activity and significant
decay, and prolong the life of their structures.
A hands-on accurate and thorough bridge inspection
process is a challenging task for bridge owners and engineers as the bridge
population continues to age. Shifting through the bridge observations and
noting key trends such as consistent rust staining is enormously valuable
for managing future bridge repair efforts.
The most cost-effective bridge programs will use
accurate and thorough condition state data, notes, and photos to understand
and assess its overall performance. Although bridge owners are trying to
balance their immediate bridge repairs and rehabilitations, they must also
recognize and prioritize tomorrow’s repairs that are evident today.
The impending need is a better approach to identify
future potential developing expenditures, such as localized deficiencies
found in specific members.
Looking at problems
For P/S concrete box beam structures, poor
performance can develop in the bottom of the box in unprotected units.
Problems may include longitudinal cracking and water staining, beginning
signs of longitudinal tendon rusting, exposed P/S tendons, and longitudinal
concrete cracking.
Original design of these types of structures,
naturally, relies on the interaction.
Keeping it safe
It is now up to the bridge owner to take steps to
provide safe passage across the structure, which may include reducing the
use of the structure or even temporarily closing the structure under the
guidance of a professional engineer.
At this point the owner should take appropriate
steps to make the necessary repairs, even if for a temporary manner. Repairs
and in some cases replacements of these members are necessary to secure an
infrastructure system that meets the needs of the local community.
Some structural problems require immediate and
semi-urgent design and construction efforts due to significant deficiencies
in the structure members.
In order to reduce or eliminate immediate repairs,
proactive steps are necessary.
This is possible through a detailed review of the
bridge inspection photos and notes.
An excellent bridge inspection effort under review
by a professional engineer knowledgeable with bridge mechanics and
performance will be in position to identify condition states, which may lead
to rehabilitation or total replacement. In addition, bridge owners should
plan and coordinate this form of information and request from their
professional engineer.
By identifying field condition states of corrosive
P/S tendons, bridge owners are in position to begin the planning process to
design repairs.
It is reasonable to assume that bridges with members
that display significant deficiencies will require immediate to moderate
time frames for repairs. For immediate repairs, temporary reduced loading
conditions or temporary bracing may also be necessary.
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