Page 31 - Bridge and Highway Structure Rehabilitation and Repair

6 SECTION 1 ADMINISTRATIVE ISSUES

Developing effective methods of repair and rehabilitation should result in minimum cost
of maintenance for the innumerable situations. This would lead to selection of the most
promising and emerging preservation methods to ensure continuity. One of the goals is to
focus on safety, serviceability, and economy.
4. New methods of prefab design: Development of LRFR and LRFD guidelines may apply
to prefabricated elements, drainage guidelines, and methods for scour protection, seismic
design, software applications, and check lists in QA/QC documents.
5. Innovative applications: New materials include FRP composites, SIKA CarboDur and SIKA
Wrap or equivalent, accelerators, air entraining admixtures, water reducers, super plasticiz-
ers, pozzolans, emulsions, anti-washout admixture for underwater concrete, use of HPC and
HPS, scour countermeasures, seismic retrofi t, etc.
6. New aids in planning: The use of GIS and imaging technology, stay-in-place formwork,
precast deck panels, and orthotropic decks is becoming popular.

1.2.3 New Traffi c Loads
In Europe and many other countries, bridges built prior to the 18th Century still exist and

continue to serve traffic needs. Older bridges were originally designed to carry much lighter
carriages, carts, and wagons, but now heavy trucks, automobiles, and military vehicles are using
them. The aim of the new generation of bridges is to provide for heavier truck loads. Such old
bridges also need to be rated and posted for maximum live load.
A fresh approach to the evaluation of maintenance issues will help in mitigating the inevi-
table deterioration of bridges, thus leading to minimal discomfort. An insight into the needed
approach is highlighted in this book. Such an approach is likely to reduce costs and construction
durations. It may also result in increased standardization, introduce uniformity of construction
and lead to longer-lasting, low-maintenance structures.

1.2.4 Explaining the Proposed Rehabilitation Process
Current practice: Inspection reports serve as the eyes and ears of the design engineer. Recom-
mendations coming from the field assessment are evaluated by rating analysis programs. FHWA

rating criteria is generally used. Alternatives based on repair methods and cost consideration
are studied before preparing rehabilitation designs and drawings. However, newer monitoring
methods have emerged using remote sensors and robotics. Examples of other innovations are
HPC and HPS materials, isolation bearings and scour countermeasures, LRFR methods, etc.
The following questions need to be re-addressed in light of changing technology:
Why repair and rehabilitate?
Safety, continuity of use, and failure prevention are the primary reasons. The following
considerations are of paramount importance:

1. Improving traffic conditions, geometry, sight distance, and clearances.

2. Addressing environmental concerns.
3. Increasing load carrying capacity.
4. Correcting defi ciencies.
5. Providing for possible future widening.
6. Minimizing costs to be incurred.

When to repair and rehabilitate?
Repairs should directly follow the recommendations presented in inspection reports. Emer-
gency repairs are generally required immediately after an emergency or after extreme events,

such as vessel collision, flood scour, or earthquake. Chapter 3 analyzes various types of failures,
their causes, and methods of preventing failures.