BRIDGE REPAIR/REHABILITATION FEASIBILITY STUDY

MAINTENANCE AND REHABILITATION OF TIMBER BRIDGES
14.1 lNTRODUCTlON
Wood is one of the most durable bridge materials, but over extended
periods it may be subject to deterioration from decay, insect attack, or
mechanical damage. Timber bridges must be periodically maintained or
rehabilitated in order to keep them in a condition that will give optimum
performance and service life. Effective bridge maintenance programs
improve public safety, extend the service life of the structure, and reduce
the frequency and cost of repairs. The objective is not only to repair
existing deficiencies, but also to take corrective measures to prevent or
reduce future problems. When tied to a competent bridge inspection
program, regular maintenance represents the most cost-effective approach
for achieving long service life from existing structures. Unfortunately,
maintenance is often neglected until critical problems develop that require
major restoration or replacement of the structure. In times of declining
budgets, the first program reduced as a money-saving measure is often
maintenance, when, in fact, reduced maintenance substantially increases
long-term costs.
In general terms, bridge maintenance includes those activities necessary to
preserve the utility of a bridge and ensure the safety of road users. In
practice, all maintenance is either preventative or remedial. Maintenance
activities are divided into categories that vary in definition and scope
among different agencies. In this chapter, timber bridge maintenance is
divided into the three following categories:
1. Preventative maintenance involves keeping the structure in a
good state of repair to reduce future problems. At this stage, decay
or other deterioration has not started, but the conditions or
potential are present.
2. Early remedial maintenance is performed when decay or other
deterioration is present but does not affect the capacity or
performance of the bridge in normal service. At this stage, more
severe structural damage is imminent unless corrective action is
taken.
3. Major maintenance involves immediate corrective measures that
restore a bridge to its original capacity and condition.
Deterioration has progressed to the point where major structural
components have experienced moderate to severe strength loss
and repair or replacement is mandatory to maintain load-carrying
capacity.
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