Page 72 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 2 DIAGNOSTIC DESIGN AND SELECTIVE RECONSTRUCTION 47

2.2.3 Engineers to Supervise Bridge Repairs and Retrofi ts
1. Background: The subject of bridge repair and reconstruction has developed as a craft. It
still maintains some of the ad hoc planning approach. The early engineering reconstruction

practice was based on apprenticeship. It was performed mainly in the field under an expe-
rienced artisan or “guru.” Builders did not require a formal education. A concept or hidden
theory was built into the construction process and was applied indirectly, without expressing
it in a mathematical format.
Practical experience requirements for engineers are still applicable. A professional
engineer’s license cannot be granted before many years of supervised training.

2. Experience: The success of any craft requires successful field practice verification and time

tests. Practical experience gained in the field has become one of the major strengths of bridge

design. It provides guidelines for a healthy continuity of design and generates structural
refi nements.
The word “engineer” was coined a long time ago. It is used both as a noun and sometimes
as a verb, “to engineer.” In the U.S., an engineer is generally referred to as a consulting
engineer. A resident engineer usually represents the owner on the construction site. Due
to the unpredictability of deficiencies, a maintenance engineer is required to be a licensed

professional engineer.
These days the intuitive practice and in-built logic of age-old craftsmanship is being

interpreted in the light of familiar scientific principles. The formation of the Institution of
Civil Engineers in many countries has set the education standards for practicing engineers.
The training and continuing education process is making steady progress to keep up with
technology advancements.
3. A common approach: Due to the high risk factor for failure, a similar level of repair is needed
for bridges as is normally required for regular maintenance of a dam, nuclear power plant,
or even an aircraft structure. Research may be required to select the best repair material or
method. Repairs, whether long-term or short-term, need to be carried out under the guidance
of a professional or licensed engineer following initial diagnostic design.

2.2.4 Efficient Planning and Regular Inspection Lead to Minimum Maintenance

Maintenance engineering: It includes planning, diagnostic design, and selective reconstruc-
tion.

1. Efficient planning: If sufficient thought has gone into the planning of a new bridge there will
be fewer problems down the road and maintenance will be minimized. Proper investment at
the construction stage will minimize subsequent repair and rehabilitation cost.
Total cost 3 Initial cost 4 Life cycle cost
Life cycle cost 35 (Cost of routine inspections 4 Maintenance and retrofi ts) 4
5 (Repairs from extreme events 4 Cost of demolition)
The total cost is computed over the life of the bridge.

Extreme events may or may not apply within its life. There can be unforeseen events in-
cluding accidents resulting from vehicle and vessel collision, floods and scour, earthquake

damage, fire and bomb blasts, etc.

2. Life cycle costs are linked to concrete spalls, beam corrosion, and other defi ciencies (Figure
2.8). If the initial cost does not cover all structural requirements, the life cycle cost for repair
and rehabilitation will be much higher.
The most sensitive elements of a large project are life cycle costs and value engineering
(Figure 2.8).