Page 30 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 1 OVERVIEW OF BRIDGE ENGINEERING 5

The success of metal bridges has continued, from wrought iron, cast iron, and mild steel to
high performance steel. Even in reinforced and prestressed concrete bridges, higher grade steel
rods and high tensile steel strands are being used.
Rehabilitation requirements for both older and historic categories demand that safety, durabil-
ity, and economy be selected as the main criteria with optimization of materials in superstructures,
substructures, and foundations serving as secondary criteria.
Figure 1.1 shows the relationship between the percentage decrease in the useful life of a
bridge versus time.
It appears that in the last two decades, considerable advancement in an increased array of
construction materials, details, components, structures, and foundations has taken place. Hence,
it is an opportune time to inculcate thought processes, develop structural solutions, and introduce
modern technology such as remote health monitoring.
The dotted line shows continued use of a bridge, but with higher maintenance costs. Deferred/no
maintenance, low maintenance, and regular maintenance alternatives need to be considered.

1.2.2 Strategic Topics and Their Advancement

1. Rehabilitation technology: It is more diverse than the original design effort. It involves in-
spection, interpretation of data, selection of repair and rehabilitation methods, in addition to
analysis, computer aided design, and application of AASHTO and state codes of practice.
2. AASHTO’s objectives: A plan was developed by the AASHTO Highway Subcommittee on
Bridges and Structures in June 2005 to help achieve “safe, cost-effective, low-maintenance,
long-life structures.” Some of their recommendations, such as accelerated bridge construc-
tion, serve as strategic topics and require further attention. Other topics are added here as
deemed necessary by practitioners.
3. Technology developments at the state level: It is important to specialize in developing
structural solutions for specific issues that may relate to local traffic, topography, geography,

environmental loads, and extreme events. Currently, their diversity restricts them from being
adequately addressed in the national level design specifications or in the maintenance manu-

als. In resolving local specific issues in a timely manner, existing bridge design manuals in
each of the 50 states serve as necessary supplements to The American Association of State

Highway and Transportation Officials (AASHTO) Load and Resistance Factor (LRFR) and
Load and Resistance Design (LRFD) design and construction specifi cations.

Figure 1.1 The relationship between the percentage decrease in the useful life of a bridge versus time. The
dotted line shows continued use of a bridge, but with higher maintenance costs. Deferred/no maintenance, low
maintenance, and regular maintenance cases are considered.