Page 60 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 1 OVERVIEW OF BRIDGE ENGINEERING 35

• No patchwork in concrete or dissimilar steel painting.
• Use of innovative ideas and new technology: Lightweight and weather-resistant transpar-

ent noise varrier sheets incorporate polyamide filaments that hold broken sheet in place
in the event of impact by a car or truck.
5. Cost considerations related to aesthetics
The aesthetics of the structure can generally be accomplished within the guidelines of design,
requiring only minor project cost increases. If form liners are being considered, the depth
of the projections should be as deep as possible in order to have the desired visual effect.
Using shallow depths provides very little visual effect or relief when viewed from a distance.
The depth of the form liner shall not be included in the measurement of the concrete clear
cover.

1.12.2 Pedestrian and Equestrian Traffi c
In practice, aesthetic requirements are more important in pedestrian and foot bridges located
in parks and highways than for other bridge types. Aesthetic planning of rural area bridges is
different than that for urban areas. Each structure should be evaluated for aesthetics.

1.12.3 Long Spans
The architecture of long span bridges, such as cable stayed or suspension cable bridges, has
always attracted attention. They are pleasant to look at and also serve as cultural icons. Like mov-
able bridges they are a subject in themselves requiring specialized analysis and design. Modern
structural engineering and construction technology have contributed to ever increasing longer
spans (world’s longest span Akashi-Kaikyo Bridge) in addition to addressing safety, security,
and maintenance issues.
Existing long spans using steel and concrete have used the following types of structural
systems:
1. Suspension cables with towers, their foundations, anchorages, and approach spans.
2. Cable stayed bridges.
3. Truss bridges.
4. Arch bridges.
5. Segmental bridges.
Figure 1.16 shows aesthetic planning of curved approaches to a cable stayed bridge.

1.12.4 Rural Settings
Planning of rural area bridges for aesthetics will be different from urban area bridges. While
girder types are more common in urban settings, arches and deep trusses are easier to blend in
rural areas.

1.13 MAINTAINING THE ENVIRONMENT
1.13.1 Environmental Concerns

1. The purpose of reconstruction is to benefit transport facility users. The process of short term
construction and long term impacts should not be adverse to road users or local residents.
A large number of environmental concerns must be addressed related to water, including:
• Maintaining water quality
• Providing fi sh passage
• Avoiding wetlands contamination
• Avoiding stream encroachment