Page 42 - Bridge and Highway Structure Rehabilitation and Repair

CHAPTER 1 OVERVIEW OF BRIDGE ENGINEERING 17

Figure 1.6 A scenic countryside concrete bridge with a waterfall.

6. Construction materials
Old bridges contain older types of materials while new bridges contain more modern materi-
als. Science and technology offer us the opportunity to develop high performance materials
that make bridges more durable and easy to maintain. Providing a longer lifespan can justify
a greater initial investment.
• New timber materials: Laminated or composite timber, bamboo sheets
• New concrete materials: Normal weight, lightweight, high performance concrete with
corrosion inhibitor overlays
• Metal: High performance weathering steel, aluminum
• Composites and fiber reinforced polymers

• Recycled materials.
The girders commonly used for small or medium spans are made of timber, steel I beam,
reinforced concrete, prestressed concrete I shapes, or box sections. Arches have been con-
structed in masonry, timber, steel, and concrete. Steel cables and trusses are used for long
spans. Aluminum and composites used for pedestrian bridges result in lightweight decks.
7. Geometry
Structural analysis is based on bridge geometry:
Type 1–Normal right angle plan
Type 2–Skew plan
Type 3–Horizontally curved plan
Type 4–Bridge on curved vertical alignment
8. Span length
Construction issues are based primarily on span lengths:
Type 1–Short span < 50 feet