1. Steel plate girders offer lower initial material costs than precast concrete
2. Precast concrete girders cannot typically achieve 45 m spans reliably
3. ) Steel plate girders can provide greater strength-to-depth ratio, maximizing clearance
4. Precast concrete girders require more complex foundation systems for this span

Explanation

Explanation: Steel plate girders provide superior strength-to-depth ratios compared to precast concrete, allowing engineers to minimize structure depth while maintaining capacity—critical for sites with limited vertical clearance. For a 45 m (150-foot) span, steel plate girders might require only 1/25 of the span in depth (approximately 1.8 m or 6 feet), while comparable precast concrete girders typically need 1/18 to 1/20 of span (2.3-2.5 m or 7.5-8.3 feet). This difference can be decisive for clearance-constrained sites. Initial costs (A) typically favor concrete; span capability (B) exists for both materials at this length; and foundation requirements (D) are primarily driven by overall loads, not girder material.

Learning Resources:
• Review AASHTO LRFD Bridge Design Specifications, 9th Edition (2020), Table 2.5.2.6.3-1 for span-to-depth ratio guidelines.
• Digital Resource: Explore NSBA's "Steel Bridge Design Handbook" (https://www.aisc.org/nsba/design-resources/steel-bridge-design-handbook/)