Civil Engineering Professional Engineer Practice Exam

What is a common reason for using combination bridges?

1. To reduce construction costs

2. Sometimes a single bridge type does not meet needs

3. To enhance aesthetic appeal

4. To simplify design requirements

The correct answer is: Sometimes a single bridge type does not meet needs

Using combination bridges is commonly driven by the fact that a single bridge type may not adequately meet the diverse needs of a specific location or application. Different bridge designs have unique benefits, strengths, and limitations. For instance, a combination of a beam bridge and an arch bridge allows engineers to harness the efficiency of the beam for shorter spans while utilizing the arch's strength for longer spans, thereby providing a more effective solution overall. The need for adaptability in design, especially in complex environments or where varying span lengths and load requirements exist, further underscores the rationale behind utilizing combination bridges. This approach assists in balancing considerations like load-bearing capacity, construction methods, available materials, and site-specific constraints, leading to a structurally sound and efficient outcome that a single bridge type might not achieve as effectively. The other options touch on valid aspects of bridge design but are not specific to the concept of combination bridges. While aesthetic appeal and cost considerations are important in general, they do not directly address the need for employing multiple bridge types to solve various structural challenges. Similarly, while simplifying design requirements could be a goal in some contexts, the complexity of needs often outweighs this benefit, thus reinforcing why combination designs are favorable.