NHI Bridge Safety Inspection Practice Exam (Midterm) for In-Service Bridges

Flexure cracks in the top of a concrete deck are primarily observed above intermediate supports due to the way load is distributed across the bridge structure. When a bridge is subjected to traffic loads or other forces, the concrete deck experiences bending moments, which create tension in the upper regions of the deck.

At the points between supports, the bending moment tends to be lower, leading to a reduced likelihood of flexure cracks occurring in those areas. Near the edges, while some cracking may happen due to shear forces or different types of loading, the primary concern for flexure is further from the edges where the bending moments are more pronounced. Similarly, joints often accommodate movement and design considerations, which typically mitigates cracking. Therefore, flexure cracks are most likely to develop directly above intermediate supports, where the moment reaches its peak, reflecting the structural behavior of the deck under loading conditions.