Which of the following is a sign of vertical movement in bridges?

Answer: A — Unusual cracks in concrete

Unusual cracks in concrete are a key sign of vertical movement in bridges. Such cracks can indicate that there is settlement or heaving occurring within the structure. This movement can happen due to various factors, including soil settlement under the bridge or changes in moisture levels that can affect the foundation. These cracks may appear diagonal, vertical, or horizontal, and their patterns can provide essential clues about the type of movement taking place. While flaking paint and color changes in steel can indicate deterioration or corrosion, they do not specifically signal vertical movement. These signs may reflect environmental factors or general aging of the materials rather than structural shifts. Therefore, the primary indicator of vertical movement in bridges is indeed the presence of unusual cracks in concrete.