What are the common distress types observed in piers and abutments?

• A. Cracking only.
• B. Scour and scour-induced undermining, settlement, cracking, spalling, and corrosion of steel components.
• C. Paint peeling as the primary distress.
• D. Thermal expansion of concrete only.

Answer: (B)

Piers and abutments face a mix of failure modes that directly threaten their foundations and load transfer, so the most complete and accurate description includes scour effects, movement, cracking, surface loss, and metal deterioration. Scour and scour-induced undermining remove supporting soil around the foundations, which can lead to movement, tilting, or even loss of bearing capacity if not addressed. Settlement reflects differential or progressive downward movement of the foundation or structure, causing misalignment, bearing issues at bearings, and cracks or separation at joints. Cracking is common in concrete members due to flexural stresses, temperature changes, shrinkage, and restraint; cracks can propagate if not repaired, allowing faster ingress of water and chemicals. Spalling occurs when surface concrete flakes away, often as a result of freeze-thaw cycles or corrosion of embedded reinforcement; once the surface is breached, the underlying steel is exposed to moisture and chlorides, accelerating deterioration. Corrosion of steel components—like reinforcing bars, bearing connections, or anchor bolts—reduces cross-section and stiffness, increases stress concentrations, and leads to expansion that widens cracks and destabilizes connections. Together, these distresses capture the typical conditions seen in piers and abutments. Paint peeling or thermal expansion alone are not primary distress categories for these members, though they may appear as secondary symptoms or contributing factors.