Name two common nondestructive evaluation methods for bridge steel.

• A. Destructive testing and material sampling.
• B. Magnetic Particle Testing and Ultrasonic Testing.
• C. Visual inspection and hammer tapping.
• D. Radiography and thermal imaging.

Answer: (B)

Nondestructive evaluation aims to detect flaws without damaging the bridge material, which is essential for inspecting steel members while they remain in service. Magnetic Particle Testing uses magnetic fields on ferromagnetic steel and applies iron particles to reveal surface and near-surface cracks: the particles gather at discontinuities, producing a visible indication that guides repair decisions. Ultrasonic Testing sends high-frequency sound waves into the steel; by analyzing the reflections and travel times, inspectors can locate internal flaws and measure remaining thickness, giving insight into internal integrity without cutting or removing material. These two methods cover both surface and internal defect detection in a practical, field-friendly way, which is why they’re commonly used for bridge steel. Destructive testing and material sampling destroy the part, so they aren’t nondestructive. Visual inspection and hammer tapping provide quick, general surface assessment but can miss hidden flaws. Radiography and thermal imaging are useful in some scenarios but are less routinely applied for day-to-day bridge inspections due to safety, access, and interpretation considerations.