What tool is commonly used to measure deflection in bridges?

The tool commonly used to measure deflection in bridges is a laser measurement device or deflection gauge. These instruments are specifically designed to provide precise measurements of structural deformation or deflection under various loads. They use laser technology or mechanical methods to ensure accuracy and reliability. This capability is crucial in bridge inspections as detecting deflection can indicate potential structural issues or the need for maintenance.

Vibration meters, while valuable for assessing the vibrational behavior of structures, do not specifically measure deflection. Concrete strength testers are used to evaluate the compressive strength of concrete but do not measure deflection. Visual inspection tools can help identify signs of distress or failure, but they rely on the inspector's judgment and are not as precise as dedicated measuring instruments in quantifying deflection. Thus, the laser measurement device or deflection gauge is the most appropriate option for accurately measuring deflection in bridges.