Experimental Study of Bridge Expansion Joint Damage Based on Natural Frequency

Area of Science:

• Civil Engineering
• Structural Health Monitoring
• Experimental Mechanics

Background:

• Modal bridge expansion joints are critical components in ensuring bridge integrity.
• Assessing the structural health of these joints requires reliable monitoring techniques.
• Understanding the influence of environmental factors and damage on joint dynamics is essential.

Purpose of the Study:

• To compare the efficacy of acceleration and fiber optic strain sensors for modal bridge expansion joint testing.
• To investigate the impact of concrete curing periods on the natural frequency of these joints.
• To analyze the effect of localized damage on the natural frequencies of different joint components.

Main Methods:

• Experimental investigation using three modal bridge expansion joint specimens.
• Comparison of acceleration sensors versus fiber optic strain sensors.
• Analysis of natural frequency variations during concrete curing (days 3 to 28).
• Controlled damage introduction to center beam, support bar, and anchorage zone concrete.
• Impact hammer excitation and modal analysis.

Main Results:

• Acceleration sensors demonstrated superior performance for modal bridge expansion joint testing.
• A notable increase in natural frequency (approx. 10 Hz) was observed from day 3 to day 28 of concrete curing.
• Gradual damage to the center beam and support bar led to a decreasing trend in natural frequencies.
• Damage to the anchorage zone concrete exhibited less pronounced changes but still contributed to a decrease in overall natural frequency.
• Frequency sensitivity to damage varied across different joint components.

Conclusions:

• Acceleration sensors are recommended for modal bridge expansion joint monitoring.
• Concrete curing significantly influences the natural frequency of bridge expansion joints.
• Damage detection in bridge expansion joints can be achieved through modal analysis, with varying sensitivity depending on the location and type of damage.