Feasibility of a Capacitive Strain Sensor for Fatigue Crack Detection of Steel Bridges

Abstract

Cracks induced by fatigue have been a major issue for steel bridges. Currently, the most effective method to examine bridges for detecting fatigue crack activities is the inspection by human which is time consuming, labor intensive, cost inefficient and prone to error. As a replacement, measuring strain induced by cracks attracts many interests. However, traditional strain sensors such as metal foil strain gauges, are small and limited measurement range which make them not suitable for large cracks detection. Although some flexible materials developed to detect the strain, the parameter changed according to the strain is normally capacitance. This paper presents a capacitive strain sensor board transforming capacitance to analog voltage. Experimental tests show the linearity and real-time detection. Furthermore, the feasibility for using in fatigue crack detection by employing a strain-to-capacitance material is demonstrated.