Monitoring the Evolution of Concrete Strain Using Vibrating Wire Strain Gauges

Abstract

Time dependent material properties, such as creep and shrinkage, are fundamental properties of concrete. Therefore, monitoring of concrete structures can help for a better understanding of these properties. This publication deals with the continuous monitoring of concrete strain using vibrating wire strain gauges. The vibrating wire strain gauges are cast inside large-scale specimen and the monitoring is fulfilled for more than five years. The first part of this publication introduces the time dependent behavior of concrete and presents the applicability of vibrating wire strain gauges in concrete structures. Afterwards, long-term measurements of large-scale concrete specimens with cross-sectional areas up to 1 m2 are presented. The large-scale specimens are exposed to environmental influences and the measuring was fulfilled with several vibrating wire strain gauges. The measuring results show that vibrating wire strain gauges are capable for long-term concrete strain measurements. Comparison with additional measurements with an extensometer confirm the accuracy of the vibrating wire strain gauges. The long-term measurements identify two main advantages of vibrating wire strain gauges: (i) the accuracy of the sensor, which enable small strain measurements resulting from hygro-thermal and mechanical loading, and (ii) the possibility to measure early age strain from the time of concrete setting.