Abstract
This study investigates the temperature-drift effect on strain measurement of concrete beams and proposes a method for determination of the mechanical strain of stressed concrete beams. In the study, wireless electrical resistance strain gauges were used to measure the strain of concrete beams. This study first examined how temperature changes affected the strain gauge attached to concrete beams. Subsequently, a concrete beam experiencing changes in temperature and load was monitored for six consecutive days. The test results showed that the apparent strain response of the concrete beam was significantly affected by temperature changes. After adjusting for the temperature effect, the mechanical strain generated by a load could be obtained. However, temperature-induced drift was still observed in the mechanical strain response. Based on the assumption that temperature changes are slow and gradual, and mechanical strain changes are momentary, an adjacent data subtraction method can be used to eliminate the temperature-induced drift present in the mechanical strain data. The subtraction results show that the mechanical strain generated by a load was accurately obtained. The proposed data-processing method could also be used to find the residual strain of the nonelastic response of a beam subjected to substantial short-term forces.
Highlights
In recent years, structural health monitoring (SHM) has been a popular topic
The research performed long-term load tests for a steel beam and a concrete beam, and nonelastic response tests for a concrete beam, to examine the effects of temperature changes on the strain responses obtained by the tests
When the load-generated mechanical response was smaller than the thermal strain response induced by temperature changes, the measured apparent strain response would be influenced by temperature changes, and the load-generated mechanical strain could not be obtained through analyzing apparent strain
Summary
Structural health monitoring (SHM) has been a popular topic. Structural health monitoring is the installation of various types of sensors (such as accelerometers, tiltmeters, displacement meters, strain gauges, and thermometers) in structures for monitoring structural responses to external stimuli [1,2,3,4]. In the use of electric resistance strain (ERS) gauges on bridge structures, the measured apparent strain includes strain induced by temperature changes and mechanical strain. Because the ERS gauge is affected by long-term temperature changes, a drift phenomenon is present in the measured strain, causing the signal analysis to become more complex. A technique based on the use of a dummy gauge can eliminate the thermal effect provided that the dummy gauge is attached on an additional material component that undergoes the same thermal variations as the active gauge but is free from mechanical strain This method is practically difficult for a heterogeneous material, such as concrete. Using the proposed innovative strain data analysis method, temperature effects were eliminated to obtain the mechanical strain generated by load changes. The feasibility of using the proposed strain data analysis method to monitor the residual strain generated by a huge load within a short time was examined
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