Abstract
To study the variations in modal properties of a reinforced concrete (RC) slab (such as natural frequencies, mode shapes and damping ratios) under the influence of ambient temperature, a laboratory RC slab is monitored for over a year, the simple linear regression (LR) and autoregressive with exogenous input (ARX) models between temperature and frequencies are established and validated, and a damage identification based on particle swarm optimization (PSO) is utilized to detect the assumed damage considering temperature effects. Firstly, the vibration testing is performed for one year and the variations of natural frequencies, mode shapes and damping ratios under different ambient temperatures are analyzed. The obtained results show that the change of ambient temperature causes a major change of natural frequencies, which, on the contrary, has little effect on damping ratios and modal shapes. Secondly, based on a theoretical derivation analysis of natural frequency, the models are determined from experimental data on the healthy structure, and the functional relationship between temperature and elastic modulus is obtained. Based on the monitoring data, the LR model and ARX model between structural elastic modulus and ambient temperature are acquired, which can be used as the baseline of future damage identification. Finally, the established ARX model is validated based on a PSO algorithm and new data from the assumed 5% uniform damage and 10% uniform damage are compared with the models. If the eigenfrequency exceeds the certain confidence interval of the ARX model, there is probably another cause that drives the eigenfrequency variations, such as structural damage. Based on the constructed ARX model, the assumed damage is identified accurately.
Highlights
Actual civil structures are susceptible to the influence of varying environmental factors and operational conditions such as humidity, wind and moving vehicles, the most important factor has proven to be temperature [1,2,3]
Huang et al [25] proposed a non-destructive global damage identification method based on a genetic algorithm (GA) to identify the damage location and severity of the structure under the influence of temperature variation and noise, which is verified by a number of damage scenarios using a three-span continuous beam
The main aim of this paper is to investigate the influence of varying temperature on the performance of damage detection based on long-term monitoring data
Summary
Actual civil structures are susceptible to the influence of varying environmental factors and operational conditions such as humidity, wind and moving vehicles, the most important factor has proven to be temperature [1,2,3]. Huang et al [25] proposed a non-destructive global damage identification method based on a genetic algorithm (GA) to identify the damage location and severity of the structure under the influence of temperature variation and noise, which is verified by a number of damage scenarios using a three-span continuous beam. It shows good robustness under random noise levels with a lab steel grid experiment. The method can identify the damage location and severity, which is more accurate for damage identification based on temperature variation
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