The Coupled Effect of Temperature Changes and Damage Depth on Natural Frequencies in Beam-Like Structures

Abstract

A significant amount of research is concerned with dynamic modal parameters for damage detection of structural conditions due to their simplicity in use and feasibility. However, their use for damage detection should be performed with special attention, particularly in operational and environmental conditions subjected to temperature changes. Beams in construction industries experience different loading types, such as temperature changes leading to crack initiation and propagation. Changed physical and dynamic properties such as natural frequencies and mode shapes indicate that damage has occurred within the structures. In this study, vibration analysis of cantilever and cantilever simply supported beams has been carried out on intact and damaged beams to investigate the coupled effect of temperature changes and damage depth on natural frequencies. A numerical analysis of beams is completed using ANSYS software. The results of numerical simulation are validated using two other studies from literature. Numerical results revealed that in order to perform a successful damage assessment using the frequency shift, the vibration modes should be selected properly. In addition, an increase in temperature results in a decrease in structural frequencies. The assessment of the effect of damage depth on natural frequencies also confirms that when damage depth is increased, there is a significant decrease in natural frequency responses.

Temperature Effects on the Natural Frequencies of Composite Girders

“…Therefore, these quantities are typically expressed as functions of temperature [18][19][20]. The elastic modulus of concrete tends to decrease with increasing temperature and can be calculated using Equation (1) proposed in Model Code 2010 [21]. In contrast to the elastic modulus, the specific heat and thermal conductivity are less affected by concrete temperature [22][23][24][25].…”

“…Over the past several decades, various studies have been conducted to monitor the health conditions of bridges based on modal parameters such as natural frequencies and mode shapes [1][2][3]. However, modal parameters can be affected by environmental factors, which limits their application as health monitoring indicators.…”

“…Many studies have indicated that natural frequencies decrease as temperature increases [1,[6][7][8]. For example, experimental tests conducted on a simply supported beam to investigate the impact of temperature variations on its natural frequency in a temperature range from −40 to 60 • C demonstrated that the natural frequency decreased by up to 0.148% as the temperature increased [5].…”