Abstract:It is well known that temperature has great influence on modal characteristics of bridges. The relationship between them has been studied by using statistical mathematics, numerical analysis, and field's monitoring methods, which have relatively narrow applicability. Therefore, it is necessary to analyze their relationship theoretically. In this paper, the relationship between temperature and modal characteristics of the simply supported beam is investigated based on theoretical calculation method. Firstly, th… Show more
“…The experimental and the calculated results are both listed in Table 1, in which the results in bold are the change rates of the morning and noon frequencies relative to the night frequencies. The air temperature both under the bridge (Tu) and over the bridge (To) during the test were also recorded and listed in Table 1, and the temperature distribution of the whole structure can be calculated by the widely used thermal analysis model (Liu et al, 2017; Zhang et al, 2021). Figure 7.Amplitude spectrums of 1# accelerometer at different times of day: (a) Spectrums graph, (b) Local enlarging graph, (c) Local enlarging graph.…”
Section: Engineering Verification and Numerical Examplesmentioning
confidence: 99%
“…However, it is very difficult to describe the modal characteristics of bridges in theory at different temperatures, and there is little research paying attention to this. Herein, a theoretical method of the simply supported beam under the effect of temperature is proposed by our research group, which considers the temperature-induced change in elastic modulus, deflection and shear stiffness of bearings (Liu et al, 2017). In addition, a discussion is conducted around the effects of different temperature modes on the modal characteristics of Timoshenko beam, which leads to exact solution in closed form (Liu et al, 2018).…”
The effect of temperature on structural modal characteristics plays an important role in structural health monitoring and evaluation. Herein, the free vibration analysis of rigid-frame bridge is conducted by taking into account the effect of temperature. Firstly, the non-uniform rigid-frame bridge is divided into several members to develop the flexural and axial vibration equations for members under the effect of temperature in accordance with Hamilton’s principle. Secondly, each member is further divided into several segments, and the transfer relationship between segments is established to obtain the generalized dynamic stiffness matrix of the member. Then, the generalized dynamic stiffness matrix of each member is constructed by using the numerical assembly method similar to the finite element method so as to obtain the characteristic equation of rigid-frame bridge. Furthermore, the natural frequency and mode shape of the whole rigid-frame bridge are calculated by using the algorithm of Wittrick-Williams. Finally, the dynamic characteristic test of Yong-an bridge and the numerical calculation of the rigid-frame bridge are carried out to verify the generality and accuracy of the proposed method. The results indicate that the change of temperature will lead to the secondary internal force and the change of Young’s modulus, which together affect the modal characteristics of the structure, and the change of natural frequency caused by the change of Young’s modulus is greater than that caused by the secondary internal forces. In addition, there is a negative correlation between temperature and natural frequency of the rigid-frame bridge, and different temperature gradient modes also have certain influence on the mode shape of rigid-frame bridge.
“…The experimental and the calculated results are both listed in Table 1, in which the results in bold are the change rates of the morning and noon frequencies relative to the night frequencies. The air temperature both under the bridge (Tu) and over the bridge (To) during the test were also recorded and listed in Table 1, and the temperature distribution of the whole structure can be calculated by the widely used thermal analysis model (Liu et al, 2017; Zhang et al, 2021). Figure 7.Amplitude spectrums of 1# accelerometer at different times of day: (a) Spectrums graph, (b) Local enlarging graph, (c) Local enlarging graph.…”
Section: Engineering Verification and Numerical Examplesmentioning
confidence: 99%
“…However, it is very difficult to describe the modal characteristics of bridges in theory at different temperatures, and there is little research paying attention to this. Herein, a theoretical method of the simply supported beam under the effect of temperature is proposed by our research group, which considers the temperature-induced change in elastic modulus, deflection and shear stiffness of bearings (Liu et al, 2017). In addition, a discussion is conducted around the effects of different temperature modes on the modal characteristics of Timoshenko beam, which leads to exact solution in closed form (Liu et al, 2018).…”
The effect of temperature on structural modal characteristics plays an important role in structural health monitoring and evaluation. Herein, the free vibration analysis of rigid-frame bridge is conducted by taking into account the effect of temperature. Firstly, the non-uniform rigid-frame bridge is divided into several members to develop the flexural and axial vibration equations for members under the effect of temperature in accordance with Hamilton’s principle. Secondly, each member is further divided into several segments, and the transfer relationship between segments is established to obtain the generalized dynamic stiffness matrix of the member. Then, the generalized dynamic stiffness matrix of each member is constructed by using the numerical assembly method similar to the finite element method so as to obtain the characteristic equation of rigid-frame bridge. Furthermore, the natural frequency and mode shape of the whole rigid-frame bridge are calculated by using the algorithm of Wittrick-Williams. Finally, the dynamic characteristic test of Yong-an bridge and the numerical calculation of the rigid-frame bridge are carried out to verify the generality and accuracy of the proposed method. The results indicate that the change of temperature will lead to the secondary internal force and the change of Young’s modulus, which together affect the modal characteristics of the structure, and the change of natural frequency caused by the change of Young’s modulus is greater than that caused by the secondary internal forces. In addition, there is a negative correlation between temperature and natural frequency of the rigid-frame bridge, and different temperature gradient modes also have certain influence on the mode shape of rigid-frame bridge.
“…Several bridges were studied for vibration analysis. A detailed report (Gaunt and Sutton, 1981) about bridges in the USA presented frequency and acceleration for 62 bridges that were spanning less than 30 m. A problem with the change of frequency during the day was identified (Liu et al, 2017) because of several factors, one of which was the temperature change during the day or the season. Another study identified the temperature variation in seasonal change (Magalha˜es et al, 2012).…”
Section: Energy Harvesting For Bhm Systemsmentioning
Vibration energy has the advantage of abundant availability in the environment of the bridge structure due to consistent traffic flow and high-speed wind blowing. The vibration energy present at the bridge site can be harvested for powering the wireless sensors mounted on the bridge for health monitoring and making the system self-powered. The bridge vibrations are usually low frequency and low acceleration excitations, therefore, its transduction to useful electrical energy is a challenge. However, several techniques are being utilized to harvest the bridge vibration and a variety of bridge energy harvesters are being developed for this purpose. This work has reviewed energy harvesters claimed to be designed for bridge vibrations. The study is split into two categories, first section discusses the energy harvesters developed for bridge vibrations tested only in-lab environments. The second section is about the harvesters that have been characterized on real bridge structures to verify their effectiveness. The study reveals that the bridge energy harvesters can extract enough power to operate the wireless sensors for the health monitoring of bridge structures. Moreover, the architecture, fabrication, input excitation, and output performance of the reported harvesters with modeling techniques are discussed.
“…The bridges were of span less than 30 meters. The conducted study of bridges identified another problem, that was the frequency change with different factors one of which is change with temperature (Liu et al, 2017) during day time as well as with season (Magalhães et al, 2012). This necessitated a broad band device for energy harvesting.…”
Section: Low Frequency and Low Acceleration Vibration Energy Harvementioning
This paper presents an electromagnetic energy harvester to extract low frequency and low acceleration vibration energy available in a bridge environment. The developed harvester is a multi-mode oscillator with dual electromagnetic transduction mechanisms. The harvester consists of two cantilever beams. The first cantilever beam is split into two equal pieces along its length and the second beam placed in between them coming back to the fixed end and attached at outer end to the first beam. This way instead of a long conventional cantilever beam a compact harvester is fabricated. Two magnets as proof masses are attached to each free end of the beam making it a two degree of freedom system (2-DOF). The magnets are positioned to oscillate inside hand wound coils during operation. An analytical model was developed and COMSOL multiphysics was used to simulate the mode shapes of the harvester. The mathematical model was simulated for open circuit voltage in MATLAB and showed closely matching results with the experimental values. The harvester is characterized in lab for its performance under sinusoidal vibrations at low frequency (3 Hz–15 Hz) and low acceleration (0.01–0.09 g) levels. The 2-DOF harvester has two resonant frequencies of 4.4 Hz and 5.5 Hz and a volume of 333 cm3. It produces maximum voltage of 0.6 V at first resonance on coil-1 and maximum voltage of 1.2 V on coil-2 at second resonance at 0.09 g. At acceleration of 0.09 g the harvester produced 2.51 mW at first resonant frequency and 10.7 mW at second resonance. Moreover, the AC output voltage of the harvester is rectified to DC voltage by a three-stage Cockcroft-Walton multiplier type circuit. The DC power output at 0.05 g was 0.939 mW at first resonance and 0.956 mW at second resonance while maximum voltages of 5.4 V on coil-1 and 4 V on coil-2 were produced.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
