Abstract
The natural frequency change of reinforced concrete (RC) members during damage when subjected to low cycle loading was studied through horizontal cyclic loading experiments. Three groups of RC flexural members were subjected to horizontal, harmonic, low cycle loading to simulate earthquake conditions. The relation of instantaneous load, instantaneous displacement, and instantaneous natural frequency during loading was deduced. Using the resulting equation, the test members’ natural frequencies at any moment during loading could be calculated accurately. Then the natural frequency change curves and their fitting equations were also obtained. The impact of loading period T and loading amplitude A on a test member’s damage rate V was analyzed, which showed that the impact of T on V was quadratic, and the relation between A and V was linear. Finally, by fitting experimental data of number of loading cycles N, loading amplitude A, loading period T, and natural frequency ω, a three‐variable function, ω(N, A, T), was determined, revealing the change process of test members’ frequencies under arbitrary harmonic vibrations.
Highlights
It is important for engineers to assess the integrity or damage status of a structure after severe cyclic loading, such as from an earthquake
One method for diagnosing the status of structural damage relies on the structural natural frequency [1,2,3,4,5,6,7,8], as the damage of structural members will lead to changes in this parameter. erefore, determining the variation in structural natural frequency can help identify structural damage
Structural natural frequency-change characteristics under low cycle loading are important to identify structural damage caused by earthquakes
Summary
It is important for engineers to assess the integrity or damage status of a structure after severe cyclic loading, such as from an earthquake. Erefore, determining the variation in structural natural frequency can help identify structural damage. Most recent research focuses on identifying structural damage through the natural frequency change. Another study [12] focused on differentiating between the effects of changes in the natural frequency of a suspension bridge due to environmental variations and those resulting from structural damage. A study [13] showed how to use the method of natural frequency determination of a cracked reinforced concrete beam to assess its damage. Studies of natural frequency changes during structural damage are insufficient, and most research on this topic is qualitative rather than quantitative. Ere is scant work on the characteristics of natural frequency change during the damage process under a low cycle fatigue load. Shock and Vibration process under low cycle loading and established a quantitative functional relationship of natural frequency change. is study provided some theoretical basis for quantitative research of the damage process of an RC structure due to an earthquake
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