Abstract
Transmission towers are structurally complex, which makes it challenging to choose the right place and number of sensors for health monitoring. In this paper, optimal sensor placement of a cat-head-type transmission tower is conducted by using the Effective Independent Method (EIM) and a method is proposed for calculating the minimum number of sensors for structural health monitoring by combining EIM and Modal Assurance Criterion (MAC). The method for calculating the number of sensors prescribed in this paper derives a curve that shows the relationship between MAC value and the number of sensors. It is found that the MAC value decreases with increase in the number of sensors. When the number of sensors reaches a certain threshold, the curve tends to stabilize. Then, the number of sensors corresponding to the minimum MAC is proposed as the minimum number of sensors. Through calculation, the minimum number of sensors of the cat-head-type transmission tower is obtained. Also, the optimal sensor placement results show that the position of a large number of sensors includes the position of a smaller number of sensors.
Highlights
Transmission towers often operate in adverse and harsh environments with complex and varying loads and may experience failure, including collapse, from extreme conditions or vibration fatigue damage [1, 2]
Evaluation Criterion. e Modal Assurance Criterion (MAC) [27] is an effective tool for evaluating the intersection angle of modal vectors. It can reflect the correlation of two space vectors. e calculation formula of MAC is where Φi is the ith modal vector and Φj is the jth modal vector and the values of MACij fall between 0 and 1. e MACij value will be 0 if the two vectors are orthogonal, while the value equals 1 if the two vectors are completely correlated. e smaller the value of MACij is, the stronger the structural characteristics are reflected
It is generally believed that when MACij is greater than 0.9, the two modal vectors are completely related and cannot be distinguished
Summary
Transmission towers often operate in adverse and harsh environments with complex and varying loads and may experience failure, including collapse, from extreme conditions or vibration fatigue damage [1, 2]. E number of sensors is the prerequisite for optimal sensor placement, which in turn affects accuracy, sensitivity, and economy of acquiring the structural health information. With these problems in mind, this paper proposes several sensor placement schemes of a cat-head-type transmission tower and a method for determining the number of sensors to be used for health monitoring. To solve this problem, the optimal sensor placement should first be performed by the EIM under different numbers of sensors. The point corresponding to the minimum value of the curve is taken as the best number of placed sensors
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