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Experimental estimating deflection of a simple beam bridge model using grating eddy current sensors.

Lü C, Liu W, Zhang Y, Zhao H - Sensors (Basel) (2012)

Bottom Line: Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints.In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection.Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches.

View Article: PubMed Central - PubMed

Affiliation: Department of Instrument Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. chunfenglv@sjtu.edu.cn

ABSTRACT
A novel three-point method using a grating eddy current absolute position sensor (GECS) for bridge deflection estimation is proposed in this paper. Real spatial positions of the measuring points along the span axis are directly used as relative reference points of each other rather than using any other auxiliary static reference points for measuring devices in a conventional method. Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints. In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection. Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches. Principles of the three-point method and displacement measurement of the GECS are introduced in detail. Both static and dynamic experiments have been carried out on a simple beam bridge model, which demonstrate that the three-point deflection estimation method using the GECS is effective and offers a reliable way for bridge deflection estimation, especially for long-term monitoring.

No MeSH data available.


Related in: MedlinePlus

Schematic diagram of the three-point method.
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f1-sensors-12-09987: Schematic diagram of the three-point method.

Mentions: The schematic diagram of the three-point method is shown in Figure 1. The absolute deflections of measuring point i and the two adjacent measuring points i − 1 and i + 1 are defined as yi, yi-1 and yi+1, respectively. A straight connecting bar is used to link the measuring points i − 1 and i + 1, and a displacement sensor is installed on it corresponding to the measuring point i. When deformation occurs, the absolute deflection of each measuring point relative to the span axis is different in value, and meanwhile, the relative position between the measuring point i and the connecting bar will be changed along the deflection direction. Therefore, the displacement can be measured by the displacement sensor installed on the connecting bar. The obtained displacement value is named as the relative deflection zi. It is to be noted that there is an angular deviation between zi and yi, but this can be ignored because it is a very slight angle deflection (often less than 2 min of angle). Thus, the absolute deflection yi of the measuring point i can be calculated from yi-1, yi+1 and zi (i = 1, 2, …, n − 2, n − 1), the relational expression of yi and zi is as follows:(1)yi=ki(yi−1+yi+1)+ziwhere ki is the proportionality coefficient which is related to the distance between the measuring points, especially when ki = 1/2, the measuring points are selected equidistantly.


Experimental estimating deflection of a simple beam bridge model using grating eddy current sensors.

Lü C, Liu W, Zhang Y, Zhao H - Sensors (Basel) (2012)

Schematic diagram of the three-point method.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3472811&req=5

f1-sensors-12-09987: Schematic diagram of the three-point method.
Mentions: The schematic diagram of the three-point method is shown in Figure 1. The absolute deflections of measuring point i and the two adjacent measuring points i − 1 and i + 1 are defined as yi, yi-1 and yi+1, respectively. A straight connecting bar is used to link the measuring points i − 1 and i + 1, and a displacement sensor is installed on it corresponding to the measuring point i. When deformation occurs, the absolute deflection of each measuring point relative to the span axis is different in value, and meanwhile, the relative position between the measuring point i and the connecting bar will be changed along the deflection direction. Therefore, the displacement can be measured by the displacement sensor installed on the connecting bar. The obtained displacement value is named as the relative deflection zi. It is to be noted that there is an angular deviation between zi and yi, but this can be ignored because it is a very slight angle deflection (often less than 2 min of angle). Thus, the absolute deflection yi of the measuring point i can be calculated from yi-1, yi+1 and zi (i = 1, 2, …, n − 2, n − 1), the relational expression of yi and zi is as follows:(1)yi=ki(yi−1+yi+1)+ziwhere ki is the proportionality coefficient which is related to the distance between the measuring points, especially when ki = 1/2, the measuring points are selected equidistantly.

Bottom Line: Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints.In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection.Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches.

View Article: PubMed Central - PubMed

Affiliation: Department of Instrument Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China. chunfenglv@sjtu.edu.cn

ABSTRACT
A novel three-point method using a grating eddy current absolute position sensor (GECS) for bridge deflection estimation is proposed in this paper. Real spatial positions of the measuring points along the span axis are directly used as relative reference points of each other rather than using any other auxiliary static reference points for measuring devices in a conventional method. Every three adjacent measuring points are defined as a measuring unit and a straight connecting bar with a GECS fixed on the center section of it links the two endpoints. In each measuring unit, the displacement of the mid-measuring point relative to the connecting bar measured by the GECS is defined as the relative deflection. Absolute deflections of each measuring point can be calculated from the relative deflections of all the measuring units directly without any correcting approaches. Principles of the three-point method and displacement measurement of the GECS are introduced in detail. Both static and dynamic experiments have been carried out on a simple beam bridge model, which demonstrate that the three-point deflection estimation method using the GECS is effective and offers a reliable way for bridge deflection estimation, especially for long-term monitoring.

No MeSH data available.


Related in: MedlinePlus