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Abstract
This paper describes an effort to refine a global dynamic testing technique for evaluating the overall stiffness of timber bridge superstructures. A forced vibration method was used to measure the frequency response of several simple-span, sawn timber beam (with plank deck) bridges located in St. Louis County, Minnesota. Static load deflections were also measured to establish the benchmark stiffness level for each bridge superstructure. Analytical models based upon simple beam and plate theory were utilized to characterize the relationship between the 1st bending mode frequency and the stiffness of the bridge superstructure. The results indicate that forced-vibration methods have potential for quickly assessing timber bridge superstructure stiffness. However, improvements must be made to the measurement system to correctly identify the 1st bending mode frequency of the field bridges. The beam theory model matched the physics of the single-span, timber beam superstructures better than plate theory. This global vibration technique has potential benefits for routine inspections and long-term health monitoring of timber bridge superstructures.
Keywords
Dynamic testing,
service life,
wood deterioration,
deterioration,
nondestructive testing,
vibration,
wooden bridges,
inspection,
bridges,
frequency response,
bending strength,
simple beam theory,
bending mode frequency,
stiffness,
timber bridges
Citation
Wacker, James P.; Wang, Xiping; Brashaw, Brian; Ross, Robert J. 2006. Estimating bridge stiffness using a forced-vibration technique for timber bridge health monitoring. Proceedings : NDE Conference on Civil Engineering : a joint conference of the 7th Structural Materials Technology: NDE/NDT for Highways and Bridges and the 6th International Symposium on NDT in Civil Engineering, 2006 August 14-18, St. Louis, MO. Columbus, OH : American Society for Nondestructive Testing, Inc., 2006: ISBN: 1571171487: pages 63-70.
