Thesis
Field implementation of stress wave timing inspection and fracture resistance of in-service timber guardrail posts
Washington State University
Master of Science (MS), Washington State University
2019
Handle:
https://hdl.handle.net/2376/102398
Abstract
A previous research project conducted for Washington Department of Transportation (WSDOT) produced field trials with a new stress wave timing (SWT) device and determine an effective inspection strategy for guardrail systems (Olszko and Bender, 2015). This project started with 498 guardrail posts in five regions of Washington State. The field inspections revealed an overall SWT rejection rate of approximately 25%, but the western regions had the majority of the rejected posts (up to 37% in one region) and the central region had a low rejection rate of 5%. Further analysis investigated factors leading to higher rejection rates. The strongest factor was climate index. Material and preservative treatment testing shown that poor preservative retention could also be a factor in the high rejection rates. Lastly, pendulum impact tests were conducted on 15 posts with varying SWT velocities at the ground level. The pendulum was 3,773 lbs and impacted the posts at approximately 9.13 mph. Fracture energy of posts was calculated utilizing two methods, the difference in kinetic energy right before and after impact and the difference in potential energy from the start of the test to when the pendulum was at the apex of its motion after impact. It was shown that the two methods produce different fracture energies due to the timeframe over which they capture dissipated energy. The author believes that fracture energy calculation utilizing the potential method is most appropriate for guardrail impacts because it captures more of the dissipated energy during the crash. The results determined that posts with lower SWT velocities at the ground level have lower impact resistance, as measured by fracture energy using either method. Posts with SWT velocities less than 20 in./ms had 50% less fracture energy on average than posts with SWT velocities from 20 in./ms to 37 in./ms. That is different from Olszko and Bender (2015) static bending test result, SWT velocity was not correlated to loss of post integrity as defined by the standard. Therefore, future work is needed to determine if the AASHTO standard should define guardrail post integrity based on static flexural strength or pendulum impact resistance.
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Details
- Title
- Field implementation of stress wave timing inspection and fracture resistance of in-service timber guardrail posts
- Creators
- Qiyang Luo
- Contributors
- Adam R. Phillips (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Civil and Environmental Engineering, Department of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525153401842
- Language
- English
- Resource Type
- Thesis