Maximum Impact Force of Woody Debris on Floodplain Structures
Abstract
We collided woody debris (i.e. logs) with structures using flume and test basin laboratory facilities to investigate the maximum impact force that floodplain structures are exposed to by floating woody debris. The tests investigated the influence of collision geometry and construction material of the structure face on the maximum impact forces. Collision geometry was determined by the debris orientation on impact. We reviewed the three approaches that represent the existing guidance on maximum impact forces. Each approach estimates the maximum impact force based on the debris velocity and mass. We show that all the existing approaches can be derived from a single degree-of-freedom model of the collision and can be considered to be equivalent. The laboratory data show that the maximum impact force was associated with a log striking a rigid structure with its end. Oblique and eccentric collisions reduced the maximum impact load in a predictable and consistent manner. The approach we refer to as contact stiffness, a linear, one-degree-of-freedom model with no damping, was able to reproduce the laboratory results over the entire range of data, with an effective contact stiffness of 2.4 MN/m. All the existing guidance was applied to the laboratory data, and the strengths and weakness of each are discussed.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 2002
- Accession Number
- ADA398916
Entities
People
- Robert B. Haehnel
- Steven F. Daly
Organizations
- Engineer Research and Development Center