Research Papers: Structures and Safety Reliability

Experimental and Analytical Study of Water-Driven Debris Impact Forces on Structures1

[+] Author and Article Information
H. R. Riggs

Department of Civil and
Environmental Engineering,
University of Hawaii at Manoa,
Honolulu, HI 96822

D. T. Cox, H. T.-S. Ko

Department of Civil
and Construction Engineering,
Oregon State University,
Corvallis, OR 97331

C. J. Naito, P. Piran Aghl

Department of Civil
and Environmental Engineering,
Lehigh University,
Bethlehem, PA 18015

M. H. Kobayashi

Department of Mechanical Engineering,
University of Hawaii at Manoa,
Honolulu, HI 96822

E. Khowitar

Department of Civil
and Environmental Engineering,
University of Hawaii at Manoa,
Honolulu, HI 96822

1Modified version of OMAE2013-11128.

Contributed by the Ocean, Offshore, and Arctic Engineering Division of ASME for publication in the JOURNAL OF OFFSHORE MECHANICS AND ARCTIC ENGINEERING. Manuscript received April 27, 2013; final manuscript received August 10, 2014; published online September 15, 2014. Assoc. Editor: Solomon Yim.

J. Offshore Mech. Arct. Eng 136(4), 041603 (Sep 15, 2014) (8 pages) Paper No: OMAE-13-1042; doi: 10.1115/1.4028338 History: Received April 27, 2013; Revised August 10, 2014

Water-driven debris generated during tsunamis and hurricanes can impose substantial impact forces on structures that are often not designed for such loads. This paper presents the design and results of an experimental and analytical program to quantify these potential impact forces. Two types of prototypical debris are considered: a wood log and a shipping container. Full-scale impact tests at Lehigh University (LU) were carried out with a wooden utility pole and a shipping container. The tests were carried out in-air. The purpose of these tests was to provide baseline, full-scale results. Because of size limitations, a 1:5 scale shipping container model was used for in-water tests in the Oregon State University (OSU) large wave flume. These tests were used to quantify the effect of the fluid on the impact forces. Results from both experimental programs are presented and compared with analytical predictions. The predictions are found to be in sufficient agreement such that they can be used for design. A fundamental finding is that the impact forces are dominated by the structural impact, with a secondary effect provided by the fluid. Both forces are quantified in the paper.

Copyright © 2014 by ASME
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Fig. 1

Longitudinal impact of a rod

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Fig. 2

Impact force versus time for a range of k¯ (after [15])

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Fig. 3

Percent error in peak force from Eq. (4) as a function of k¯

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Fig. 4

Transverse impact of a beam

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Fig. 5

Wood utility pole in pendulum test setup. Pole swings down and impacts load cell just off the bottom of the photo.

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Fig. 6

Shipping container in pendulum test setup. Container was winched back toward the camera, released, and then it swung forward toward load cells mounted on a stiff frame.

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Fig. 7

Impact force time histories for utility pole and shipping container at the impact velocity of 1.3 m/s

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Fig. 8

Nondimensional peak impact forces

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Fig. 9

Nondimensional impact duration

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Fig. 10

Schematic of OSU tests in large wave flume

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Fig. 11

Aluminum specimen for in-water tests showing guide wires. View is toward the wavemaker.

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Fig. 12

Aluminum specimen for in-water tests showing column in upper portion of the figure. Submersible camera is at top right of photo normal to column and load cell.

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Fig. 13

Aluminum specimen for in-air tests as viewed from submersible camera. Note lip on aluminum specimen to assure clean contact with bottom plate during impact.

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Fig. 14

Aluminum box for in-water tests as viewed from submersible camera

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Fig. 15

Comparison of impact loads for in-air tests and in-water tests at same impact speed

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Fig. 16

Comparison of maximum force versus speed for several tests with aluminum specimen. Each symbol style represents a unique combination of water depth and mass of contents. Solid line shows the predicted value from Eq. (4), based on data derived from measured in-air tests of empty container.




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