Download Use of Sacrificial Embankments to Prevent Bridge Findings ABSTRACT

Use of Sacrificial Embankments to Prevent Bridge
Collapse Due to Scour Under Extreme Events
Author: Matthew Brand
Mentors: Donna Rizzo, Mandar Dewoolkar, Dryver Huston, Ian Anderson, Jon Lens
Findings
ABSTRACT
The leading cause of highway bridge failure in the United
States is bridge scour. High flow events in streams lead
to foundational bridge scour by enhancing erosion and
scour processes. These bridges are at a critical risk of
collapsing during extreme flooding events, and are a
major risk to human life and economic sustainability.
Currently, agencies and designers have limited resources
to predict the increasing severity of flooding that has
occurred over the last five decades. Retrofitting the
thousands of undersized and scour critical bridges
throughout the country to the current standards is
prohibitively expensive, and current countermeasures
inadequately address the core problems related to scour.
Recent research efforts on scour are geared towards
modeling and pattern analysis for designing standards for
newly built or planned bridges. Very limited research is
focused on the design or retrofit standards for the tens of
thousands of bridges already built, yet still vulnerable to
scour. This research focused on the design and
implementation of a simple and effective retrofit for
bridges already built using an embankment system that
acts as a “fuse” during high flow events. This
embankment design increases the streams cross
sectional area during high flow events, thereby
decreasing the energy and scour potential. This research
can provide a more inexpensive, safer, and quicker
retrofit for vulnerable bridges compared to current
methods.
Figure 1: Physical model of bridge abutment with erodible embankment post 100 year
storm simulated in 6x1 meter flume in Votey Hall.
Figure 2: Physical model of bridge abutment with non-erodible embankment post 100
year storm simulated in 6x1 meter flume in Votey Hall.
Bridge S cour RS = 3.5
Bridge S cour RS = 3.5
510
510
Legend
Legend
WS Q100
WS Q100
Ground
Ground
Levee
Levee
500
Bank Sta
500
Ineff
Contr Scour
Bank Sta
Total Scour
Contr Scour
Total Scour
490
490
480
Approach
Elevation (ft)
Elevation (ft)
480
470
470
460
460
450
• Accurately calculating future design storms for
bridges and culverts is very difficult
450
440
440
800
• Sought out innovative approaches to reduce
bridge scour accounting for future uncertainty
• Based on interview with FEMA consultant
decided to create new “fuse” embankment
design
• Designed physical and computational
experiments to determine effectiveness of
design
• Analyzed effectiveness of experiments
quantitatively
1000
1200
1400
1600
1800
430
800
1000
Station (ft)
Figure 3: Computer simulation of abutment scour in response to 100 year
storm using HEC-RAS with fuse system. Scour depth = 25ft
1200
1400
1600
1800
Station (ft)
Figure 3: Computer simulation of abutment scour in response to 100 year
storm using HEC-RAS with traditional embankment. Scour depth = 35ft
Summary
Special Thanks
• Due to climate change, extreme storm events are
happening with greater frequency and magnitude.
• The Transportation Research
Center for funding this research.
• Lengthening existing bridges is not an economically
feasible solution.
• My mentors and advisors for
their support and guidance
• New design acts a “fuse” during extreme storm events
and embankment fuse is an order of magnitude
cheaper to repair than scour.
• Embankment fuse reduced scour during a 100 year
storm event significantly enough that collapse due to
scour could be avoided.
References
• Arneson, L.A., Zevenbergen, L.W., Lagasse, P.F., & Clopper, P.E. (2012)
“Evaluating scour at bridges”, No. FHWA-HIF-12-003
• Kattell, John, P.E., and Merv Eriksson, P.E. "Bridge Scour Evaluation:
Screening, Analysis, & Countermeasures." US Forest Service (1998): n. pag.
Web. 11 Oct. 2014.
• Laursen, E.M., & Toch, A. (1956). “Scour around bridge piers and abutments
(Vol. 4)”. Ames, Iowa: Iowa Highway Research Board.
• Walsh, J., et. al. 2014: Ch. 2: Our Changing Climate Change Impacts in the
United States: The Third National Climate Assessment, J. M. Melillo, Terese
(T.C.) Richmond, and G.W. Yohe, Eds., U.S. Global Change Research Program,
19-67. doi: 10.7939/J0KW5CXT.