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General Card #2266
Coastal Structures: Designing for Uncertainty, Designing for Failure
Updated: 10/14/2022 11:57 AM by Michael Johnson
Reviewed: 10/14/2022 1:58 PM by Becky Benishek
Pile supported structures: develop alternate designs reducing cost by designing certain part(s) to fail at or before design loading

This Card outlines a lesson in design of coastal structures that addresses the uncertainty in the design process. The focus of this module is a pile supported pier structure; however, instructors can substitute a more appropriate structure based on the courses they teach at their institutions. 

Not only is there uncertainty in designing for the present environmental conditions, but any structure with a design life of 10+ years will need to incorporate the uncertainty of sea level rise and coastal storm conditions.  The design process requires that one take into account not only the risk of an event occurring, but also the cost of designing to that event.  It may be more cost effective to rebuild a structure than to build a structure to withstand a particular event.  Sometimes we design for failure, allowing our structure to fail in predetermined modes, so as to make rebuilding more cost effective (e.g. breakaway decking on a bridge).  

This assignment is offered at the senior level, for groups of 3-4 students.  The course is taught as a MWF 50 minute class.  

This module ran as a 4 class day Jigsaw with the final day being the report out and gallery walk.  Group assignments are made in advance using Canvas to randomly select the groups.  

New in 2020, students will use supplies provides to make a low-fidelity model of their group design.  The model should highlight the key features of their design that will fail under greater than design forcing.  After the Gallery walk, groups will deploy their design in the Florida Tech Wave Channel.  Their model will be tested under wave attack. 

At this point in the semester, the students have already had lessons in design forcing, risk and return interval wave forcing.  This is important so they already know what the design conditions need to be for a range of allowable risk.  For my class wave forcing is the design condition, but again you can substitute for wind or whatever the design event is for your chosen structure (perhaps you are focused on California and your design event is an earthquake.)

DAY 1 (Implemented on a Monday)

Part 1a: Form Project home teams and Intro 
First 1/4 of class

Part 1b: Identify and meet in expert groups 
Middle 1/2 of class

Part 1c: Return to your original home group and brainstorm next steps.
Last 1/4 of class

Homework: Research expert group topic, thinking about structure design and design optimization. 

DAY 2 (Implemented on a Wednesday)

Part 2: TOPIC EXPERTS: Meet in Expert groups
Structure Components:
Failure Modes:

Homework: Research expert group topic and how it fits in with the rest of the design.

DAY 3 (Implemented on a Friday)
Part 3: DESIGN: Work in home group sharing expert knowledge to produce design

Each Group builds a 3D model from supplies that focuses on the design features developed by the group. 
Each group builds a Quad Chart (Due on Day 4 (Implemented on a Monday))
Homework: Group finishes analysis and creates Quad Chart on 4 separate sheets of 8.5 X 11 paper. 

DAY 4 (Implemented on a Monday)
Part 4: REPORT-OUT:  Meet in Home groups
Gallery Walk and Report-out to the class 

The students should find examples of structure performance, forces on the structure, looking for failure and how that failure was mitigated.  An assessment rubric is included to help evaluate student performance. 

In the first folder below I have included: the activity handout, a more detailed Description of each day, my course notes in PPT format for Forces on Piles, the CEM chapter that covers piles, guidance on fishing pier design, and the assessment rubric I created.  
The second folder contains images of the student submissions from the first implementation of the module in Fall 2019, providing an idea of what the outcome will be.
Lastly, I have a folder that contains the uploaded student feedback / evaluations of the module.  

Keywords: design, failure, coastal, structures, risk

  • Demonstrate constant curiosity about our changing world
  • Explore a contrarian view of accepted solution
  • Integrate information from many sources to gain insight
  • Assess and manage risk
Creating Value
  • Persist through and learn from failure
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