There is a documented need for failure awareness in the undergraduate engineering curriculum. Engineering students can learn a lot from failures, and failures play an important role in engineering design. This need has been expressed in a number of papers and at a number of conferences over the past two decades. This book is a specific response to that need and will provide (1) much needed access to examples, and (2) a heightened appreciation of the role failure analysis knowledge can play in higher education and public safety.
Many of the key technical principles that civil engineering students should learn can be illustrated through case studies. For example, the author has discussed the Hyatt Regency walkway collapse, the Tacoma Narrows Bridge failure, and other well-known cases with students in Statics, Mechanics of Materials, and other courses. These cases help students:
- Grasp difficult technical concepts and begin to acquire an intuitive feel for the behavior of systems and structures,
- Understand how engineering science changes over time as structural performance is observed and lessons are learned,
- Analyze the impacts of engineering decisions on society, and
- Appreciate the importance of ethical considerations in the engineering decision making process.
The main obstacle to integrating case studies and lessons learned from failures into existing courses has been that many faculties does not have time to research and prepare case studies. Although there are many references available, they are difficult to translate into classroom lectures without considerable added effort on the part of the instructor.
There are three ways to introduce failure analysis and failure case studies into civil engineering education. A small number of colleges and universities, probably only a few percent, offer courses in forensic engineering or failure case studies. Often, these are at institutions such as the University of Texas, Mississippi State University, or the University of Colorado at Denver that have practicing forensic engineers on the faculty (Delatte and Rens, 2002). Clearly, this approach depends on the availability of qualified and interested faculty.
Another method is to use case studies in capstone (Senior) design projects (Delatte and Rens, 2002). This is also dependent on the interested and qualified faculty, as well as on the availability of appropriate projects (which must be sufficiently free of liability concerns).
These two approaches offer great depth in the topic, but due to their inherent limitations, their application is likely to remain limited. As a result, even at colleges and universities where courses are offered in this area, few undergraduates are likely to be able to take them. While some might argue for a required stand-alone course in failure analysis for all undergraduate civil engineering students, the argument is likely to fall on deaf ears as programs shrink their credit hour requirements. However, this book would be an excellent text for a civil engineering failure analysis course.
A more promising approach is to integrate failure case studies into courses throughout the curriculum. Many professors have done this on an informal basis for years. The author used this approach at the United States Military Academy (USMA) while teaching two courses in engineering mechanics, Statics and Dynamics and Mechanics of Materials (Delatte, 1997). He continued the approach in engineering mechanics and civil engineering courses at the University of Alabama at Birmingham (UAB) (Delatte, 2000, Delatte and Rens, 2002, Delatte, 2003) and at Cleveland State University.
Why Study Failures?
In a survey conducted by the ASCE Technical Council on Forensic Engineering (TCFE) Education Committee in December 1989, about a third of the 87 civil engineering schools responding indicated a need for detailed well-documented case studies. The University of Arizona said ASCE should provide such materials for educational purposes and Swarthmore College suggested ASCE should provide funds for creating monographs on failures that have occurred in the past (Rendon 1993a).
The ASCE TCFE conducted a second survey in 1998, which was sent to all Accreditation Board for Engineering and Technology (ABET) accredited engineering schools throughout the United States (Rens et al, 2000a). Similar to the 1989 survey, the lack of instructional materials was cited as a reason that failure analysis topics were not being taught. One of the unprompted written comments in that survey was a selected bibliography is needed on the topic, which could be accessed via the Internet.
The use of case studies is also supported by the latest pedagogical research. From Analysis to Action (Center, 1996) refers on page 2 to textbooks lacking in practical examples as an emerging weakness. Much of this document refers specifically to the breadth of understanding, which may be achieved through case studies. Another issue addressed (Center, 1996, p. 19) is the need to incorporate historical, social, and ethical issues into courses for engineering majors. The Committee on Undergraduate Science Education in Transforming Undergraduate Education in Science, Mathematics, Engineering, and Technology (Committee, 1999) proposes that as many undergraduate students as possible should undertake original, supervised research. How People Learn (Bransford et al., 1999, p. 30) refers to the need to organize knowledge meaningfully, in order to aid synthesis and develop expertise.
This work raises the question of whether failure analysis is merely tangential to, or is, in fact, fundamental to, civil engineering education. Put another way, are failure case studies simply interesting, or should they be an essential component of a civil engineering curriculum?
Failure Case Studies and Accreditation Requirements
ASCE TCFE Education Committee surveys of civil engineering departments reported in 1989 and 1998 (Rendon-Herrero, 1993a, 1993b, Bosela, 1993, Rens et al., 2000) found that many respondents indicated a need for detailed, well-documented case studies. Some of those replying felt strongly that incorporation of failure case studies should not become part of accreditation evaluations. However, unless something is specifically mandated by the Accreditation Board for Engineering and Technology (ABET), it is likely to be a low priority for inclusion in a curriculum.
There is certainly an argument to be made that failure analysis should be mandated by ABET. It may also be argued that, in a sense, it already is. Under Criterion 3, Program Outcomes and Assessment,
Engineering programs must demonstrate that their students attain:
(a) An ability to apply knowledge of mathematics, science, and engineering
(b) An ability to design and conduct experiments, as well as to analyze and interpret data
(c) An ability to design a system, component, or process to meet desired needs within realistic constraints such as economic, environmental, social, political, ethical, health and safety, manufacturability, and sustainability
(d) An ability to function on multi-disciplinary teams
(e) An ability to identify, formulate, and solve engineering problems
(f) An understanding of professional and ethical responsibility
(g) An ability to communicate effectively
(h) The broad education necessary to understand the impact of engineering solutions in a global, economic, environmental, and societal context
(I) a recognition of the need for, and an ability to engage in life-long learning
(j) A knowledge of contemporary issues
(k) An ability to use the techniques, skills, and modern engineering tools necessary for engineering practice.
Programs often struggle with how to document that their graduates understand the impact of engineering solutions in a global and societal context, engage in life-long learning and demonstrate knowledge of contemporary issues (criteria h, i, and j, respectively). These outcomes can be difficult to demonstrate. One method of documenting these particular outcomes is to include case studies of failed engineering works in the curriculum. Many case studies show the direct societal impact of failures and demonstrate the need for life-long learning by highlighting the evolutionary nature of engineering design procedures.
Case studies also address the revised criterion c, design within realistic constraints. Case studies and specifically failure case studies illuminate how economic, environmental, social, political, ethical, health and safety, manufacturability, and sustainability impact design, behavior, and performance of engineered systems.
Criteria for civil engineering programs are more specific. Students must demonstrate an understanding of professional practice issues such as procurement of work, bidding versus quality-based selection processes, how the design professionals and the construction professions interact to construct a project, the importance of professional licensure and continuing education, and/or other professional practice issues.These professional issues are integral to many of the case studies addressed through the workshops. As an example, some project failures may be traced to poor interaction and communications between the designers and the builders.
Failure Case Studies and the Civil Engineering Body of Knowledge
The ASCE report Civil Engineering Body of Knowledge for the 21st Century: Preparing the Civil Engineer for the Future, prepared by the Body of Knowledge Committee of the Committee on Academic Prerequisites for Professional Practice, goes beyond ABET. The Body of Knowledge (BOK) defines 12 outcomes. The first 11 are identical to the ABET a k. BOK outcomes 12-15 are:
- An ability to apply knowledge in a specialized area related to civil engineering.
- An understanding of the elements of project management, construction, and asset management.
- An understanding of business and public policy and administration fundamentals.
- An understanding of the role of the leader and leadership principles and attitudes.
For those failures with complex technical causes, failure case studies may be used to deepen understanding within specialized civil engineering areas (outcome 12). Failures can expose and highlight the subtleties of structural and system behavior that are the province of the specialist. Some specialties, such as earthquake and geotechnical engineering, have historically relied heavily on failure case studies to advance the state of the practice.
Outcomes 13, 14, and 15 may also be addressed through failure case studies. In many failures, the technical issues involved may not be particularly complex or unusual. Instead, breakdowns may come in the project management and construction processes or in the management of the facility by the owner (outcome 13). Pressures of business and public interests may encourage engineers to take short cuts, with harmful consequences (outcome 14). Some failures might have been averted with stronger leadership (outcome 15). A more thorough discussion of the relationship between failure case studies, ABET, and BOK outcomes is provided in Delatte (2008).
Pedagogical Benefits of Case Studies
Learning that occurs in multiple learning skills domains and exercises higher level learning skills is crucial to successful engineering education. This must, however, occur efficiently because engineering curricula are already overcrowded. This is one reason why failure case studies should be an essential part of engineering classes. The single activity of using a case study as part of a traditional course lesson plan simultaneously fosters learning in three different learning domains, thus making learning more efficient:
1. Affective: The failure is interesting and sometimes dramatic, thus increasing initial acquisition and permanent retention of knowledge from the learning exercise because of the emotional state of the student during the learning process.
2. Cognitive: The failure validates the science, showing that our engineering tools work and thus motivating the students to learn and retain more knowledge.
3. Social: Students discover or rediscover how engineering decisions impact individuals, communities, and society
As a result of case study inclusion, students will demonstrate an ability to process failure analysis, apply ethics in engineering, and demonstrate an understanding of the engineer’s role in and their value to society. Students will also demonstrate a greater depth of knowledge by developing intuition about the expected behavior of engineered systems, understanding load paths, and better visualizing the interaction of components of engineered systems. Finally, students should experience a change in attitudes about quality engineering as a result of studying failures of engineered systems.
Use of Cases
Some of the ways to use case studies and a suggested format were reviewed in Delatte and Rens (2002). These include:
- Introductions to topics use the case to illustrate why a particular failure mode is important. Often the importance of a particular mode of failure only became widely known after a failure examples include the wind-induced oscillations of the Tacoma Narrows Bridge and the failure of Air Force warehouses in the mid-1950’s that pointed out the need for shear reinforcement in reinforced concrete beams.
- Class discussions link technical issues to ethical and professional considerations. Add discussions of the standard of care, responsibility, and communications to coverage of technical topics.
- Example problems and homework assignments calculate the forces acting on structural members and compare them to design criteria and accepted the practice. This can have the added benefit of requiring students to compare design assumptions to actual behavior in the field under service loads and overloads.
- Group and individual projects have students research the cases in depth and report back on them. This will also help build a database of cases for use in future classes. Students gain valuable research, synthesis, and communication skills.
The use of case studies as common threads through the curriculum can best be illustrated through an example. The 1907 collapse of the Quebec Bridge during construction, discussed in Chapter 3, represents a landmark of both engineering practice and forensic engineering. The Quebec Bridge was the longest cantilever structure attempted until that time. In its final design, it was 548.6 m (1,800 ft) long. The bridge project was financially troubled from the beginning. This caused many setbacks in the design and construction. Construction began in October 1900. In August 1907, the bridge collapsed suddenly. Seventy-five workers were killed in the accident, and there were only eleven survivors from the 86 workers on the span.
A distinguished panel was assembled to investigate the disaster. The panel’s report found that the main cause of the bridge’s failure was the improper design of the latticing on the compression chords. The collapse was initiated by the buckling failure of Chord A9L, immediately followed by Chord A9R. Theodore Cooper had been the consulting engineer for the Quebec Bridge project, and most of the blame for the disaster fell on his shoulders. He mandated unusually high allowable stresses and failed to require recalculation of the bridge dead load when the span was lengthened.
This case study illustrates a number of important teaching points from engineering courses.
1) Statics truss analysis. The bridge was a cantilever truss. As the two arms of the bridge were built out from the pier, the moments on the truss arms increased, and the compressive stresses in the bottom chords of each arm also increased. Both the method of joints and the method of sections, traditionally taught in statics courses, may be used to analyze the compressive strut forces at the different stages of bridge construction. See Chapter 2.
2) Mechanics of Materials allowable stresses. Mr. Cooper increased the allowable stresses for his bridge well beyond the limits of accepted engineering practice, without experimental justification. He allowed compressive stresses that were considerably higher than that provided by the modern AISC code and were highly unconservative given the state of knowledge at the time. The compression struts of the truss were too large to be tested by available machinery, so their capacity could not be precisely known. Development of engineering codes and standards requires tradeoffs between structural safety and economy, and there must be mechanisms for resolving disputes between competing criteria. See Chapter 3, which has this case study.
3) Mechanics of Materials structural deformation. The bending of the critical A9L member reached 57 mm (2-inches) and was increasing at the time of the collapse. The bending was discussed at the site and by Mr. Cooper, attempting to supervise the project from New York, but no action was taken. In fact, the bending showed that the member was slowly buckling.
4) Mechanics of Materials buckling of columns and bars. The critical A9L compression member failed by buckling. It was a composite section, which meant that it required lacing to require the members to bend together. The moment of inertia, and buckling capacity, of the composite section, may be compared to that of the individual truss members, showing the importance of the latticing system.
5) Structural Analysis predicting, computing, and correcting dead loads. One critical error made in the design was that the dead load was greatly underestimated. When material invoices showed that 17-30 % more steel had gone into parts of the structure than had been planned for in the design, no attempt was made to analyze the bridge for the new loads. See Chapter 4.
6)The design of Steel Structures analysis and design of built-up members. This point follows from the discussion of buckling of columns and bars, above. Many existing steel bridges use built-up members, and engineers involved in assessing and rehabilitating such structures need to know how to evaluate member capacity and likely failure modes. See Chapter 6.
7) Engineering Management the requirement for the engineer of record to inspect the work on the site. Mr. Cooper attempted to supervise the construction of a bridge in Quebec from his office in New York City. When problems arose, the problems were referred to him for a decision. The absence of an onsite engineer with authority to stop the work meant that there was no way to head off the impending collapse. A meeting was held to decide what to do, and the bridge collapsed just as the meeting was breaking up.
8) Engineering Ethics professional responsibility. Mr. Cooper planned for the Quebec Bridge to be the crowning achievement of an illustrious career as a bridge engineer. However, by this time his health was poor and he was unable to travel to the site. He was also poorly compensated for his work. Following the collapse, organizations such as ASCE began to define better the responsibility of the engineer of record. Unfortunately, the collapse of the Hyatt Regency Walkways three-quarters of a century later showed that much remains to be done.
As an example, the following problem statement may be used in a structural analysis or capstone design/professionalism course, in conjunction with the Quebec Bridge collapse case study. The problem should be assigned before the discussion of the case study, probably as an overnight homework. Following discussion of the case study, students should be better able to identify potential problems with an unusual construction technique.
You are the engineer for a cantilever truss bridge across a major river in North America. The bridge owner has asked you to prepare specifications, including allowable stresses, and has emphasized that they have a very shaky financial situation. The bridge was initially intended to be 1,600 feet long to reduce the cost of the piers, they have been moved into shallower water and it will now be 1,800 feet long. When completed, it will be the longest bridge of this type in the world.
Problem: list all of the things you can think of that can go wrong during this bridge construction project.
Once the collapse case has been discussed, the problem may be reassigned with the additional assignment to propose communication and quality control measures to ensure against collapse. Students should refer to the case study in formulating their answers.
The case study materials developed so far have been very well received by faculty across a wide range of civil engineering programs, as well as some other related programs. To date, however, the benefits identified have been anecdotal (although nevertheless impressive). There remains a need to identify, quantify, and assess the impact of case studies on teaching and learning.
Surveys have found widespread agreement that faculty consider failure case studies important and useful (Rendon-Herrero, 1993a, 1993b, Bosela, 1993, Rens et al., 2000). Several of the faculty failure case study workshop participants have reported back that the case studies have been excellent for motivating their students to learn. So far, the formal assessment of the impact of using case study materials in courses has been limited. Some assessment methods and results have been published by Delatte et al. (2007, 2008).
Desired student learning outcomes are:
- Improved understanding of technical issues in civil engineering and engineering mechanics
- Improved understanding of ethical, professional, and procedural issues in civil engineering and engineering mechanics
The primary assessment question is: In what ways does the use of failure case studies improve students ability to demonstrate competencies that prepare them to be better professional civil engineers?
The assessment questions are as follows:
- Does the use of failure case studies improve student’s ability to demonstrate competencies that better prepare them as professional engineers for the 21st century?
- How does the implementation of failure case studies encourage deep learning in civil engineering students?
- What has been the time commitment and value-added experience for faculty who integrate failure case studies in the course curriculum that improves student learning of civil engineering concepts?
For Delatte’s papers published in ASEE Conference Proceedings, go the ASEE Proceedings web page, and use the “Author” search on Delatte