3.6. CONSIDERACIONES PARA LA DIAGNOSIS DEL DESEQUILIBRIO
3.6.7. RESONANCIAS
in the atrium area of the Hyatt Regency Hotel in Kansas City, Missouri collapsed, killing 114 people and injuring 185. The collapse was one of the most serious structural failures in the history of the United States.
The hotel included a 40-story guest room tower, a four-story wing con-taining restaurants and meeting rooms, and a large, open atrium. The atrium contained three suspended walkways at the second-, third-, and fourth-floor levels which connected the tower section with the restau-rants and meeting rooms. Each walkway was 120 feet long and approxi-mately 81/2feet wide.
The second- and fourth-floor walkways were constructed one above another along the west wall of the atrium. The third-floor level walkway was independently suspended from the atrium roof trusses and was built about 13 feet toward the center of the room. The third-floor walkway was not involved in the collapse. The second-floor walkway was suspended from the fourth-floor walkway, which in turn was suspended from the roof framing.
In the aftermath of the tragedy, the mayor of Kansas City requested that the National Bureau of Standards (NBS) conduct an independent inves-tigation to determine the cause of the collapse (16). There were, of course, other investigations and hearings as well as at least 150 lawsuits seeking total damages of $1.5 billion.
Each of the walkways consisted of four spans of about 30 feet.
Intermediate supports consisted of three pairs of 11/4-inch diameter steel hanger rods. Each walkway was supported from underneath longitudi-nally by 16-inch deep wide flange steel beams and laterally by 8-inch deep steel box beams. The box beams were made of pairs of 8-inch steel channels that were welded together at their open ends. The walkway deck consisted of a formed steel deck overlain by a 31/4-inch lightweight concrete slab which acted compositely with the 16-inch deep stringers.
Figure 5.8 shows a cross-section of the walkways as well as the hanger rod connection.
The National Bureau of Standards discovered that a significant design change had been made after the completion of the original design draw-ings in the way in which the walkways were connected to the hanger rods. The original drawings called for both the fourth- and second-floor walkways to be hung from the same continuous steel rods. As originally conceived, pairs of single rods about 45 feet long would have been passed through the box beams at the fourth-floor walkway and continued down to pass through the box beams at the second-floor level. The walkways were to have been supported by a nut-and-washer connection under the box beams at each level.
Figure 5.8 Cross section of walkways and detail of walkway hanger rod-box beam connections. (Source: Neil Schlager, ed., When Technology Fails, Gale Research, Inc., Detroit, 1994.) (Reprinted by permission of AP/Wide World Photos.)
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Instead of using continuous rods, however, the contractor hung the walkways from two separate sets of rods. Each fourth-floor box beam had two holes at each end, one 2 inches from the end and the other 6 inches from the end. The upper hanger rod passed through the outer hole, while the lower hanger rod, onto which hung the second-floor walkway, passed through the inner hole. A nut-and-washer connection was used on the ends of the rods.
The effect of this change was to essentially double the load on the box-beam hanger connection at the fourth floor walkway. In fact, it was con-cluded that the collapse was initiated when the welding of one of the fourth-floor beams split, and the nut-and-washer connection supporting that part of the walkway slipped through the hole. The load of both walk-ways was then transferred to the remainder of the fourth floor connec-tions, which also failed. The fourth-floor walkway then collapsed onto the one below it, and both walkways crashed onto the lobby floor.
It was reported that the failed connection was designed by the project’s steel erector and fabricator, a common practice in the construction indus-try. It was noted, however, that the shop drawings submitted by the fabri-cator had been signed by the chief structural engineer and the project engineer. Missouri law states that: “Any registered engineer who affixes his signature and personal seal to any such plans . . . shall be personally and professionally responsible therefore.” The Board of Architects, Professional Engineers, and Land Surveyors voted unanimously to revoke the licenses of these two engineers permanently (17) and to revoke the certificate of authority of their firm. The firms’ assets were sold to another civil and structural engineering firm.
An expert witness appearing before the Missouri Administrative Hearing Commission stated that the engineer of record usually has to delegate his duties because there is too much work. “But he cannot del-egate his responsibility. . . . There has to be a point where the buck stops.” (18)
REFERENCES
1. CLELAND, DAVID I., AND HAROLD KERZNER, Engineering Team Management, Van Nostrand Reinhold Company, New York, 1986.
2. PEARSON, DONALDS., Creativeness for Engineers, 3rd Edition, Pennsylvania State University, University Park, PA, 1960.
3. WHITING, CHARLESS., Creative Thinking, Rheinhold Publishing Corporation, New York, 1958.
4. DUDERSTADT, JAMES J., GLENN F. KNOLL, AND GEORGE F. SPRINGER, Principles of Engineering, John Wiley & Sons, Inc., New York, 1982.
5. WRIGHT, PAULH.,ANDJ. N. THOMASSON, JR., “Simulation of Traffic at a Two-Way Stop Intersection,” Traffic Engineering, Vol. 37, No. 11, August 1967.
6. ROLAND, ALEX, Model Research, The National Advisory Committee for Aeronautics 1915–1958, Vol. 2, National Aeronautics and Space Administration, Washington, DC, 1985.
7. GRANT, EUGENE L., W. GRANT IRESON,AND RICHARD S. LEAVENWORTH, Principles of Engineering Economy, 8th Edition, John Wiley & Sons, Inc., New York, 1990.
8. WRIGHT, PAUL, H. Highway Engineering, 6th Edition, John Wiley & Sons, Inc., New York, 1996.
9. WRIGHT, PAUL H., NORMAN J. ASHFORD,AND ROBERTSTAMMER, JR., Transportation Engineering: Planning and Design, 4th Edition, John Wiley & Sons, Inc., New York, 1998.
10. General Information About Patents, U.S. Department of Commerce, Patent and Trademark Office, Washington, DC, Revised December, 1990.
11. KRAUSE, JOHN K., Computer-Aided Design and Computer-Aided Manufacturing, Marcel Dekker, Inc., New York, 1982, p. 12. Reprinted by courtesy of Marcel Dekker, Inc.
12. PETROSKI, HENRY, To Engineer Is Human, St. Martin’s Press, New York, 1985.
13. FITZSIMONS, NEAL, AND DONALD VANNOY, “Establishing Patterns of Building Failures,” Civil Engineering, Vol. 54, No. 1, American Society of Civil Engineers, January 1984.
14. Report of the Presidential Commission on the Space Shuttle Challenger Accident.
Report to the President, Government Printing Office, 1986.
15. SCHLAGER, NEIL, ed., When Technology Fails, Gale Research, Inc., Detroit, 1994.
16. PFRANG, EDWARD O.,ANDRICHARDMARSHALL, “Collapse of the Kansas City Hyatt Regency Walkways,” Civil Engineering, July, 1982, pp. 65–68.
17. ALM, RICK, “Hyatt Engineers Lose Licenses in Missouri,” Engineering News Record, January 30, 1986, p. 11.
18. “Hyatt Hearing Traces Design Chain,” Engineering News Record, July 26, 1984, pp.
12–13.
EXERCISES
5.1 Write a report comparing the scientific method and the engineering method of problem solving.
5.2 List three ideas for overcoming the problems of drivers locking their keys in their automobiles.
5.3 Describe three ways for reducing or eliminating flying insects from a patio area.
5.4 Give an example of a technological development that was delayed because tech-nologists failed to properly identify the problem.
5.5 Prepare a report describing the Delphi technique for developing ideas for solving problems. Describe the background of the development of this technique. How does it differ from brainstorming? Indicate how it can be used to facilitate the solution of engineering problems.
5.6 Prepare a scheme for developing:
a. A system for measuring or monitoring heat loss from a residential house.
EXERCISES
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b. A device to measure the distance a jogger runs.
c. A device mounted on the instrument panel of a car to indicate the distance from the edge of a curb.
5.7 List two types of problems that could suitably be modeled by:
a. Mathematical models.
b. Simulation models.
c. Physical models.
5.8 Suppose that you wished to improve the design of bathroom scales. Prepare an attribute list showing how each of the attributes might be improved.
5.9 Using the forced relationship technique, develop a list of ideas for designing a better mousetrap. For the random element, use a mail box.
5.10 Using morphological analysis, prepare a list of possible attributes of a device to remove dust from a warehouse floor.
5.11 Write a report on a significant and well-publicized engineering failure. Discuss any lessons that were learned, and describe any changes in engineering codes and design procedures that resulted from that failure. For ideas, consult Reference 15.
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Loops of a hair-thin glass fiber, illuminated by laser light, represent the transmission medium for lightwave systems. Typically, 12 fibers are embedded between two strips of plastic in a flat ribbon, and as many as 12 ribbons are stacked in a cable that can carry more than 40,000 voice channels. (Courtesy of American Council of Engineering Companies.)
141 6.1 INTRODUCTION
It is difficult to overstate the importance of effective communications to the success of engineering. No matter how creative and elegant a design may be, it is of no value until it can be communicated to those who must accept it, pay for it, support it, and translate it into physical reality. Successful engineers must be able to communicate effectively with their supervisors, peers, and with the general public. Often, these individuals are not in close proximity, so effective communication via technology and traditional sources is essential. In this chapter, we describe some of the resources and guidelines for effective engineering communications.
6.2 COMMUNICATIONS AND INFORMATION RESOURCES
With developments in computer technology and the rapid growth of the Internet, information has become ubiquitous in our lives. A wealth of informa-tion is available in a variety of formats through a vast number of gateways. The World Wide Web, scholarly journals, textbooks, reference sources, virtual com-munities, colleagues, and full-text databases are examples of the various sources to which engineers turn for information. With information available in such abundance, the problem for modern engineers is not simply locating infor-mation but also learning how to filter, evaluate, process, and use it. From the undergraduate student completing a semester project to the professional work-ing on a design problem, engineers are called upon to perform research, use that research to solve problems, and communicate their solutions to others.