VIEWS: 21 PAGES: 24 POSTED ON: 9/28/2012
Ethics in Engineering Outline •Case Studies •Hyatt Regency Walkway Collapse •Hartford Civic Center Roof Collapse Kansas City Hyatt Overview The Attrium The Hyatt Regency Hotel Today… …From Microsoft Live Maps Kansas City Hyatt Disaster Overview The Event – • July 17, 1981, the Hyatt Regency Hotel in Kansas City, Missouri, held a dance party in their atrium lobby. • With party-goers standing and dancing on the suspended walkways, the second and fourth-floor story walkways across the atrium failed, and both walkways collapsed onto the crowded first-floor atrium below. The fourth-floor walkway Kansas City Star collapsed onto the second-floor walkway, while the offset third- floor walkway remained intact. …Information taken from Engineering.com and http://ethics.tamu.edu/ethics/hyatt/hyatt1.htm Kansas City Hyatt Disaster Overview The Kansas City Hyatt Regency walkways collapse left 114 dead and in excess of 200 injured. In addition, millions of dollars in costs resulted from the collapse, and thousands of lives were adversely affected. Kansas City Star Kansas City Hyatt Who did What • Over a year before the collapse, the design of the walkway hanger rod connections was changed in a series of events and communications (or disputed miscommunications) between the fabricator (Havens Steel Company) and the engineering design team (G.C.E. International, Inc., a professional engineering firm). • The fabricator changed the design from a one-rod to a two-rod system to simplify the assembly task, doubling the load on the connector, which ultimately resulted in the walkways collapse. Kansas City Hyatt Who did What • Second, the fabricator, claimed that his company (Havens) telephoned the engineering firm (G.C.E.) for change approval. G.C.E. denied ever receiving such a call from Havens. Though G.C.E. did put a stamp of approval on a later copy of the modified blueprints! • Third, on October 1979, while the hotel was still under construction, more than 2700 square feet of the atrium roof collapsed because one of the roof connections at the north end of the atrium failed. In testimony, G.C.E. stated that on three separate occasions they requested on-site project representation to check all fabrication during the construction phase; however, these requests were not acted on by the owner (Crown Center Redevelopment Corporation), due to additional costs of providing on-site inspection. Kansas City Hyatt Who did What • Fourth, even as originally designed, the walkways were barely capable of holding up the expected load, and would have failed to meet the requirements of the Kansas City Building Code. Kansas City Hyatt The Failure Analysis Kansas City Hyatt The Failure Analysis Kansas City Hyatt The Failure Analysis Kansas City Hyatt The Failure Analysis Kansas City Hyatt Details Original design called for walkways that were each supported by three crossbeams attached to three pairs of support rods from second floor to ceiling…would have only supported 60% required by Kansas City Building Code! Havens Steel Company, the contractor responsible for manufacturing the rods, objected to one threaded rod through the fourth floor since threads would be ruined during installation…suggested the two rod design. New design meant that instead of each floor supporting it’s own weight, the fourth floor walkway’s crossbeams had to support itself AND the second story walkway… this design led to a configuration that could support only 30% required by Kansas City Building Code!! Kansas City Hyatt Details Also, the failures were compounded by the fact the nuts that were supporting each crossbeam were situated directly under weld-joints in the boxbeams… the weakest point in the structure! Kansas City Hyatt Ethical Questions • ASME Code Of Ethics Of Engineers • The Fundamental Principles – Engineers uphold and advance the integrity, honor, and dignity of the Engineering profession by: • I. using their knowledge and skill for the enhancement of human welfare; • II. being honest and impartial, and serving with fidelity the public, their employers and clients; and • III. striving to increase the competence and prestige of the engineering profession. • The Fundamental Canons – Engineers shall hold paramount the safety, health and welfare of the public in the performance of their professional duties. – Engineers shall perform services only in areas of their competence. – Engineers shall continue their professional development throughout their careers and shall provide opportunities for the professional development of those engineers under their supervision. – Engineers shall act in professional matters for each employer or client as faithful agents or trustees, and shall avoid conflicts of interest. – Engineers shall build their professional reputation on the merit of their services and shall not compete unfairly with others. – Engineers shall associate only with reputable persons or organizations. – Engineers shall issue public statements only in an objective and truthful manner. Kansas City Hyatt Ethical Questions Ethical Questions – Who is ultimately responsible for checking the safety of final designs as depicted in shop drawings? …When we take the implicit social contract between engineers and society, the issue of public risk and informed consent, and codes of ethics of professional societies into account, it seems clear that the engineer must assume this responsibility when any change in design involving public safety carries a licensed engineer's seal. Kansas City Hyatt Ethical Questions Ethical Questions – In terms of meeting building codes, what are the responsibilities of the engineer? The fabricator? The owner? If we assume the engineer in the Hyatt case received the fabricator's telephone call requesting a verbal approval of the design change for simplifying assembly, what would make him approve such an untenable change? Some possible reasons include: • saving time; • saving money; • avoiding a call for re-analysis, thereby raising the issue of a request to recheck all connector designs following the previous year's atrium roof collapse; • following his immediate supervisor's orders; • looking good professionally by simplifying the design; • misunderstanding the consequences of his actions; or • any combination of the above. All these pave the way for legitimate charges of negligence, incompetence, misconduct and unprofessional conduct in the practice of engineering. Kansas City Hyatt Ethical Questions Other Ethical Questions – What about the owner, or fabricator?? What if the call was not made? While responsibility rests with the fabricator for violating building codes, would the engineers involved in the case be off the hook? Why or why not? The Hartford Civic Center Collapse …text from ‘Hartford Civic Center Arena Roof Collapse’ by Rachel Martin http://www.eng.uab.edu/cee/faculty/ndelatte/case_studies_project/Hartford%20Civic%20Center/hartford.htm The Hartford Civic Center Collapse On January 18, 1978 the Hartford Arena experienced the largest snowstorm of its five-year life. At 4:15 A.M. with a loud crack the center of the arena's roof plummeted the 83-feet to the floor of the arena throwing the corners into the air. Just hours earlier the arena had been packed for a hockey game. Luckily it was empty by the time of the collapse, and no one was hurt (Ross, 1984). The Hartford Civic Center Collapse – Construction Concerns To save time and money, the roof frame was completely assembled on the ground. While it was still on the ground the inspection agency notified the engineers that it had found excessive deflections in some of the nodes. Nothing was done. After the frame was completed, hydraulic jacks located on top of the four pylons slowly lifted it into position. Once the frame was in its final position but before the roof deck was installed, its deflection was measured to be twice that predicted by computer analysis, and the engineers were notified. They, however, expressed no concern and responded that such discrepancies between the actual and the theoretical should be expected (Levy and Salvadori, 1992). When the subcontractor began fitting the steel frame supports for fascia panels on the outside of the truss he ran into great difficulties due to the excessive deflections of the frame. Upon notification of this problem, the general contractor "directed the subcontractor to deal with the problem or be responsible for delays." As a result the subcontractor coped some of the supports and refabricated others in order to make the panels fit, and construction continued (ENR, April 6, 1978). The roof was completed on January 16, 1973 (Feld and Carper, 1997). The next year, a citizen expressed concern to the engineers concerning the large downward deflection he noticed in the arena roof, which he believed to be unsafe. The engineers and the contractor once again assured the city that everything was fine (Levy and Salvadori, 1992). The Hartford Civic Center Collapse – Failure Analysis • LZA (hired by Hartford to investigate the collapse) discovered that the roof began failing as soon as it was completed due to design deficiencies. A photograph taken during construction showed obvious bowing in two of the members in the top layer. Three major design errors coupled with the underestimation of the dead load by 20% (estimated frame weight = 18 psf, actual frame weight = 23 psf) allowed the weight of the accumulated snow to collapse the roof (ENR, April 6, 1978). The load on the day of collapse was 66-73 psf, while the arena should have had a design capacity of at least 140 psf (ENR, June 22, 1978). The three design errors responsible for the collapse are listed below. • The top layer's exterior compression members on the east and the west faces were overloaded by 852%. • The top layer's exterior compression members on the north and the south faces were overloaded by 213%. • The top layer's interior compression members in the east-west direction were overloaded by 72%. • In addition to these errors in the original design, LZA discovered that the midpoint braces for the rods in the top layer had not been installed. The exterior rods were only braced every 30-feet, rather than the 15-feet intervals specified, and the interior rods were only partially and insufficiently braced at their midpoints. This significantly reduced the load that the roof could safely carry. The table on the next slide compares some of original details to actual designs used in the building, demonstrating the reduction in strength that these changes caused. Connection A was typically used on the east-west edges of the roof, while connection B was used on the north- south edges. Most of the interior bars used connection C, while a few used connection D. The key difference between the original and the as-built details is that the diagonal members were attached some distance below the horizontal members, and thus were unable to brace the horizontal members against buckling. The Hartford Civic Center Collapse – Failure Analysis The Hartford Civic Center Collapse – Failure Analysis The Hartford Civic Center Collapse – Ethical Questions Ethical Questions: Multiple subcontractors without an overseeing structural engineer left the project with the construction manager to determine what to do with a sagging roof! The excessive deflections apparent during construction were brought to the engineer's attention multiple times. The engineer, confident in his design and the computer analysis which confirmed it, ignored these warnings and did not take the time to recheck its work. An ethical engineer would pay close attention to unexpected deformations and investigate their causes. They often indicate structural deficiencies and should be investigated and corrected immediately. Unexpected deformations provide a clear signal that the structural behavior is different from that anticipated by the designer. Also this collapse raises the important question of whether the factor of safety should be increased for buildings with high occupancy. Should the impact of a possible failure be taken into account in determining the factor of safety (Kaminetzky, 1991)?
Pages to are hidden for
"Topic 13: Ethics and Design"Please download to view full document