Whendesigning a structure, the engineer must take numerous factors intoconsideration in order to create a stable design. The design for an outdoorstructure must account for the possible effects of wind to ensure the integrityand safety of the structure.
An example of the failure to incorporate the windeffects into the structure is the Tacoma Narrows bridge collapse of 1940 andthe engineering crisis of the Citigroup Center in 1978. Both structures were designedin such a way that the wind acting upon the structure caused collapse in onecase and serious possibility of catastrophe in the other. With the TacomaNarrows collapse, miraculously a dog was the only casualty. The CitigroupCenter vulnerability was discovered and resolved before any catastrophe occurred.This resulted in the former collapsing with a dog as the only casualty, and thelatter needing immediate repairs to resolve the vulnerability. Key points: Tacoma Narrows During the planning phase ofthe bridge, there were two competing designs being considered. One design forthe bridge was a commonly used suspension type with 25 foot high trusses underthe road to strengthen and stabilize the bridge. This design had an estimated cost11 million dollars.
The other design used eight foot girders with an estimatedcost of eight million dollars, and thus was chosen due to its reduced cost. Theeight foot girders did not make the deck sufficiently rigid, and therefore itwas susceptible to movement caused by winds. Some vertical movement was noticedduring construction. There was a failed attempt to stabilize the bridge, yet itwas opened to traffic when the engineers declared the structure was safe. Twoadditional attempts to stop the oscillations were made without success and thecollapse followed. On the day the bridge collapsed, the movement of the deckdeveloped a yet unobserved movement with an oscillating in a torsional, ortwisting, pattern. As the amplitude of the oscillations increased, thesuspension cables started to snap, and the weight of the deck could not be heldby the remaining cables, resulting in collapse of the deck.
Key Points: Citigroup Building Thedesign called for the building to be set on four columns positioned at the centerof each side of the building. This was because of an agreement with a churchlocated in the northwest corner of the building. The design included multiple V-shapedbraces on each side of the building, centered on each of the four columns.These braces were designed to collect forces placed on the building to theirpoint, where it would be then be absorbed into the ground through the columns. Duringconstruction, the builder requested and was granted permission by theengineer’s firm to substitute the welded joints of the braces with boltedjoints. A student was working on her thesis when she discovered that the boltedjoints of the braces were significantly susceptible to failure when subjectedto quartering winds OEC citation here. Quartering wind is when wind hits abuilding’s corner, hitting both sides at once, and causes significantly moreforce to be put upon the building. Upon her discovery, she notified theengineer of the design flaw.
He found that while the welded joints would havebeen strong enough to withstand the additional forces, the bolted joints wouldbe susceptible to failure under the same forces. With his confirmation, theengineer notified the architect and Citicorp that repairs needed to be madeimmediately. Comparison: Tacoma Narrows and Citigroup Building KeyPoints Inboth cases, the original design of the structure would have been able towithstand the forces that compromised the final product. However, changes weremade to the design in order to cut costs. These changes compromised theintegrity of the Tacoma Narrows Bridge to the point of collapse, and theCitigroup center had the possibility of collapsing if repairs were not made.Interestingly, both structures used the same construction and steel supplycompany, Bethlehem Steel.
There is a significant difference between the twocases that is peculiar. With the Tacoma Narrows Bridge, they actually observed a problem manifesting asoscillations but chose not to close and investigate but to remain open andattempt to repair the bridge, and as a result no successful solutions wereimplemented to fix the problem before the bridge collapsed. The difference withthe Citigroup building is that the flaw was discovered by chance and in time tomake repairs.
This difference is interesting, as the structure with an obviousproblem wasn’t fixed in time, while the one with no visible problem was able tobe fixed before it had the chance to collapse. Ethical Issues: TacomaNarrows Rather than using the industrystandard suspension bridge design, a new and relatively untested design waschosen due to its lower cost. The less expensive choice had inherent risks asan unproven design, but they were accepted, resulting in a collapse and needfor constructing a new bridge. Another poor choice was made when the engineersdeclared that the oscillations were safe and opened the bridge, despite havingno factual basis in their claim of safety. These choices run counter to theconcept of Mill’s Utilitarianism, in which the best choice to make is the onethat produces the maximum benefit for the greatest number of people. Instead ofusing a more expensive design that was standard, an untested design was usedand ultimately failed, negatively affecting numerous people who relied on thebridge for quick and easy transportation.Ethical Issues: CitigroupBuilding Duringthe design process of the Citigroup Building, the engineer failed in his dutyto ensure that his design would be structurally sound under all conditions.
While the design of the building did meet the New York Building Code of thetime, which did not explicitly state the need to consider quartering winds, theCode is intended to be a minimum requirement, and all possible factors shouldbe properly accounted for (Kremer, 2002). Furthermore, the engineer should haveensured that if any changes or substitutions were made in construction, that hewould be consulted before any decisions were made. Moreover, the engineeractively misled the public and remained silent about the matter until almost 20years after the affair, preventing other engineers from learning from hismistake and possibly finding similar problems in projects of their own (Kremer,2002). The engineer’s actions are in direct opposition to Immanuel Kant’sconcept of Duty Ethics, which describes that every person has a duty to preventharm and to consider the well being of society as supreme.
By failing toprevent the crisis initially and choosing not to inform the public of thedanger, the engineer risked not only the Citigroup Building, but tens ofthousands of lives and potentially billions of dollars lost if the buildingwere to collapse. Legal Issues: TacomaNarrows The engineering andconstruction firms could have been held liable under tort law for theconstruction of an unsafe bridge that eventually collapsed. By accepting thetask of designing and building the bridge, the firms accepted the duty of carein providing the public a safe and functional bridge. They failed in theirduty, as evidenced by the oscillations and eventual collapse of the bridgewhich would not have occurred had the more expensive but reliable design beenused. Through the collapse, the people who relied on the bridge for fastertransportation and better business strategies lost their ability to do so forthe next 11 years, causing them various degrees of financial injury.Legal Issues: CitigroupBuilding Through the rapidresponse of the engineer and repair team, the Citigroup Building evadedcatastrophe.
However, had the student not chosen to research the building, theresulting disaster would have rivaled the Bhopal Union Carbide disaster.Because the engineer was careless in his calculations and design of thebuilding, thousands of lives could have been lost and caused potentiallybillions of dollars in property damage alone. As such, the engineer, his firm,the builder, and Citicorp could all have been charged with criminal negligenceand corporate manslaughter due to the numerous losses by result of thecollapse. Code of Ethics Review Inboth of the cases, the engineers involved violated the first and thirdprinciples as outlined by the American society of civil engineers (ASCE, 2017).The Tacoma Narrows engineers violated the first through their desire for acheap bridge to construct over a proven safe and reliable design, and violatedthe third by their public statement that the oscillations were safe despitethem not knowing whether or not they truly were safe. The engineer in charge ofdesigning the Citigroup building violated the first principle by allowing thedanger to arise as a result of his oversight in the design, and violated thethird through his actions to ensure the public did not learn of the affair inorder to save his reputation.
In addition to the first and third, the engineeralso violated the seventh principle (ASCE, 2017). Through his efforts to hidehis mistake, the engineer prevented any of his peers to learn from his mistakeand stop any similar design flaws from moving on from the design stage. Solutions: Tacoma Narrows. Shortlyafter the collapse, the Bronx Whitestone Bridge was reinforced with steeltrusses. This was because the design of the Bronx Whitestone Bridge was verysimilar to the design of the Tacoma Narrows Bridge. In the long term, thecollapse greatly increased the research into bridge aerodynamics andaeroelastics.
This research has greatly influenced the design of all subsequentlong-span bridges. Solutions: CitigroupBuilding Immediatelyupon the discovery and reporting of the flaws, steps were quickly taken to repairthe building before any damage could be done. These repairs were successful, asthe Citigroup building has not collapsed in the time between when the repairswere made and present day. The lasting results of this incident, while delayeddue to the secrecy, manifested themselves as lessons for engineers to learnfrom. The affair provided an example of ethical behaviour for engineeringtextbooks to use in teaching engineers in training, and demonstrated the possiblerisks of aiming to meet building code alone. Conclusion: Inthe cases of the Tacoma Narrows Bridge collapse and the engineering crisisinvolving the Citigroup Building, the decisions and statement made, or lackthereof, were both professional and ethical blunders.
Designs were improperlytested before construction, and changes were made that compromised thestructure’s stability in order to reduce costs. Fortunately, no loss of lifebeyond a dog occurred as a result of these two cases, and the engineeringprofession benefited from the knowledge gained in the aftermath. Both casesdemonstrated the necessity that the design of an outdoor structure must accountfor all the possible effects that wind may have upon it. Failure to account forthese factors compromises the integrity and safety of the structure, whichrisks considerable damage and loss of life should the structure fail.