Construction on the 49-story Conde Nast Tower building began in 1996 and was scheduled for completion in spring 1999. The building extends the full block between 42nd Street and 43rd Street with a western exposure onto Broadway, in the Times Square area of New York City.
New York zoning regulations require high-rise building setbacks; this was the case for the Conde Nast Tower. Because of the building's height and setbacks, external hoists with substantial support were required.
On the morning of Tuesday, July 21, 1998, construction workers noticed slight arching near the 20th floor of the 49-story scaffold system located at the east end of the north face of the building on 43rd Street and warned other workers and pedestrians to run for cover. Minutes later the scaffold above the 20th floor crashed and dropped approximately 8 feet weakening the ties between the personnel hoist system and the attached scaffold, which provided lateral restraint to the hoist structure. The top 24 floors (approximately 300 feet) of the 3-ft. by 2-ft. lattice hoist shaft fell into 43rd and 44th Street. One portion of the shaft went through the roof of a building across 43rd Street killing a woman on her 12th floor apartment. A dozen people were injured by falling debris.
A workgroup consisting of N.Y. City officials and private engineering firms performed on-site observations evaluating the failure mode of the structure and developed a stabilization plan, which ended with the demolition of the scaffold-hoist system. Stabilization and demolition work lasted more than a month.
An independent engineering firm was retained by the N.Y. City Department of Buildings to determine the cause of the scaffold collapse. They observed and documented deformations and orientation of the scaffold debris, the remaining structural elements, and loads on all scaffold floors. In addition, they reviewed construction drawings provided by the scaffold supplier. From the site investigation they noticed that several X-braces, which were intended to provide lateral support to the aluminum scaffold, were missing from floors 21 and 22.
After the investigators performed a buckling analysis and several parametric finite elements analyses, it was revealed that the strength of the scaffold to resist vertical load was decreased approximately 34% as a result of the missing lateral braces on floors 21 and 22. They concluded that the failure mechanism of the scaffold was buckling of the frame legs below the 21st floor-- the same location where the construction workers observed the deformation of the scaffold prior to its collapse.
A New York City Board of Inquiry also revealed the following irregularities concerning the July 21 accident: the scaffold was missing several cross braces, the missing braces could only have been left out during construction, there was no proper inspection procedure, there was storage of material on the scaffold (in violation of rules), the allowable weight for each hoist cage was likely exceeded, the allowable height of the scaffold was exceeded, and the official scaffold and hoist applications and plans were signed by an unlicensed engineer.
“It was a day like every other day on this project – full of challenges and frustrations and not enough time to take care of them all. Then it happened...” Hundreds of businesses in world-famous Times Square - including theaters, hotels, restaurants and other mainstays of the tourist trade - had been shut down along with many of the streets for many days, when a construction scaffold collapsed just off Broadway. Amazingly, no one on the street was killed; but an 85-year-old woman died in a nearby single-room-occupancy residence across 43rd Street from the skyscraper when a scaffold section pierced the roof of the Woodstock Hotel and collapsed the ceiling of her room.
This accident has been described as one of the worst construction accidents in the past decade. The theories around the facts that have lead to the collapse abounded. Was it metal fatigue or runway or hoist overload? Was it an error in hoist design, construction or operation? Did someone forget to rebuild a strut that connects the scaffold to the building, after a facade panel was installed? Or was it a combination of factors that caused the collapse? For whatever reason though, one thing is for sure: an engineer was involved. An engineer who did not perform his/her duties the way he/she should have: according to the Laws and the Ethic code governing the profession.
The Conde Nast Tower case is a very interesting one since it introduces a number of misconducts in many areas of engineering. A non-licensed engineer signed the drawings, construction engineers not only accepted them without checking, but also did not hesitate to change them according to their own judgment, and an on-site engineer who failed to monitor the process of removing and re-installing parts of the temporary tower and the scaffolds, are some of the actors in this tragedy.
Tuesday July 21, 1998
43rd street & Broadway Ave., Times Square, New York City, NY
Note: for the analysis of this case, it will be assumed that the Acts and Regulations of Ontario and the Code of Ethics of the PEO[ii] are applicable.
There are no ethical dilemmas in this case. Rather, the action of the involved engineers will be analyzed and evaluated. Possible consequences will be stated and different courses of action will be discussed.
Some particulars are considered as common knowledge for structural engineers who are involved in building or managing large-scale constructions of the size and type of the Conde Nast Tower. These particulars involve the OSHA[iv] rules and guidelines for scaffold safety, the usual procedures of having to remove braces in order for the workers to gain access to the façade of the building, and the zoning regulations for building setbacks in Metropolitan Areas. Knowledge of other particulars, such as maximum load capacity, and proper calculations for height to area ratios, as well as the effect of the environmental conditions (such as wind, snow, etc.) is also expected from these engineers. Any unfamiliarity of these details is considered ignorance with respect to the engineer in charge.
Note: it is assumed that all engineers are professional, licensed engineers unless stated otherwise.
ENG. A is the most evident engineer to blame for a great percentage of this accident. His failure to monitor the process, and especially the action of removing X-braces that were essential for the strength and the load capacity of the tower, is inexcusable. He/She has also failed to consult with the structural engineer before giving his permission for the disassembling of the beams to allow access to the building's facades. Even when this process was carried out -- and it seems that such a process is not unusual—he/she has failed to supervise it. There was storage of material on the scaffold (in violation of rules) during construction of the building, and the allowable weight for each hoist cage was likely exceeded. These matters are filed under the responsibility of the on-site construction engineer whom in order to have not noticed that he/she must have not been inspecting the process very carefully. This engineer can therefore be accused for "professional misconduct" under sec.72 of the P.E. Act. He/She proves to be negligent; he/she fails to make reasonable provision for the safeguarding of life, health or property of a person who may be affected by the work for which he/she is responsible, which resulted in the death of a woman; and he/she fails to act to correct a situation that endangers the safety and the welfare of the public.
The construction engineer is first of all to be accused under sec.72 (2.m) of the P.E. Act for permitting and counseling a person who is not a practitioner to engage in the practice of professional engineering. He/She does so when he/she does not hesitate to use the drawings of a non-licensed engineer for this project. He/She has also failed to prepare the scaffold to hold its weight even when the X-braces were removed. He/She should have been aware that such an action would have been necessary, since removing braces to allow access to the façade of the building is expected in every structure. If he/she was indeed aware of the limitations and the weaknesses of the structure, it was his responsibility to inform the workers and the on-site engineers for such. He/She is therefore accused for negligence, and professional misconduct.
ENG C. has broken the law by signing his drawings without being licensed to do so. He/She therefore breaks the Law stated in sec.12 (1) of the P.E. Act, which states: “No person shall offer to the public or engage in the business of providing of the public services that are within the practice of professional engineering except under and in accordance with a certificate of authorization.” This person cannot be accused for professional misconduct since he/she is not a professional engineer. Had he/she been one, he/she would face charges under sec. 72 (1.e) for signing the drawings without having them checked by a professional. There is no indication in the case that the drawings parse, had any technical weaknesses.
It seems that this team carried out a thorough investigation. They have double-checked the structure; they have tested the beams; they have traced failure reasons all the way back to the designer engineer; they have ensured further stabilization f the structure; and they have taken measures to prevent further accidents (by installing a safety net and a heavy curtain). As a team they seem to be reasonable and prudent engineers.
Since the incident involved a death and several injuries of civilians the consequences from this failure are probably more severe than the collapse of any other structure that did not involve innocent bystanders. In a similar case in Missouri on July 17, 1981 at the Hyatt Regency Hotel in Kansas City, connections supporting the ceiling rods that held up the second and fourth-floor walkways across the atrium failed. Both the second and fourth-floor walkways collapsed onto the crowded first-floor atrium below resulted in millions of dollars in damage, one hundred fourteen people dead and more than two hundred injured. This case involved many engineers losing their engineering licenses, a number of firms filing bankruptcy, and a great many expensive lawsuits settled out of court. Of course this case was at a larger scale, but nevertheless it has also been a consequence of engineers’ negligence in the same realm.
This tragedy could have been avoided had all the engineers involved performed according to the P.E. Act and the Code of Ethics governing their profession. Had they regarded their duty to the public welfare as paramount, they would have not taken the chances they did by allowing the workers to randomly remove X-braces that were essential for the balance and support of the structure. The origin and the authenticity of the drawings ought to be checked before proceeding with the construction process. Better load capacity estimations had to be calculated. The on-site engineer owed to pay more attention to the procedures happening on the site and he/she ought to inform his/her workers for the consequence of their actions. He/She was responsible for ensuring that all the regulations were met and if according to the calculations, the structure could not be used for storage of materials it was his/her sole responsibility to arrange for removal. The structural engineer who built the structure should have conferred with the construction manager to get informed about the details of the use of the scaffold and the hoist before proceeding with his construction. The design engineer should not have been involved with this process unless he was supervised by a licensed professional or he had his drawings checked by one.
1. Robert T. Adams & William D Motherway, Esq. When the walls come tumbling down: a case study of four times square. Presentation. November 15, 2000.
2. OSHA Regional News Release. Online. OSHA cites Mount Vernon, New York, scaffold company for alleged safety violations in July 21 scaffolding collapse at Times Square construction site. Accessed on March 13, 2001. Available http://www.osha.gov/media/oshnews/jan99/reg2ny106.html
3. Thelen Reid & Priest Construction Weblinks.
YORK REPORT: Collapsed Scaffold and Hoist in Times Square Fail to Provide Basis
for Class Action Economic Loss Claims. March 13, 2001. Available
4. The New York Times. Scaffold Collapses, Paralyszing Times Square. Wednesday, July 22, 1998.
5. Engineering News Record. Online. Causes probed as crippled hoist comes slowly down. Accessed on March 14, 2001. Available http://www.enr.com/new/C0810.asp
6. D.L.Masrston. Law for Professional Engineers, 2nd edition. McGraw-Hill Ryerson Ltd. Canada. 1985.
7. Texas A&M University Engineering Ethics Cases. Hyatt Regency Walkways Collapse. March 15, 2001. Available http://onlineethics.org/cases/texindex.html#collapse
[i] Title was borrowed from a 20th IRMI Construction Risk Conference presentation. – see ref 1.
[ii] The Professional Engineers of Ontario.
[iii] The names for the Engineers are given to assist in analyzing the case.
[iv] Occupational Safety and Health Administration.
[v] The consequences described here are not based on the outcomes of the real court decisions or disciplinary committee decisions for this case; rather, it is possible consequences that any engineer can face if found in a similar situation. The suggestions are based on either the P.E. Act laws, or from outcomes of other similar cases as mentioned in the text.