WORLDRWDI helps design Freedom TowerCanadian engineers are playing an important part in the design of the World Trade Center to be rebuilt in New York City.Colin Williams, P.Eng. and a team from Rowan...
RWDI helps design Freedom Tower
Canadian engineers are playing an important part in the design of the World Trade Center to be rebuilt in New York City.
Colin Williams, P.Eng. and a team from Rowan Williams Irwin Davies (RWDI) of Guelph, Ontario are doing wind tunnel testing and design for the Freedom Tower. It will rise 1,776 feet above the site where the skyscrapers came tumbling to the ground after the terrorist attacks on September 11, 2001. The height is a symbolic number, chosen as the year of the American Declaration of Independence.
The tower design was unveiled in December by the Lower Manhattan Development Corporation, which is in charge of the overall site. David Childs of SOM is the architect for the developer, together with Daniel Libeskind, who is responsible for the site’s master plan. Structural engineers are Guy Nordenson and Cantor Seinuk.
The structure will have a concrete core and diagonal structural grid, or “diagrid” around the perimeter. Wind loads are a critical factor given the tower’s asymmetrical and twisting design. Said to “evoke the dynamic twisting form of the Statue of Liberty,” the glass-walled tower rises from a parallelogram-shaped base, then tapers and torques to meet the prevailing winds. It culminates in a spire consisting of a “lacy system of cables.” Between the occupied floors and the tower will be wind turbines to generate 20 per cent of the building’s energy.
Not surprisingly safety features are extremely robust: the tower will have concrete-encased stair and elevator cores, concrete protection for all sprinklers and emergency risers, and biological and chemical filters in the air supply system. The lobby will be clad in blast resistant glazing.
Green design more than points chasing
That was a great article by Gordon Shymko P.Eng. on “True Green” (December 2003), and one that I am in agreement with.
While I am a LEED-accredited professional and support the intent of the program, I, too, am becoming disillusioned by the point-hunting approach by many designers, and the balkanization of LEED. We now have LEED BC, LEED Canada and other lobbying for regional “adjustments” to the LEED program.
One of the issues I have with North American based energy modelling software packages is their reliance on “air temperature” and conventional all-air HVAC system approaches. Having experienced the difficulty of dealing with programs like DOE-2 and EE-4 for modelling building mass radiant temperature conditioning systems, we have chosen to use European software that does a much more accurate and realistic job of thermal mass storage and building physics reactions, using the space “resultant temperature,” which includes the mean radiant temperature component. The folks at Lawrence Berkeley Labs in California are doing research and coming up with newer software to deal with radiant heating and cooling systems, and I’m waiting to see what comes of it.
Geoff McDonell, P.Eng.
The editor welcomes comments from readers: e-mail: firstname.lastname@example.org
The Canadian War Museum
The new Canadian War Museum is being built on LeBreton Flats in Ottawa’s capital Region. The $136-million facility has 4,180 square metres of exhibition space to house Canada’s military artifacts. Consulting engineers are Adjeleian Allen Rubeli (structural), The Mitchell Partnership (mechanical) and Crossey Engineering (electrical). Architects are Moriyama & Teshima and Griffiths Rankin Cook. The building is a composition of horizontal volumes with a landscaped roof. It is due to open in late 2005.
The museum’s existing location at 330 Sussex Drive is showing “Mission Possible,” an exhibition on Canada’s military engineers, until September.
The Canadian Construction Association is about to issue guidelines on controlling mould in buildings, said Richard Shaban, a lawyer from Borden, Ladner & Gervais, at the Construct Canada trade show in December.
Shaban said mould in buildings has resulted in multi-million dollar lawsuits in the U.S. and Canada, including a $19-million class action suit over the Newmarket Courthouse in Ontario.
The new document, “Mould Guidelines for the Construction Industry,” is the product of a task force involving 22 academics, scientists, lawyers, engineers, contractors and owners.
Bruce Stewart of Pinchin Environmental also spoke at the show. He said the guidelines explain, for example, how important it is to keep materials dry at the construction site, and to ensure enough time is given for drying and curing.
Stewart said the construction document CCDC-2 may have new clauses added to allow stop work orders if mould is found in materials. He warned that disputes over whether the mould was pre-existing could lead to tricky situations where engineers will find themselves in the middle of a dispute between the owner and contractor. The guidelines will be available at www.cca-acc.com
Brain drain in reverse
“We, as registered Canadian engineers, are being pushed by some of the largest engineering companies to treat and view work done overseas in just the same way as if it were done in our own offices in our own country. But is the work just the same?
“There are large time zone differences. Is a phone conversation at 9:30 at night, at home with no back-up data, as good as a 15-minute meeting in the office? Almost certainly not. Is a phone conversation anything like as good as a direct meeting anyway …”
— Nigel Histon, P.Eng., in The PEGG, Association of Professional Engineers, Geologists and Geophysicists of Alberta, November 2003.
A young engineer who copied 52 details and notes from drawings he had sealed when working for one consulting engineer and used them in a project for a new employer in another area of the province was found guilty of professional misconduct by Professional Engineers Ontario. The unnamed individual was reprimanded, conditionally had his licence suspended for three months, and was asked to return the documents to his first employer. However, he was allowed “for professional liability and reference purposes.” to retain copies of plans he prepared and sealed. The case was reported in PEO’s Gazette, September/October 2003.
Consulting Engineers of Saskatchewan held their 3rd Annual Awards in Saskatoon in late November. Called the CES Brian Eckel Awards of Excellence, they are given for technical excellence, added value and benefit to society.
Awards of excellence went to Wardrop Engineering for the T.C. Douglas Building rehabilitation in Regina (building science), and for the composite steel-glulam roof trusses in the Biggar Jubilee Stadium rehabilitation (infrastructure). Associated Engineering won an award of excellence for the South East Sector Storm Water Management Master Plan for the city of Saskatoon (environment). Loken Engineering Services won two awards of excellence for the Soft X-Ray Spectromicroscopy Beamline for the Canadian Light Source (project partnering/ technology innovation).
Wayne Clifton, P.Eng., president and chief executive officer of Clifton Associates of Regina, won the Lieutenant Governor of Saskatchewan Meritorious Achievement Award.
Degrees of Belief: Subjective Probability and Engineering Judgement.
By Steven G. Vick.
ASCE Press, 2002, 455 pp.
Review by Dr. Brian Stimpson
Degrees of Belief is a uniquely crafted work that combines engineering, probability theory, philosophy, history, biography and psychology.
For its clarity and insight, the book should position its creator, an American geotechnical engineer, alongside another outstanding American engineer/scholar/writer: Samuel Florman (The Civilized Engineer, The Introspective Engineer, The Existential Pleasures of Engineering).
This is not simply another book on probability theory. There are plenty of
those. Rather, it tackles the broader issues of the duality between probability as an objective schema, and the use of subjective probability and judgement, which actually play an important role in the practice of engineering.
Within this overarching context, the book skillfully articulates three complementary purposes (a) to revitalize the essential role of judgement in engineering practice, (b) to promote and demonstrate how the tools for evaluating and incorporating uncertainty can inform that judgement, and (c) to encourage the appropriate and sensible use of probability.
In a fascinating chapter on “Experts and Expertise,” Vick draws upon the achievements of some engineering “greats” such as Karl Terzhagi in order to distinguish the cognitive processes they used that separate them from “ordinary experts.”
His explanation of heuristics and biases that can distort an engineer’s judgement opened my eyes to the constant requirement for self-examination. Motivational biases such as the need to achieve the client’s goal in the time and budget are well known, but what of the cognitive biases that occur in the interpretation of data and how evidence is weighed? It is sobering to realize that research has shown that the judgement of experts is as prone to overconfidence as that of the public in general.
While uncertainties in some branches of engineering (e.g. geotechnical) loom so large that the response to the use of reliability or risk analyses may be “Why bother?” the author does not fall into that category. Vick believes great benefit is to be derived from confronting uncertainty “explicitly, personally and in no small detail.”
It is my judgement that this book should interest all engineers. Indeed, I am quite certain of that.
Dr. Brian Stimpson, P.Eng. Ph.D. is a geological engineer and associate dean and professor of civil engineering at the University of Manitoba.