Tag Archives: construction

Roof collapse investigations: Engineers Say Codes Adequate

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snow collapses roof deck Following on last week’s story about green roofs, including one which collapsed under a weight of snow and ice, engineers speaking to the ENR have stated that Codes are adequate, but that they may need to be adjusted in certain situations:

[E]ngineer sources for this article say existing building codes are adequate if designers allow for a factor of safety. But Levy [Matthys Levy, chairman emeritus at Manhattan-based Weidlinger Associates]  recommends designers make proper allowances for snow accumulation such as when designing roof structures near parapet walls, especially those that are four feet or higher.

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Multi-level roofs with steps instead of roof flashing can also be problematic with snow accumulation on a first-story portion, for instance, piling up against the second story, Levy says. “It’s best to avoid stepped designs unless you design for them,” he says. While an average of 40 psf may be adequate for designing most of a roof, designers should allow 60 psf to 80 psf for the parapet wall, he says. And mountainous regions may require twice as much strength, he says.

Garrick Goldenberg, professor of structural engineering at Wentworth Institute of Technology in Boston and chief structural engineer at Chappel Engineering Associates in Marlboro, Mass., said that while state building codes address snow drifts with requirements for the shape and slope of a roof, this year’s record snowfalls and ice accumulation with little thawing has led to a greater number of collapses.  In sampling snow at Chappel Engineering in early February, Goldenberg says his group found that even two feet of freshly fallen snow or more totaling 16 to 20 lb/sf was not a danger to buildings. On average, people assume fresh fallen snow produces eight pounds of pressure on a roof per square foot.

However, invisible loads caused by accumulation of ice have been a serious problem since ice weighs 7.5 to 8 times more per cu ft than snow. “In many cases, even before reaching two-foot snow loads, we were in excess of 30 pounds because of the ice,” he claims.

For more, go to the ENR full story: Ice, Snow Take Toll on Northeast Roofs, But Engineers Say Codes Are Adequate.

What are your thoughts about current Codes, in light of the many collapses in the Northeast and Midwest?  Legally, does designing to Code, but failing to take into account likely weather events, make your design deficient?  I’ll post some of my thoughts in a subsequent post, but share yours below.

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 Photo: “Deck roof collapse”   by Derek K. Miller via Creative Commons license/Flickr

A tale of 2 green roofs

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green roof

Chicago City Hall’s Green Roof

Two commercial “green” roofs have been in the news this week.   One involves a collapse; one involves energy savings.

Green Roof Collapse

The green roof at the Aquascape, Inc. warehouse in Illinois collapsed over the weekend, likely due to melting snow and ice.   A 50 foot wide section of th 256,000-square-foot roof (allegedly the largest sloping green roof in North America) collapsed on Sunday, although no injuries were reported.  A team of structural engineers from the building’s design firm is investigating the cause.  As noted in a company press release, St. Charles, IL, where Aquascape Inc’s head office is located, had been recently hit with a major snow storm where 20.6 inches of snow had fallen in less than 24 hours, followed by above freezing temperatures causing a quick thaw.  An ice damn at the base is suspected to have backed the water up over the parking structure causing its collapse.

Solar Roof goes “live”

While Aquascape’s engineers are investigating their roof collapse, there is some good green roof news closer to home.  Raleigh-based marble company David Allen Company has recently “flipped the switch” on a photovoltaic solar energy facility that  it claims is one of the largest rooftop photovoltaic systems in the Triangle, with  700 solar modules covering 23,000 square feet of the rooftop of the company’s warehouse.  The company hopes to offset at least 35% of its current electrical costs, and sell energy to Progress Energy as well, according to Triangle Business Journal.

Legal Implications related to Roof Design?

Both of these roofs bring up legal issues.  Was the Aquascape green roof designed appropriately to accommodate loads in a winter climate?

With so many roof collapses this winter (including, of course,  the Minneapolis metrodome) , is there, or should there be, a duty on the building’s owner/maintenance crew to proactively remove snow accumulations?

For new solar roofs, such as at David Allen Company, who assumes the risk if the expected cost savings are not realized?

Based on the sheer number of roof collapses this winter, and the number of green projects growing steadily, there is sure to be some litigation addressing at least some of these issues in the near future.  Stay tuned.

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Photo Courtsey Wikipedia/Creative Commons license 

Video of NYC Subway Tunnel Construction (Tue Tip)

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subway

The Engineering News & Record has released a two-part video tour of the ongoing construction of a three-tunnel subway project totalling $15 bilion.  The subway expansion includes a $4.5 billion Second Avenue Subway, a $7.3 billion East Side access, and a $2.1 billion No. 7 line subway extension.

The clips, especially Part 2, are very interesting– check them out:

Tunnel Tour video clip Part 1 (run time 4:40)– Touring the first phase of the Second Avenue Subway extension

Tunnel Tour video clip Part 2 (run time 5:06)– Touring the East Side access, scheduled to be complete by September 2016

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Photo:  Alewife Red Line Subway Station by Freephoto.com via Creative Commons License.

Engineering Firms in the Cross-hairs

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Two national engineering companies are in the cross-hairs of the Delaware Department of Transportation.

The Delaware Department of Transportation (DelDOT) has filed suit against Florida-based Figg Bridge Engineers and its subcontractor, Atlanta-based Mactec Engineering, for alleged geotechnical engineering errors involved in a failed effort to build a new bridge over the Indian River Inlet in Sussex County, Delaware.   According to a Press Release issued by the State of Delaware, as embankment construction was nearing completion in early 2007, excessive settlement, bulging, tilting and other deformation of the embankment walls were observed. After investigation, DelDOT concluded that the embankments would pose continual and costly maintenance, as well as construction and safety risks and should be replaced with elevated roadway approaches to the new bridge. The Federal Highway Administration, which is providing a large portion of the funding for the replacement bridge, agreed with DelDOT’s conclusion to remove the embankments.

DelDot bridge

The lawsuit states that the deficiencies in the embankments are directly attributable to the failures and omissions of MACTEC, and that MACTEC, as sub-consultant to Figg, breached the standard of care that it owed to DelDOT. The facts in the complaint  “are based upon comprehensive studies prepared by the engineering firm of O’Connell & Lawrence, Inc. and the geotechnical consulting firm of Golder Associates, Inc., as well as observations of experts made during deconstruction of the embankments. ”  The lawsuit specifically alleges that:

  • MACTEC did not adequately analyze monitoring data and thus did not recognize that the intended embankment stability had dropped below minimally acceptable levels during and upon completion of construction; 
  • The embankments settled and deformed substantially more than MACTEC had advised DelDOT would be the case. This is because MACTEC miscalculated the nature and extent of settlement in the soft clay under the embankments, and did not take into account other types of settlement.
  • MACTEC miscalculated the time intervals over which settlement would occur.
  • MACTEC failed to specify a process for monitoring data or implementing necessary action if required by field conditions.

DelDot is seeking over $19.6 million in damages from Figg and Mactec.

In a vigorous detailed response, Mactec has stated, among other things, that:

  • In November 2005, despite the fact that the original bridge design was canceled, DelDOT authorized spending millions of dollars to construct embankments for the original bridge. DelDOT knew and understood that the original bridge would never be built and that any other bridge design would require that changes be made to the embankments which would likely include the removal of large sections.
  •  In October 2007, DelDOT prepared a Proposed Path Forward. When this document was reviewed by the Federal Highway Administration, they labeled it as “full of scare tactics and misdirection to avoid doing the proper engineering.” Rather than performing the engineering requested by the federal government’s primary technical agency for bridge design and construction, DelDOT forged ahead on its predetermined path without involving the design team.
  • In January 2008, DelDOT hired outside counsel and two consulting claims firms to assist in the investigation at an estimated cost of $2.1 million. Neither consulting firm was asked to review/recommend methods to address technical issues of concern. Both firms have acknowledged they cannot support the report of the ‘independent’ geotechnical firm upon which the DelDOT Proposed Path Forward was based, that they had not considered the bases of DelDOT’s decision, and that they did not investigate the installation of certain critical aspects of the embankments by the contractor.
  • In April 2008, geotechnical monitoring data showed that the embankments had reached the required settlement and the original bridge design plan could have been constructed without removal of the constructed embankments. The predictions on the amount and length of time for settlement by the “independent” geotechnical firm were clearly overstated.
  • In May 2008, DelDOT, again, authorized spending millions of dollars to deconstruct the embankments. DelDOT claims the decision to be based on the engineering report from the “independent” geotechnical firm. Factually, however, this expenditure was the direct result of DelDOT’s 2005 decision to proceed with building embankments for a bridge design that was never intended to be built. DelDOT had to accommodate the new bridge design by removing significant amounts of the embankment on both sides regardless of the accuracy of any predictions made by anyone as to settlement.

It will be interesting to see how the case enfolds.  Stay  tuned!

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 Photo (c) DelDot

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Can a designer limit his liability to his fees for service?

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Architects and engineers (and the owners/contractors with whom they contract) often wonder whether limiting liability language is enforceable.  The answer, as in much of construction law, is very much dependent on what state’s court will be interpreting the contract.  Some states allow such limiting language, and others do not.  Josh Glazov’s Construction Law Today blog recently tackled the enforceability of such provisions in the context of a recent Illinois case, in which the Illinois court found such limitations perfectly acceptable, so long as they (1) are not “unconscionable” and (2) do not violate public policy.

sign: proceed at own risk
 

North Carolina takes a very similar approach to such limitations of liability.  Here, so long as the limitation of liability is not also an agreement to be liable for the other party’s negligence (which is barred as against public policy), such a limitation of liability is enforceable.  A case discussing this issue from the engineering perspective is Blaylock Grading Co., LLP v. Smith et al, 189 N.C. App. 508, 658 S.E.2d 680 (2008).  In that case, a surveying engineer limited his liability, via contract, to $50,000.  The Court, citing an earlier state Supreme Court decision, ruled that the limitation was valid and enforceable:

People should be entitled to contract on their own terms without the indulgence of paternalism by courts in the alleviation of one side or another from the effects of a bad bargain.  Also, they should be permitted to enter into contracts that actually may be unreasonable or which may lead to hardship on one side.  It is only where it turns out that one side or the other is to be penalized by the enforcement of the terms of a contract so unconscionable that no decent, fairminded person would view the ensuing result without being possessed of a profound sense of injustice, that equity will deny the use of its good offices in the enforcement of such unconscionability.  Id. at 511, 658 S.E.2d at 682.

Is this rule absolute?  Clearly not, as the above quote indicates.  Unconscionable limitations will not be enforced.  Moreover, a third party, not subject to the contractual terms, is free to sue in negligence.  But as between the contracting parties, such a limitation on damages can be a powerful tool to minimize exposure to risk.

Questions about limitations on liability?  Comment below or drop me a line.  And be sure to sign up for email delivery of blog posts directly to your inbox.

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Photo:  “Proceed at own risk” by Dave Nicoll via Flickr/Creative Commons license