• Field Notes 30.06.2010

    Reading the editorial at the back of the June 7, 2010, ENR about the lessons being learned in the oil disaster in the Gulf of Mexico reminded me that we’ve been pretty fortunate as a whole in the curtain wall and window world.

    Decisions made due to financial and schedule pressures are all too real in this business as they are in any other. While such factors are probably huge in scale in other industries, in the curtain wall or glazing industries they haven’t led to the type of disasters where public safety or well-being have been jeopardized. And may God grant us the blessing they never will.

    A quote from the editorial brought home to me the curtain wall tie-in: “The U.S. hasn’t reconciled the idea that engineers can render miracles – cloud-piercing towers, low-cost instantaneous digital communications, deep-sea drilling – with the idea that each fresh miracle hurls us into unfamiliar territory.” “…the Gulf of Mexico … will be remembered as the place where engineering prestige dipped to a new low in an age known for disasters as much as for progress.”

    We’re a little bit lucky in this business. When involved with a professional engineer, it’s usually on the structural side of the business, and a lot of peace of mind can follow. Shop drawing preparation ought to be done hand in hand with a structural engineer as every bit the player as the fab and field people. Calculations verifying the size of the frame members, the suitability of the anchor design, and the overall adequacy of the construction are all critical. It’s a pretty safe bet that the wall when installed that way will stay on the building and perform as intended, at least from a structural standpoint.

    Fortunately, building codes, project specifications, and more importantly, industry standards, make sure that compliant walls can eliminate most of the bad things from ever happening. New technologies keep appearing, too. Warm-edge spacers, blast- and hurricane-resistant walls, cable walls, glass mullions, etc., all require some degree of engineering to assure they work as intended. One of the fun things about going to the testing laboratories is to see the inventiveness of other systems, especially some of the anchor configurations that are developed, not to mention the wall systems themselves.

    As static as the wall may appear, there are still a lot of dynamic forces in play:

    • Wind loads are always with us, sometimes just a slight breeze, but at other times in the form of tornadoes, straight-line wind bursts or hurricanes.
    • Thermal loading also causes framing to expand and contract over seasonal or daily temperature swings.
    • Building frame movement, either from the wind loads the curtain wall passes into the frame or from seismic activity, or from frame shrinkage or occupant loads deflecting a slab edge beam.

    All of these things have to be accounted for in frame-member-to-frame-member connections, as well as creating expansion and fixed anchoring conditions tying the wall back to the building.

    While most companies have “engineering” departments, often these are not fully staffed with licensed engineers. That’s not a deficiency, because more often than not, the systems designed and drawn by these staffs are reviewed and checked by a licensed P.E., thus the “life and safety of the general public” is addressed. And thankfully, in more times than not, that system, including the “checks and balances” of submitting calculations for review by the project engineer, hasn’t failed us.

    One of the backstops to assure “the system” works before it ever gets put up on a building is testing, be it manufacturer or independent third-party testing. Mockup testing is an awfully expensive proposition, but it’s always been my belief that no one has yet built a mockup where nothing was learned. Yes, there may have been mockups or tests that passed the first time through. In those instances, the lesson learned was, “We did it right.”

    Please don’t be the one to suggest a mockup or testing shouldn’t be done. One of the lessons learned is that sometimes it’s not done right, requiring revisions to materials or assembly methodologies. At times, the field will get an idea of things they can do to maximize their efficiency, which can lead to lower field installation costs. For owners and architects, once the wall passes the testing, they learn their wall contractor knows how to put up and install the wall, and they’ll get what they paid for.

    It’s a costly proposition, and usually jumps out to an owner looking to cut costs, but it is a way of assuring everyone involved that it can be done correctly. And in the end, it can save the cost of a mockup if/when a flaw is found.

    The single biggest factor in making sure all this works: the people that make up this industry want to get it right. All of us look to cut costs, improve efficiencies, and find better, cheaper and faster ways of doing things. But I have yet to hear any stories or witness first-hand someone talking about a decision dealing with structural integrity that would cut that corner to save even a single dollar. If they exist, I hope they’re tarred and feathered on their way out of Dodge.

    But for the “getting it right” part: may God grant that blessing will always be a part of this business, too.

    Posted by Blogger @ 10:51 am

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