How experience for design calculations saves time and money

Some glazing contractors don’t budget enough for appropriate engineering calculations (structural calcs) on projects. Those who do, understand the value of industry expertise. Some glaziers brag, “I’ve got a guy that does it on the side.” The truth is, a structural engineer with industry experience will save you time and money.

Structural engineers with glazing system experience are familiar with industry manufactures and have worked with their components and framing, so you’ll end up with system components and anchors that will work. An experienced engineer will always look at the boundary joints to make sure that excessive movement will not compromise the joint water barrier. In addition, years of experience usually results in a quick turn around using better software, specifically for aluminum curtain wall and storefront design.

Experts in aluminum code won’t over design your project. Aluminum design is specialized and requires adherence to the complex 2010 Aluminum Design Manual. This 469 page book larger is larger than the steel code! Few engineers ever pick up aluminum design, due to it’s specialization. University curriculums for structural engineers focus on steel, concrete and CMU. Aluminum is never used in the design of building or bridge structures so most structural engineers just don’t come across it in their everyday work. This type of experience is essential if you want your glazed system to work without problems for years to come.

So next time you need design calculations, hire experience. You’ll save money in the end.

Requirements for Blast Resistant Glazing Projects

Are you considering jumping into the fray to receive some of the trickle down recovery money? Perhaps you’re considering a project that requires blast resistant glazing, but you are not sure what to expect. Many of the architect design teams have hired blast consultants to review submittals in detail. I’m not trying to scare you away, but I do think that its important to know what to expect. The “stickiness” of the submittal process really depends on who’s looking at the submittals and who is preparing the submittals. I’ve listed some typical submittal requirements that are usually needed for a blast resistant project:
• Cover-all Performance - Usually the specs will have a cover-all performance statement like, “Provide design of glazing system to meet the minimum blast requirements of UFC 4-010-01.” But what’s usually missing are the specific performance design requirements - level of protect, explosive weight category and stand-off distance. Getting these items identified at the beginning of a project is essential for a project to flow smoothly.


• Glass Thickness Design – UFC 4-010-01 Tables B-2 and B-3 have minimum thickness listed for single pane and insulated glass. Usually the minimums work in every case, but it must be shown by calculations according to ASTM E1300.


• Framing Components Design - Calculations are typically required showing that mullions deflections and stress do not exceed allowed limits. The limit for deflection is typically L/160 for static blast loads determined from the UFC criteria.


• Connections/Joinery Design – Calculations are required to demonstrate that all of the internal joinery including glazing stops and the anchors to the structure are able to resist the minimum of 2 times the static blast load from UFC criteria or the glazing resistance determined from ASTM E1300.


• Glazing Frame Bite – The UFC requirements point to ASTM F2248. The glazing pane must be adhered on the inside face of insulated units to the framing either with structural silicone or glazing tape. The only way to have a bite with out tape or silicone is under the alternative of blast testing.


• Alternative of Blast Testing – All of the above requirements may be usually be neglected with submittal of appropriate blast testing in accordance with ASTM F 1642. Many times this has already been performed by the manufacturer. However, if the proposed size of the glass and span of the mullions exceed that which was tested, you may be required to go back and fulfill all of the other requirements. Usually anchors from the framing to the structure are still required to be designed and submitted even with the blast testing results.

So, I hope this helps with your decision to go after some of these types of projects. The government recovery money is finally making it down the glazing industry. Just make sure that you have the right help to get the job done. Really these projects aren’t that bad, they just sound much worse than their “bite”.

Avoid Delays On Recovery Funded Projects

The glazing industry is starting to see the trickle down of government recovery money, but it’s not without a price. These projects are tagged with important features that glaziers will do well to be aware of. Most of the projects are for Department of Defense installations or GSA and have blast resistance requirements.

A significant percentage of the recovery money ends up in the hands of architectural firms responsible for design and construction oversight. The design budgets are nice and fat and many of the architectural firms hire blast load consultants to provide design input, write specifications, and …review your submittals during the construction phase. So now the typical submittal has to jump through an additional hoop. The blast load consultant is usually eager to make their value known, and that translates to a necessity for every “t” being crossed and every “i” dotted.

Submittals which are rejected (for what ever reason) require time, effort and often a tangible dollar amount to be resubmitted. Sometimes the blast load consultants may not be altogether familiar with glazing systems and this results in a nightmare of rejections and resubmittals. Glazing contractors who want to cash in on the recovery money should be prepared for the additional efforts that are being required.

Projects with recovery earmarks are good business when you understand their process.

Stay tuned! Next time we’ll cover some of the items typically required in the submittals for blast resistant glazing.

Antiterrorism: Blast-resistant Glazing Systems

The environment of rapidly evolving antiterrorism codes has left estimators and manufacturers in a whirlwind of confusion asking themselves, “Why do blast resistant requirements seem to be a moving target?” It’s important for us to understand what is driving this part of the glazing industry. A great emphasis has been placed on protecting the inhabitants of government buildings from flying shards of glass due to explosion. The U.S. government will be investing great amounts of capital into protective glazing systems during the next 10 to 15 years to make the changes necessary to their existing buildings and for all new construction. The two major codes driving the changes are GSA/Interagency Security Committee Security Design Criteria and the U.S. Department of Defense Unified Facilities Code UFC 4-010-01, Minimum Antiterrorism Standards for Buildings. The UFC code requires all future DoD programming beginning in 2004 to include blast resistant glazing systems. Over the last couple of years we have begun to see many of these projects entering into construction and it’s essentially the same story for the GSA’s programmed projects.

For more insight on this topic see:

http://www.glassmagazine.com/article/commercial/antiterrorism-blast-resistant-glazing-systems-and-moving-target

Government Bid Lists - glass & glazing specific

Do you want the best industry specific government bid list?

Checkout: http://www.jeistructural.com/web/govt-bids

Recovery money is starting to flow into the glass and glazing industry. Now is the time to position your company to recieve business.

Misinterpretations of UFC Requirements

Are the anchors for your blast resistant glazing systems appropriately designed?

There are many misinterpretations of UFC requirements for blast resistant design among engineers. Some engineers solely design anchors for two times the static equivalent blast load determined from ASTM F2248.

However, UFC 4-010-01 (2007) also requires a minimum anchor design equivalent to the resistance of the glass determined from ASTM E1300.

Many engineers miss this requirement, but UFC, under section B-3.1.1.4 Connection Design, state, "The actual connection design load is dictated by the glass type and thickness determined by ASTM E 1300."

Therefore, the correct design load is the maximum of either two times the static equivalent blast load from ASTM F2248 or the resistance of the glass from ASTM E1300. The intent of UFC is to design anchors such that they will not fail before the glass.At JEI Structural, we stay up-to-date on the latest codes and offer many value-added services.

Let's build together,

Stewart P. Jeske, P.E.
President
www.JEIstructural.com

"Expert engineers for commercial glazing calculations."