Glass, Glazing Systems and Blast Engineering Calculations

Gathering Missing Info on Blast Projects Saves Time.

2012-01-31T13:41:00.000-06:00

Many blast project specs do not provide enough information to come up with the equivalent 3-second blast design pressure from ASTM F2248. Glazing contractors can save time by requesting the following information in advance.

Explosive Weight - (Typically for most projects explosive weight II)
Standoff Distance - (For most projects it is the Conventional Construction Stand Off = 82 ft)
Level of Protection - (Typically Low Level of Protection)

This criteria is usually determined during the design phase of a project by the using agency or the design team.

For more helpful information on blast projects see JEI Structural Engineering WINGARD, Windas, Window Blast, Blast Mitigation Design

lateral-torsional buckling on storefronts

2012-01-26T20:15:00.002-06:00

Regulations have changed so there is a need to design for the lateral-torsional buckling on storefronts now.

Section 8.4.B.3.a of the ‘Aluminum Windos and Doors, and Glazing’ specifications states the following:

The AAMA standard dealing with storefront design is ‘AAMA SFM-1-87: Aluminum Storefront and Entrance Manual’.

Engineering Section 6.0 (shown below) directs us to the current Aluminum Association’s Aluminum Design Manual (2010):

The Aluminum Design Manual, section F.2 (shown below), indicates that when framing members are subject to lateral buckling, the nominal flexural strength must consider the un-braced length of the framing in question:

We want you to have this information to give you a better understanding of why we are designing open shaped verticals mullions to prevent lateral-torsional buckling. This increases the stablity and life of the storefront wall installation providing a higher level of client statisfaction to the end user.

Glass Roads - the prototype

2012-01-03T19:59:00.002-06:00

Solar powered glass highways on zooming toward you. How will it impact the glazing industry?

http://www.jeistructural.com/blog/?p=300

FUTURE CHANGES TO UFC CODE / ASTM F2248 STANDARD

2011-08-12T16:01:00.002-05:00

For the past several years, the Unifed Facilities Criteria (UFC 4-010-01) has been the governing code for all U.S. Department of Defense (DoD) blast mitigation projects. Referencing the current ASTM F2248-03 standard, the UFC provides a guideline for determining an appropriate static design blast pressure for both framing and connections of blast resistant glazing systems.
Surprisingly, many engineers and glazing contractors are unaware of the requirements set forth by ASTM F2248-03 for the design of framing connections for blast resistant glazing systems. ASTM F2248-03 specifies connection design loads of at least 2.0 times the magnitude of the 3-second equivalent design load or the glazing resistance as determined from ASTM E1300, whichever is greater. Often the glazing system connections to the main structure are only designed to resist 2.0 times the 3-second equivalent design load, despite the glazing resistance of the system.

The UFC 4-010-01 is currently undergoing revisions that should clairify blast design loads and reference a more stringent version of the ASTM F2248 standard (ASTM F2248-09). The revised ASTM F2248-09 sets forth the following criteria for the design of blast resistant framing connections to the main structure:

a. 2.0 times the magnitude of the load resistance of the blast resistant glazing if the maximum air blast pressure is greater than one half the magnitude of the load resistance of the blast resistant glazing.

b. 1.0 times the magnitude of the load resistance of the blast resistant glazing if the maximum air blast pressure is less than one half the magnitude of the load resistance of the blast resistant glazing.

Currently, UFC 4-010-01 (2007 revision) references ASTM F2248-03 and not the more up-to-date F2248-09 edition. It is our understanding that ASTM F2248-09 is not required in the design of blast resistant systems until referenced in the most current version of the UFC which is anticipated this year or early next year.

The changes may be difficult to accommodate with static equivalent analysis and may require a larger push for dynamic blast analysis to maintain reasonable connections.

Written by Matt Quinlivan, E.I.T.

Be Careful With Manufacture Storefront Design Charts

2011-07-16T12:08:00.000-05:00

Design wind load charts put out by manufactures are usually only good for estimating overall span deflection of a mullion, and do not typically consider proper methods for stress design.

The 2010 Aluminum Code has new criteria for considering the unbraced length of open sections. The unbraced length for a vertical mullion is usually considered to be the distance between horizontal mullions. However, design wind load charts put out by many manufactures of storefront systems are often based on the assumption that the mullion has full lateral buckling support and an unbraced length of zero. How can this be?

I believe that the manufacturers are considering lateral bracing from the glass and the mechanical gaskets. However, after review of many industry specs it is clear that mechanical gaskets should not be considered as a means of lateral bracing for open shaped storefront mullions. Therefore, the charts error on the side of being too liberal. When it comes to the calculations, they can’t match up and the mullions usually don’t perform as well as the charts indicate.

Unfortunately, it’s in the interest of the manufactures to keep the charts the same because they are competing against one another for framing systems with the highest performance standards.

Glaziers should keep this in mind when selecting open shaped vertical mullions and stay well under the curve projections that are indicated. If glaziers use the charts, as is, reinforcing structural glazing or heavier mullions will likely be needed.

Automatic Sliding Doors Have Operational Limitations

2011-07-16T07:25:00.000-05:00

It’s important for glazing contractors to get information from the automatic sliding door manufacturers, in advance, on operational limitations for their systems.

Some automatic door manufacturers have stringent criteria on how much the supporting header and jambs can deflect from wind load and how much can be supported vertically on top of the header.

Floor Movement & Glass Railing

2011-07-16T07:10:00.002-05:00

For interior glass railing one of the things you need to watch out for is glass railing on stairs that traverse floor levels. If the floors are designed to deflect with live load, care is needed to make sure load doesn’t transfer to the glass railing system.

We saw a project with glass railing that goes between floors and the top portion of the metal handrail continued to the second floor wall framing. There is the possibility that the second floor framing can deflect and if you have a continuous rail that goes between the second floor wall and is attached to the stair, load can be transferred into the glass causing breakage.

It’s more appropriate to break the railing at the floor transition or provide a joint that slides.

Title: Staircase Glass Railing Designs, Glass Railing, Glass Balustrade

Description: JEI offers staircase glass railing designs, glass railing, glass balustrade and glass railing calculations for glazing contractors.

Kauffman Performing Arts Center - Built for snow

2011-01-22T19:25:00.000-06:00

JEI Structural was honored to do a small part of the glazing calculations on the lower portion of this structure. We didn't work on the roof, but we're happy to see that the Kauffman Performing Arts Center performs well with snow loads.
http://www.kmbc.com/news/26577116/detail.html

Recent Developments in Small Business Government Contracting

2010-12-03T08:51:00.000-06:00

Recent Developments in Small Business Government Contracting

The past few months have seen a flurry of federal activity with regard to small business government
contracting – from Congress, SBA and other federal agencies, and even a special Presidential Task Force.

Following is a brief recap of some of these measures:

SBA Finalizes New Size Standards

On October 6, 2010, the U.S. Small Business Administration published revised size definitions for three
broad commercial sectors affecting businesses in retail trades, accommodations and food services, and other services.

Originally proposed in October 2009, the changes will broaden small business eligibility and help an estimated 17,000 additional firms gain access to SBA’s financial assistance, contracting and other programs. Before this comprehensive review, the last overall review of size standards occurred more than 25 years ago.

The three final rules will affect the following industries:

Sector 44-45 - Retail Trade: A change in the new car dealer industry plus increased size standards in 48 other retail trade industries are estimated to result in 14,400 additional retail firms being classified as small businesses.

Sector 72 – Accommodation and Food Services: Size standards were increased for five industries with an estimated 2,050 additional firms becoming eligible for small business programs.

Sector 81 – Other Services: Size standards were increased for 18 industries, resulting in an estimated 1,400 additional firms falling under the small business classification.

Increase in Small Business Set-Aside Thresholds

On October 1, 2010, Small Business set aside thresholds changed from $100K to $150K and from $250K to $300K for operations defined in FAR 2.101 under Simplified Acquisition Threshold.

The new inflationary thresholds became effective 1 October 2010. Specifically FAR Part 19 changed as follows:

- Subcontracting dollar amounts changed from “550,000” to $650,000” (“$1 million” to “$1.5 million” for construction).

- The total value of contracts for 8(a) and HUBZone sole source awards changed from "$5.5million" to "$6.5 million" for manufacturing and "$3.5 million" to "$4 million" for all other acquisitions.

- The total value of contracts for SDVOSB changed from “$5.5 million” to $6 million” for manufacturing and “$3 million” to “$3.5 million” for all other NAICS.

- The requirement to evaluate SDB performance for negotiated acquisitions changed from greater than "$550,000" to "$650,000" and from "$1 million" to "$1.5 million" for construction.

A Final Rule for SBA’s Women-Owned Small Business Program

The U.S. Small Business Administration (SBA) expects to have a federal contracting women-owned small
business (WOSB) program up and running February 4, 2011, per publication of its final rule on October 7, 2010.

The new rule identifies 83 industries in which WOSBs are under-represented or substantially underrepresented in the federal contract marketplace, a major increase from the 4 industries identified in an
earlier rule. These industries were identified based upon the combination of both a “share of contracting dollars” analysis, as well as a “share of number of contracts awarded” analysis. (The earlier rule was based solely on a “share of contracting dollars” analysis). In addition to opening up more opportunities for WOSBs, the rule is another tool to help achieve the statutory goal that 5 percent of federal contracting dollars go to women-owned small businesses.

The SBA, in conjunction with the Federal Acquisition Regulatory Council, has now begun a 120-day implementation period, including building the technology and program infrastructure to support the certification process and ongoing oversight. With implementation expected to take several months, the SBA expects agencies to start making contracts available to WOSBs under the program in early 2011.

Components of the Women-Owned Small Business rule include:

Firms must be 51 percent owned and controlled by one or more women, and primarily managed by one
or more women. The women must be U.S. citizens. The firm must be “small” in its primary industry in accordance with SBA’s size standards for that industry. In order for a WOSB to be deemed“economically disadvantaged,” its owners must demonstrate economic disadvantage in accordance with the requirements set forth in the final rule.

The final rule authorizes a set-aside of federal contracts for WOSBs where the anticipated contract price does not exceed $3 million - or $5 million in the case of manufacturing contracts. Contracts with values in excess of these limits are not subject to set-aside under this program. The final rule removes the requirement, set forth in a prior proposed version, that each federal agency certify that it had engaged in discrimination against women-owned small businesses in order for the program to apply to contracting by that agency.
• The proposed rule allows women-owned small businesses to self-certify as “WOSBs” or to be certified by third-party certifiers (such as the National Women Business Owners Con?? http://www.nwboc.org ), including government entities and private certification groups.

o The final rule requires WOSBs which self-certify to submit a robust certification verification, to complete the certifications at the federal Online Representation and Certification Application (“ORCA”) Web site, and also to submit a core set of eligibility-related documents to an online “document repository” to be maintained by the SBA. Each agency’s contracting officers will have full access to this repository.

o The SBA intends to engage in a significant number of program examinations to confirm eligibility of individual WOSBs.

o In the event of a contract protest or program review, the SBA has the authority to request substantial additional documentation from the WOSB to establish eligibility.

o SBA intends to pursue vigorously punitive action against ineligible firms which seek to take advantage of this program and in so doing to deny its benefits to the intended legitimate WOSBs.

A Compliance Guide for the Women Owned Small Business Program was published in the Federal Register on October 27, 2010.

How experience for design calculations saves time and money

2010-11-21T19:48:00.003-06:00

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

2010-06-05T15:25:00.000-05:00

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

2010-04-30T07:47:00.000-05:00

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

2010-04-11T08:14:00.000-05:00

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

2010-04-09T07:46:00.001-05:00

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

2010-04-08T11:58:00.000-05:00

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."