Which ASCE provision do you typically use when designing a rooftop screenwall for wind loads?  Several options have been used by structural engineers in the past, but the best option has been debatable since the code has not explicitly spoken on the subject.  New guidance in ASCE 7-16 helps clarify this frequently asked question.

In the May 2022 SEU Session, Emily Guglielmo, SE, PE, from Martin/Martin Inc., presented Wind Loads: Updated Frequently Asked Questions.  Emily explained how to deal with commonly encountered wind load situations that are not fully addressed in the code.  She also identified the latest code updates and examined some complicated wind load provisions and how they relate to real world examples.

One of the most frequently asked questions, in regard to wind load provisions, is what wind load should engineers use for a roof top screen wall or equipment?  Emily noted that while there are several commonly used provisions for these calculations, there is an approach that may be considered ‘more right’ than others.  Typically, engineers have used one of the following three different options for determining the wind loads on rooftop screen walls:

A. Rooftop Structures and Equipment

B. Solid Freestanding Signs

C. Parapet Pressures

While Emily noted that none of these approaches are necessarily incorrect, the code now offers some guidance in the commentary:

New to the commentary in ASCE7-16, C29.4.1 states that “Mechanical equipment screens… located away from the edge of the building roof such that they are not considered parapets…” should use the wind load determined with Section 29.4.1.  This statement implies that if the screen is located near the edge of the roof, that perhaps a parapet pressure might be more appropriate.  Emily noted that it would be reasonable to conclude that if the screen wall falls within the typical rooftop wind zone, then Sections 29.4.1 should be applied and when the screen falls within an edge or corner zone, a parapet pressure could be more appropriate.

This new addition to the commentary with the 2016 revision helps provide more clarity to this frequently asked question, and engineers now have more guidance for common rooftop screens and equipment.


Carine Magalhaes Leys, Odeh Engineers

In April 2022, SEU welcomed Carine Magalhaes Leys, from Odeh Engineers, to present 2022 Post-Tensioning Design: Finite Element Method-Based Solutions.  Carine has designated GRAACC Support Group for Adolescents and Children with Cancer in Brazil (https://www.globalgiving.org/projects/better-chances-of-cure-for-childhood-cancer-in-br/) for our SEU Speaker Inspires donation for the month.

Carine wished to support children in Brazil where there is an estimated 16,000 new cases of cancer in every 100.000 children and adolescents. Cancer is the first leading cause of death by disease in the population up to 19 years old. The GRAACC manages and maintains a hospital that offers diagnostic, treatment and after treatment for children and adolescents with cancer in Brazil.

Thank you, Carine, for helping structural engineers with your SEU session, and for your designation of GRAACC Support Group for Adolescents and Children with Cancer as our SEU Speaker Inspires Organization of the Month!

 

 

SEU began the SEU Speaker Inspires program in 2015 as a way to “pay it forward”, enabling our speakers to designate a charity/organization of their choice for SEU to make a donation to help improve our world.


Natural born leaders are a rare breed, but many skills needed to empower and motivate teams can be learned and improved.  However, it takes great intentionality to make meaningful change.  Changing patterns and behaviors can be a challenge, but learning the art of building successful working relationships will pay dividends over the course of a career.  Check out these helpful articles and resources which aim to identify excellent leadership qualities and tips to hone your skills:

5 Traits That Will Instantly Point to Someone With Bad Leadership Skills | Inc.com

Why The Distinction Between Leader And Manager Matters (forbes.com)

How Can You Be Sure Someone Has What It Takes to Lead People? Look for 4 Rare Habits | Inc.com

9 Skills to Manage Your Team | Blog.SHRM.org

The Leadership Skills To Be Learned From Parenting – Young Upstarts

 


Have you ever had a phone call from a building owner whose occupants are complaining of cracked partitions or noticeable slopes in their office flooring?  Building occupants are quick to notice when doors or cupboards get jammed, wall finishes crack, or concrete slabs show cracks larger than ordinarily expected, and many of these serviceability issues are the result of long-term deflections of the concrete floor.

In the February 2022 SEU Session, Dave Adams, PE, SE, from BWE, Inc., presented Serviceability for Concrete Slabs.  Dave covered a variety of topics addressing serviceability of slabs including strategies for improving the performance of concrete, short- and long-term deflections, the influence of reinforcement on potential cracking, prestressed tendon layout, and the effects of floor vibrations.

Dave explained how to calculate long-term deflections and important considerations when predicting the sustained dead and live load on the slab.  To hear Dave review the process when considering long-term deflections, click on the following 3 minute video:

 

Long-term deflections are an important consideration to the serviceability of a concrete slab, and Dave clarified the use of the various factors and multipliers which help predict the future deflections.  Accurately assessing the sustained load on the slab can be challenging, however Dave offered reasonable predictions for which live-loads should be considered “sustained.” 

While strength considerations tend to get the most attention during slab designs, serviceability issues can render a slab unusable for its intended purpose.  It is essential that short- and long-term deflections be considered to ensure the slab does not cause future alarm to occupants, cracking or movement of partitions, or issues with furniture or fittings within the structure.


What kinds of ethical dilemmas could arise from a straightforward brochure offering your engineering services?  What legal rules exist to regulate professional advertising?  Are you familiar with the ethical guidelines of any professional society to which you are a member?

In the March 2022 SEU session, Matthew Rechtien, PE, Esq., from Walter P Moore, presented our 2022 Engineering Ethics Update: The Ethics of Competition.  Matt explained how qualifications-based selection works and its legal and ethical implications.  He also reviewed the legal and ethical implication of gifts and reviewed the ethical constraints on advertisement.

Matt explored the legal limits in regard to professional advertising for a variety of states and the general consensus is that advertisements must be truthful and not deceptive or misleading.  Some states include more specific language regarding resumes, brochures, or solicitations, however, the general legal requirements for professional advertisements focus on truthfulness.  Truthful advertisement is protected “commercial speech” guaranteed by the 1st and 14th Constitutional Amendments, and Matt noted that the Supreme Court has stricken most attempts at regulation of professional advertising. 

While the Constitution may govern our legal rights to professional advertising, the First Amendment does not apply to private regulations such as those set forth by voluntary professional societies.  Ethical guidelines drafted by agencies such as NSPE and ASCE certainly require a higher benchmark for their membership.  For instance, NSPE requires that “Engineers shall not attempt to obtain… professional engagements by … other improper or questionable methods” and ASCE requires engineers to “uphold the honor, integrity, and dignity of the profession…”  These requirements certainly create an additional burden of responsibility for engineers to advertise in such a way as to not impugn the profession itself while also meeting the legal obligation of being truthful and not deceptive.

Both NSPE and ASCE publish examples of previous ethical dilemmas considered by their board members.  NSPE’s Board of Ethical Review publishes all of their opinions, and you can search by topic for previous rulings.  ASCE’s Committee on Professional Conduct also publishes cases that have been considered which can be found monthly in Civil Engineering Magazine or you can search by topic on their website.  For example, Matt used a case example that was similar to a case highlighted by NSPE, as shown in the following slide:

Matt noted that NSPE “…was deeply troubled by the manner in which the Engineer undertook to promote his new engineering firm because we believe there was a clear effort on the part of the Engineer  to engage in misleading and deceptive acts…”  In the ruling by NSPE, the committee notes how the engineer violated its Code of Ethics and ways in which the engineer could have avoided the charge of being misleading in their advertisement.

Both NSPE and ASCE can offer insight on precedents set by these ethics committees when engineers have encountered ethical dilemmas in their advertising.  While advertising may not be as heavily regulated as ethical quandaries such as gifts to elected officials or bribery, there are still many instances where improper advertisements for engineering services have resulted in disciplinary actions from these voluntary societies.  Be sure to check out these excellent resources of past cases, and avoid any ethical infractions in your resumés, brochures, or website advertising.


Matthew Rechtien, PE, Esq., Walter P. Moore

In March 2022, SEU welcomed Matthew Rechtien, PE, Esq., from Walter P. Moore, to present 2022 Engineering Ethics Update: The Ethics of Competition.  In prior years, Matt has designated Friends of Perryville Battlefield (https://www.friendsofperryville.org) for our SEU Speaker Inspires donation for the month and he has chosen to do the same in 2022.

Matt shared, “On October 8, 1862, nearly 8,000 Americans fell in the drought-parched Chaplin Hills of Kentucky during the Battle of Perryville. Perryville played a pivotal role in our nation’s most impactful event. Although the clash is oft-forgotten, those Americans should be remembered and that sacred ground, one of the most pristine civil war battlefields remaining, should be protected. The Friends of Perryville Battlefield is committed to both missions, which I am humbled to advance.”

Thank you, Matt, for helping structural engineers with your SEU session, and for your designation of Friends of Perryville Battlefield as our SEU Speaker Inspires Organization of the Month!

 

 

SEU began the SEU Speaker Inspires program in 2015 as a way to “pay it forward”, enabling our speakers to designate a charity/organization of their choice for SEU to make a donation to help improve our world.


Engineers are often more familiar with strength provisions for concrete slabs, but building codes require adequate strength and serviceability.  Excessive cracking and sloping or bouncy floors can be a nuisance and render a building unusable for its intended purpose.  Thus, engineers should be familiar with the available resources providing guidance for serviceability issues above and beyond the basic requirements in the building code.

In the February 2022 SEU Session, Dave Adams, PE, SE, from BWE, Inc., presented Serviceability for Concrete Slabs.  Dave covered a variety of topics addressing serviceability of slabs including strategies for improving the performance of concrete, short- and long-term deflections, the influence of reinforcement on potential cracking, prestressed tendon layout, and the effects of floor vibrations.

Throughout the presentation, Dave offered resources to learn more about serviceability of concrete slabs and to find additional design examples for reference.  Most of the presentation was based on guidelines in our usual Design Codes, such as 2018 International Building Code, ACI 318-14 Building Code Requirements for Structural Concrete, and ASCE/SEI 7-16 Minimum Design Loads and Associated Criteria for Buildings and Other Structures.  But many other resources are available to provide further guidance for serviceability which tends to get less coverage in the main Design Codes.

Since mix design and placement can greatly affect the performance of concrete slabs, Dave noted that ACI 209R Prediction of Creep, Shrinkage, and Temperature Effects in Concrete Structures offers guidance for the practicing engineer on concrete mix designs and how to plan for serviceability concerns.   ACI SP-20, Causes, Mechanisms, and Control of Cracking in Concrete is another useful document to prevent excessive short- or long-term cracks in concrete slabs along with 224R-01 Control of Cracking in Concrete Structures.

Two excellent resources that offer a detailed understanding of prestressed concrete member deflections are the PCI Design Handbook and Deflections of Prestressed Concrete Members from the ACI Journal Proceedings, V60, No.12, 1963. Also, Dave recognized the ACI Journal Proceedings V6, No, 6, from June 1963 Load-Balancing Method for Design and Analysis of Prestressed Concrete Structures by T.Y. Lin.  This article is useful for learning more about determining acceptable tendon profiles for prestressed concrete and the load balancing method based on elastic prestressed concrete beam theory.

For vibration control of concrete slabs, engineers can refer to AISC Design Guide 11: Floor Vibrations Due to Human Activity and Design Guide for Vibrations of Reinforced Concrete Floor Systems from CRSI.  Vibration issues are often subjective, but they can have important ramifications on the usefulness of concrete floors for a variety of activities.

Some of these resources are available free of charge, and others are available for purchase, but all of these materials are helpful to eliminate serviceability concerns in concrete slabs.


https://vimeo.com/665823370/b6d01893ea

ASCE 7 wind maps have changed!  While the changes to the maps alone are significant, there have been other changes within the provisions which will largely affect most of the country.  Depending on your region of practice, the updates may have significant implications for new building construction.  Are you aware of the most significant changes between ASCE 7-10 and ASCE 7-16?

In the December 2021 SEU session, Don Scott, PE, SE, from PCS Structural Solutions, and Cherylyn Henry, PE, from Zapata, presented ASCE 7-16 Wind Provisions (plus Updates).  Don and Cherylyn explained the significant changes to the wind maps and provisions in ASCE 7-16 including the differences between ASCE 7-10 and 7-16 low-rise components and cladding roof pressures.  They also covered the wind chapter changes between ASCE 7-16 and 7-22 including the tornado provisions.  

Don gave an excellent visual demonstration of how significant the changes to the low-rose component and cladding roof pressures were between ASCE 7-10 and 7-16.  Click below to watch a short 3 minute video to see some examples of how the roof zone areas and pressures have changed:

The above examples show the new effects of the ASCE 7-16 wind map changes including the decrease of wind speeds along the west coast, the unchanged wind speeds through the great plains and hurricane prone regions, as well as how the elevation factor can affect the wind pressures.  Most significantly, the changes to the roof pressure coefficients are apparent due to the results of new testing and more data.  Most of the country will experience some change to the component and cladding wind pressure updates in ASCE 7-16, as a result, so it’s important to be aware of the changes in the code.


Have you been using the ASCE 7 Hazard tool to look up important site-specific information for your building projects?  Are you aware that the new ASCE 7-22 provisions are now included in the Hazard Tool, including Tornado speeds?

During the December 2021 SEU session ASCE 7-16 Wind Provisions (plus Updates), Cherylyn Henry noted that the ASCE 7 Hazard Tool now includes the ASCE 7-22 provisions and users can now access 3 editions of ASCE 7 site specific information for their projects.  This tool is FREE for all users.

According to the ASCE 7 Hazard Tool website, the following site-specific data is provided in both customary and SI units for ASCE 7-10, 7-16 and 7-22:

  • Three-second gust wind speeds at 33 feet above ground for Exposure Category C, including identification of hurricane-prone and wind-borne debris regions.
  • Seismic coefficients plus the seismic design category.
  • Radial ice thickness with concurrent 3-second gust speeds for 50-year mean recurrence interval and temperature concurrent with ice thickness due to freezing rain.
  • Ground snow load, 20-year MRI value, and Winter Wind parameter (W2).
  • Median 15-minute and 60-minute duration rainfall intensities for 100-year mean recurrence interval.
  • Flood zone and static base flood elevation.
  • Tornado speeds.
  • Whether the site is in a mapped tsunami design zone.

The ASCE 7 Hazard Tool eliminates having to interpolate from contour lines on a map and saves time by noting when certain parameters need not be considered for specific risk categories.  This FREE tool is especially helpful to determine differences between editions of ASCE 7.


HSS connections tend to be heavy on welded applications rather than field bolted options.  However, there are many viable options for using bolted connections in place of historically welded connections.  How many resources do you have in your arsenal for the use of bolted connections in your HSS designs?

In the January 2022 SEU session, Brad Fletcher, SE, from Atlas Tube, presented HSS Bolted Connections.  Brad identified options for bolted field connections between HSS and reviewed how the limit states for HSS bolted connections are similar to other bolted connections.  Brad also suggested several helpful resources for HSS bolted connections for the practicing engineer.

Most structural engineers are familiar with AISC 360 and Brad noted Chapter J contain the limit states necessary for HSS bolted connections. Chapter K covers additional requirements for welded HSS connections.  AISC also has published Design Guide #24 Hollow Structural Section Connections which contains guidance for bolted and welded connections, and an updated version is due out later this year.

Brad also suggested the CISC Design Guide 1997 which reads more like a textbook for the design of HSS connections.  While the code references are out-of-date at this point, the principles discussed are still valid and useful.  This resource is no longer in print, however you can download a PDF version at the CISC website by clicking here.

The CIDECT Design Guides also contain useful design examples and may address more specific concerns such as stability or fatigue of HSS members and connections.  These resources contain mostly references to the EURO design codes, however the content still translates for use in North America.

Additional guidance can be found at the Steel Tube Institutes website which includes the popular HSS CONNEX OnlineHSS CONNEX is a program that performs code checks for welded HSS connections.  Also available are design spreadsheets which can help engineers efficiently design their HSS connections.  Many additional design manuals and reference articles can be found in their Resource Library, including their HSS Design Manual Volume 3: Connections at HSS Members which has been updated to the 2016 code.

Many of these resources are available for FREE download or can be purchased at a discounted rate with membership to the various organizations that publish them.   



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