Condition assessments after a fire often involve determining the load capacity of the remaining structural elements.  Are you familiar with the equations used to determine the effective depth of char and the remaining cross-sectional dimensions as prescribed in the NDS for mass timber structural elements?

In the July 2025 SEU session, Erica Fischer, PhD, PE, from Oregon State University presented Hot Topic: The Fire Performance of Mass Timber.  Erica reviewed the current code and standard guidance for the fire protection design for mass timber, and noted current research on mass timber and fire to enable performance-based design.  She also summarized some challenges with mass timber and fire.

Erica walked through the following example to determine the depth of char and the effective depth of char for a glulam beam exposed to fire.  

To hear Erica explain this procedure, watch this short video:

As Erica explained, it is necessary to use the effective depth of char to account for the zero stiffness layer beneath the char.  This effective char depth should be used to calculate section properties on reduced cross-sectional dimensions for structural calculations.  These equations for the char depth and effective char depths for sawn lumber and mass timber, as well as CLT can be found in the National Design Specification (NDS) in Chapter 16.  While both char depth equations are non-linear and proportional to the nominal char rate, CLT also includes factors to account for the lamination thickness, the number of laminations charred, and the time for the char front to reach the glulam interface, as shown below.

This specific equation used for CLT char depths accounts for known gaps in the layers of laminations which accelerates the char rate and gives additional pathways for the fire to propagate.  Engineers should be aware of the difference when using CLT members to account for this acceleration in the char rate, to ensure accurate remaining section properties can be established.

Emily Guglielmo, PE, SE, Martin/Martin

In March 2025, Emily Guglielmo, PE, SE, from Martin/Martin, presented Refining Wind Load Approaches for
Non-building Structures. She nominated SEAOC SE Pathways Program (SE Pathways Intro – Structural Engineers Association of California) for the SEU Speaker Inspires donation of the month.

SEAOC’s SE Pathways to the Profession initiative aims to address the disparity of engagement and lack of diversity within the California structural engineering profession. SE Pathways to the Profession brings together students and early career professionals and engages them in dialog about engagement, retention and equity in the structural engineering profession.

Thank you, Emily, for helping structural engineers with your SE University session, and for your designation of SEAOC SE Pathways Program as our SEU Speaker Inspires Organization of the Month!

SE University 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 SE University to make a donation to help improve our world.

When using delegated connection design, which responsibilities belong to the EOR and which belong to the detailer?  Who is ultimately responsible for the adequacy of the connection design and what does the Code of Standard Practice require?

In the May 2025 SEU Session, Kyle Jenkins, PE, from Advantage Structural Engineers, presented Tips for the EOR when Delegating Steel Connection Design.  Kyle explained ways to produce better drawings that provide the information needed for safe and efficient delegated connection design.  He described the importance of communication in the delegated design process and gave examples of negative outcomes that can come from poor communication.  Kyle identified some best practices for setting up and delegating types of shear, moment, and bracing connections.

Kyle referenced the Code of Standard Practice which is located in the back of the steel manual, and specifically noted sections 3 and 4, as it applies to delegated connection design.  As you can see in the slide below, Kyle noted that the COSP Section 3.2.3 states the requirements for connections:

Option 3 specifically relates to delegated connection design; however it is worth noting that the COSP requires that the EOR indicate which option is being utilized for each connection.  The EOR has the option to design some connections while delegating others.  This should be clearly indicated on the drawings so that the fabricator can properly bid the cost.

When using Option 3, the COSP specifies that the EOR supply the necessary information for bidding, which includes connection reactions, whether ASD or LRFD is to be used, and required member reinforcement needed, such as stiffeners and thru-plates.  Failure to provide this information can result in inaccurate bidding or costly change orders, and possibly an inadequate design.  Kyle noted that Section 4 of the COSP lays the final authority of the connection design on the EOR, as you can see below.  This responsibility is fulfilled through the submittal review and approval process.  

The use of delegated design can only be successful with open lines of communication between the EOR and the detailer.  Delays or poor communication can have costly consequences.  A team mindset is necessary to ensure the detailer understands the intent of the EOR and is able to provide connections that meet the code standard.  However, the EOR is ultimately responsible for the complete design of a safe, code-compliant structure, which includes adequate connections.

Delegated connection design can be a beneficial way for the EOR to provide a superior product, but only if done correctly.  Delegating connections allows the fabricator to use preferred, and often more economical connections, however good communication is necessary to prevent inaccurate bidding, change orders, and delays due to RFIs.

In the May 2025 SEU Session, Kyle Jenkins, PE, from Advantage Structural Engineers, presented Tips for the EOR when Delegating Steel Connection Design.  Kyle explained ways to produce better drawings that provide the information needed for safe and efficient delegated connection design.  He described the importance of communication in the delegated design process and gave examples of negative outcomes that can come from poor communication.  Kyle identified some best practices for setting up and delegating types of shear, moment, and bracing connections.

Kyle noted the importance of providing realistic reactions on design drawings.  Accurate reactions lead to more efficient structural designs and decrease costs for the owner.  Providing reactions also promotes better quality control for the EOR when reviewing the shop drawing details.  To hear Kyle explain this best practice, watch this short video:

Kyle also noted the EOR should specify whether reactions are ASD or LRFD and avoid using terms like “Factored” or “Service” since these terms are no longer relevant as wind and snow loads now are factored to ASD levels.  Specifying reactions to be ASD or LRFD eliminates confusion and clear communication prevents negative outcomes.

The burden to provide an efficient and safe design is shared by the EOR and the delegated design professional.  Establishing good communication and providing accurate reactions at connections will benefit the team throughout the design and construction administration process.

Buckling-Restrained Braces are becoming more widely incorporated into seismic designs worldwide.  As their use increases, design engineers should be aware of ways to improve the communication and implementation of BRBs into their projects, as well as the code provisions and requirements for the use of BRBs.

In the June 2025 SEU session, Ben Sitler, PE, Dr.Eng., from Buro Happold, presented Seismic Design with BRBs – Pushing to the Limit.  Ben noted recent changes to the BRB design and testing provisions of AISC 341-16 and 341-22.  Ben explained how BRBs respond in extreme design cases and how to ensure good performance in long and jumbo BRBs, and he reviewed the fundamental behavior of BRBs.

Ben showed how higher-mode buckling and frictional behavior impacts the compressive strains in long BRBs, and how higher strength steel grades may be a valid and even desirable option for large capacity BRBs.  He discussed the need for the design engineer to provide stability bracing for BRBs in the scope of their design.  While the BRB supplier will perform the necessary stability analysis and physical testing as required on a project-specific basis, the design engineer should communicate with the supplier to discuss what connections or bracing may be required to ensure the BRB is torsionally restrained in both directions.  To hear Ben discuss some tips for design engineers providing stability bracing, watch this short video from his presentation:

As Ben discussed, engineers should provide torsional braces and connections on beams framing into BRB connections.  Closed beam sections may also be required where diaphragms are absent.  Maintaining global stability is essential when using BRBs and the design engineer plays a crucial role in ensuring the framing provided can resist these out of plane forces.  Ben also noted that AISC 360 Appendix 6 does provide some guidance on bracing stiffness and strength provisions, however, these were not specifically developed for BRBs and are typically intended for lateral-torsional buckling calculations.  While the torsional forces from BRBs are not usually large, they are still present and need adjacent framing to provide resistance.

Which section of ASCE 7 do you typically use to determine design wind loads for rooftop screenwalls?  Would they be considered roof top equipment?  Or perhaps you consider them to be a parapet or a freestanding sign?  Does the location on the roof affect which provision to use?

In the March 2025 SEU session, Emily Guglielmo, PE, SE, from Martin/Martin, presented Refining Wind Load Approaches for Non-building Structures.  Emily reviewed the applicability of ASCE 7 wind load provisions for rooftop equipment, screenwalls, PV panels, signs and canopies, and other non-building structures.  She also addressed ways to approach wind loads on structures not explicitly addressed in ASCE 7 such as trellises, tall parapets, and balcony rails.  Emily presented rational analysis strategies to address gaps in code provisions for non-building structures and industry best practices.

Emily addressed a common but often debatable topic: wind loads on screenwalls.  Engineers often vary on whether they consider screenwalls to be rooftop equipment, solid freestanding signs, or parapets.  Along with confusion on which provision to use, engineers also might wonder whether shielding can be considered on the equipment enclosed within the screenwalls.  To hear Emily address how ASCE 7 considers screenwalls and shielding, click below to watch this short video:

While some wind provisions in ASCE 7 are explicit, there are some gray areas especially as it applies to non-building structures which often encompasses unique situations.  Screenwalls are not explicitly included in the body of the code, however the commentary provides ample feedback on how to appropriately address these rooftop structures.

Brad Davis, PhD, SE, PE, Davis Structural Engineering

In November 2024, SEU welcomed Brad Davis, PhD, SE, PE, from Davis Structural Engineering, to present Vibration Analysis of Steel Joist / Concrete Floors.  Previously in 2020, Brad designated Doctors without Borders (https://www.doctorswithoutborders.org/) for our SEU Speaker Inspires donation for the month, and he has chosen to do the same in 2024.

Doctors without Borders, or Medicins Sans Frontieres, provides medical humanitarian aid where the needs are greatest, and often go to places where other organizations can’t or won’t operate. Historically, they have not run medical projects in the US, however in March 2020, MSF launched temporary operations in the United States in response to the unprecedented COVID-19 pandemic.  In key sites around the country, MSF is working with local authorities and partner organizations that serve vulnerable communities with limited access to health care, such as migrants, homeless people, and other marginalized or neglected groups

Thank you, Brad, for helping structural engineers with your SEU session, and for your designation of Doctors without Borders as our SEU Speaker Inspires Organization of the Month!

SE University 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 SE University to make a donation to help improve our world.

Openings in wood diaphragms are unavoidable but can cause significant changes to the shear distribution in the diaphragms.  Openings complicate the design procedure, however, there is a simplified method available when certain conditions are met.

In the April 2025 SEU Session, Kimberly Kramer, PhD, PE, SE, from Kansas State University, presented Designing for Openings in Wood Diaphragms.  Kimberly walked through how to calculate wood-frame diaphragm deflections to classify diaphragms as flexible or rigid.   She identified the mechanisms of the concentration of shear around openings and reviewed designs for openings in flexible diaphragms using the Truss Frame Analogy.

Kimberly noted that a simplified analysis criteria was developed by the Canadian Wood Council after extensive research on shear forces in flexible wood diaphragms with openings.  This criteria allows for the diaphragm to be designed for a 10% increase in the maximum shear force if all four criteria are met.  The four criteria are included on the slide below:

The maximum aspect ratio requirement in the fourth criteria can be found in SDPWS Table 4.2.2.  If these four criteria are met, the maximum shear in the diaphragm must be calculated, as demonstrated below:

The shear is calculated along the edge of the diaphragm as well as each edge of the opening, and the largest shear is selected. Then, it is increased by 10% and then the entire diaphragm is designed for this increased shear force.  

This useful design procedure can save time when the diaphragm opening meets these basic four conditions.  This procedure eliminates the need to complete a detailed Truss Frame Analysis of the diaphragm and provides a simplified design for the entire diaphragm based on an increased shear force throughout.  Although this procedure does not currently appear in any US building codes, the research is useful to determine when a more detailed analysis should be performed. To learn more about this research performed by FP Innovations and the Canadian Wood Council, you can read the full report here.

Andrea Shear, PE, Murray Engineering

Matthew Fadden, PhD, PE, WJE

In October 2024, SEU welcomed Matthew Fadden, PhD, PE, from WJE, and Andrea Shear, PE, from Murray Engineering, to present Identifying, Evaluating, and Correcting Punching Shear Deficiencies in Flat Plate Construction.  Matt and Andrea have designated the Dick Woods Student Impact Fund (Dick Woods Student Impact Fund – 338683 – Michigan Giving) for our SEU Speaker Inspires donation for the month.

The Dick Woods Scholarship Fund exists to honor of Professor Woods (1935-2021) and his willingness to help CEE students in need. The fund supports students with a demonstrated financial need.

Thank you, Matt and Andrea, for helping structural engineers with your SEU session, and for your designation of the Dick Woods Student Impact Fund at the University of Michigan 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.

Temporary structures can be an enigma for structural engineers.  ASCE 7 does not directly address temporary structures, so engineers are left to their own judgment to determine the appropriate wind load provisions to use.  

In the March 2025 SEU session, Emily Guglielmo, PE, SE, from Martin/Martin, presented Refining Wind Load Approaches for Non-building Structures.  Emily reviewed the applicability of ASCE 7 wind load provisions for rooftop equipment, screenwalls, PV panels, signs and canopies, and other non-building structures.  She also addressed ways to approach wind loads on structures not explicitly addressed in ASCE 7 such as trellises, tall parapets, and balcony rails.  Emily presented rational analysis strategies to address gaps in code provisions for non-building structures and industry best practices.

Emily noted that, in the past, there was no nationally recognized standard that addresses wind load provisions for temporary structures.  More recently, a proposal was initiated through IBC to use ASCE 37 Design Loads on Structures during Construction which includes minimum design loads on buildings and other structures during construction.  ASCE 37 does allow for a reduction in wind loads.  However, this was strongly discouraged by SEI within the committee meeting for two reasons.  First, there is an implied risk while on a construction site which does not exist in public venues which are typically housed in temporary structures such as tents with platforms and bleachers.  Second, these temporary structures typically travel and are used countless times over the span of many years.  This extended life of the structure, although only used in short, temporary circumstances, increases the chance of high speed wind loads on the structure.  Thus, SEI put together a group of experts who studied and issued guidelines which are now included in the body of IBC 2024 and will be included in a future Chapter 35 of ASCE 7-28.  Check out these new guidelines in IBC 2024 until they become part of ASCE 7 the next time you have a temporary structure to design.