The Structural Engineering Channel (TSEC) focuses on helping structural engineering professionals stay up to date on technical trends in the field. Our hosts for the show, Mathew Picardal, PE, and Cara Green, EIT interviews engineers ranging from recent engineering graduates to professionals from top engineering organizations on professional development topics for structural engineers to facilitate career advancement.
Topics covered include but are not limited to performance-based design, fasteners and connections, post-tensioned structures, smart structures, tsunami modelling, earthquake engineering, software solutions, seismic design, blast resistant design, wood, business issues and professional development for structural engineers, how to specify things effectively, and more.
TSEC 80: How Engineers Can Help Preserve and Protect Historic Landmark Structures
In this episode, we talk to René Vignos, SE, a structural engineer and Principal with Forell/Elsesser Engineers in San Francisco, about retrofitting historic buildings and how engineers can help preserve and protect historic landmark structures.
Here Are Some of the Questions We Ask René:
What interests you about working on projects that preserve historic structures?
What are the first steps you take when you start one of these projects?
What are some of the challenges with retrofitting historic buildings in seismic zones?
Why and how have you used base isolation technology to retrofit historic buildings?
What have been some of the challenges in using this technology in a historic building?
What challenges did you face in retrofitting Memorial Stadium at UC Berkeley and how did you overcome those challenges?
What are some of the things engineers can do to help preserve and protect historical sites?
Do you have any advice for young engineers starting in their careers?
Here Are Some of the Key Points Discussed About How Engineers Can Help Preserve and Protect Historic Landmark Structures:
To enjoy working on projects that preserve historic structures, you must enjoy the history behind the structure. Seeing the old drawings that were done more than 100 years ago is quite an experience. Looking at how much time the workers put into making all the details in the building is very enjoyable.
Many things must be done when starting projects that preserve historic structures. All the drawings that you can find of the building must be gathered. There could also be photos of the early construction of some of the historic landmark structures that can also be a great help in understanding their cladding systems. Tour the structures thoroughly and take as many photos of them as possible. The materials used must be taken into consideration. Pull testing rebar, brick tests, and laser scanning are some of the tests that must be done.
Most historic landmark structures are built using unreinforced brick, nonductile concrete, and an array of heavy brittle materials. The heavy building materials make the structure heavy, and the seismic force is related to how heavy the structure is. Having highly brittle materials and high seismic forces can make it difficult to find a way to get structure in the building to make it work. Very robust systems like concrete can be used, but preserving the historic element that everyone wants to see must always be of utmost importance.
Base isolation is separating the building from the ground laterally. When the ground shakes violently, the isolators filter the vibrations out and the building gets a small fraction of the seismic energy. It reduces the movement and the force that the building experiences.
Base isolation can be a technical task because the historic landmark structures are heavy and brittle. An active jacking method is used by inserting needle beams through a wall that can be individually jacked up to lift the wall and replace the foundation with the isolators under it.
The Memorial Stadium at UC Berkeley was primarily constructed with non-ductile concrete, which made it very brittle. This big, brittle structure is sitting on an active earthquake fault. The exterior wall is the main part of the structure that everyone wanted to preserve, so a new structure was built behind the exterior wall to save and preserve it. Bunker-type structures were built under the parts of the stadium that were on the earthquake fault. It allowed those parts of the building to move in response to what the ground is doing.
Engineers can help preserve and protect historical sites by checking things in the code for historic buildings. Have a mindset of thinking outside the box and doing thi...
TSEC 79: Structural Changes to the 2021 International Building Code
In this episode, we talk to Sandra Hyde and John "Buddy" Showalter about the significant structural changes to the 2021 International Building Code and how they will affect structural engineers. They also talk about mass timber buildings and how they compare to concrete and steel buildings.
Here Are Some of the Questions We Ask Sandra and Buddy:
What is mass timber and how tall can a mass timber building be built?
What are the main fire safety requirements for this type of construction?
Can you describe the research that went into the development of these new code provisions?
What are some of the significant load changes to the 2021 IBC?
What are the changes to structural observation and special inspection, and how will these changes affect structural engineers?
How do mass timber buildings compare to concrete and steel buildings?
What are the changes to concrete, steel, masonry, and wood requirements?
Do you have any final advice for young engineers starting in their careers?
Here Are Some of the Key Points Discussed About the 2021 International Building Code:
Mass timber buildings are the older buildings that have large and heavy timber members inside them. Mass timber buildings are some of the first building types to be in the building codes. Engineered wood products are making it easier to build larger and taller mass timber products. The 2021 IBC now has provisions for three new types of construction that can be built taller and have larger areas
The main fire safety requirements for mass timber construction are passive and active protection. Active protection involves things like installing NFPA 13 sprinkler systems in mass timber buildings that are taller and larger than the existing timber buildings. Passive protection comes in the form of fire-rated gypsum that protects large portions of the mass timber elements.
There are not many 2021 IBC significant load changes. The wind zones must be included in the plans. Hotels with a connected conference center are rated as risk category two, but if the conference center is bigger than the hotel, it will be rated as risk category three. The snow maps are becoming like ASCE 7-16 snow maps.
All risk category three and four buildings now require structural observation. Mass timber now has some special inspections because it is new in construction. There are minor changes to the fire stop and concrete inspections. If problems occur with deep foundation construction, a geotechnical engineer must be brought in to evaluate the situation.
Committees and associations propose code changes, which are followed by a series of hearings. The membership of the ICC then has a final vote on the proposed changes that have gone through the entire process. The new codes are then published in a three-year cycle.
All building material types have their place in various building applications. They have similarities in the sense that the fire protection requirements are comparable. The height and area limits are different for each building material. Mass timber costs less because the construction time, weight, foundations, materials, and the required labor are all greatly reduced. Wood sequesters carbon, which leaves a good environmental message for wood products.
Concrete and steel tolerances are now directly referenced in the code. Cast-in-place concrete is referenced to ACI 117. Precast concrete is referenced to ITG-7-09. Steel is referenced to AISC 358. Wood special design provisions are being updated about the 2021 code.
Engineers must get out onto the job site and see how the design is implemented in the field, the inspections being done, and the issues arising, because it is a valuable part of your growth.
TSEC 78: Transmission Line Design in Structural Engineering
In this episode, we talk to Cody Forell, Structural Design Engineer at Sunflower Electric Power Corporation, about transmission line design and what it is like working as a structural engineer at an electrical utility.
Here Are Some of the Questions We Ask Cody:
What was passing the PE Exam like for you, and what do you hope to accomplish with your PE License?
What is your involvement in transmission line design and what kind of transmission line structure configurations do you work with?
Which factors need to be considered while designing a transmission system?
What are the factors which limit the loading capabilities of transmission lines?
What are Phase-to-phase and Phase-to-ground clearances?
What is aeolian vibration in transmission lines and how does it affect transmission lines?
What roles do substation foundations play in the design process, and how does it affects the clearance requirements?
Do you have any advice for young engineers starting in their careers?
Here Are Some of the Key Points Discussed About Transmission Line Design in Structural Engineering:
The state of Kansas allows engineers to take the PE Exam before they have completed four years of engineering experience. Taking the test early means you will have to complete your four years of engineering experience before you can apply for your PE license.
Transmission lines move electric power from one point to another and connect a network of substations and generating facilities. Three-phase alternating current transmission lines have 3 conductors and static wires. The structures are mostly made of wood or steel, but there are other structure material types available. There are 3 main types of transmission line structures namely, tangent structures, angle structures, and dead-end structures.
Transmission line structures must be strong enough to support the conductors and static wires. The conductors and static wires also have strength properties. Aluminum Conductor Steel Reinforced (ACSR) conductors have external aluminum strands that carry the electrical current and steel core strands help with the strength. The National Electrical Safety Code (NESC) has limits on a conductor and static wire tensions and sags, which forms a big part of the design and analysis. PLS-CADD and PLS-POLE are the programs used for the modeling and analysis of transmission lines.
Phase-to-phase clearance is the clearance that must be maintained between any two conductors on a circuit. Phase-to-ground clearance is the clearance from the conductor to anything besides another conductor. The clearance distances are dependent on the operating voltage of the transmission line.
Aeolian vibration is a high-frequency low amplitude oscillation that is caused by a steady wind perpendicular to the wire. Conductors with high tension are most susceptible to experiencing aeolian vibration. Galloping is the opposite conductor movement, which is a low-frequency high amplitude oscillation, that is caused by freezing rain or sleet combined with a steady crosswind on the conductor. The rain or sleet freezes on the conductor in the shape of an airfoil. The wind then lifts the conductor like an airplane wing causing the conductor to gallop. Dampers are used to mitigate the movement of the conductor. The dampers are weights that are strategically placed on the wire to disrupt a range of vibration frequencies.
Substation foundations consist of drill piers, slabs on grid, or spread footings depending on the equipment it is supporting.
Young engineers should explore intern options to figure out what they like and do not like. Always be prepared and organized so you can take advantage of opportunities that come your way.
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TSEC 77: Top Career Takeaways From Two Successful Engineers
In this episode, Mat and Cara talk about three career takeaways that stood out for them throughout their careers, and how those experiences helped them to grow as engineers.
Here Are Some of the Key Points Discussed About Their Career Takeaways:
Cara’s first career takeaway: If you are a student or an engineer who is pivoting in your career, look for opportunities outside of what you have studied or have been working in. You might be surprised how your previous experiences can help you in other fields, and you might enjoy the other field more than you initially thought you would. Engineering fundamentals span multiple disciplines, especially in civil engineering.
Mat’s first career takeaway: Get good at what you can do technically. Be the best that you can be. Study and try to be as efficient as you can. It will help you endlessly later in your career. When you get to be in a position where you are making decisions, you must know what you are doing technically.
Cara’s second career takeaway: Maintain some sort of mentorship throughout your career journey. Your mentors will always have something new you can learn from and have great advice when you need it. They don’t only give you the confidence to move forward with certain opportunities, but they will also support you if you stop doing it after you realize it is not for you.
Mat’s second career takeaway: Finding mentorship and finding people to support you is very important. You cannot get far in your career without other people helping you. Having people supporting you from different organizations is a good way to get unbiased opinions and advice.
Cara’s third career takeaway: Staying up to date on the latest trends can give you the ability to change the future. You can influence your career and your career path, and become a big asset to the organization that you work for.
Mat’s third career takeaway: Self-reflection is important because it is very easy to get caught up in the career rollercoaster. Self-reflect every few months about what you enjoy about your job, what your long-term goals are, and how you want your life to look in a certain number of years. You do not want to find yourself in a place you do not want to be 10 years down the line because you did not self-reflect regularly.
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About the Hosts
Mathew Picardal, P.E.
Mathew is a licensed engineer, practicing on structural projects in California, with an undergraduate degree from Cal Poly Pomona and an M.S. in Structural Engineering from UC San Diego. He has designed and managed various types of building structures, including residential wood apartment buildings, commercial steel buildings, and concrete parking structures and towers. He also hosts the new YouTube channel “Structural Engineering Life,” through which he promotes the structural engineering profession to engineering students who are not familiar with the industry perspective.
Cara Green, P.E.
Cara Green, P.E., works in Hilti’s North American headquarters as the Structural Engineering Trade Manager for the U.S. and Canada. She is currently an EIT in Texas and received her bachelor’s in civil engineering from the University of Alabama in Huntsville.
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TSEC 76: Mass Timber in Structural Engineering: Seeing the Bigger Picture
In this episode, we talk to Michelle Kam-Biron, P.E., SE, F. SEAOC, SECB, mass timber specialist at Structurlam, about mass timber in structural engineering and how engineers can become more involved in the industry.
Here Are Some of the Questions We Ask Michelle:
What does a career in mass timber entail, and what should people considering a career in mass timber know about it?
What would you say is the secret to being successful in the industry with the rise of mass timber?
How can engineers become more involved in the industry and support future engineers?
What are a few innovative projects that you have worked on in the past, and some of the new uses of mass timber in structural engineering?
What are some of the ways that engineers can gain more information on mass timber?
Do you have any final advice for structural engineers considering working more with mass timber?
Here Are Some of the Key Points Discussed About Mass Timber in Structural Engineering:
Many universities do not offer wood design engineering courses. It could be difficult for you to learn about basic wood engineering if it is not offered at your university. A place like the American Wood Council, Woodworks, and APA do offer training, but it is targeted more for continuing education. You need the foundation in wood design to get into mass timber.
Practicing engineers should have a foundation in wood design but must also gather more knowledge from the American Wood Council, Woodworks, and APA. Consider getting a specialty engineer to assist the engineer on record with mass timber. It will ensure that the project is designed correctly, and the engineer on record will also learn more about mass timber design.
Wood construction was limited to six floors, but with the code change in 2021, wood construction can now go to 18 floors depending on occupancy protection. The three new types of heavy timber type IV-HT construction do not require any additional fire resistance.
The secret to being successful in the industry with the rise of mass timber is to talk to people who have experience in mass timber engineering. Get your training online but talking to and connecting with people is where you will get the secret ingredient. Joining a committee like the SEASCM where they talk about mass timber issues, will also be a great benefit to your company.
Mass timber designers must connect with manufacturers to ensure they optimize the wood or fiber in their projects. Bringing in the manufacturer early in the design phase will help to identify the grid and optimize the framing based on what the manufacturer can provide.
I am currently working on a hybrid structure that is the only mass timber project in Chinatown, Los Angeles. It is a large office building that is two floors higher than the surrounding buildings. It is a hybrid project because it has CLT panels on steel construction.
Engineers can gain more information on mass timber by visiting manufacturing facilities. It is a good learning experience for structural engineers to see the manufacturing process and talk to the people manufacturing the wood and creating the fabrication drawings.
The International Code Council (ICC) has a webinar series on mass timber specifically to the 2021 code and a publication that covers the changes that occurred in the mass timber segments of the 2021 code.
The Timber Strong Design-Build Competition is a great way for students to learn about wood construction. The students must design a wood structure, purchase the materials, make a team, and then build the structure. They gain experience in designing the wood structure, sourcing the materials, and then building the wood structure.
Engineers considering working with mass timber must have an open mind and ask...
TSEC 75: Engineering Safer Skies With Performance-Based Seismic Design
In this episode, we talk to Joe Maffei, SE, Ph.D., LEED AP, an internationally recognized expert on the seismic evaluation, design, and retrofitting of structures, about the SFO Air Traffic Control Tower, for which his company, Maffei Structural Engineering, also received an excellence award. He talks about their involvement in the project and how they designed the first-ever control tower that used a nonlinear analysis performance-based seismic design.
Here Are Some of the Questions We Ask Joe:
The SFO tower was the first-ever control tower that used a nonlinear analysis performance-based seismic design. Can you please talk to us about that and explain what the difference is between linear and nonlinear analysis?
In prescriptive design, how much new research do you adapt into your designs?
What are some of the other unique aspects of this structure?
What unique approach did the tower have to address overturning?
How did you define the seismic objective for the project?
What did you learn about nonlinear analysis while working on this project?
How would ground motion affect a structure like this?
What are concrete core wall high-rises and what do you think engineers should know about them?
Do you have any advice for engineers considering a career in structural engineering?
Here Are Some of the Key Points Discussed About Engineering Safer Skies With Performance-Based Seismic Design:
Non-linear analysis means that you take advantage of the parts of the building code that allow alternate methods with equivalent performance. It is a win-win situation because all the extra analysis evaluations being done ensure more reliable performance in a seismic event and can help reduce the costs of a project.
It takes a while for the technology transfer to happen to prescriptive designs. From real projects you get rules, those rules then become guidelines, and then only later start to make their way into the building code. Extensive analysis and research are done on many different scenarios before the guidelines are added to the building codes for specific areas.
The SFO tower has many unique aspects. Vertical post-tensioning has been used in seismic systems for many years. It vastly reduces the displacement of the structure after a seismic event. It is achieved through unbonded vertical post-tensioning, which was used in the SFO tower performance-based seismic design. The tower was designed for functioning in high wind and seismic events and is situated close to the San Andreas Fault on soft soil. Mid-height seismic isolation was implemented, which lets the top move with respect to the tower. It has a concrete core structure with vertical post-tensioning. A criterion was made for story drifts to reduce shear deformation. The tower has a three-story office building at its base that had to be incorporated into the design. It was done by eradiating four spokes from the tower into the roof of the building. The spokes were made from buckling restraint bases that are designed for controlled non-linear behavior.
With a performance-based seismic design, you are required to do both the linear and non-linear analysis so that the non-linear design can be compared to the linear design to see that the non-linear design's performance is on par with the linear design.
Non-linear analysis tells you much more than linear analysis, but it is not perfect. Sometimes there are things in the non-linear analysis that must be examined to ensure they are realistic. You must know exactly what the yielding is, take control, and tell the structure what to do, as opposed to it being a matter of chance.
If you are applying to graduate school, ask structural engineering professors about interactions they have with practicing structural engin...