Annie Kao

About Annie Kao

Annie Kao, PE is a senior field engineer for Simpson Strong-Tie, where she connects and educates engineers, architects, building officials, and contractors on design and product solutions for wood, concrete, steel, and masonry construction in the Southwest region of the US. Prior to joining Simpson Strong-Tie in 2006, she worked as a project engineer on commercial and multi-family projects for a structural engineering consulting firm in Irvine, CA. She is currently serving as co-chair for the 2016 SEAOSC Summit, an annual event to promote building resiliency in Southern California. She is a registered PE in California and earned her BS from Harvey Mudd College and MS from UC Berkeley.

Q&A About CFS Designer™ Software

I recently had the pleasure of presenting a webinar with Rob Madsen, PE, of Devco Engineering on our CFS Designer software, “Increase Productivity in Your Cold-Formed Steel Design Projects.” The webinar took place on September 28, and a recording is available online on our training website for anyone who wasn’t able to join us. Viewing the recording (and completing the associated test) qualifies for continuing education units and professional development hours. The webinar covers how to use the CFS Designer software to design complex loading conditions for beams, wall studs, walls with openings, and stacked walls using cold-formed steel studs, tracks, built-up sections, and even custom shapes. We received some excellent questions during the webinar, but due to time constraints were only able to answer a few during the live webinar. Rob and I did get a chance to answer all the questions in a Q&A document from which I’d like to share some excerpts. The complete Q&A webinar list can be accessed here, or through the online recording.

Where can I download the CFS Designer program?

Please visit strongtie.com/cfsdesigner to download a free 14-day trial version of the software or to purchase a license. Webinar attendees should check their email for a special discount code. There are different licensing options based on the number of users.

Is the price for the software an annual subscription fee or is it a one-time purchase price? Is there any maintenance cost?

There’s no annual maintenance fee or subscription fee. You pay only a one-time fee for the license. CFS Designer is based on an update-and-upgrade program. All updates to the program are free to licensed users and occur every few months to correct software bugs and add functionality. Upgrades, which include new design modules and updated code information, will require an additional purchase. Simpson Strong-Tie anticipates releasing upgrades on a two-year cycle, and the next upgrade has a projected release of early 2019. If you elect not to upgrade your version of the software, the current version you have will still work, but will not have the new upgrade features.

Is CFS Designer fully compliant with AISI S100-12?

CFS Designer is compliant with AISI S100-12. You can also access earlier versions of the AISI Specification in CFS Designer by selecting Project Settings/Code and selecting the version.

Are load inputs in ASD or LRFD? Do the load combination factors have to be applied prior to entering loads in the program? Should factored or unfactored loads be input?

The current software is all in ASD (allowable strength design). The next upgrade version will feature up to eight stories of stacked x-bracing and shearwalls, which will be in LRFD. Everything else will be in ASD. The stacked x-brace and shearwalls will be LRFD because of the ACI requirements for concrete. We will also make it much more clear in this version which input is ASD and which is LRFD.

What is a web stiffener? How would you use one at a stud, header, or jamb?

A web stiffener is typically a stud or track piece that is used to support the wall stud or joist from crippling at a point load or bearing support. There are different ways to design a stiffener at different locations. Some examples include using a cut piece of stud or track attached to the stud or using a clip attached to the beam. Essentially, a web stiffener is a member that is added to the stud to help stiffen the stud from crippling.

Does this program take into consideration the cold work of forming in the design/analysis?

Yes, per AISI the program’s Project Settings default is to include cold work of forming in the design and analysis.

We generally try to size our cold-formed members to avoid the need for web stiffeners, just to save on construction and material costs. Something that helps quite a bit with the web bending and crippling calc is the bearing length. Are there code requirements for bearing lengths, or is this simply based on how much bearing we anticipate the member to have at its supports?

There are no specific code requirements for calculating bearing length for web crippling; the calculation is usually based on engineering judgment and connection detailing to determine how much bearing there will be at the support. A reasonable bearing length may be the length of the connection clip you are using for the attachment. Since web crippling is a “bearing” phenomenon, where attachments are made through the web, provided the attachment is not isolated near a flange, you may not need to consider web crippling. For stud-to-track types of connections, it’s common to use the track leg length as the bearing length.

Does this software give any stud-to-stud connection calculation like stud tearing and shearing? Checks?

The studs are designed per the AISI code for shear, moment, web crippling, axial load, and the related code-required interactions. Net-section rupture near connections is not checked by the CFS Designer™ software.

What is the difference between flexural bracing and axial bracing?

Flexural bracing is bracing that is used to increase the moment capacity of the stud, and axial bracing is bracing that is used to increase the axial capacity of the stud. These might be the same for your design, but we have given the user the ability to designate different spacings.

Do you have recommendations for how to properly terminate bridging at the end of the wall?

We agree that termination of bracing is often overlooked by engineers and should definitely be considered in design. Accumulation of bridging forces should also be considered. AISI S100-12, D3.3 and AISI S240-15 D3.4 provide methods of estimating brace forces. Simpson Strong-Tie has provided some suggestion in our cold-formed steel typical details sheets that show our SFC clip as one method to properly terminate a line of bridging.

Can the kicker connection be used on the underside of concrete fill over metal deck?

Yes! The SJC kicker connection has been tested and code listed to support diagonal brace loads. Simpson Strong-Tie has also provided a wide range of anchorage solutions for the kicker application that include connecting to the underside of concrete fill over metal deck. Concrete over metal deck may be normal weight or sand-lightweight with f’c of 3,000 psi minimum and 2.5″ minimum slab height above upper flute. Minimum deck flute height is 1.5″ (distance from top flute to bottom flute). Please visit strongtie.com for more information and design tables.

Why do some engineers use steel posts welded to a base plate for low wall applications?

For walls that are not top-supported, some Designers use a welded steel post at a certain spacing and infill with cold-formed steel studs and a top track. Simpson Strong-Tie has developed an innovative moment-capacity connection called the RCKW rigid kneewall kit, which can support many of these same conditions using cold-formed steel studs and eliminate the need for structural steel.

Are there any plans to expand the software capabilities?

We have a long list of enhancements and additions for the software and will continue to make the software more efficient, more user friendly, and with additional design capabilities.

Thanks again to everyone who joined us for the webinar and sent us questions. For complete information regarding specific products suitable to your unique situation or condition, please visit strongtie.com/cfs or call your local Simpson Strong-Tie cold-formed steel specialist at (800) 999-5099.

The Top 5 Helpful Tips for Using CFS Designer™ to Optimize Your Workflows

Back in April of last year, I had the opportunity to show how our new CFS Designer software  could help structural engineers “go lean” in their design process by eliminating repetitive tasks (while still meeting required design standards, of course!). Since then, I’ve had the opportunity to visit with hundreds of engineers in person to teach them about CFS Designer and how it can help them improve and optimize their workflows. As a power user of the software, I want to share my top tips for letting CFS Designer help you save the maximum amount of time.

Tip #1. You need to create only one design file for each project.
CFS Designer has to generate lots of code-compliant designs quickly, but that doesn’t mean you need to end up with dozens of unrecognizable file names on your desktop. The software includes a very handy WorkSpace area in the lower left-hand area of the screen that enables you to save all your wall, jamb, header, and general interaction designs in a single project space. This means that you will be saving only ONE file for each project, a feature that can save you a lot of confusion over time.

Figure 1. The orange box is highlighting the file name (which doubles as the Project Name on the summary reports), which shows up at the top of the WorkSpace area. In this example, I’ve added just one beam/stud model for the sake of simplicity.

Tip #2. Quickly duplicate similar wall sections or design types by right-clicking on the model name in the WorkSpace.
On cold-formed steel projects, there are often very similar wall sections or jambs that you’ll need to design. They may have slightly different parapet heights, different loading or different wall widths. Instead of starting from scratch and creating a new section every time, CFS Designer allows you to right-click on any existing design. The right-click action brings up a “Duplicate” pop-up which lets you create an identical model in your WorkSpace. You then have the ability to change the model name, make slight modifications, and then re-save your project to see it show up as a new model in the WorkSpace area.

Figure 2. Here’s where to right-click in order to get the “Duplicate” pop-up to appear.

Tip #3. Expand the “Member Forces” and “Connection Summary” sub-menus in the Beam Design module to get real-time updates of the reaction loads, member stresses and connection solutions.
A critical area of member design is the reaction points, because it doesn’t really matter whether your cold-formed steel member is adequately designed if the connection points don’t have a solution. Many engineers I met with thought they had to click on the “Summary Report” button every time they wanted to know the reaction forces, waiting anywhere from 10 to 15 seconds for the PDF file to load and then having to scroll through to find the correct section. Thankfully, there’s a much quicker way to view the reactions. CFS Designer instantly updates the reaction values on the design screen, but the onscreen menus that have this useful information need to be opened up first. Within the Beam Design module, click on the small down arrows to the left of “Member Forces” and “Connection Summary,” and that will expand these two useful sections and display the design information without your having to wait and generate the output. On a related note, another useful area to keep an eye on during design is the very bottom of the screen, where green text will let you know when your maximum member stress and web crippling check are compliant, red text will alert you if your member design is insufficient, and the deflection ratio limit is always displayed.

Figure 3. Here’s where to find the collapsed “Member Forces” and “Connection Summary” menus.

Figure 4. Click on the arrows to the left of the menu titles to see your important design information in detail.

Tip #4. Use the “WorkSpace Report” button for a one-click method of combining ALL the individual summary pages into a single PDF file.
After you’re done generating all your different models and saving them to your WorkSpace, you’re probably going to want to generate the output files you can print and add to your calculation package for submittal. One engineer I met with a couple of years ago told me that this was the most dreaded step because it meant she had to open each model, click on the “Summary Report” button, wait those 10–15 seconds for the PDF file to generate, and then print it out or save it. For large projects, this would need to occur 20–30 times – yikes! Thankfully, a huge part of the development of CFS Designer relies on feedback such as this to help Simpson Strong-Tie continuously improve the program’s functionality. The latest version of CFS Designer introduces a “WorkSpace Report” button, which takes a single click to create all of the summary reports for each model type, saved in a single PDF file.

Figure 5. Be sure to use the “WorkSpace Report” button to save yourself a ton of time generating all your printable output.

Tip #5. Use the onscreen tip pop-ups. Small gray question mark icons are strategically placed throughout CFS Designer to offer helpful tips and tricks for specific input boxes.
Structural engineers are expected to know a lot, but it isn’t always necessary to remember all the details if you know where to look them up. Because the information requested by some of the input boxes may not be completely self-evident, we built in some handy pop-up tips to help out. A small gray circle with a question mark inside makes its appearance next to input boxes. Hovering your mouse over one of these question marks will cause an info box to appear, letting you know what information is required, what code section to reference, or what design methodology is being used. I have found these pop-up tips to be immensely helpful, especially in conjunction with the program’s User’s Manual (located under the Help menu, at the top of the program).

Figure 6. I got this box to pop up by hovering over the question mark next to the “Load Modifiers” section of the Beam Input module. If you search for “Load Modifier” in the User’s Manual, it will direct you to the relevant AISI code section.

I’ve had fun sharing some of my top tips with everyone today, but there is a great opportunity coming up to learn even more about our CFS Designer software from one of the original developers of the software. Join me and Rob Madsen, P.E., Senior Project Engineer from Devco Engineering, for a one-hour live demo of the software and connection solutions. Rob has been described as one of the premier structural engineers in the cold-formed steel design arena, and he will walk you through detailed wall stud, jamb, header and stacked wall design examples using CFS Designer. I’ll be presenting on the innovative, tested and code-listed product solutions that Designers can use to save time in addressing the critical connection points in CFS design. We hope you can join us for the live demo, but if you have other commitments at that time, a recording of the webinar will be made available on our website for your viewing convenience. The course will also earn professional development hours (PDHs) and continuing education units (CEUs) for any folks who need credits to renew their professional licenses.

Bonus Tip: Sign up for our upcoming CFS Designer™ webinar on Thursday, September 28!

Further Reading

For additional information or articles of interest, check out these available resources:

    • AISIStandards – A free download of all the cold-formed steel framing standards adopted by the 2015 International Building Code.

 

    • CFSEI – The Cold-Formed Steel Engineering Institute, an incredibly useful technical and professional resource for Designers of cold-formed steel structures, with a huge library of technical notes.

 

 

 

5 Steps to a Successful Soft-Story Retrofit

Last year, I gave a presentation at the annual National Council of Structural Engineers Associations (NCSEA) Summit in Orlando, Florida, titled “Becoming a Trusted Advisor: Communication and Selling Skills for Structural Engineers.” As this was a summit for the leaders of the structural engineers associations from across the country, I wasn’t sure how many people would find it valuable to spend their time learning about a very nontechnical topic. To my surprise and delight, the seminar ended up being standing-room only, and I was able to field some great questions from the audience about how they could improve their selling and communication skills. In the many conversations I had with the conference attendees after my presentation, the common theme was that engineers felt they needed more soft-skills training in order to better serve their clients. The problem, however, was finding the time to do so when faced with the daily grind of design work.

Structural Engineers In a Training for Seismic Retrofits

Presenting at the NCSEA Summit, I’m the tiny person in upper left hand corner.

When I started my first job as a design engineer at a structural engineering consulting firm straight out of school, I was very focused on improving and expanding my technical expertise. Whenever possible, I would attend building-code seminars, design reviews and new product solution presentations, all in an effort to learn more about structural engineering. What I found as I progressed through my career, however, was that no matter how much I learned or how hardworking I was, it didn’t really matter if I couldn’t successfully convey my knowledge or ideas to the person who really mattered most: the client.

Contractors discussing building plans with an engineer.

Contractors discussing building plans with an engineer.

How can an engineer be most effective in explaining a proposed action or solution to a client? You have to be able to effectively sell your idea by understanding the needs of your client as well as any reasons for hesitation. The importance of effective communication and persuasion is probably intuitive to anyone who’s been on the sales side of the business, but not something that occurs naturally to data-driven folks like engineers. As a result of recent legislation in California, however, structural engineers are starting to be inundated with questions from a group of folks who have suddenly found themselves responsible for seismically upgrading their properties: apartment building owners in San Francisco and Los Angeles.

Imagine for a moment that you are a building owner who has received a soft-story retrofit notice under the City of Los Angeles’ Ordinance 183893; you have zero knowledge of structural engineering or what this term “soft-story” even means. Who will be your trusted advisor to help you sort it out? The City of Los Angeles Department of Building and Safety (LADBS) has put together a helpful mandatory ordinance website that explains the programs and also offers an FAQ for building owners that lets them know the first step in the process: hire an engineer or architect licensed in the state of California to evaluate the building.

Simpson Strong-Tie Structural Engineer Annie Kao at a jobsite.

Checking out some soft story buildings in Los Angeles. The Los Angeles Times has a great map tool.

I’ve had the opportunity to be the first point of contact for a building owner after they received a mandatory notice, because it turns out some relatives own an apartment building with soft-story tuck-under parking. Panicked by the notice, they called me looking to understand why they were being forced to retrofit a building that “never had any problems in the past.” They were worried they would lose rent money due to tenants needing to relocate, worried about how to meet the requirements of the ordinance and, most importantly, worried about how much it was going to cost them. What they really wanted was a simple, straightforward answer to their questions, and I did my best to explain the necessity behind retrofitting these vulnerable buildings and give an estimated time frame and cost that I had learned from attending the first Los Angeles Retrofit Resource Fair in April 2016. With close to 18,000 buildings in the cities of San Francisco and Los Angeles alone that have been classified as “soft-story,” this equates to quite a number of building owners who will have similar questions and be searching for answers.

To help provide an additional resource, Simpson Strong-Tie will be hosting a webinar for building owners in the Los Angeles area who have received a mandatory soft-story retrofit notice. Jeff Ellis and I will be covering “5 Steps to a Successful Retrofit” and helping to set a clear project path for building owners. The five steps that Simpson Strong-Tie will be recommending are:

  1. Understanding the Seismic Retrofit Mandate
  2. Partnering with Design Professionals
  3. Submitting Building Plans with the Right Retrofit Product Solutions
  4. Communicating with Your Building Tenants
  5. Completing Your Soft-Story Retrofit

We encourage you to invite any clients or potential clients to attend this informative webinar, which will lay the foundation for great communication between the two of you. As part of the webinar, we will be asking the building owners for their comments, questions and feedback so we can better understand what information they need to make informed decisions, and we will be sure to share these with the structural engineering community in a future post. By working together to support better communication and understanding among all stakeholders in retrofit projects, we will be well on our way to creating stronger and more resilient communities!

For additional information or articles of interest, there are several resources available:

SEAOSC Safer Cities Survey Results: How Are We Building Strength and Transparency in Our Communities?

Back in January, employees at Simpson were given the opportunity to learn more about the 401K retirement and investment plan. The big takeaways from my training session were a) save as much as you can as early as you can in life and b) use asset allocation to diversify your portfolio and avoid too much risk. Now, I’m not a big risk taker in general, so I dutifully picked a good blend of stocks and bonds with a range of low to high risk. It seems like a pretty sound strategy and it made me think of all the other ways I tend to minimize risk in my life. When I head to a restaurant, for example, I almost instinctively look for the county health grade sign in the window. When my husband and I went to go buy a new family car a couple years ago, I remember searching the National Highway Traffic Safety Administration (NHTSA) website for crash test ratings. Even when I’m doing something as mundane as having a snack, I will invariably flip over the Twinkie package to see just how many grams of fat are lurking inside (almost 5 per serving!). For all the rankings and information available to the general public for restaurants, cars and snacks, there isn’t much, if any, information to help us know if we’re minimizing our risk for one of the most common activities we do almost every day: walking into a building.

Risk level knob positioned on medium position, white background and orange light. 3D illustration concept for business security management.

 

Now before you accuse me of being overly dramatic about such a trivial activity, here’s some food for thought: research has shown that Americans spend approximately 90% of their day inside a building. That’s over 21 hours a day! Have you ever once thought to yourself, “I wonder if this building is safe? Would this building be able to withstand an earthquake or high wind event?” Or how about even taking a step back and asking, “Are there any buildings that are already known to be potentially vulnerable or unsafe, and has my city done anything to identify them?” Unfortunately, that kind of information about a city’s building stock is not usually readily available, but some in the community, including structural engineers, are working to change that.

Los Angeles skyline on a partly cloudy day with a row of palm trees in the foreground.

 

The charge is being led in California, a.k.a. Earthquake Country, where structural engineers are teaming up with cities to help identify buildings with known seismic vulnerabilities and provide input on seismic retrofit ordinances. Structural engineers have learned quite a bit about how buildings behave through observing building performance after major earthquakes, and building codes have been revised to address issues accordingly. However, according to the US Green Building Council, “…the annual replacement rate of buildings (the percent of the total building stock newly constructed or majorly renovated each year) has historically been about 2%, and during the economic recession and subsequent years, it’s been much lower.” This means that there are a lot of older buildings out there that have not been built to current building codes and were not designed with modern engineering knowledge.

Several cities in California have enacted mandatory seismic retrofit ordinances that require the strengthening of some types of known vulnerable buildings, but no state or nation-wide program currently exists. The Structural Engineers Association of Southern California (SEAOSC) recently decided to launch a study of which jurisdictions in the southern California region have started to take the steps necessary to enact critical building ordinances. According to SEAOSC President Jeff Ellis, S.E., “In order to develop an effective strategy to improve the safety and resilience of our communities, it is critical to benchmark building performance policies currently in place. For southern California, this benchmarking includes recognizing which building types are most vulnerable to collapse in earthquakes, and understanding whether or not there are programs in place to decrease risk and improve recovery time.” These results were presented in SEAOSC’s Safer Cities Survey, in partnership with the Dr. Lucy Jones Center for Science and Society and sponsored by Simpson Strong-Tie.

safer-cities-ca

This groundbreaking report is the first comprehensive look at what critical policies have been implemented in the region of the United States with the highest risk of earthquake damage. According to the Los Angeles Times, the survey “found that most local governments in the region have done nothing to mandate retrofits of important building types known to be at risk, such as concrete and wooden apartment buildings.”

The Safer Cities Survey highlights how the high population density of the SoCal region coupled with the numerous earthquake faults and aging buildings is an issue that needs to be addressed by all jurisdictions as soon as possible. An excerpt from the survey covers in detail why this issue is so important:

No building code is retroactive; a building is as strong as the building code that was in place when the building was built. When an earthquake in one location exposes a weakness in a type of building, the code is changed to prevent further construction of buildings with that weakness, but it does not make those buildings in other locations disappear. For example, in Los Angeles, the strongest earthquake shaking has only been experienced in the northern parts of the San Fernando Valley in 1971 and 1994 (Jones, 2015). In San Bernardino, a city near the intersection of the two most active faults in southern California where some of the strongest shaking is expected, the last time strong shaking was experienced was in 1899. Most buildings in southern California have only experienced relatively low levels of shaking and many hidden (and not so hidden) vulnerabilities await discovery in the next earthquake.

 The prevalence of the older, seismically vulnerable buildings varies across southern California. Some new communities, incorporated in the last twenty years, may have no vulnerable buildings at all. Much of Los Angeles County and the central areas of the other counties may have very old buildings in their original downtown that could be very dangerous in an earthquake, surrounded by other seismically vulnerable buildings constructed in the building booms of the 1950s and 1960s. Building codes do have provisions to require upgrading of the building structure when a building undergoes a significant alteration or when the use of it changes significantly (e.g., a warehouse gets converted to office or living space). Seismic upgrades can require changes to the fundamental structure of the building. Significantly for a city, many buildings never undergo a change that would trigger an upgrade. Consequently, known vulnerable buildings exist in many cities, waiting to kill or injure citizens, pose risks to neighboring buildings, and increase recovery time when a nearby earthquake strikes.

1994-northridge

The survey also serves as a valuable reference in being able to identify and understand what the known vulnerable buildings types are:

  1. Unreinforced masonry buildings: brick or masonry block buildings with no internal steel reinforcement — susceptible to collapse
  2. Wood-frame buildings with raised foundations: single-family homes not properly anchored to the foundation and/or built with a crawl space under the first floor — possible collapse of crawl space cripple walls or sliding off foundation
  3. Tilt-up concrete buildings: concrete walls connected to a wood roof — possible roof-to-wall connection failures leading to roof collapse
  4. Non-ductile reinforced concrete buildings: concrete buildings with insufficient steel reinforcement — susceptible to cracking and damage
  5. Soft first-story buildings: buildings with large openings in the first floor walls, typically for a garage — susceptible to collapse of the first story
  6. Pre-1994 steel moment frame buildings: steel frame buildings built before the 1994 Northridge earthquake with connections — susceptible to cracking leading to potential collapse

1933-earthquake-shot

Along with the comprehensive list of potentially dangerous buildings, the survey also offers key recommendations on how cities can directly address these hazards and reduce potential risks due to earthquakes. As a good starting point, the survey recommends having “…an active or planned program to assess the building inventory to gauge the number and locations of potentially vulnerable buildings…is one of the first steps in developing appropriate and prioritized risk mitigation and resilience strategies.

Economic costs can be substantial for businesses whose buildings have been affected by an earthquake. After a major seismic event, a structure needs to be cleared by the building department as safe before it can be reoccupied, and it will generally receive a green (safe), yellow (moderately damaged) or red (dangerous) tag.  A typical yellow-tagged building could take up to two months to be inspected, repaired and then cleared, meaning an enormous absence of income for businesses. The survey offers a strategy for getting businesses up and running quickly after an earthquake, in order to minimize such losses. The Safer Cities Survey recommends that cities adopt a “Back-to-Business” or “Building Re-Occupancy” program, which would “create partnerships between private parties and the City to allow rapid review of buildings in concert with City safety assessments…Back-to-Business programs…[allow] private parties to activate pre-qualified assessment teams, who became familiar with specific buildings to shorten evaluation time [and] support city inspections.

oes-inspectors-program

Basically, a program like this would allow a property owner to work with a structural engineer before an earthquake occurs. This way, the engineer is familiar with the building’s layout and potential risks, and can plan for addressing any potential damage. Having a program like this in place can dramatically shorten the recovery time for a business, from two months down to perhaps two weeks. Several cities have already adopted these types of programs, including San Francisco and Glendale, and it showed up as a component of Los Angeles’ Resilience by Design report.

Ultimately, the survey found that only a handful of cities have adopted any retrofit ordinance, but many cities indicated they were interested in learning more about how they could get started on the process. As a result, SEAOSC has launched a Safer Cities Advisory Program, which offers expert technical advice for any city looking to enact building retrofit ordinances and programs. This collaboration will hopefully help increase the momentum of strengthening southern California so that it can rebound more quickly from the next “Big One.”

We all want to minimize the risk in our lives, so let’s support our local structural engineering associations and building departments in exploring and enacting seismic building ordinances that benefit the entire community.

For additional information or articles of interest, please visit:

Get There Quicker! How CFS Designer Can Help Speed Up Your Design Process

Did you know that Simpson Strong-Tie is celebrating its 60th birthday this year? We started out with one punch press and the ability to bend light-gauge steel. Then, one Sunday evening in the summer of 1956, Barclay Simpson’s doorbell rang and a request for our first joist hanger led us into the wood connector business. Since then, we’ve continued to grow that business by focusing on our engineering, research and development efforts. Some might say that nowadays we’re an engineering company that also happens to manufacture products, as evidenced by our focus on developing technology tools over the past few years such as web calculators, an updated website and design software. Our focus on technology, however, is really another aspect of our continued commitment to excellence in manufacturing and our application of the tenets of lean manufacturing.

Many of you may already be familiar with the idea of lean manufacturing made famous by Toyota in the early 2000s, along with the principles of continual improvement and respect for people. The concept of continual improvement is based on the idea that you can always make small changes to improve your processes and products. Although they were established in a manufacturing setting, these ideals ring very true for engineering as well; eliminate steps in your design process that don’t add any value to the final project and always be on the lookout for tools or techniques that can speed up your process. Thinking lean isn’t about cutting corners to get your result faster, it’s about mindfully getting rid of the steps that aren’t helping you and finding better ways of doing everyday tasks.

As structural engineers, we can find ourselves working on a variety of projects that lead us to perform repetitive calculations to check different conditions, such as varying parapet heights on the exterior of a building, or we may find ourselves working with an unfamiliar material, such as light-gauge or cold-formed steel (CFS), where we have to take some time away from design to review reference materials such as AISI S200-12 North American Standard for Cold-Formed Steel Framing. Wouldn’t it be great if there were a design tool that could help you complete your light-gauge projects more quickly, in complete compliance with current building codes?

It turns out that Simpson Strong-Tie offers a design tool called CFS Designer™ to help structural engineers improve their project design flow. This program gives engineers the ability to design light-gauge stud and track members with complex beam loading and span conditions according to building code specifications. What does that actually mean, though? Allow me to illustrate with an example of a design project.

Let’s say you’re designing a building and part of your scope is the exterior wall framing, or “skin” of the building. You probably get sent some architectural plans that look something like this:

Figure 1. Sample building elevation with section marks.

Figure 1. Sample building elevation with section marks.

The architectural elevations will have wall section marks indicated for different framing situations. Two sample wall sections are shown in Figure 2.

Figure 2. Sample building wall sections.

Figure 2. Sample building wall sections.

This building has several different wall section types that include door and window locations, varying parapet heights, diverse finish materials that need to meet different deflection criteria, and different connection points back to the base building. The traditional design calculation that you would need to run for one wall section might begin with a loading diagram similar to Figure 3 below.

Figure 3. Sample calculation of wall stud loading diagram.

Figure 3. Sample calculation of wall stud loading diagram.

Once you have your loading diagram generated, you would need to use reference load tables or a computer analysis program to solve for the axial and moment demands, the reactions at the pinned supports, and the member deflections. 

After you determine the demand loads, you would then need to select a CFS member with sufficient properties, and you may need to iterate a few times to find a solution that meets the load and deflection parameters. After you’ve selected a member with the right width, gauge and steel strength, you’ll need to select an angle clip that can handle the demand loads, as well as fasteners to connect the clip to the CFS stud and to the base building. You would also need to also check the member design to ensure that it complies with bridging or bracing requirements per AISI. Then, after all that, you’d have to repeat the process again for all of the wall section types for your project.

Figure 4. Hmm, CFS design would sure be a lot easier if buildings were just huge windowless boxes…

Figure 4. Hmm, CFS design would sure be a lot easier if buildings were just huge windowless boxes…

Just writing out that whole process took some time, and you can imagine that actually running the calculations takes quite a bit longer. I think we can all agree that the design process we’ve outlined is time-consuming, and here’s where using CFS Designer™ to streamline your design process can really help.

CFS Designer is a structural engineering design program that can automate many of the manual steps that are required in the design process. It has an easy-to-understand graphical user interface that allows you to input your project parameters within a variety of design modules from walls and beams, jambs and headers, X-brace walls, shearwalls, floor joists, and roof rafters. The program also enables the design of single stud or track members, built-up box-sections, back-to-back sections, and nested stud or track sections. Figure 5 shows an example of how you would input the same stud we looked at before into the program.

Figure 5. CFS Designer™ user interface for wall stud design.

Figure 5. CFS Designer™ user interface for wall stud design.

The program will generate the loading diagrams and complete calculation package for all of these different situations. And along with checking the member properties and deflection limits, CFS Designer will also check bridging and bracing requirements and provide connector solutions for the studs using tested and code-listed Simpson Strong-Tie products. Figure 6 shows an example of the summary output you would receive.

Figure 6. The comprehensive summary output page that covers the complete member design down to the bracing and connection solutions.

Figure 6. The comprehensive summary output page that covers the complete member design down to the bracing and connection solutions.

One unique part of the output is toward the center of the second page, under the heading “Simpson Strong-Tie Connectors.” This section summarizes the tension and compression loads at each reaction point and then shows a connector solution (such as the SCB45.5) along with the number of screws to the stud and the number of #12 sheet-metal screws to anchor back to the base building. Simpson Strong-Tie has developed and tested a full array of connectors specifically for CFS curtain-wall construction as well as for interior tenant improvement framing, which allows designers to select a connection clip straight out of a catalog without needing to calculate their own designs per the code. It’s just another way we’re helping you to get a little leaner!

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Figure 7. A typical SCB/MSCB bypass framing slide-clip connector showing directional loading along with the table of allowable connector loads.

Figure 7. A typical SCB/MSCB bypass framing slide-clip connector showing directional loading along with the table of allowable connector loads.

The last part of the output shown in Figure 6 is titled “Simpson Strong-Tie Wall Stud Bridging Connectors.” It checks the bridging and bracing requirements per AISI S100 and selects a SUBH bridging connector, an innovative bridging solution developed by Simpson Strong-Tie that snaps into place and achieves design loads while only requiring one #10 screw to connect for 75% of applications.

Figure 8. A close-up of the SUBH installed (left) and a wall of studs with bridging installed using the LSUBH clips (right).

Figure 8. A close-up of the SUBH installed (left) and a wall of studs with bridging installed using the LSUBH clips (right).

You can download a free trial of CFS Designer™ and give it a test drive to see how much time it can save you on a design project. The trial version has almost full functionality, with the exception of not being able to print the output sheets. You can see purchasing information online, and you should always feel free to contact your local Simpson Strong-Tie engineering department with any questions you may have. I hope you are able to take advantage of this great tool to further improve your everyday design processes. We will be sure to keep you updated on our latest technology tools that help speed up the design process.  If you’re using CFS Designer, we’d like to hear your thoughts about the program. Please share them in the comments below.