What You Need to Know About Differences in Wind-Speed Reporting for Hurricanes

This week’s post was written by Darren Conrad, PE. Engineering Manager, Truss at Simpson Strong-Tie.

With Hurricane Irma wrapping up, the cleanup after Hurricane Harvey’s devastation underway in Houston and more big storms already churning in the Atlantic, it seems like a good time to discuss hurricanes and high wind. There is a great deal of good information out there to help us better understand hurricanes and their impact on people, structures and other property. To improve awareness of wind speeds and their measurement, this article will discuss a commonly misunderstood aspect of hurricane wind-speed reporting.

When a storm is approaching, you will hear meteorologists report wind speeds. They often refer to storm categories. These categories attempt to generalize expected damage to structures based on the wind speed of the storm. The wind speed for a given storm is a measure of the severity of the storm and the danger it poses to life and property. But how do meteorologists determine the wind speed that they are reporting? It seems so concrete and certain, but anyone who has been outside during a storm or windy day knows that wind isn’t constant at any one location over a period of time. It varies continuously in magnitude and direction over time. So how can something so variable be the subject of knowledge that is precise enough to be useful? How do we understand wind-speed measurements and make sure that when comparing them we are doing so in such a way that they are comparable? That is a great question.

The good news is that even though wind is variable, we have a commonly accepted way to measure wind speed and know something about a wind field or event that is occurring at a time and place. This is done by averaging measured wind speeds over specified lengths of time, or picking the highest average wind speed that occurs for a specified averaging interval from a longer period of time. A great resource for understanding how wind speeds are measured and reported can be seen here. From this explanation, it can be seen that a reported wind speed is meaningless without a specified averaging time. The shortest averaging intervals will yield the highest reported wind speeds. The longer averaging times will capture more peaks and lulls and yield lower reported wind speeds. The most common averaging intervals used to report wind speeds are three seconds, one minute and two minutes. Some countries even use a ten-minute averaging interval for reporting wind speeds. So the question arises, which average is correct? And the answer is, none of them and all of them. They are just different ways of looking at measured wind data. That is not very comforting, but one thing we can know is that none of them can be truly interpreted or compared without understanding this idea of averaging time. To make it more confusing, meteorologists and building codes do not use the same averaging interval when reporting or specifying wind speeds. This can lead to misunderstandings.

In general, you will hear meteorologists report sustained wind speeds when covering an approaching hurricane. They might also mix in some peak gusts, but for the most part they focus on sustained wind speeds. Sustained wind speeds for tropical cyclones use a 60-second averaging time. Sustained wind speed is also used by the Saffir-Simpson scale to roughly quantify the likely damage that the wind from a storm might cause typical buildings and other structures. There are criticisms of the accuracy of the Saffir-Simpson scale method, but it is widely used by the public to generalize about the severity of tropical cyclones; therefore, it is likely that the public might and commonly does attempt to compare reported sustained wind speeds to building-code-specified three-second-gust wind speeds to determine if their house or structure will withstand the storm. There is danger in making that comparison.

We need to be careful when comparing the reported sustained wind speed for a storm with the three-second-gust design wind speeds referenced in building codes and design standards. They are not the same and need to be converted before they can be compared for equivalence. After seeing the following example, one could easily see the possibility of the public or a public official comparing the sustained wind speeds reported by the weatherman to the wind speeds used by building codes and design standards and drawing conclusions that may underestimate the force and effect of the storm.

Let’s take a hypothetical situation where a building jurisdiction has adopted a wind speed of 130 mph three-second-gust design wind speed for structures built in that jurisdiction. There are various methods to convert wind speeds between different averaging times, and many factors that may need to be considered when doing that. One method for converting is the Durst method referenced in ASCE 7. Another more recent method recommended by the World Meteorological Organization provides a pretty straightforward conversion between sustained wind speed and three-second-gust wind speeds for near-surface applications. So for the sake of simplicity, we will use it for this example. If we convert a reported sustained wind speed of 130 mph to a three-second-gust average wind speed using this method, it equates to a three-second-gust wind speed for Off-Sea of 160 mph (Off-Sea is appropriate for an approaching hurricane). The adopted130 mph three-second-gust wind speed converts to 105 mph sustained wind speed. This difference could lead individuals in the path of the storm to underestimate its severity if they are not aware of the difference between averaging intervals for wind speeds. They could see the sustained wind speed of 130 mph being reported by the weather service when the storm is over open water and assume that their structure, or structures in their jurisdiction, will stand up fairly well. This would be a serious underestimate, since those structures would need to be designed to resist a 160 mph three-second-gust wind speed using ASCE 7 in order for that to be true. To say that a different way, one might think that their structure was designed for a Category 4 storm (130 mph sustained), when in fact it was actually designed for a Category 2 storm (105 mph sustained) using the Saffir-Simpson scale. Hurricane Irma at its maximum sustained wind speed of 185 mph would equate to a 227 mph three-second-gust wind speed using this conversion method. From a roof anchorage, lateral design and load path design perspective, the difference between 130 mph and 160 mph can be substantial, especially when the building is located on flat open terrain where Exposure C or Exposure D are appropriate assumptions for the design.

There is a lot more background and detail to this very complicated discussion, but the general point is to know your averaging times when comparing reported wind speeds, so as not to underestimate a storm’s force. If a storm is headed your way, hopefully you have already selected the proper hurricane tie for your structure; you have a well-defined and properly designed continuous load path; and you are protecting your exterior openings from windborne debris. Remember, the objective is not to protect the window or door product itself. Unless you are in the insurance business, you are preventing the breach of the opening to keep wind from pressurizing the structure, increasing loads on the structure and potentially causing catastrophic failure.

Know how to secure your structure against high winds, and be safe.

What Structural Engineers Need to Know About the New OSHA Silica Dust Standards

This week’s post was written by Todd Hamilton, PE. ICI Field Engineer at Simpson Strong-Tie.

In March of 2016, the United States Department of Labor issued new OSHA standards on how crystalline silica dust should be handled in various workplaces including within the construction industry. The changes are intended to limit workers’ exposure to and inhalation of silica dust on the jobsite. These regulations will replace the current standard, which was issued in 1971. Compliance with the new rules will be required on construction jobsites starting September 23, 2017, and will be enforced through OSHA from that time forward.

Crystalline silica is a naturally occurring mineral that is found in sand, sandstone, shale and granite, and since some of these materials can be found on jobsites on their own or as a component of a construction material such as concrete and mortar, changes to how workplaces contain and dispose of silica dust will affect the way our industry operates. Some of the processes performed on a construction jobsite that can expose workers to crystalline silica dust are drilling, grinding and sawing concrete and masonry; jackhammering; and sand blasting. Inhaling crystalline silica can lead to long-term illness and early death. Illnesses caused by inhaling silica dust include silicosis, lung cancer and chronic obstructive pulmonary disease (COPD).

The new OSHA standards do the following:

  • Reduce the permissible exposure limit (PEL) for respirable crystalline silica to 50 micrograms per cubic meter of air, averaged over an eight-hour shift. Previous PEL was 250 micrograms per cubic meter of air, averaged over an eight-hour shift.
  • Require employers to use engineering controls (such as water or ventilation) to keep worker silica exposure within the PEL; provide respirators when engineering controls cannot adequately limit exposure; limit worker access to high-exposure areas; develop a written exposure-control plan; offer medical exams to highly exposed workers; and train workers on silica risks and how to limit exposure.
  • Provide medical exams to monitor highly exposed workers and give them information about their lung health.
  • Provide flexibility to help employers – especially small businesses – protect workers from silica exposure.

Beyond that, the OSHA standards offer three methods an employer can use to demonstrate compliance:

  • A list of common jobsite activities and the required engineering control method, plus the additional respiratory protection (if needed) to meet the 50 PEL.
  • For activities/protection methods not included in the preceding list, the use of credible third-party assessment is allowed to show that the exposure level is < 50 PEL. This includes data from universities, trade associations, etc. that can be used provided they are based on conditions similar to, or more inherently hazardous than, the employer’s current conditions.
  • Manufacturers can generate their own data on their workers’ exposure level using an air-monitoring system.

Visit the US Department of Labor’s OSHA website for more in-depth information and useful links.

All these new requirements directly affect contractors onsite, but it’s also important for structural engineers to have an understanding of them. Beyond that, there are some key things that structural engineers should consider when specifying products such as post-installed anchors where the installation process includes drilling concrete, which does generate crystalline silica dust. Back in 2006 when Acceptance Criteria 308 was adopted, it made a lot of changes to how adhesive anchors are tested and qualified, but it also required that the manufacturers’ printed installation instructions (MPII) be published as part of the code report. This tied the published data in the code report to the installation procedures that could be used to achieve those data. And with the adoption of ACI 335.4 in 2015, the requirement for the MPII to be included in the code report continues. Therefore, with MPIIs being a part of the code report, a structural engineer needs to understand the importance of having an installation method that accounts for silica dust generated during the installation process and verify that the MPIIs include an installation process which utilizes a high-efficiency dust-collection system.

To get a better understanding of how these high-efficiency dust-collection systems work, let’s look at the Simpson Strong Tie Speed Clean™ DXS dust extraction system. This system was developed through a partnership with Bosch. Here is a video that clearly explains the system and its method:

So as structural engineers, we should consider what the MPII says when we are specifying a product.  Does it have an installation procedure, such as the Simpson Strong-Tie/Bosch DXS, that properly controls the crystalline silica dust generated? Does the code report lock the contractor into a specific brand of vacuum? Some code reports may only allow the use of a specific brand and model of vacuum and drills that can be used, which in some cases could require the purchase of new tools.

The new OSHA standard is very beneficial to installers because it will protect them from potential long-term health hazards. When it comes to anchor installation, the new regulations, along with compliant technologies such as the Speed Clean DXS, will eliminate the blow-brush-blow installation method that creates a lot of harmful airborne crystalline silica dust and is also often a source of installation error. Even though it will take time and effort for contractors and engineers to come to grips with the full ramifications for their projects, the new regulations are a positive development for the construction industry.

Meet the First Simpson Strong-Tie Engineering Excellence Fellow with Build Change

Introducing James P. Mwangi, Ph.D., P.E., S.E. – our first annual Simpson Strong-Tie Engineering Excellence Fellow with Build Change. James Mwangi will write a quarterly blog about his experience throughout the Fellowship.

I’m delighted to have been asked to contribute this post and feel honored to be the first-ever Simpson Strong-Tie Engineering Excellence Fellow with Build Change. It’s my hope that this post will inform you about my professional background, why I applied to the Fellowship and how I think the Fellowship can benefit people and the structures they live, work and go to school in.

I grew up in Kenya and went through my basic education and my undergraduate coursework in civil engineering there. I worked for the government of Kenya as a junior roads engineer before proceeding to Nigeria for my masters in structural engineering. I returned to Kenya and worked for the government as a junior structural engineer. I joined the faculty of civil engineering shortly after that as a lecturer.

Central Kenya – including Nairobi, where I lived – is subject to moderate seismic activity, and I felt several earth tremors growing up. This puzzled me from a very young age, and I always wanted to learn how buildings behaved during these events. Since I didn’t acquire this understanding during my undergraduate or my master’s studies, I headed to California in 1988 for doctoral work in structural engineering at UC Davis. I didn’t have to wait long for first-hand experience of the effects of major seismic activity, because the Loma Prieta earthquake happened hardly a year after my arrival. This earthquake helped shape my career by giving me the opportunity to visit the destruction sites in the San Francisco Bay Area. Through my professors at Davis, I led a very successful Caltrans-funded project on full-scale testing of repair methods (steel jacketing and epoxy injection) of pile extensions that we harvested from a bridge that collapsed along Highway 1 in Watsonville. From completing my doctoral studies at UC Davis, I joined Buehler and Buehler Structural Engineers (B&B) in Sacramento. The 1994 Northridge earthquake happened while my steel moment frame school building in Milpitas was undergoing review by DSA. When we realized that no DSA engineer would sign off on this system from the field observation of the behavior of steel moment frames, I had to redesign the building over a weekend with a steel-braced frame system to meet the client’s schedule. At B&B, I was able to design building structures of wood, steel, masonry and concrete ranging in use from public schools, hospitals, and other essential service facilities to commercial buildings.

Since 2003, I have been a university professor, having joined the Architectural Engineering department (ARCE) at Cal Poly, San Luis Obispo, where I teach both undergraduate and graduate design courses in timber, masonry, steel and concrete. As a certified disaster safety worker in the governor’s office of emergency services, I have participated in the Structural Assessment Program in Paso Robles following the 2003 San Simeon earthquake; in Port-au-Prince following the Haiti earthquake of 2010; in Napa following the Napa earthquake of 2014; and in Kathmandu following the Nepal earthquake of 2015. I have contributed my experience from these deployments to the profession by serving in the technical activities committee of The Masonry Society (TMS) and also representing the seven western states in the TMS Board of Directors.

After my two-week building assessment in Haiti in 2010, I returned to Haiti for a year with the Mennonite Central Committee (MCC), participating in capacity building and safe building-back-better workshops targeting homeowners, contractors, engineers, architects and government officials. It was during this time that I first met Build Change as we shared information on our projects in Haiti. Since then, I’ve led a group of ARCE students to Haiti and Nepal every summer, and we have made it part of our itinerary to visit Build Change projects in each of the countries.

As a structural engineer, I have used Simpson Strong-Tie (SST) products throughout my career here in the US. I’ve not only used the SST products to teach my timber and masonry design courses at Cal Poly but have also supervised ARCE senior projects where we have used SST products. One of these projects led to a naming of one of our design laboratory rooms as The Simpson Strong-Tie Laboratory. It was only natural, then, that when I saw the advertisement for the Simpson Strong-Tie Engineering Excellence Fellowship, I couldn’t believe that two organizations with whom I have worked so closely as an individual and as a teacher were teaming up to create such a great opportunity. My familiarity with the two organizations, along with the fact that I already had a sabbatical leave approved from Cal Poly for the year of the Fellowship, made it a must for me to apply for the Fellowship. Natural disasters only cause human devastation where naturally occurring events (earthquakes, hurricanes, etc.) are not mitigated. The missions of the two organizations – BUILD Disaster-Resistant Buildings and CHANGE Construction Practice Permanently, alongside Simpson Strong-Tie’s No-Equal commitment to creating structural products that help people build safer, stronger homes and buildings –added to my desire to apply for the Fellowship.

Build Change projects involve helping local governments provide safe school buildings and other structures so their communities can better withstand damaging natural events, whether hurricanes, tornadoes or earthquakes. Where possible, we’ll use Simpson Strong-Tie products for the repair or retrofit of roofs, walls and anchorage. Build Change currently has projects in Indonesia, the Philippines, Nepal, Haiti and Colombia, all of which are located in areas susceptible to high winds and earthquakes. Indonesia is the fourth most populous country in the world. It’s my hope that I’ll be able to participate in projects in each of these countries, and I certainly believe that Build Change and Simpson Strong-Tie together can help millions of people live in better structures, built from better local, sustainable materials, which will be safe from strong winds and earthquakes.

If you’d like more information about the fellowship or my involvement over the next year, I can be reached at james@buildchange.org.

How Heat Treating Helps Concrete Anchoring Products Meet Tougher Load Demands

Joel Houck is a senior R&D engineer for Simpson Strong-Tie’s Infrastructure-Commercial-Industrial (ICI) group based out of the new West Chicago, IL location. He has spent the last 17 years with Simpson developing new mechanical anchors and adhesive anchor components, as well as developing a lot of the lab equipment required to test these products. This experience has given him extensive knowledge and insight into the concrete anchor industry, especially when it comes to the proper function and performance of anchors. Joel is a professionally licensed mechanical engineer in the state of Illinois.

There’s a saying in Chicago, “If you don’t like the weather, just wait fifteen minutes.” That’s especially true in the spring, when temperatures can easily vary by over 50° from one day to the next. As the temperature plunges into the blustery 30s one evening following a sunny high in the 80s, I throw my jacket on over my T-shirt, and I’m reminded that large swings in temperature tend to bring about changes in behavior as well. This isn’t true just with people, but with many materials as well, and it brings to mind a thermal process called heat treating. This is a process that is used on some concrete anchoring products in order to make them stronger and more durable. You may have heard of this process without fully understanding what it is or why it’s useful. In this post, I will try to scratch the surface of the topic with a very basic overview of how heat treating is used to improve the performance of concrete anchors.

According to the ASM Handbook: Heat Treating, heat treatment is a process of heating and cooling a solid metal or alloy in such a way as to obtain desired conditions or properties.1 In practical terms, metals (usually steel in the case of most concrete anchors) are heat treated in order to improve their properties in some way over their base condition. When steel wire is formed into the complex shapes of anchors during the manufacturing process, the steel needs to be soft and formable; however, it is often beneficial to the performance of the final anchor product to be much harder and stronger than the base steel from which it’s formed. That’s where heat treating comes into play. By heating and cooling soft steel in a controlled manner, changes are made to the crystal structure of the steel in order to improve mechanical properties such as hardness, toughness, strength or wear resistance. Although the steel undergoes very complex microstructural changes during the heat treatment process, the end result is fairly straightforward – the once soft steel becomes harder and stronger as dictated by the heat treating process. As concrete anchors become more and more complex in order to meet the needs of building codes and designers, heat treating is becoming a more common and necessary component of high-strength anchors.

Figure 1. Steel microstructures: (a) soft steel example; (b) heat treated steel example.2

Depending on the desired results, there are many different types of heat treating processes that can be considered. The type of heat treatment and the parameters that are used can be customized for the steel type and the specific anchor application. There are several different types of heat treatments that are typically used for anchors. Two of the most common types are through hardening (also called neutral hardening) and surface hardening (also called case hardening).

Figure 2. Fasteners entering a heat treating furnace.3

Through hardening changes the mechanical properties (hardness, strength, ductility, etc.) of the steel without affecting its chemical composition. In order to alter the microstructure of the steel, it is heated in a furnace to a very high temperature, and then rapidly cooled, usually by submerging it in a liquid quench medium such as water or oil. This process will generally result in a very hard, but brittle material, so a secondary operation, called tempering, is employed after quenching. To temper steel, it is reheated to a lower temperature and then cooled in order to remove the stresses and brittleness created during the original quenching operation. Through hardening is useful where increased strength and toughness are required and surface wear isn’t a big concern, such as in our Crimp Drive® and split-drive anchors, setting tools for drop-in type anchors, high-strength all-thread-rod for adhesive anchors, and gas- or powder actuated fasteners. In order to effectively through harden an anchor, moderate levels of hardening elements must be present in the base steel, usually in the form of carbon. As the carbon content in the steel increases, so does the ability to harden it. The chemical composition of the steel along with the specific heat treating parameters will determine the level of hardness, strength and toughness of the final parts.

Surface hardening changes the hardness of the steel at the surface of the part by modifying the chemical composition of the steel at its surface only. This is done by altering the atmosphere in the heat treating furnace in order to get alloying elements, usually carbon, to diffuse into the surface of the steel. The increased carbon content increases the hardenability of the steel at the surface, but it can’t penetrate deeply into the steel, so a thin case forms around the surface of the steel with higher strength and hardness than the interior of the part. This creates parts that have high ductility throughout most of the interior, but that also have hard, wear-resistant surfaces. This type of heat treatment is useful in heavy-duty anchors where components of the anchors are sliding against each other during the setting process. It’s also useful in screw anchors, where the steel threads need to be very hard and wear resistant in order to cut into the concrete, but the ductility of the anchor must be maintained in order to avoid brittle failures in service. Just as with through hardening, there are many variations of surface hardening used in anchors, depending on the specific application.

Figure 3. Cross-section of surface hardened bar showing different hardness zones at the surface and in the interior.4

By using these two processes along with other heat treating processes, we are able to expand our ability to meet the higher demands placed on anchors in an industry that continues to evolve. As heat treating and steel chemistry continue to innovate, we will continue to use these developments to provide our customers with No-Equal concrete anchors that meet our high standard for performance and safety.

Mechanical Anchors

From complex infrastructure projects to do-it-yourself ventures, Simpson Strong-Tie offers a wide variety of anchoring products to meet virtually any need.


 

1 Lampman et al. (1997). ASM Handbook: Heat Treating. Materials Park, OH: ASM International.

2 “Microstructure of the AISI 4340 Steel.” Digital Image. Research Gate, n.d. Web. 14 June 2017 https://www.researchgate.net.

3 “Heat Treat Furnace.” Digital Image. ThomasNet Web Solutions, n.d. 14 June 2017 http://www.morganohare.com/heat-treating.html.

4 “Macrographs Showing Case Depth of Steels.” Digital Image. Science and Education Publishing Co. Ltd, n.d. 14 June 2017 http://pubs.sciepub.com.

What Makes a Good Training Facility?

This blog post was written by Charlie Roesset, Director of Training for Simpson Strong-Tie.

When it comes to training, there are many well-researched principles about what makes an environment conducive to improved adult learning.

While we try to hold all training events in facilities that meet most of these principles, (even when traveling to our customers or users means we have to conduct events in hotel meeting rooms) we prefer to host you at our own locations.

To this end, we invest a tremendous amount of time and resources to build and offer dedicated training facilities across the country. These facilities meet all the basic requirements for improved adult learning, but much more as well.

By having our own dedicated training facilities, we can provide learners with a much richer experience and contextually relevant displays.

These displays include partially deconstructed wall segments, foundations and roof systems that give learners a bigger picture of the applications being studied.

Many displays allow for hands-on installations and exercises that allow for improved comprehension of the product use and limitations. Even for the engineering community, who typically are limited to images from a catalog, the hands-on activities add great value. It’s always interesting to see the reaction that engineers have to actually seeing a system approach and having an opportunity to participate in learning that goes way beyond sitting and listening to a lecture.

Sometimes learners just need to see, feel or hold something in order to really understand a concept or product application. We make every effort to bring legitimate educational content to our workshops, supported by products that we hope will furnish solutions to your needs.

Many of our facilities include a plant tour and/or testing-facility tour as well. While these components don’t always align directly with the learning objectives, they do offer a chance for our guests to raise their energy levels and get a better understanding of that scale, capabilities, and commitment to quality that we bring to bear in our endeavor to help people build safer structures.

Additionally, we offer our facilities to customers, associations and industry organizations to use for their own meetings and training events. If you haven’t been to one of our workshops or visited one of our facilities, I highly encourage you to join the 35,000 plus who have over the last four years. You can find a complete list of workshops on our training home page. I expect that you’ll find it an educational and highly engaging experience that helps you build safer structures as well.

3 Hot Tips for Structural Engineers Who Want to Earn Education Credits and Stay Sharp

Written by Minara El-Rahman in collaboration with the Simpson Strong-Tie Training Department.

Do you ever get so busy that you can’t keep up with the training opportunities that are available? We have previously shared online resources and webinars that are available to structural engineers, but did you know that you can take advantage of Simpson Strong-Tie regional training centers that offer complimentary workshops and classes about proper specification, product installation and inspection of connectors and structural systems? Here are some tips on staying current with your training.

Simpson Strong-Tie training courses and webinars are focused on improving building standards and the overall safety of structures. With eight training centers across North America, Simpson Strong-Tie provides hundreds of complimentary classes to engineers, architects, builders and code officials each year. In fact, we have trained more than 24,000 participants online and in-person in 2016 alone.

“The workshops are very interactive,” explained Charlie Roesset, Director of Training for Simpson Strong-Tie. “Depending on the course, students may have the opportunity to view product samples or take part in product testing and installations.”

Tip #1 Make Training Offerings Work for You

If you specialize in a specific discipline, look for courses that are targeted to your area of interest or expertise. Simpson Strong-Tie courses include a broad range of topics from anchor system installation and engineered wood frame construction to seismic and high-wind design. We also incorporate the latest building-code updates and industry trends into our training curriculum. No matter where you are in your professional career, we offer a course that’s right for you. There are introductory courses as well as more advanced workshops for repeat and seasoned attendees.

Training participants receive a certificate of attendance with professional development hours (PDHs) at the end of each workshop, and may earn continuing education units (CEUs) and/or learning units (LUs) by completing additional requirements. Simpson Strong-Tie is a registered education provider with a number of industry organizations and associations including CSI, BIA, ACIA, AIBD, ICC, AIA* and IACET**.

Tip #2 Find Trainings That Are Current

Do your research to find workshops and online courses that are regularly updated to reflect changes within the industry. For example, we have regular trainings that focus on the new seismic retrofit ordinances in various municipalities on the West Coast (such as Los Angeles’ Soft-Story Retrofit Ordinance) and others on high-wind design and construction in the Southeast. Our trainings are tailored to your design needs based on your practice’s location.

Full-day workshops typically run from 8:00 a.m. to 4:00 p.m. Classes are often tailored toward specific audiences types to ensure that the training is appropriate and effective. Many courses are team-taught by registered engineers to provide in-depth technical expertise in the subject matter. While much of the instruction is technical in nature, many real-life examples and hands-on demonstrations are provided to help all attendees fully understand the material presented.

Tip #3 Hear What Other Structural Engineers Have to Say

Training

It is always a good sign when others in your field have good things to say about the courses they have taken. Below are some comments past participants have said about our training offerings:

Fred B., S.E., an engineer from Las Vegas, NV, has been a regular attendee of Simpson Strong-Tie workshops. He says the training keeps him informed of topics relevant to his industry and is a great way to keep up with his professional development hours. “Some of the courses offered by other groups are just not that interesting and they can be quite expensive. Simpson programs are interesting, hands-on and free. It’s the whole package.”

Bob N., an engineer from Richmond, VA, wrote, “Keep up the good work; I have found your seminars to be well done, pertinent, and useful. We also specify a lot of your products because of the training and the fact that you have an excellent product line.”

Kathy P., an engineer from Somerville, TX, shares: “You guys are so great! You teach well and keep it interesting. . . . . You support the industry to the benefit of everyone, not just your bottom line, and you make educational credits cost effective. Thank you, thank you, thank you!”

Sign up for a workshop and find out more about Simpson Strong-Tie training programs, including our latest online courses, by visiting www.strongtie.com/workshops.

* Simpson Strong-Tie is registered with the American Institute of Architects, Continuing Education System (AIA CES) as a provider of AIA Learning Units (AIA LUs).

** Simpson Strong-Tie is accredited by the International Association for Continuing Education and Training (IACET) and is authorized to issue the IACET CEU.

 

 

Use Strong-Wall® Shearwall Selector to Design Shearwalls

This blog post was written by Travis Anderson.

Strong-Wall Shearwall Selector-Homepage

In time for spring and summer 2017 construction projects, Simpson Strong-Tie has launched the newest version of the Strong-Wall Shearwall Selector for use with engineered design. The latest release is an easy-to-use Web-based application (that’s right, no software to download) that has been updated to comply with the 2015 IBC and now provides solutions for all three Strong-Wall Shearwall types: the Steel Strong-Wall® shearwall (SSW), the Strong-Wall wood shearwall (WSW) and the wood Strong-wall shearwall (SW). If you are familiar with the Strong-Wall Shearwall Selector, you can begin using the web application immediately. For those of you who would like to know more about the web app, please read on.

The Strong-Wall Shearwall Selector was created to help the Designer select the appropriate shearwall solution for a given application in accordance with the latest building code requirements. By performing a technical analysis, the web app provides actual drift and uplift values for a wind or seismic design shear load.

The Strong-Wall analysis also considers simultaneous, vertically applied load. In cases of multiple walls in a line, the program performs a rigidity analysis and determines the actual distributed shear to each wall. When walls are stacked in a two-story configuration, the program evaluates cumulative overturning effects to ensure that the wall, anchor bolt and anchorage to the foundation are not overstressed.

The web app provides two modes for generating an engineered solution: Optimized In-Plane Shear or Manual In-Plane Shear. The Optimized mode lists several possible solutions for the selected criteria in the order of cost. The Manual mode evaluates any number or combination of walls for adequacy based on the selected criteria. The Designer has the option to generate an Anchorage Solution based on foundation type. Once a solution has been selected, the web app will generate a pdf output. Files can be saved and reused for future designs.

Input Variables Within the Two Solution Modes:

Job Name: Enables the Designer to provide a specific job name for a project.

Wall Name: Enables the Designer to provide a name for each wall line in a project.

Wall Type (Manual Only): Solutions are provided for the selected Strong-Wall panel type: SSW, WSW, SW

Application: Defines the proposed application (use) of the wall. The choices are for walls in a garage front, a standard wall on concrete, on a first-story wood-floor system, in a second-floor non-stacked application, in a two-story stacked application, or in a balloon-framed application. For the Steel Strong-Wall® (SSW) and Strong-Wall wood shearwall (WSW), garage front may be chosen with or without the portal kit. Higher shear capacities are available when the portal kit is used.

Cold-Formed Steel Construction (CFS): This option appears for “Garage Front,” “Standard Wall on Concrete,” “First-Story, Raised-Floor System” and “Two-Story Stacked” applications. If the check box is enabled, the program will provide the proper Steel Strong-Wall model for use in CFS construction.

1st Story Wall on Wood Floor (SW – Wood Strong-Wall Shearwall only): This check box only appears if a Two-Story Stacked application has been selected. If enabled, the program will then assume the lower story wall, in a stacked application, is installed on a wood floor.

Strong-Wall Shearwall Selector-Input Variables

Design Criteria:

The design criteria may now be selected. Drop-down menus provide options for Applicable Building Code, load type, concrete strength, wall height, wall geometry and floor depth (if applicable). Entry fields may be used to indicate shear- and axial-loading information. The following applies once the appropriate design criteria have been input: If Optimized In-Plane Shear has been selected, the possible solutions are displayed in the Strong-Wall Panel Solutions list. If Manual In-Plane Shear has been selected, a list of available walls will be displayed in the Strong-Wall Panel Solutions list, any of which may then be selected and added to the desired Solution.

Strong-Wall Shearwall Selector-Design Criteria

Code: Wall solutions are provided in accordance with the requirements of the 2015 and 2012 International Building Code (IBC). Code reports may be found here.

Load Type: This criterion defines whether the input shear load is due to wind or seismic forces. The Designer must input the controlling load. The appropriate seismic “R” values are provided for the selected code.

Concrete Strength: Concrete strength may be selected based on specific project conditions. Default concrete strengths of 2500 psi, 3000 psi, 3500 psi, 4000 psi and 4500 psi are provided in the drop-down menu. Note that for shearwall selection purposes, concrete strengths are only applicable to Steel Strong-Wall® (SSW) and Strong-Wall wood shearwall (WSW). In some cases, lower anchorage forces may be obtained with a higher concrete strength. The concrete strength is also used for determining the anchorage tension capacity.

Wall Height: Select the nominal wall height. Actual wall heights are shown under the “H” column of the Solution(s).

Shear Load: Input the total Allowable Stress Design (ASD) design (demand) shear load along the wall line. Include all appropriate load factors on the shear load prior to input for the load combination under consideration. For Two-Story Stacked applications, input the story shear at each level and the program will evaluate the first-story walls for the total shear.

Floor-Joist Depth: This option appears only with first-story raised-floor systems and two-story

stacked applications. Floor-joist depth affects the capacity of Steel Strong-Wall panels installed on wood floors. Floor-joist depth is also considered in the cumulative overturning evaluation of two-story stacked wood or steel walls.

Header Thickness: This option appears only when “Garage Front” applications and wall heights of 7′ or 8′ with a header on top are selected. This option is used to select the proper Wood Strong-Wall panel model (thickness) based on the nominal header thickness of 4″ or 6″.

Header Type: This option only appears when “Header Thickness” of 4″ is selected. It then provides an option to select a solid or double-ply header. Values for the wood Strong-Wall panels will slightly decrease if the double-ply header option is selected. Steel Strong-Wall panels with multi-ply headers are limited to wind designs and SDC A-C.  .

Maximum Number of Wall Segments per Wall Line (Optimized mode only): Here the maximum number of available wall segments along a particular wall line is specified. The program enables the Designer to select a maximum of four wall segments per wall line (3 segments maximum for garage fronts.) For more wall segments per wall line, use the Manual mode.

Fill Each Segment (Optimized mode only): If this checkbox is disabled, then the minimum number of Strong-Wall shearwalls that can serve as solutions is provided up to the “Max # of Wall Segments” previously specified. If this checkbox is enabled, then the “Max # of Wall Segments” will always be used and filled with Strong-Wall shearwalls.

Segment Number, Maximum Width, Axial (lb.) (Optimized mode only): For each wall segment along a wall line, the maximum desired width of that segment and the axial load on that particular segment may be specified. The axial load is the total vertical upward or downward load assumed to act on the entire panel width. Include all appropriate load factors on the axial load prior to input for the load combination under consideration. A positive axial load reduces the actual uplift of the panel, while a negative axial load increases the actual uplift of the panel. The combined effect of the vertical axial load and overturning force is considered in the Steel Strong-Wall® (SSW) and Strong-Wall wood shearwall (WSW) solutions. The combined effect of the vertical axial load and overturning on the wood Strong-Wall (SW) shall be evaluated by the Designer so as not to exceed the “C4” and “T1” allowable vertical loads. Download an excerpt from our catalog for more information.

Axial Load 1st Story (Manual mode only): See discussion above on axial load. The axial load selected is initially applied on all Available Wall solutions. As walls are selected using the “Add” button, the axial load remains constant. If it is desired that each wall have a different axial load, then input the corresponding axial load value for the first wall and click on “Add Solution” to send it to the Selected Solution. Then enter the new axial load value for the next wall and continue this process until all the product selections are complete.

Maximum Wall Segment Width: This optional input limits the Available Strong-Wall Panels to the maximum width specified.

Available Wall(s) (Manual mode only): Based on the input Design Criteria, all Available Strong-Wall Panels and their allowable loads are listed as an option for selection. The Available Strong-Wall list is independent of the input shear load and instead represents a list whereby any quantity or combination of walls can be selected to resist the shear load.

Solution(s) and Output :

 Possible Solution(s) (Optimized mode only): Up to four possible solutions may be displayed and are designated as Sol # (solution number) in the order of relative cost (lowest to highest material cost).

Selected Solution (Manual mode only):

Add Another Solution: Click on the “Add” button to select wall from Available Wall(s) list, which enters it into the Selected Solution list. You may also double-click on an Available Wall to add it to the Selected Solution.

Clear: Click on the “Clear Selected Solutions” button to entirely remove all previously selected walls in the Selected Solution.

Generate PDF: This button creates a .pdf summary of the wall solution. Under Optimized mode, the output solution is created for the Sol# (solution number) that is highlighted. Under Manual mode, the Output is created for all walls shown in the selected solution list.

Design Anchorage: This option appears at the bottom of the page. If desired, enable the check box next to “Design Anchorage” and select Foundation Type. Anchorage design solutions will then be included in the PDF output.

Notes for Designer: Special notes related to the input variables are displayed in this window during the input process. When the Manual In-Plane Shear tab is selected, the Notes for Designer will indicate whether the Selected Solution is adequate to resist the applied design loads.

Strong-Wall Shearwall Selector-SolutionsStrong-Wall Shearwall Selector-Solution Output

Anchorage Solutions and Output:

 The Designer will have the option to generate an Anchorage Solution appended to the Strong-Wall shearwall solution. If desired, Select Foundation Type, then enable the check box next to Design Anchorage, and the .pdf file will be generated with the anchorage solution on subsequent pages. The designer can choose anchorage solutions based on foundation type for all shearwalls. The two foundation types are slab-on-grade and stemwall and are selected from a drop-down menu. Within each foundation type, the Designer can choose a specific footing type as follows:

Slab-on-Grade Footing Types: Garage curb, slab edge, brick ledge and interior.

Stemwall Footing Types: Garage front and perimeter.

Anchorage solutions are provided based on the shearwall solution(s) selected and the following design criteria: application, load type, actual uplift and concrete strength.

Anchor Bolt: Two anchor bolt solutions are available for the wood Strong-Wall®. They are the PAB7 and the SSTB, both of which are ASTM F1554 Gr. 36 material. The Steel Strong-Wall® uses a single anchor type, SSWAB, which may be either ASTM F1554 Gr. 36 or ASTM A449 (high-strength) material depending on the actual uplift. The Strong-Wall wood shearwall uses a single anchor type, WSW-AB, which may be either ASTM F1554 Gr. 36 or ASTM A449 (high-strength) material depending on the actual anchor tension.

Concrete Service Condition: This criterion refers to whether the concrete is determined to be cracked or uncracked based on analysis at service loads. See ACI 318 for the different reduction factors associated with cracked and uncracked concrete.

Strong-Wall Shearwall Selector-Anchorage Strong-Wall Shearwall Selector-Anchorage Output

The anchorage design .pdf output summarizes all applicable design details including the footing type, minimum footing dimensions, anchor bolt and shear anchorage. The Designer is responsible for foundation design (size and reinforcement) to resist overturning, soil pressure, etc.

Product Information:  Select for more product and application information.

Upload a Saved File: Designer can upload any previously used solution.

Report Applications Issues or Provide Feedback: If you are experiencing issues with the application or simply would like to provide feedback, please use this link. Simpson Strong-Tie values your feedback.

Strong-Wall Shearwall Selector-Info Save Issue

Get started on your next design project with the Strong-Wall® Shearwall Selector web application!

Top Three Reasons Why Structural Engineers Should Attend Webinars

We encourage all our employees to always keep learning and seeking out resources that can stimulate new ideas or help improve processes in their jobs. Webinars are a great way for you to stay engaged in your profession and learn new things about the industry. They mix the convenience of online availability with the interactivity of live seminars, and because some are free or offered at a much lower cost than live trainings, they make it even easier to stay up to date on current issues in your field. Our top three reasons why you should attend structural engineering webinars are below:

Close up shot of webinar on a laptop.

Close up shot of webinar on a laptop.

Some Webinars Offer Continuing Education Credits

Webinars for structural engineers can be very useful for staying current with professional development requirements. Look to see if the webinar you are interested in attending offers credits. Simpson Strong-Tie offers a wide range of webinars that allow structural engineers to earn CEU and PDH credits. There are plenty of other professional organizations that offer accredited webinars for structural engineers, also. Paul McEntee shares his list of recommended professional resources (including webinars) for structural engineers here.

Learn About Code Changes and Requirements

Staying up to date on code changes and requirements is one of the reasons why continuing education is so important. The Structural Engineers Association of California (SEAOC) has a helpful lunchtime webinar series that delves into 2015 International Building Code (IBC) changes. Simpson Strong-Tie webinars always review current code requirements for the kinds of structural design under discussion. For example, the Best Practices on Prefabricated Wood Shearwall Design webinar covers code reports on shearwall applications.

Learn About the Latest Products and Technology

 If you can’t make it to a live training session, using webinars to learn about the most recent products and technology is an effective way to stay current in the field. Whether you want to learn about the latest in prefabricated Strong-Wall® Shearwall panels or to gain fuller understanding of Best Practices for FRP Strengthening Design, webinars can help you design using the most advanced technology.

What was the best webinar you’ve attended? Why was it so good, or what was it you learned? Let us know in the comments below.

Q&A: Best Practices for FRP Strengthening Design

frp-design-banner

On December 1, 2016, Simpson Strong-Tie hosted a webinar titled “The Design Fundamentals of FRP Strengthening” in which Justin Streim, P.E. – one of our Field Engineers – and I discussed the best practices for fiber-reinforced polymer (FRP) strengthening design. The webinar examines FRP components, applications and installation. It also features an example of the evaluation that went into a flexural-beam-strengthening design and discusses the assistance and support Simpson Strong-Tie Engineering Services offers from initial project assessment to installation. Watch the on-demand webinar and earn PDH and CEU credits here.

During the live webinar, we had the pleasure of presenting to more than 1,500 engineers who asked nearly 300 questions during the Q&A session. Here is a curated selection of Q&A from that session:

q-a-graphic

Can you discuss the flexural strengthening for reinforced masonry walls?

Out-of-plane flexural strengthening can be provided with FRP on the required face of wall. In-plane (or shear wall type) flexural strengthening can also be provided with vertical FRP strips near the ends of walls.

In general, by what percentage can FRP solutions increase the strength of existing concrete shearwalls?

This really depends on the existing wall, but we have seen strength increases of 22% in our testing of one layer of glass fabric installed on 8″ thick ungrouted CMU shearwall.

How does FRP compete in terms of cost? It seems like a cost-prohibitive solution compared to other remediation techniques in the absence of other limiting factors (space limitations, etc.).

FRP may be expensive on a cost/SF basis. However, if you compare it with the materials and labor involved in section enlargement or demolishing parts of buildings, it becomes cost effective. FRP installations are also not unsightly like bolted steel plates or wide flange members slung under concrete slabs/beams.

Who designs the FRP system: Simpson Strong-Tie or the Structural Designer?

The Simpson Strong-Tie Engineering Services group provides the FRP design on most projects, but we have also worked with the engineer on record (EOR) to check their FRP design on projects.

Are there any deformation compatibility issues between carbon fiber or glass and existing reinforcing bar that need to be accounted for in design? Is long-term creep similar to that seen with reinforcing bar?

CFRP and GFRP have different elastic moduli from each other and from steel. When designing an FRP strengthening solution, these differences must be taken into account. For flexural applications, the FRP should be designed to fail from debonding after the internal rebar begins to yield. Creep is taken into account in design equations through reduction factors and stress checks.

Will ACI 440 be updated to include the use of FRP with post-tensioned beams (i.e., unbonded tendons)? Does Simpson Strong-Tie do all stress checks based on gross section properties when total stress is < 12sqrtf’c?

Yes, there is an ACI 440 committee working on including an unbonded PT section in ACI 440.2R. We will work with the EOR to determine what section properties are most appropriate for the specific member being evaluated.

Can you increase deflection limits with FRP?

While FRP does help to limit deflection in members, members with deflection issues are not typically candidates for FRP repair. Prestressed laminates as used in Europe would be a better solution for a member with deflection issues. We do not currently offer prestressed laminates but may in the future.

Does an aesthetic coating interfere with bridge inspection? What is inspection looking for? Delamination or other defects?

A coating could interfere with a visual inspection of the FRP surface. A visual inspection can reveal changes in color, debonding, peeling, blistering, cracking, crazing, deflections, indications of reinforcing-bar corrosion, and other anomalies. In addition, ultrasonic, acoustic sounding (hammer tap) and thermographic tests may indicate signs of progressive delamination. ACI 440 and AC 178 have extensive special inspection recommendations.

Advanced FRP Design Principles

In this free webinar we will dive into some very important considerations including the latest industry standards, material properties and key governing limits when designing with FRP.


For complete information regarding specific products suitable to your unique situation or condition, please visit strongtie.com/css or call your local Simpson Strong-Tie RPS specialist at (800) 999-5099.

 

Being an Engineering Intern at Simpson Strong-Tie

Editor’s Note: This week’s blog post is written by one our college interns in the Engineering Department. Ian Kennedy spent the summer of 2016 as an intern for the McKinney office of Simpson Strong-Tie. He will be starting his second year at Calpoly San Luis Obispo in Fall 2016 studying Mechanical Engineering. As an intern, he spent his time helping the branch engineering department with numerous projects, as well as exploring projects of his own. He enjoys metalworking, fitness, and the outdoors. Thank you to Ian Kennedy for this week’s post.

As I write this, I can’t help but laugh that of all the interns studying structural, civil or architectural engineering in school, the intern writing the post for our Structural Engineering Blog is studying mechanical engineering. I haven’t met too many mechanical engineers during my time here at Simpson Strong-Tie. I know there are a few, but while a lot of mechanical engineers are focused on making things move, most of the people here concentrate primarily on making things stay still. I’ve found what Simpson does to be more important than a lot of my peers at school may realize – it seems ME students are more preoccupied with cars and equipment than with what’s keeping the roof from coming down on top of them. Still, my exigence alone wasn’t enough to cancel the uneasiness of a first-time intern doing things he never knew he would be doing.

Simpson Strong-Tie intern Ian Kennedy.

A headshot of Simpson Strong-Tie intern Ian Kennedy.

If I had to go back and give myself a one-sentence explanation of what would be expected of me here, it would be this: “You’re going to find out what it takes to make a structure or system not work, then make sure no one else ever has that happen.” Although I doubt I would have appreciated what that meant at the time, I now think that it’s the most succinct explanation both of what Simpson Strong-Tie does, and of how I would need to approach my new position.

Engineering intern Paul Casabag working on a DIY porch swing project.

Engineering intern Paul Casabag working on a DIY porch swing project.

It started to click with me when I worked on load-rating calculations for some of the Simpson Strong-Tie products. A rating isn’t determined by what a product’s strengths are, but rather its weaknesses: “Here, here, and here are the ways things can go wrong, these are the ways it’s going to break, and finally, this is a list of the ways it’s going to be misused in reality. Now make sure none of that can feasibly happen, or people can get hurt.”

diy-porch-swing-progress2

Engineering interns building a DIY porch swing that is sturdy and durable.

That’s a heavy burden, even if you’re just an intern. It’s given me a solemn respect for the engineers that sign off on calculations, testing and construction plans. It’s a respect I wasn’t anticipating: Respect for their intellect, sure; for their work ethic, absolutely; but I can’t say that I expected myself to develop a respect for the people I work with because of the weight of human life they carry. Maybe that’s because it’s my first experience with real engineering. Maybe it’s something every engineer develops through classes or experience – I hope it is, because the effect I believe it can have on the decisions engineers make is incredible.

I continued to realize the truth behind my view when I spent time in the onsite test lab. Things break. Sometimes it happens slowly, and sometimes it happens faster than you can blink. A lot of the time it doesn’t even happen how I expected, but, without fail, an engineer had made sure to check that failure mode in the calcs. And the message in my head reminded me – figure out how it can break, so that no one else has to.

DIY porch swing DIY porch swing

The DIY porch swing complete and ready to enjoy.

In adjusting to my role as an intern, I found my view to be crucial to my growth. I made mistakes, as everyone does. There were countless things I didn’t consider, or hadn’t learned before, and in a way these were failures. But they were small failures, ones that could be addressed and learned from with the support and experience of the people I work with. I wouldn’t have grown without these failures, and I wouldn’t have been able to anticipate them in the future. Just like the products Simpson makes, I was strengthened by being tested and corrected. I used what I learned from my mistakes, and I’ll make sure that those aren’t ways in which I’ll fail in the future.

I can’t say for sure yet how being an intern here has strengthened my future specifically in mechanical engineering, but I can clearly identify the skills it’s given me that translate across anything I hope to do: continuous improvement, preparation for anything to go wrong, and respect for the one load not covered by ASD or LRFD – the weight of human life. These are the lessons I’ve learned above everything else at Simpson Strong-Tie. These are things I’ve found not only the company to stand for, but everyone working for it as well. Internships are supposed to simply provide an opportunity to gain skill and experience in the industry; however, more than that, my internship with Simpson Strong-Tie has taught me invaluable lessons that I hope my peers can someday have a chance to learn as well.