Welcome to our Structural Engineering Blog! I’m Paul McEntee, Engineering R&D Manager at Simpson Strong-Tie. We’ll cover a variety of structural engineering topics here that I hope interest you and help with your projects and work. Social media is “uncharted territory” for a lot of us (me included!), but we here at Simpson Strong-Tie think this is a good way to connect and even start useful discussions among our peers in a way that’s easy to use and doesn’t take up too much of your time. Continue reading
This week’s post was written by Frank Ding, Engineering Analysis & Technical Computing Manager at Simpson Strong-Tie.
Computer-simulated product testing is being used increasingly in modern engineering and manufacturing because it provides a low-risk, time- and cost-efficient means of modeling system performance using a wide array of variables before a physical prototype has been created. The following Blog post outlines some of the uses and advantages of integrating this technology into the product development process.
The role of test simulation in product design might not be the general focus of the Structural Engineering Blog. However, you may have noticed that computer simulation plots have been cited in a few previous postings. Nowadays, it’s rare to talk about product development without mentioning computer simulation at some point. The aim of this post is to give you a better sense of how test simulation can benefit product development and innovation.
Simpson Strong-Tie is a manufacturing company specializing in structural product solutions. Product innovation has been key to the company’s success ever since the production of the first joist hanger in 1956 by the company founder, Barclay Simpson. And with increasing competition and market pressure, product innovation becomes ever more critical to the company’s bottom line.
The ultimate goal of product development is to produce the best design as efficiently as possible. At Simpson, physics-based computer numerical modeling and simulation already form a key tool in our design process. Research published by the Aberdeen Group in 2014 reported that best-in-class companies were leading the way in utilizing simulation software to arm their employees with the insight needed to develop and optimize today’s products.
Finite element analysis (FEA) tools have been an essential component of any engineer’s toolbox for years. The ability to create a virtual prototype or realistic representative model of a part or assembly before physical prototyping offers companies a much faster product development path than was previously possible. Most of the time, simulation is used early in the design cycle to investigate a set of predetermined candidate designs — in which it has proven to be a more efficient method than running physical tests alone for isolating the best design. At other times, simulation is used alongside physical validation tests to determine whether the design meets specifications and to explore potential failure modes.
How can simulation power innovation?
When Thomas Edison was asked about finding success amidst failure, he stated, “If I find 10,000 ways something won’t work, I haven’t failed. I am not discouraged, because every wrong attempt discarded is another step forward.”
With computer simulation, one can evaluate many design concepts in a shorter time than one can with physical prototyping. A virtual test workflow drastically reduces the design, prototype and test cycle that are required in a typical product innovation process. For example, a typical concrete product development cycle involves a long process of concrete pouring, curing and producing physical prototypes. The physical design iteration cycle could take months, whereas a simulation design cycle may take only a couple of weeks.
Another key part of the virtual design process is to try out many variations of design parameters in “what if” scenarios once the computer simulation model is validated and designers have the confidence to use simulation results to guide design decisions. With more and more affordable, high-performance computing power available from cloud or onsite servers, more complex simulations can be performed at a given time. As a result, a faster cycle of virtual trials speeds up the entire product innovation process. In many cases, hundreds of design concepts are virtually tested before physical prototyping begins.
Besides improving the speed of development and cutting costs, simulation also helps improve product quality. For example, the global and detailed aspects of product performance can be identified and measured easily using simulation. The insight gained from simulation can be used to troubleshoot product failure and optimize the design.
Simulation enables us to develop new products in a virtual environment built on real-world data with much lower cost or risk. Simulation is already an essential part of the innovation process. Simulation is powering modern manufacturing innovation. We will see this trend accelerate further in the future.
Let me start by wishing everyone a happy holiday season.
My fellowship activities started in July 2017. I spent two weeks in New Jersey getting oriented to the Build Change organization and engineering activities around the world. I then spent two days in Pleasanton getting to meet the engineering team and getting updated on Simpson Strong-Tie products and the team leaders.
In August, I headed to my first assignment in Indonesia. My tasks were:
- Work with the Build Change technical team in Indonesia to review the school building design guidelines and make recommendations to the government on their adherence to the design codes.
- Prepare construction documents for a retrofit of a typical five-classroom school building.
- Visit school sites and select a school building that is a typical candidate for retrofitting whose retrofit scheme can be replicated at other school sites.
- Work with the Better Building Materials team to find out ways to make quality clay bricks economically.
- Provide mentorship (in capacity building) to the engineering team.
The first thing I had to do was to translate the documents to be reviewed from Bahasa Indonesia (a language I had never heard spoken before) to English – Thanks to Google document translator! I was based in Padang, West Sumatra. I am used to long flights from California, but getting to Padang (+14 hour time difference) was very long. Indonesia is the fourth most populous country in the world (after China, India and USA), comprising more than 17,000 islands of which only 6,000 are inhabited.
My team accomplished the following during the two months I was in Indonesia:
- Reviewed and provided comments on the Ministry of Education’s School Construction Guidelines for both new and existing buildings and included sketches, details, supporting calculations, etc.
- Reviewed and provided comments on the National Disaster Risk Management Agency’s School Design Guidelines.
- Reviewed the Minister of Public Works No. 45 / PRT / M /2007’s Technical Guidelines for the Development of Buildings.
- Reviewed the National Standardization Agency (SNI) Planning Procedures for the Earthquake Resistance of Buildings and Non-Building Structures in order to ascertain that the SNI’s school building design requirements are incorporated in the design guidelines of items 1–3 above.
- Provided a Report of Build Change comments and suggestions, with explanations, on the Ministry of Education’s School Construction Guidelines for both new and existing buildings and the National Disaster Risk Management Agency’s School Design Guidelines.
- Provided construction documents, materials list and cost estimate for a typical example new school building. This was a prototype classroom building that incorporated the comments from the reviewed school building design guidelines.
- Provided construction documents, calculations, bill of quantities and cost estimate for the retrofit of the five-classroom building in SD42 school.
- Visited and selected a possible school for the next retrofit project. The schools visited were the ones with highest need (most vulnerable, have most students, representative of most common school buildings). Fundraising efforts are underway to finance the retrofit of the selected representative school building.
- Went to the field with the Better Building Materials team and visited the clay brick making and firing kilns. Suggested possible changes in the kilns and alternative fuels (from firewood) to make better-quality bricks and make the process more environmentally friendly, more sustainable and more economical.
- Conducted hands-on brick wall sample construction activity for the Build Change technical team to illustrate quality mortar mix and the correct mortar thickness for both bed and head joints.
- Moderated technical team presentations given to the communities and made suggestions on how to improve the technical content of those presentations.
The climate in Padang was humid, hot and rainy almost every day I was there. I was amazed by how friendly the people were, even though I could not communicate with them directly (very few speak English). If you think you can handle spicy food, you have not tasted Padang food. Most of the food is served cold, but everyone sweats a lot as they eat. I was also lucky to have time to visit historical Minag chief’s palace and enjoy great snorkeling in one of the private islands.
My second country and current assignment is Colombia. I arrived here in mid-October, having spent two weeks in California after Indonesia. I spent one week in Bogota, and now I am in Medellin, which is going to be my base for the next few months. The food here is not very different from what I get in my home town of Paso Robles, California. The climate in Medellin is pleasant and sightly warmer than in Bogota, which is at a much higher elevation. In both Bogota and Medellin, more than 80% of the respective city populations live in informal housing. These are homes built with low-quality materials, are not engineered and follow no building design or construction guidelines. The informal housing sector is mostly located in very steep mountain slopes and the homes are constructed over time, sometimes reaching four or five stories using unreinforced masonry clay tile blocks.
I have embarked on the following activities:
- Review and comment on Build Change’s Manual of Evaluation and Seismic Strengthening for Vulnerability Reduction in Housing. This manual has been approved by the building departments in Bogota and Medellin for evaluating existing informal housing and as a guide to retrofitting vulnerable buildings and reducing their damage in future earthquakes.
- Coordinate with three universities (two in Bogota and one in Medellin) on full-scale testing of the wall systems used in the informal housing in order to get correct design parameters to use in the Build Change manual update. The walls will be tested for in-plane and out-of-plane (shake table) load conditions. Different wall conditions such as plaster on one or both sides, plaster with wire mesh on one or both sides, etc., will also be tested. Nonlinear building analysis will be carried out using results from the tests in order to access the effectiveness of incremental retrofit schemes such as only adding a ring beam, only providing plaster on one side, etc.
- Help with the training of building professionals (civil engineers, architects, project managers) from the Medellin Social Institute for Housing and Habitat (ISVIMED) on how to implement the Build Change Manual both in the classroom and in the field as a form of capacity building in the two cities.
The work has started, and it keeps us very busy. But I have also had a chance to get out of the city and scale all 747 steps of the 650-foot-tall Piedra del Peñol, “Rock,” in Guatapé, located 50 miles east of Medellin.
If you’re curious, don’t hesitate to contact me at email@example.com before my Fellowship year ends to find out what part of the world I’m in at the time.
This week’s post was written by Carolyn O’Hearn, Software and App Marketing Manager at Simpson Strong-Tie.
Accessing engineering drawings, determining whether you have the right ones and loading them into AutoCAD can seem like an exhausting endeavor. Wouldn’t it be nice to have an application that does everything you need in one package? An application that will also save you time, on both retrieval and installation, and give you access to additional applications? Simpson Strong-Tie has developed a new tool that can take care of all these needs.
We want to make it easier for you to retrieve your drawings without using up valuable design time switching applications. We’ve made substantial improvements to our AutoCAD tools by creating a plugin that now integrates the familiar functionality of our Drawing Finder into our legacy AutoCAD Menu so you can now download drawings, and store only the drawings you need, without ever leaving AutoCAD.
From the menu, the Downloaded drawings area allows you to quickly view all the drawings that you’ve previously downloaded. (See Figure 2.) We’ve also built in a feature that will allow you to customize our drawings and save them to this area as well.
Need to use some other Simpson software in your design? Click the Other applications button in the menu to be taken to our Software and Web Applications page on our website.
The AutoCAD Plugin also solves installation problems you may have experienced with the AutoCAD Menu. We understood it was a time-consuming process to download all of our drawings and that the installation wasn’t as easy as we would like it to be. We’ve eliminated that barrier by building a plugin that connects you directly to the Drawing Finder from inside of AutoCAD with an installer that works the way you would expect. This allows you to download only those drawings that are applicable to the design you are working on. And every drawing you download is automatically stored for quick reference later. With these features combined, your design process is now streamlined!
One more benefit of the AutoCAD Plugin is our ability to add or change drawings in Drawing Finder and update them dynamically on both the tool and our website immediately. You no longer have to install and update a new version with every change. And if you ever run into an issue or need to request additional drawings from the website, you can now use our Help button on the tool to send a request directly to the support team for this specific application.
AutoCAD LT does not support the installation of plugins, therefore our Plugin cannot be installed in LT versions of AutoCAD. However, the content available in our browser based Drawing Finder is the exact same as in the plugin.
Start experiencing our new AutoCAD Plugin today at https://www.strongtie.com/drawing/autocad-drawing-menu. to experience the ease of use and faster designing process we now offer.
If you have questions, please use this simple form to send the team your input.
This week’s post was written by Kari Martin, Marketing Communications Content Manager at Simpson Strong-Tie.
There are a couple of turkeys that like to hang out around our home office in Pleasanton and, no, I’m not referring to any of my colleagues — we actually have a gang of wild turkeys that comes up from the creek behind the office. Almost every day, these colorful birds feel safe enough to stroll onto the office walkway pecking for food outside our office windows and doors. It’s surprising to me that these beautiful creatures could be so fearless (or is it simply naïve?), especially around Thanksgiving time. Their presence reminds me that being fearless is important, because nothing new would ever be discovered if we were too afraid to venture outside our comfort zones.
The beauty and strangeness of the turkeys also remind me to be thankful, because everything we have in life is ultimately a gift. Their consistent return to our office is a gentle reminder as I walk into work to give thanks to you, our readers, our customers and our partners every day. Thank you!
We hope you enjoy the holiday with your family and friends. We’ll be back with another post next week.
This week’s post was written by Griff Shapack, FRP Design Engineer at Simpson Strong-Tie.
Specifying our Composite Strengthening Systems™ (CSS) is unlike choosing any other product we offer. In light of the unique variables involved with selecting and using fiber-reinforced polymer (FRP) solutions, we encourage you to leverage our expertise to help with your FRP strengthening designs. To get started, we first need to determine whether FRP is right for your project. The fastest way to do that is for you to fill out our Design Questionnaire. Our new Excel-based questionnaire collects your project information and helps you use the existing capacity check to evaluate whether or not FRP is suitable for your project per the requirements of ACI 562-16 Section 5.5.2. After the feasibility study, the questionnaire creates input sheets specifically for your project.
Open the FRP Design Questionnaire spreadsheet using Microsoft Excel. If a yellow warning appears at the top of the sheet, click “Enable Content” to ensure that the workbook will function properly. You will start on the worksheet tab named “Main”. “Main” will be the only worksheet tab when you begin, but more worksheet tabs will be created as you use the spreadsheet.
Enter the project information and your contact information in Section 1 of the worksheet. The contact information should be for the Designer that you would like Simpson Strong-Tie to work with for this project’s FRP design. See Figure 1.
Enter the FRP strengthening information in Section 2 of the worksheet. If the application will require an existing capacity check, an input form requesting the information needed for the check will appear in Section 3 of the worksheet.
For members that support gravity loads, an existing capacity check must be performed to verify that FRP strengthening is suitable before a design can be generated. For these members, the spreadsheet will generate a check table for you in Section 3 of the worksheet. Enter the number of members to be checked and the dead load (D), live load (L) and snow load (S) for each member. Use consistent units for the input. See Figure 2. The spreadsheet will calculate the demand-to-capacity ratio (DCR) for each member. The ratio must be less than or equal to 1.0.
- A result of “OK” means the existing capacity check is passed. Proceed to Step 5 below.
- A result of “NG” (no good) means the existing capacity check is failed and FRP strengthening is not likely to be suitable. However, consider contacting Simpson Strong-Tie about your design condition to ensure that this is the case.
You are now ready to create an element input worksheet for those members that passed the existing capacity check. Click “FRP Questionnaire” from the Excel menu bar. Then click the “Input Sheet” button in the ribbon bar. See Figure 3.
This will create an element input worksheet as a new worksheet tab. See Figure 4.
Enter the number of elements to be checked and fill in the design information for each member. The “No. of elements” cell features a drop-down menu with the numbers 1–5, but any number can be typed into the cell. (Each member should have passed the existing capacity check in Step 4.) See Figure 5.
If you would like to add different member types that need to be strengthened, click “Another Type of Strengthening” button in the ribbon bar. See Figure 6. This will create a new “Main” worksheet. Repeat the steps above, until all strengthening types and member data have been entered.
When you have finished inputting all required data, save the spreadsheet file and email it to firstname.lastname@example.org. You should expect confirmation of receipt from us within one business day.
From there, if FRP is a viable option, you can decide to utilize our no-cost, no-obligation design services. Our team will design a unique solution specifying the most cost-effective CSS products that address your particular needs. The design calculations, drawings, notes and specifications are prepared by Simpson Strong-Tie Engineering Services and can then be incorporated into the design documents that you submit to the building official.
Don’t know which FRP solution is the right one for you? We do. Give our new Design Questionnaire a try, and let us be your partner during the project design phase. Our new Excel-based questionnaire collects your project information and helps you use the existing capacity check to evaluate whether or not FRP is suitable for your project per the requirements of ACI 562-16 Section 5.5.2 or AASHTO FRP Guide Spec Section 1.4.4. After the feasibility study, the questionnaire creates input sheets specifically for your project. For projects in Canada designed per the requirements of CSA S806 or CSA S6, please use our fillable PDF questionnaire to collect your information.
Learn more at strongtie.com/products/rps/css/frp-engineering-design.
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.
This week’s post was written by Jhalak Vasavada, Research & Development Engineer at Simpson Strong-Tie.
When we launched our new, patent-pending MPBZ moment post base earlier this year, the evaluation of the moment capacity of post bases was not covered by AC398 – or by any other code, for that matter. There wasn’t a need – there were no code-accepted connectors available on the market for resisting moment loads.
We proposed adding moment evaluation to the AC398 and presented our research to the ICC-ES committee in June. After a thorough review, which included a public hearing, the provision was approved. Here are some details about the revisions to this acceptance criteria.
What is AC398?
AC398 is the Acceptance Criteria for cast-in-place cold-formed steel connectors in concrete for light-frame construction.
Acceptance criteria are developed to provide guidelines for demonstrating compliance with performance features of the codes referenced in the criteria. ICC-ES develops acceptance criteria for products and systems that are alternatives to what is specified in the code, or that fall under code provisions that are not sufficiently clear for the issuance of an evaluation report.
The criteria are developed through a transparent process involving public hearings of the ICC-ES Evaluation Committee (made up entirely of code officials), and/or online postings where public comments were solicited.
How is the moment load evaluated?
The MPBZ moment post base is a cast-in-place post base designed to resist uplift, download, lateral and moment forces. This blog post in February describes how it works, how it was tested and includes a design example. Since the MPBZ falls under the specialty inserts category of cast-in anchorage, it is not covered by the provisions of chapter 17 of ACI 318-14. Therefore, the MPBZ was evaluated based on AC398 for anchorage to concrete.
Our engineers worked closely with ICC-ES and the American Wood Council to develop evaluation criteria for moment. This revision to the criteria for moment evaluation and testing was posted for public comments on the ICC-ES website, and then presented by our engineers at the ICC-ES committee hearing last June. The presentation included the design, use, testing and load rating of the MPBZ. Following the hearing, and a thorough review, the committee approved the proposed revision to AC398.
What are the revisions to AC398?
With reference to moment evaluation, a few of the key changes to AC398 are:
- Moment Anchorage Strength: Similar to tension and shear anchorage strength, the available moment anchorage strength shall be determined using the equation
Where F = applied horizontal test force used to determine moment strength (lbf)
D = vertical distance from top of concrete member to the applied lateral test force F (ft.) (moment arm)
Other terms are as previously defined for tension and shear anchorage strength equations.
- Rotation: Testing of moment base connectors subject to an applied moment shall include measurement and reporting of the connector rotation as determined by the relative lateral displacement of gauges positioned 1″ and 5″ above the top of the connector.
- Side Bearing: Testing of moment base connectors that rely on bearing of the wood member against the side of the connector to resist moment loads shall address wood shrinkage.
Learn more about the MPBZ in our free upcoming webinar.
Join us live on December 6 for an interactive webinar on the MPBZ moment post base, its evaluation, its testing and its applications. In this webinar, we will discuss MPBZ moment post base product features, product development, design examples and much more. Attendees will also have an opportunity to ask questions during the event. Continuing education units will be offered for completing this webinar. Register today here.
Upcoming free MPBZ webinar.
Join Simpson Strong-Tie R&D engineer Jhalak Vasavada, P.E., and Simpson Strong-Tie product manager Emmet Mielbrecht for a lively and informative discussion of this new product.
This week’s post was written by Clifton Melcher, Senior Product Manager at Simpson Strong-Tie.
Structural engineers concerned with building envelopes are always looking for better solutions that help isolate the cladding from the primary structure in conditions where large building drift is a concern. Simpson Strong-Tie has an answer with a unique and innovative solution, the new DSSCB (drift strut sliding clip bypass).
The DSSCB is used to anchor cold-formed steel framing to the primary structure in bypass applications. The DSSCB is a clip that slides inside standard struts that most engineers and contractors are already familiar with. These struts will typically be attached to structural steel. However, there is also a cast-in-place strut option referred to as a strut insert. Many different manufacturers of these struts exist, but three common manufacturers are Unistrut®, PHD and B-line. The strut and strut insert requirements for the DSSCB can be found in the Simpson Strong-Tie DSSCB flier (F-CF-DSSCB17).
The DSSCB has many design features that make it easy to use, cost-effective and designer-friendly.
- The DSSCB clip has uniquely formed inserts that twist into place easily with minimal friction
- The clip features squaring flanges that help keep the clip square inside the strut
- Shoulder screws (included) prevent over-drilling and increase overall capacity
- Pre-engineered design offers clip, strut and anchorage solutions
- Pre-punched slots provide a full 1″ of both upward and downward deflection
- Sight lines facilitate proper screw placement
The DSSCB is also a hybrid clip and accompanies both slide applications as well as fixed applications. In addition to vertical slots, the clip also has round circular holes for fixed-clip conditions. This will make the clip more versatile and limit inventory.
Another great use for this product is for panelized construction. The DSSCB makes it a snap to anchor finished panels to the slab without having to waste time drilling and installing anchors. Locking panels into place is also simple with a DSHS connector clip that can be easily slid into place and attached with only one (1) #10 screw.
Accommodating for building drift and commercial panel construction just got easier with the Simpson Strong-Tie DSSCB!
Load required at bypass slide condition attached to steel with ASD reactions of 450 lb. tension (F2) and 422 lb. compression (F3) – based on CFS DesignerTM software or hand calculations
Stud member = 600S162-43 33 ksi at 16″ o.c. – based on CFS Designer software or hand calculations
Per page 4 of the DSSCB flier (F-CF-DSSCB17), allowable F2 = 785 lb. and F3 = 940 lb. for slide-clip connector (shown below)
Per page 7 of the DSSCB flier (F-CF-DSSCB17) allowable loads of F2 = 475 lb. and F3 = 2,540 lb. for strut allowable anchorage with 1″ weld at 12″ o.c. using a 13/16″ strut (shown below)
Note that, at a strut splice (if required), maximum load is not to exceed F2 of 865 lb. per note 6 on page 7 (shown below)
6. For any connector occuring within 2″ of channel strut splice, load not to exceed — F2 = 865 lb. and F4 = 785 lb.
Check connector and strut/anchorage:
F2 (tension): Pmax = 450/ minimum of (785,475) = 0.95 < 1 ok
F3 (compression): Pmax = 422/ minimum of (940,2540) = 0.45 < 1 ok
Q: How are the products sold?
A: The clips are sold in kits of 25. For the DSSCB43 and DSSCB46, one polybag of 83 screws is included. For the DSSCB48, two 55 screw polybags are included. The DSHS will be sold separately from the clips and come in bags of 100. The struts will not be sold by Simpson Strong-Tie.
Q: Can I use the 1 5/8″ x 1 5/8″ strut for the fixed-clip application?
A: No, the fixed-clip application was tested only with the 13/16″ x 1 5/8″ strut. The 1 5/8″ x 1 5/8″ strut would overhang more, which we calculate could reduce capacities.
Q: When should I use the DSHS clip?
A: The DSHS clip should be used where you want to fix the clip in place in the F1 (in-plane) direction. This clip will most likely be used for panelizing, but could be used for stick framing as well when adjustment is required before locking the clip in place.
Q: Why are there two tables that I need to use to determine my connector capacity?
A: One table is for the capacity of the clip, and the other table is for the capacity of the strut/anchorage. Two tables give the designer more flexibility in the design as well as an understanding of what is controlling the failure.
Q: How do I accommodate load requirements at a strut splice?
A: Note 6 to the Strut Channel Allowable Anchorage Loads to Steel table states the capacity of the strut with a clip directly at the splice. The values are based on assembly testing. Refer to page 7 of the flier.
Q: How do I accommodate load requirements at the strut end?
A: Note 10 to the Strut Channel Allowable Anchorage Loads to Steel table states that the connector load is to be located a minimum of 2″ from the end of the strut channel. Note 2 to the Concrete Insert Allowable Load Embedded to Concrete table gives a reduction capacity for end conditions. Reference pages 7 and 8 of the flier.
Q: Why do we show an F1 load on a drift clip?
A: The drift clip without the DSHS does not support any load in F1 direction. F1 load is only supported if a DSHS clip is used in conjunction with the DSSCB clip. This is also noted (note 4) on the DSSCB Allowable Slide-Clip Connector Loads and the DSSCB Allowable Fixed-Clip Connector Loads tables. Refer to pages 4 and 6 of the flier.
Q: How do I accommodate higher concentrated loads at jambs exceeding my typical stud loads?
A: Note 7 to the Strut Channel Allowable Anchorage Load to Steel table gives the capacity of the strut/anchorage if the strut is welded directly at the clip. Refer to page 7 of the flier.
Q: Can I drive PAFs into my strut?
A: No. The shot pin tool will not fit inside the strut channel.
Q: If I want to attach my strut to the steel edge angle with screws, what brand should I use?
A: Simpson Strong-Tie makes great fasteners, and we would recommend these fasteners (#12-24 Strong-Drive® Self-Drilling X Metal screw). However, you can use any brand fastener provided they meet our Pss and Pts capacities minimum nominal strength values in General Notes for Allowable Connector Load Tables on page 8 of the flier.
Q: At a double-stud condition, is it acceptable to double the capacity if I use two (2) clips?
A: It is acceptable to double the capacity of the DSSCB slide-clip or fixed-clip table loads (pages 4 and 6 in flier). However, the load should not exceed the load listed in the Strut Channel Allowable Anchorage Loads to Steel table (page 7 in flier). If a load is exceeded, please follow note 7 on page 7 of the flier by adding a weld connection directly at the concentrated load. This will allow you to have a wider anchor spacing for your typical studs and only reinforce the higher concentrated loads with connections directly at these locations.
This week’s post was written by Jacob McAuley, Associate Regional Marketing Manager at Simpson Strong-Tie.
Every October, millions of people across the globe participate in earthquake drills as part of an event called the Great ShakeOut in order to improve their earthquake preparedness. This year, the Great ShakeOut took place on October 19 and involved more than 60 countries. In addition to the earthquake drill, participants in the event often take part in other activities such as seminars, Q&As and more. At Simpson Strong-Tie, we practiced earthquake drills at each of our major branches, and, in our Pacific Northwest region, we were part of a Reddit Ask Me Anything event (an online live Q&A) to talk about earthquake safety and answer people’s questions. Below, I discuss our participation in both of these activities.
If you’ve ever participated in an earthquake drill, you know that they can be a bit surreal. Sure, at certain points jokes are made and people laugh, because after all, it is pretend. But at other points during the drill, you will probably recall the very real threat that an earthquake presents, and you will wonder, “Would I really be prepared?” That’s why these drills are so important and why we as a company participate every year – because in order to react quickly, you need to be well-practiced. Here’s a little about the drill we did.
The Great ShakeOut earthquake drill lasts only about 20 minutes and is fairly easy to prepare for and participate in (learn about how to participate here). At our Pleasanton office, where I work, at 10:19 am we heard a recording over the intercom that announced the earthquake drill was now under way. Each of us immediately did what the announcement instructed us to do: Drop, cover and hold on. The website of the ShakeOut expounds the three steps as follows: “Drop to the ground, take Cover under a table or desk, and Hold On to it as if a major earthquake were happening (stay down for at least 60 seconds).” They also recommend that during the drill, while you’re under the table, you should look around and imagine what would happen in a major earthquake and consider various potential hazards around you (e.g., items that might fall, break or cause a fire, such as lighting fixtures, unsecured bookcases or other furniture, computer or television screens, unstrapped water heaters) and how you might make them safer. Once the drill was over, another announcement indicated that we exit the building and go to a predesignated meeting area, where selected trained employees were responsible for taking roll of their assigned groups. Once everyone was accounted for, we went back in and resumed our usual workday.
Then, continuing in the spirit of preparedness, at 12:00 noon (PT), our very own Emory Montague, R&D engineering manager, joined Pacific Northwest earthquake-preparedness experts for a lively two-hour Reddit Ask Me Anything forum. The conversation is still live so be sure to check it out. The group of experts included a seismologist, two geologic hazards managers, a structural engineer (Emory), two geologists and an earthquake and volcano coordinator. Questions could be asked by anyone, and topics ranged from building safety to predictions about earthquakes to necessary earthquake supplies and more. Overall, the Ask Me Anything event was a success and helped make this a sobering and very informative Great ShakeOut day.
This week’s post was written by Caleb Knudson, R&D Engineer at Simpson Strong-Tie.
It’s been said that the World Wide Web is the wave of the future. Okay, maybe this is slightly outdated news, as it’s been 25 years since Bill Gates penned his internet tidal-wave memorandum, but it’s a good lead-in to this week’s blog topic – web apps. More specifically, those apps that have been developed to address the wall-bracing requirements defined in the International Residential Code® (IRC). Designers and engineers have no doubt noticed that over the last several code cycles, the wall-bracing provisions in the IRC have become increasingly complex. To help navigate these requirements and calculate the required bracing length for a given wall line, Simpson Strong-Tie introduced the Wall-Bracing-Length Calculator (WBLC) a few years back, as discussed in an earlier blog post. I’ll also mention that the WBLC has since been updated to the 2015 IRC.
Those familiar with the wall-bracing provisions in the IRC know that there are twelve intermittent wall-bracing methods and four continuous-sheathing methods to address wall-bracing requirements. Each of these methods may be used in most applications, and, while some provide advantages over others, the code-based methods provide Designers with quite a bit of flexibility. However, there may be cases where the site-specific conditions are beyond the scope of the IRC, or there just isn’t enough available full-height wall space to accommodate the required wall-bracing length. These cases are most likely to occur at large window openings or at garage fronts.
Let’s take the following example of a house on Lake Washington – assuming the house is being designed in accordance with the IRC. Presumably, one might prefer to have unobstructed lake views, which of course means lots of large picture windows and not much room left for braced wall panels. Let’s also suppose you’ve got a brand-new Chris Craft that you’d like to protect against the weather when it’s not in the water – this means wide garage doors and, again, not much room for conventional wall bracing.
So what do we do now?
Thankfully, the International Residential Code provides some guidance. Section R301.1.3 states that when a building, or portion thereof, is outside the scope of the IRC, the element(s) may be designed in accordance with accepted engineering practice. The code goes on to state that the extent of the design shall be such that the engineered element(s) are compatible with the performance of conventional methods prescribed in the code. That creates some additional options for our tool box. We could design a site-built shearwall; however, due to aspect-ratio limitations defined in the Special Design Provisions for Wind and Seismic (SDPWS), we still may not be able to get the lake views and wide garage we want. The next option, and one we’ll focus on here, is the code-approved prefabricated Simpson Strong-Tie® Strong-Wall® shearwall.
In an earlier blog post, as previously mentioned, we introduced the Strong-Wall Bracing Selector (SWBS) and defined just how we determine equivalence to conventional bracing methods. We further described the benefit of using the selector in conjunction with the Wall-Bracing-Length Calculator (WBLC). To refresh your memory, when Designers start with the WBLC to determine required wall-bracing-lengths for up to seven parallel wall lines, they can export those bracing lengths as well as project and jobsite information directly to the SWBS with the click of a button. The SWBS will then provide a list of Strong-Wall panels that provide an equivalent bracing length, evaluate their anchorage requirements, and return a list of pre-engineered anchor solutions for a variety of foundation types.
On to the present: We just launched the Strong-Wall Bracing Selector web app version 2.0, and there are a few new features worth noting.
First, I’ll mention that all Strong-Wall solutions have been evaluated according to the 2015 I-Codes. Next, and hopefully this doesn’t come as too much of a surprise, the original wood Strong-Wall shearwall (SW) is being phased out with guaranteed availability through December 31, 2018. In light of this planned obsolescence, we have removed the SW solutions from the latest version of the bracing selector.
Here’s the good news – and this is big: We’ve now added the new Strong-Wall wood shearwall (WSW) to the app and recommend this as a replacement for the SW in all applications. In the interim, while the original wall is still available, version 1.0 of the bracing selector app may be used if an SW bracing solution is required.
Lastly, we’ve provided the Designer with a bit more flexibility and control over the Strong-Wall bracing solutions provided by the app. If you recall, version 1.0 provided a solution using the minimum possible number of Strong-Wall panels to satisfy the bracing length requirement. We’ve changed that in version 2.0; Designers may still select a solution using the minimum number of panels, but they may also select the exact number of Strong-Wall panels to satisfy their wall-bracing-length requirements. Typically, it’s desirable to address the bracing requirement with the minimum number of Strong-Wall shearwall panels possible. Sometimes, however, it may be advantageous to increase the number of panels used, in order to decrease the Strong-Wall panel width used for a solution or to reduce anchorage requirements, i.e., lesser footing dimensions and anchor embedment depths. Stated a little differently, we’re providing the option to find the right balance between the braced wall panel design and the anchorage design – i.e., the Goldilocks zone for prescriptive wall bracing.
So now that we’ve reviewed just why a Designer may need to specify a Strong-Wall shearwall in prescriptive applications and how the Wall-Bracing-Length Calculator and Strong-Wall Bracing Selector web apps help to navigate this process, we’re interested to see what you think. Is there any additional functionality that you’d like to see in the future, or are these apps just right for your design needs? Let us know in the comments below.
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.