Paul McEntee

About Paul McEntee

A couple of years back we hosted a “Take your daughter or son to work day,” which was a great opportunity for our children to find out what their parents did. We had different activities for the kids to learn about careers and the importance of education in opening up career opportunities. People often ask me what I do for Simpson Strong-Tie and I sometimes laugh about how my son Ryan responded to a questionnaire he filled out that day:

Q.   What is your mom/dad's job?
A.   Goes and gets coffee and sits at his desk

Q.   What does your mom/dad actually do at work?
A.   Walks in the test lab and checks things

When I am not checking things in the lab or sitting at my desk drinking coffee, I manage Engineering Research and Development for Simpson Strong-Tie, focusing on new product development for connectors and lateral systems.

I graduated from the University of California at Berkeley and I am a licensed Civil and Structural Engineer in California. Prior to joining Simpson Strong-Tie, I worked for 10 years as a consulting structural engineer designing commercial, industrial, multi-family, mixed-use and retail projects. I was fortunate in those years to work at a great engineering firm that did a lot of everything. This allowed me to gain experience designing with wood, structural steel, concrete, concrete block and cold-formed steel as well as working on many seismic retrofits of historic unreinforced masonry buildings.

Beat Building Drift with the New DSSCB Drift Strut Slide Connector from Simpson Strong-Tie

This week’s post was written by Clifton MelcherSenior 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!

Design Example

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 — F= 865 lb. and F= 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

FAQs:

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.

Drop, Cover, and Hold On – Becoming Earthquake-Smart in the 2017 Great ShakeOut

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.

Introducing the New and Improved Simpson Strong-Tie Strong-Wall® Bracing Selector

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.

Holdown Anchorage Solutions

A couple years ago, I did a post on selecting holdown anchorage solutions. At the time, we had created a couple engineering letters that tabulated SSTB, SB and PAB anchor solutions for each holdown to simplify specifying anchor bolts. About a year later, a salesperson suggested we tabulate SSTB, SB and PAB anchor solutions for each holdown. You know, to simplify specifying anchor bolts…

This conversation reminded me of the difficulty in keeping track of where design information is. In the C-C-2017 Wood Construction Connectors catalog, we have added this material on pages 62-63. Which should make it easier to find. I thought I should update this blog post to correct the links to this information.

A common question we get from specifiers is “What anchor do I use with each holdown?” Prior to the adoption of ACI 318 Appendix D (now Chapter 17 – Anchoring to Concrete), this was somewhat simple to do. We had a very small table in the holdown section of our catalog that listed which SSTB anchor worked with each holdown.

The good old days! (Don’t use this today)

During the good old days, anchor bolts had one capacity and concrete wasn’t cracked. ACI 318 stipulates reduced capacities in many situations, different design loads for seismic or wind, and reductions for cracked concrete. These changes have combined to make anchor bolt design more challenging than it was under the 1997 Uniform Building Code.

This blog has had several posts related to holdowns. So, What’s Behind a Structural Connector’s Allowable Load? (Holdown Edition) explained how holdowns are tested and load rated in accordance with ICC-ES Acceptance Criteria. Damon Ho did a post, Use of Holdowns During Shearwall Assembly, which discussed the performance differences of shearwalls with and without holdowns, and Shane Vilasineekul did a Wood Shearwall Design Example. So I won’t get into how to pick a holdown.

Once you have determined your uplift requirements and selected a post size and holdown, it’s necessary to specify an anchor to the foundation. To help designers select an anchor that works for a given holdown, we have created different tables that provide anchorage solutions for Simpson Strong-Tie holdowns.

Two tables on pages 62-63 in the Wood Construction Connectors catalog summarize holdown anchorage solutions. The tables are separated by wood species (DF/SP and SPF/HF) to give the most economical anchor design for each post material. The preferred anchor solutions are SSTB or SB anchors, as these proprietary anchor bolts are tested and will require the smallest amount of concrete. When SSTB or SB anchors do not have adequate capacity, we have tabulated solutions for the PAB anchors, which are preassembled anchors that are calculated in accordance with ACI 318 Chapter 17.

The solutions in the letters are designed to match the capacity of the holdowns, which allows the contractor to select an anchor bolt if the engineer doesn’t specify one. They are primarily used by engineers who don’t want to design an anchor or select one from our catalog tables. We received some feedback from customers who were frustrated that some of our heavier holdowns required such a large footing for the PAB anchors, whereas a slightly smaller holdown worked with an SB or SSTB anchor in a standard 12″ footing with a 1½” pop-out.

To achieve smaller footings using our SB1x30 anchor bolts, we reviewed our original testing and created finite element (FEA) models to determine what modifications to the slab-on-grade foundation details would meet our target loads. Of course, we ran physical tests to confirm the FEA models. With a 6″ pop-out, we were able to achieve design loads for HD12, HDU14 and HHDQ14.

The revised footing solutions for the heavier holdowns require less excavation and less concrete than the previous Appendix D calculated solutions, achieving desired loads while reducing costs on the installation.

Part of the fun of structural engineering is that there are always new problems to solve. Let us know what holdown anchorage challenges or solutions you have to share!

Introducing the Building Strong Blog

Building Strong Blog

This week we want to let you know about a new resource, the Building Strong blog. It’s very different from the SE Blog in that it ranges beyond the topics important to structural engineers to cover issues and various perspectives that help construction professionals of all disciplines design and build safer, stronger structures as efficiently as possible. We developed the new industry blog to highlight issues and topics that are of special interest to construction and building professionals. Through semi-monthly articles, the blog will cover topics ranging from rising labor costs to innovative technologies and the changing landscape of the building industry.

The Building Strong blog will cover topics on:

  • Safety, codes, and compliance
  • Residential and commercial construction
  • Decks and outdoor living
  • Building resilience
  • Emerging trends and industry insights
  • Collaborations and giving
  • Pro tips

We’re excited to offer the Building Strong blog. If you enjoy the SE Blog, this new content will give you a fresh take on timely topics affecting our industry. Check it out today!

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.

Q&A About Advanced FRP Strengthening Design Principles

Our thoughts go out to everyone affected by Hurricane Harvey and this disaster in Texas. To help with relief efforts we are donating $50,000 to the American Red Cross Disaster Relief Fund. Employees at our Houston warehouse are safe and the employees from our McKinney branch will be doing as much as they can to help with relief efforts.

This week’s post was written by Griff Shapack, PE. FRP Design Engineer at Simpson Strong-Tie.

On July 25, 2017, Simpson Strong-Tie hosted the second interactive webinar in the Simpson Strong-Tie FRP Best Practices Series, “Advanced FRP Design Principles,” in which Kevin Davenport, P.E. – one of our Field Engineering Managers – and I discussed the best practices for fiber-reinforced polymer (FRP) strengthening design. The webinar examines the latest industry standards, proper use of material properties, and key governing limits when designing with FRP 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 taking questions from attendees during the Q&A session. Here is a curated selection of Q&A from that session:

While I see how you improve the flexural capacity of a beam, how do you increase its shear capacity to match new moment strength?

ACI 440.2R recommends checking the element for shear if FRP is used to increase flexural strength. U-wraps can be used to provide shear strengthening of a beam.

Are there any “pre-check” serviceability checks (deflection, vibration, etc.) similar to the ACI 440 strength check that you recommend when considering the use of FRP?

ACI 440.2R contains a few serviceability checks on the concrete, rebar and FRP that can be performed once you have designed a preliminary strengthening solution.

Are these strengthening limits for gravity loads only? What about for a seismic load combination?

Yes, the strengthening limits are just for gravity loading. Seismic loading does not require an existing capacity check as it is highly unlikely for the FRP to be damaged during a lateral event.

Did Simpson Strong-Tie perform load tests on FRP repaired timber piles?

We are currently testing our FRP products as applied to timber piles at West Virginia University. We have also implemented a full-scale testing program on damaged timber piles at our own lab using our FX-70® fiberglass jacket system.

Will any of your seminars cover FRP and CMU? Seismic applications?

Yes, these are topics we are considering for future webinars.

The 0.6 limit for compressive stress can be very limiting. Can this value be evaluated on a case-by-case basis? The Euro code allows higher limits on compressive stress?

Our designers will report this value, along with the section addressing this check from ACI 440.2R, to the EOR and discuss whether the EOR would like to proceed with the FRP strengthening on his or her project.

Which engineer (EOR or Delegated Engineer) is responsible for specifying the scope of special inspections?

We provide a draft FRP specification to the EOR to use in their final determination of the special inspection requirements for a project. It’s in the owner’s best interest to hire a qualified special inspection agency on an FRP installation project.

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.

Introducing Fabric-Reinforced Cementitious Matrix (FRCM)

February 14 marks the third interactive webinar in the Simpson Strong-Tie Composite Strengthening Systems™ Best Practices Series: “Introducing Fabric-Reinforced Cementitious Matrix (FRCM).

Join Simpson Strong-Tie engineering manager Brad Erickson, S.E., P.E., and Simpson Strong-Tie senior product manager Mark Kennedy, PMP, for an informative discussion of this new product solution. Attendees will have the opportunity to ask questions during the live event.

Continuing education credits will be offered for this webinar.
Participants can earn one professional development hour (PDH) or 0.1 continuing education unit (CEU).


Why Fire-Rated Hangers Are Required in Type III Wood-Frame Buildings

One of the first mixed-use designs I worked on as a consulting structural engineer was a four-story wood-frame building over two levels of parking. Designing the main lateral-force-resisting system with plywood shearwalls was a challenge for this project that required new details to meet the high design loads. The high overturning forces were resisted using the Simpson Strong-Tie® Strong-Rod™ anchor tiedown system, which incorporates high-strength rods, bearing plates and shrinkage compensation devices.

At the time, these construction details using Strong-Rod systems and high- load shearwall diaphragms were new, innovative concepts. However, this method of construction rapidly became commonplace as intense demand for housing fueled the trend toward denser, mixed-use developments in downtown areas. I discussed the trend toward taller, denser developments in this post.

A more recent trend in wood-frame construction has been the shift to Type III wood-frame construction, which allows designs up to five stories. To help educate designers on some of the nuances of Type III wood-frame construction and provide guidance on meeting the associated code requirements, we reached out to Bruce Lindsey, the South Atlantic Regional Director for WoodWorks. Bruce wrote a two-part article entitled Fire Protection Considerations with Five-Story Wood-Frame BuildingsPart 1 and Part 2. This post will go into more detail on connecting the floor system to the two-hour fire-rated exterior walls and discuss our new DG series joist hangers that are specially designed for this application.

As a structural engineer, I was aware of fire requirements mostly because I needed to account for the weight of fire sprinklers, added layers of gypsum board, fire-proofing on steel, or concrete slab thickness in my design. While the increased loads can affect the vertical- and lateral-force-resisting systems, I seldom needed to change the details and connections in my designs.

The exterior walls in Type III wood-frame construction require fire-retardant-treated (FRT) lumber with two layers of gypsum board to provide a two-hour fire rating. There are many established fire-rated floor and wall assemblies available. The challenge, as discussed in Part 2 of Mr. Lindsey’s post, is detailing the intersections between the floor and wall systems. Connecting the floor framing to the exterior walls in Type III construction requires careful detailing to transfer the vertical loads without compromising the two-hour fire rating of the wall assembly.

Below is a summary of some of the possible fire wall connections as discussed in Mr. Lindsey’s previous blog posts.

A solid header on top of the wall that has adequate thickness to provide a two-hour rating through its charring capability. The cost and availability of solid rim board material should be considered.

A continuous 2x ledger or blocking to provide one hour of fire resistance. The second hour of resistance is provided by ceiling gypsum board. Some jurisdictions object to this detail over concerns about a fire starting within the floor cavity.

Some jurisdictions interpret the two-hour exterior wall requirement as applying only to the wall and not the floor. In such jurisdictions, designers can sometimes use standard platform framing in Type III construction.

A variation where the ledger can be installed over two layers of gypsum board. Simpson Strong-Tie has tested and published values for ledger connections over gypsum board using our SDWH and SDWC fasteners. The testing of these fasteners was discussed in our Spanning the Gap post from earlier this year.

In this detail, one hour of fire resistance is provided by a single layer of gypsum board running the full height of the wall with a hanger installed over the gypsum board. The second hour of resistance is provided by the ceiling gypsum board.

A variation of this detail is our DU/DHU series of drywall hangers that are installed over two layers of gypsum board. These were addressed in this post.

Designs using hangers or ledgers installed over gypsum board can create construction sequencing challenges. Since the gypsum board needs to be installed before the framing, the contractor will need to coordinate between the trades.

A new solution that eliminates sequencing issues for Type III construction is our series of DG/DGH/DGB fire wall hangers, which are designed to easily install on a two-hour wood stud fire wall. These top-flange hangers feature enough space to allow two layers of 5/8″ gypsum wall board to be slipped into place after the framing is complete.

These new fire wall hangers were tested in accordance with ICC-ES AC13 and ASTM D7147, which I discussed in How We Test – Part I: Wood Connectors. These standards do not explicitly detail how to test a hanger installed on a wood stud wall, so we collaborated closely with ICC Evaluation Services to develop a test setup that meets the intent of the standards.

All three of our new fire wall hangers have been tested according to ASTM E814 and received F (flame) and T (temperature) ratings for use on either or both sides of the fire wall. These ratings verify that the DG/DGH/DGB hangers do not reduce the two-hour fire wall assembly rating.

Our testing and load tables address installation of 2×4 or 2×6 stud walls constructed of Douglas fir (DF), southern pine (SP), spruce-pine-fir (SPF) or hem-fir (HF) lumber.

DG Hanger

DGH Hanger

DGB Hanger

Drywall Notch Detail

If you are working on a Type III wood-frame construction project, check out our Fire Wall Solutions page, which has product profiles with links to further information about the new DG hanger series, as well as our DU/DHU series of drywall hangers and fire wall fastener solutions using Strong-Drive® SDWS Timber screws.

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.