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What Makes Strong Frame® Special Moment Frames So Special

In a Structural Engineering Blog post I wrote last October, “Soft-Story Retrofits Using the New Simpson Strong-Tie Retrofit Design Guide,” one item I barely touched on at the time was the benefit of using Simpson Strong-Tie® Strong Frame special moment frames to retrofit vulnerable soft-story wood-framed buildings commonly found on the West Coast. In this post, I will be diving into more detail on a few features that make the Strong Frame special moment frame truly special.

In the recent release of the ANSI/AISC 358-16 (AISC 358-16), the Simpson Strong-Tie Strong Frame moment connection has been included as a prequalified special moment frame (SMF) connection. Prequalified moment connections are structural-steel moment connection configurations and details that have been reviewed by the AISC Connection Prequalification Review Panel (CPRP) and incorporated into the AISC 358 standard. What’s unique about this newly prequalified connection is that it’s the first moment connection to be prequalified in AISC as a partially restrained (PR-Type) moment connection.

With this recent inclusion into AISC 358-16, we’ve also developed our newly released Strong Frame Design Guide to help designers understand the differences in design and detailing between the Strong Frame connection and traditional SMF connections. The following are just a few of the key differences discussed in this guide.

SMF Yielding Elements

Traditional prequalified moment frames most often require a welded connection with either a weakened beam or a stiffened connection. SMF connections are designed so that the beam will yield as necessary under large displacements that may occur during a seismic event. The yielding of the beam section provides energy dissipation and is designed to ensure that the fully restrained beam-to-column connection isn’t compromised. The current design philosophy is the product of extensive testing of SMF connections based on studying the effects of the 1994 Northridge and 1989 Loma Prieta earthquakes in California. Figures 1, 2 and 3 below depict test specimens that demonstrate yielding at the designated areas of the beam.

The Strong Frame SMF has taken a different approach to the traditional connections by utilizing a Yield-Link® structural fuse designed to provide the energy dissipation for the beam-to-column moment connection. This is a modified T-Stub that has a reduced section in the stem. The yielding during a seismic event has been moved from the beams to the Yield-Link structural fuse. The fuse can be replaced after a major event, very much like an electrical fuse when overloaded. A traditional moment frame may require a much more invasive structural repair.

Beam Lateral Bracing

The traditional types of prequalified connections, as along with other proprietary connections included in AISC 358, all require the beam to yield so as to dissipate energy as discussed above. These types of connections require that the beam be braced to resist the lateral torsional buckling per code. However, it is difficult to meet the bracing requirements in the case of a steel SMF in a wood structure.

With the Strong Frame SMF connection, the energy dissipation is moved from the beams to the Yield-Link structural fuses, with the connection following a capacity-based design approach. This allows the connection to remain elastic under factored load combinations. With the yielding confined to the structural fuses, inelastic deformation is not expected from the members and lateral beam buckling braces are not required. The beam can be designed to span the entire length without beam bracing. See also this blog post.

Column-Beam Relationship Requirements

Traditional SMF follow a strong column – weak beam requirement to ensure plastic hinging occurs in the beams and not the columns. If the energy dissipation takes place within such hinging in the beams, the column members will remain elastic so as to provide stability and strength for the above stories. If plastic hinges occur in the columns, there is a potential for the formation of a weak-story mechanism.

The Strong Frame special moment frame is unlike the traditional SMF, where the plastic hinges are formed by the buckling of the beam flange and web. In the Strong Frame SMF, the stretching and shortening of the links at the top and bottom of the Strong Frame beams are the yielding mechanisms. So instead of a strong column – weak beam check, the Strong Frame design procedure checks for a strong column – weak link condition where the ratio of the column moments to the moment created by the Yield-Link® couple is required to be greater than or equal to 1.0.

Installation

Traditional moment frame connections typically require welding in the field. Where bolted SMF connections are used, pretensioned bolts are necessary. Both welding and pretensioned bolts require third-party special inspection.

The Strong Frame SMF has been designed and tested as a 100% field-bolted connection. Unlike other bolted options, the Strong Frame’s field-bolted connections only need to be made snug tight. No onsite bolt pretensioning or special inspections are required with this system. This allows the beams and columns to be maneuvered into place, erected and installed in a fraction of the time needed for the welding, lateral-beam-bracing installation and additional inspections or repairs that traditional moment frames typically require.

Design

One last item I’d like to discuss is the design service that Simpson Strong-Tie provides for the Strong Frame special moment frame. Whether you design moment frames only once in a while or on a regular basis, the Strong Frame design team will provide you with No-Equal design support at no additional cost. Designers receive a complete package that includes drawings and calculations, which are submittal-ready. This ensures that you’ll have a frame connection design meeting the latest codes and design requirements. Contact strongframe@strongtie.com for more information or to request design support.

To learn more about the special benefits and uses of Strong Frame moment frames, check out the following links:

An Introduction to Helical Wall and Stitching Ties

This week’s post is written by Kevin Davenport, who works as a Field Engineer with Simpson Strong-Tie. Kevin is responsible for providing technical support on Simpson Strong-Tie products for Infrastructure, Commercial and Industrial market segments within his Southeastern territory. He is a registered professional engineer in Georgia and received his B.S. (’97) and M.S. (’98) from Clemson University. Kevin is a member of ICRI, ACI and various local chapters of SEA.

What do you do when brickwork is in bad condition? Depending on what state the brickwork is in, a tear-down may be called for. However, often brickwork can be restored and strengthened using helical ties such as Simpson Strong-Tie® Heli-Tie™ wall ties and stitching ties. This post introduces these two types of helical ties, which might be just what you need for your next brick restoration project.

What is a helical tie?

A helical tie is made by twisting a metal profile into the shape of a helix. The design of the Simpson Strong-Tie Heli-Tie wall tie also incorporates a large core diameter in order to provide higher torsional capacity. The benefit of this feature is less axial deflection due to a propensity for normal helix shape to “uncoil” under tension load. Since helical ties are typically used in building façades, they are generally made from stainless steel in order provide the necessary corrosion resistance. Helical ties can be used to retrofit and stabilize brickwork in two common applications: 1) Wall anchor applications, and 2) Stitching tie applications.

What are common helical wall tie applications?

Application #1: Anchoring building façades to structural members

In a wall anchor application, the helical tie is used to stabilize the façade by transferring out of plane façade forces through the anchor into the backup material. The need for this type of reinforcement arises when pre-existing wall anchors were never installed, were inadequately spaced or have corroded away over time. Helical ties are an economical solution that can be installed directly through a brick façade into various backup materials such as solid concrete, CMU block, and even wood or metal studs.

A pilot hole is drilled through the existing brick wall and any air gap into the backup material. Then the helical tie is placed in an installation tool and driven into the pre-drilled hole. As it is driven, the fins of the helical tie tap into both the masonry and backup material and provide an expansion-free connection that will withstand tension and compression loads. Some helical wall ties, like the Heli-Tie, use an installation tool that countersinks the tie below the surface of the brickwork. This allows the hole to be patched and concealed with a color matching material. Thereby, helical anchors allow the repair to be both efficient and inconspicuous when completed.

There are presently no specific U.S. design standards for the use and qualification of helical wall ties. However, a rational calculation of required spacing given the demand load can be easily calculated using ACI 530 (Building Code Requirement and Specifications for Masonry Structures), Section 6.2, and test data with an appropriate factor of safety. In addition, many Designers also follow the detailing practice for prescriptive anchored veneer in Section 6.2.2.5.6 that prescribes the following:

At least one anchor for each 3.5 ft² of wall area, and
A maximum anchor spacing of 32″ horizontal and 25″ vertical, and
Around openings larger than 16″ in either dimension: Additional perimeter anchors at maximum 36″ spacing within 12″ of the opening.

Prescriptive anchors also require bed joints to be at least twice the thickness of the embedded anchor. However, this provision is not relevant for helical anchors since they are installed into a drilled hole, rather than embedded into a wet mortar joint.

Application #2: Stabilizing multiple-wythe brick walls

In this application, the wall tie is used to attach wythes of brick to one another in an effort to stabilize the wall. By intermittently alternating installation angles (0^o, 45^o, 0^o, -45^o, etc.) the tie promotes more monolithic behavior of the wall.

What are common helical stitching tie applications?

Unlike wall anchor applications, in a stitching tie application the helical tie is used to stabilize brickwork by transferring in- and out-of-plane shear and bending forces across an existing crack. Stitching ties are placed in the plane of the wall within the horizontal bed joint.

The existing bed joint is routed out deep enough to recess the helical tie and cleaned out. Then, the recess is filled about 2/3 deep with a repair mortar (such as Simpson Strong-Tie® FX-263 Rapid Hardening Vertical/Overhead Repair Mortar). The helical stitching tie is then pressed into the mortar, followed by a trowelling with encapsulating grout. The installation provides an inconspicuous repair and preserves the appearance of the structure.

For red brick, we recommend placing stitching ties at a minimum vertical spacing of 12″ and extending the ties at least 20″ on either side of the crack.

Helical ties are not something that you see on every jobsite, however, they can provide a fast and cost-effective solution for brickwork rehabilitation. Hopefully this post provided you some background about them and an insight into our Heli-Tie product offering. The recent launch of our Repair Protection Strengthening Systems product line complements the Heli-Tie with a wide array of other repair products.

Do you have any past experience with helical wall ties, or questions? Please share in the comments below.

What Factors Contribute To A “Resilient” Community?

The world has seen many increasingly catastrophic natural disasters in the past decade, including Hurricane Katrina (Category 3) striking New Orleans in 2005, 2010’s 7.0 magnitude Haiti and 8.8 magnitude Chili earthquakes, the 9.0 magnitude Japan earthquake along with the Christchurch earthquake (6.3 magnitude) in 2011, the tornado outbreak in 2011 which included an EF4 striking Tuscaloosa, AL and a multiple-vortex EF5 striking Joplin, MO. We also saw Category 2 Hurricane Sandy, the largest Atlantic hurricane on record in 2012 and the EF5 tornado striking Moore, Oklahoma in 2013.

New Orleans was approximately $2 billion ahead of Nashville in real gross domestic product in 2002, but suffered an $80 billion loss due to Hurricane Katrina. With economic factors such as business interruption, business loss and population loss, New Orleans fell significantly behind Nashville by approximately $105 billion in real gross domestic product from 2005 to 2012 as shown in Figure 1.

Economic growth chart for New Orleans versus Nashville — Figure 1: Economic repercussions: New Orleans vs. Nashville economic growth from 2002 to 2012 (Courtesy of Dr. Lucy Jones, USGS)

A June 2014 article in Engineering News-Record noted, “Economists predict it will take some $35 billion and 50 to 100 years for New Zealand to recover from the February 2011 Canterbury earthquake, which killed 185 people and devastated Christchurch, the nation’s third-largest .” (See Figure 2)

Figure 2: 2011 New Zealand earthquake soft story building collapse (Courtesy of Dr. Andy Buchanan)

In 2008, the USGS forecasted a 99% probability that a 6.7 magnitude or greater earthquake would occur in California. An earthquake scenario was developed for the Southern California ShakeOut explaining the effects of a 7.8 magnitude earthquake on Southern California caused by a rupture of the southern portion of the San Andreas Fault. The scenario was developed by Dr. Lucy Jones of the USGS and a group of more than 300 scientists. It estimated approximately 1,800 deaths, 50,000 injuries and $213 billion of economic losses.

The economic losses included approximately $48 billion due to shaking damage, $65 billion due to fire damage, $96 billion due to business interruption costs and $4 billion due to traffic delays.

With this kind of devastation, building owners, building occupants, builders and designers are looking to better understand the performance expected from buildings built to minimum code requirements, and what the costs are of building to the minimum or above the minimum before and after a disaster.

After an earthquake, survivors often say they thought their building was built to code and wonder why it was so damaged or had to be demolished. Many don’t realize that building to the code minimum in earthquake country means there will be significant damage to the building and that it may need to be razed, as the cost to repair is too high. Christchurch is an example of this (see Figure 3).

Figure 3: 2011 Christchurch CBD earthquake impact (Courtesy of Dr. Ron Mayes, USRC)

Another consideration of the effects of a natural disaster is the interaction with the built environment. While it would seem that each building owner is responsible for the building(s) they own, their buildings’ performance in a natural disaster can adversely affect adjacent buildings, infrastructure and citizens, thereby greatly affecting the performance and recovery of neighbors and the community overall. Additionally, since natural resources are stressed and energy costs are increasing, most communities are making efforts to reduce their use with various sustainability or green initiatives. Buildings represent a significant amount of materials and energy. It’s been said that the most “green” building is the one already built versus one having to be re-built after a significant event.

These issues have led to discussion about the “resiliency” of a community. Webster’s Dictionary defines “resiliency” as “. . .able to become strong, healthy, or successful again after something bad happens” or “. . .able to return to an original shape after being pulled, stretched, pressed, bent, etc.”

There are tools that consumers already use to understand the quality and risk associated with a product or service, such as consumer report ratings for various products from cars to appliances, car crash test ratings and the restaurant grading system. To offer a similar information tool for buildings, a new non-profit organization called the United States Resiliency Council (USRC) was formed. The goal of the USRC is to serve as a credible unbiased tool for local governments, building owners, lenders, insurance providers and occupants by providing information on the quality and risk associated with a building after a natural disaster. Simpson Strong-Tie is a Founding Member of the USRC along with 63 other companies and organizations such as ATC, EERI, NCSEA, SEAOC.

The USRC vision is “. . .a world in which building performance in disasters such as earthquakes, hurricanes, tornadoes, floods and blast are more widely understood” and its mission is “. . .to be the administrative vehicle for implementing rating systems for buildings subject to natural and manmade disasters, and to educate the building industry and the general public about these risks.” Keys to the consistency and credibility of their building rating system includes certifying engineers to perform ratings and requiring a technical audit of the ratings by certified reviewers.

The rating process begins with a building evaluation by a USRC certified engineer using the Tier 1 and 2 check list procedure of ASCE 41-13, “Seismic Evaluation of Existing Buildings,” which describes a three-tiered process for seismic evaluation of existing buildings to either the Life Safety or Immediate Occupancy Performance Level. Alternately, the certified engineer may use FEMA P-58, “Seismic Performance Assessment of Buildings,” which expresses analysis results in terms of deaths, dollars and down time. Then the certified engineer converts the findings from ASCE 41 or FEMA P-58 to a USRC rating. The USRC earthquake hazard rating system describes building performance using three dimensions: Safety, Repair Cost, and Time to Regain Basic Function. Within each dimension, there are five thresholds of performance, each represented by a star as shown in Figure 4.

Figure 4: USRC earthquake hazard building rating system of three dimensions with five thresholds of performance (Courtesy of USRC)

A three star rating means loss of life is unlikely, the building repair cost will likely be less than 20% and the time to regain basic function will likely be within weeks to months. Typical buildings built to the code minimum would likely receive a three star rating.

As discussed in a previous blog post, Los Angeles Mayor Garcetti formed a Seismic Safety Task Force led by Dr. Lucy Jones which developed the “Resilience by Design” report. The report contains recommended strategies to identify and seismically strengthen vulnerable existing buildings, water infrastructure and communication framework. It included a voluntary earthquake hazard building rating using the USRC system. Los Angeles plans to lead by example by having city-owned buildings rated to better understand the quality and needs of their building stock. Importantly, the report also offered incentive recommendations such as waiving permit fees and a five-year exemption from business tax for those businesses moving into retrofitted buildings to “. . .help ensure the successful implementation of the recommendations.”

The San Francisco Community Action Plan for Seismic Safety (CAPSS) Earthquake Safety Implementation Program (ESIP) listed 50 tasks to be implemented over 30 years including a Mandatory Soft-Story Retrofit Program. This program was signed into law in the spring of 2013 as we have covered in a previous blog post.

Other cities are looking into similar strengthening strategies as L.A. and S.F. Hopefully, individuals, building owners, occupants, financiers, insurance organizations, other organizations and government officials will work together to determine the vulnerabilities in their built environment and develop strategies to address them. This will better ensure that communities not only survive coming natural disasters, but also are able to recover more quickly.

What should be the measures of a resilient community? Which organizations or efforts are working to educate and improve your community resiliency? Let us know in the comments below.

Innovative Screws Are Replacing Bolts

This week’s blog post was written by Aram Khachadourian, R&D Engineer for Fastening Systems. Since joining Simpson Strong-Tie 14 years ago, he has designed and tested holdowns, hangers, truss connectors, and anchor bolts. He has drafted numerous acceptance criteria as well as quality standards. His current focus is the development, testing, and code approval of structural fasteners. Prior to his work at Simpson he spent his time designing steel buildings including strip malls, wineries, and airplane hangars. Aram graduated from the University of California at Davis with a Civil Engineering degree, and is a registered professional engineer in California.

In the past several years, there has been an increase in the use of screws in applications that have traditionally been reserved for bolts and lag screws. Greater innovation in the wood screw market has caused this shift. Proprietary wood screws now offer many more benefits than commodity bolts and lag screws. Today, this post will discuss some of those benefits.

Two of the obvious drawbacks of installing bolts are preboring or predrilling a hole through the wood and ensuring that both sides of the connection are accessible. The drilled hole must be aligned properly in the wood, which is especially important for groups of bolts. When bolting a steel connector on each side of the wood, it takes a skilled hand to guide the drill from one side and hit the steel hole on the other side of the wood. Using proprietary wood screws instead of bolts can relieve the installer of this hassle. Because there is no predrilling, an installer can step up and drive in the screw. They don’t have to worry about lining up the drilled hole with the steel hole because the screws are driven into the connector on each side. This is a real benefit in many applications, such as installing ledgers and steel column cap connectors. Bolts also require washers between the head and the wood and between the nut and the wood. In an all-wood connection, the bolted connection requires a bolt, nut, and two washers or steel plates. Sometimes access from both sides is not possible or is not safe from the drilling position. Usually both the nut and the head of the bolt require a tool to tighten them, and that means using both hands where one may be blind. Proprietary wood screws are typically much faster to install and thus can reduce labor costs for the project.

Proprietary screws also are used as alternatives to lag screws in wood construction. Lag screw installation is included in the NDS, section 11.1.4. Lag screws greater than 3/8-in. diameter require a pre-drilled hole whether loaded in withdrawal or by lateral force. The required hole is a two-step hole. The hole for the shank is supposed to match the diameter and length of the shank and the part of the hole for the threaded shank depends on the specific gravity of the wood member and the relative diameter of the screw.

When comparing proprietary wood screws and commodity wood screws, it’s important to note that in the NDS, commodity wood screws have predrilling requirements that depend on the specific gravity of the wood. An installer cannot just grab a screw and drive it in. In some cases, there are two different diameters that must be predrilled, one for the shank and one for the threads, similar to lag screws.

When our engineers design a Simpson Strong-Tie screw, they go to great lengths so that the installer almost never has to predrill the wood. This is achieved by adding special drill tips, optimizing thread designs, and utilizing knurls or reamers that prepare the wood to receive the shank of the screw. For structural screws that require evaluation reports, qualification testing is performed with no predrilled holes so that the qualified loads are based on the installation instructions that require no predrilled holes.

The other factor our engineering team considers is the performance of screws in wood. Often, using a greater number of screws in place of larger diameter bolts or lag screws can increase the ductility of the failure mode, which is advantageous in certain applications, such as for seismic holdowns. The special features and manufacturing processes of proprietary wood screws can often result in allowable loads that are comparable to larger diameter bolts. These loads are typically determined through the testing and load rating requirements of ICC-ES AC 233.

As more types of screws are developed and more conditions are tested, proprietary screws will continue to replace bolts and lag screws in applications, including ledger connections, pile construction, girder truss and beam connections, steel connector installations, and many more.

Have you made the switch from commodity bolts and lag screws to proprietary wood screws? Let us know how you are using them or tell us how we can support a new application in your market.

How to Specify a Custom Hanger

As an engineer, it makes things easy when the buildings being designed are rectangular. This tends to make the connections occur between nice perpendicular members, and standard connectors and joist hangers can be used.

But buildings are not always rectangular and connections are not always between perpendicular members. Non-perpendicular members can have a skewed connection, where the supported member is moved side to side from perpendicular; or a sloped connection, where the supported member slopes up or down from a standard horizontal orientation; or a combination of the two.

To help with these situations, Simpson Strong-Tie offers a couple of options. The option chosen may depend on the timeframe in which the hanger is needed, the load demands on the hanger or the cost of the hanger.

If the demand load is low and an immediate solution is desired, Simpson Strong-Tie offers several adjustable hangers that can be skewed, sloped or both in the field.

A common adjustable joist hanger is the LSU/LSSU series, which can be sloped up or down and skewed right or left up to 45 degrees.

Remember that these hangers must be installed to the carried member prior to installation of the supported joist.

Other series of hangers are only adjustable for skew or slope. For example, the THASR/L series is designed to accommodate connections skewed from 22½ to 75 degrees. Conversely, the new LRU ridge hanger is designed to support rafters at ridge beams with roof slopes of 0:12 to 14:12. Finally, the SUR/SUL/HSUR/HSUL series is not adjustable, but is manufactured with a skew of 45 degrees either right or left in several sizes.

If none of these pre-manufactured solutions fits your specific need, there are still options. This entails a custom-manufactured hanger. Many, but not all, joist hangers can be custom-made for specific slopes, skews, combinations of slopes and skews, and even alternate widths and alternate top flange configurations.

If this type of hanger is needed, a good place to start is the Hanger Options Matrix at the back of the Simpson Strong-Tie® Wood Construction Connectors Catalog. It is also available at strongtie.com. An excerpt is shown below. This chart identifies which hangers can be modified, how they can be modified and to what extent they can be modified. There are two tables – one for top flange hangers and one for face mount hangers.

The Hanger Options Matrix is available in Simpson Strong-Tie(R) Wood Construction Connectors Catalog or at strongtie.com

Once the user has found a hanger that can be modified to fit the actual situation, the next step is to calculate any load reductions, if applicable. The column at the far right gives the Wood Construction Connectors Catalog page number that lists any load reductions for the various options. If multiple options with reductions are specified, only the most restrictive load reduction needs to be applied, not all the reductions.

As an example, let’s say we need to hang a heavily loaded double LVL hip member from the end of an LVL ridge beam. We would look at a GLTV top flange hanger, skewed 45 degrees to the right, sloped down 45 degrees, with its top flange offset to the left. We see from the table above that all these options are permitted. If we go to page 220 (or strongtie.com), we can see what the load reductions would be for these options. The reductions are as follows:

Sloped and skewed configuration for the GLTV has a maximum down load of 5,500 pounds.
Offset top flange for the GLTV requires a reduction factor of 0.50 of the table roof load.
BUT, skewed and offset top flange hangers have a maximum allowable load of 3,500 pounds.
Offset top flange results in zero uplift load.

So the allowable load of our skewed, sloped, offset top flange GLTV would be 3,500 pounds downward and 0 pounds uplift. In this case, it was clear what the reduction was for our combination of modifications. If it is not listed specifically and you have multiple modifications with multiple reduction factors, use only the factor that results in the biggest reduction, not all of the listed reduction factors.

The next thing to do is to call out the desired hanger properly so that Simpson Strong-Tie can manufacture it to your needs. This is typically done by taking the regular product name, adding an X, and then calling out the modifications individually at the end.

For our hanger, assuming the hip is 3-1/2″ by 11-7/8″, the standard hanger would be a GLTV3.511, and the modified hanger would be called out as a GLTV3.511X, Skew R 45, Slope D 45, TF offset L.

There is one final consideration when hangers are both sloped and skewed. In this case, the top of the supported member (joist) will not be horizontal when it is cut, one side will be higher than the other. The user must decide and specify where he or she wants the upper side of the joist to fall. There are three options: high-side flush, center flush or low-side flush. We see that often users will want to specify high-side flush so that the joist ends up flush with the top of the supporting member, but that would be up to the user. This specification is added to the end of the callout name listed above. These cases are illustrated below.

A related matter occurs when the top flange of a hanger is sloped up or down. In this case the user also has to specify whether the joist is to be low-side flush, center flush, or high-side flush. But, in this case, the side is in reference to the top flange, not the joist. Specifying low-side flush will result in the top of the joist being flush with the lower side of the sloped top flange, not the low side of the joist.

If all of this seems confusing and somewhat difficult, it can be. Fortunately, Simpson Strong-Tie has developed a new web application – the Joist Hanger Selector – which automates this entire process. This app is located on strongtie.com/software.

Once you agree to the terms and conditions, choose the type of hanger you want to specify, then select the types of members being connected. This is what it would look like for our example.

This is where the user specifies any modifications required. Required loads can also be entered at this point. This is what it would look like for our example.

Then, just click “CALCULATE” and the possible options will be shown. And here we see our GLTV3.511X, SK R 45, SL DN 45, TF Offset L, with a load of 3,500 pounds, just as we thought! I love it when a plan comes together.

Hopefully, this web app will help you specify custom hangers with ease. Are there any other applications we could develop that would make specifying connectors easier? Let us know.

Upcoming events

The 22nd International Specialty Conference on Cold-Formed Steel Structures is coming up Nov. 5-6 at the Hilton Ballpark Hotel in St. Louis, MO. It is sponsored by the Wei-Wen Yu Center for Cold-Formed Steel Structures at the Missouri University of Science and Technology.

A biannual event, this conference brings together leading scientists, researchers, educators and engineers in the field of research and design of cold-formed steel structures to discuss recent research findings and design considerations. This year’s conference features 12 technical sessions covering a wide variety of topics. For more details, visit the conference website.

Educated in a FLASH, Part 1

Happy New Year! This week’s blog was written by Branch Engineer Randy Shackelford, P.E., who has been an engineer for the Simpson Strong-Tie Southeast Region since 1994. He is an active member of several influential committees, including the AISI Committee on Framing Standards, the American Wood Council Wood Design Standards Committee, and the Federal Alliance for Safe Homes Technical Advisory Committee. He is vice-president and member of the Board of Directors of the National Storm Shelter Association. Randy has been a guest speaker at numerous outside seminars and workshops as a connector and high wind expert. Here is Randy’s post:

As part of our mission to “help people build safer structures economically,” Simpson Strong-Tie works with many non-profit groups around the country, including the American Red Cross, Habitat for Humanity, and the National Storm Shelter Association. Another group we work with is FLASH, the Federal Alliance for Safe Homes.

The mission of FLASH is “Strengthening homes and safeguarding families from disasters of all kind.” FLASH recently celebrated its 15th year, and Simpson Strong-Tie has been right there with them for most of those years.

Creating the StormStruck® Experience

The post-show area of the StormStruck exhibit includes this display showcasing a continuous load path.

Perhaps the biggest outcome of our work with FLASH is our partnership in “StormStruck: A Tale of Two Homes®, located at INNOVENTIONS in Epcot® at the Walt Disney World Resort. StormStruck is a fun, interactive 4D experience that teaches visitors the steps they can take to protect their homes and families during severe weather. Visitors experience a storm and its effects on the “house” they are sitting in, and then decide how to best rebuild to resist the next storm. StormStruck has been seen by almost 800,000 people in the past year, and more than four million since opening in 2008. If you visit EPCOT®, be sure to head over to INNOVENTIONS East to see our exhibit.Continue Reading

Happy New Year!

We are taking a break this week, but wanted to be sure to wish you happy holidays, and to especially thank you for your continued participation in our Structural Engineering Blog. See you in the New Year!

– Paul

What are your thoughts? Visit the blog and leave a comment!

Symposium Offers Sneak Peek at Lab

This week’s recap of the Light-Frame Engineering Symposium was written by Keith Cullum, one of our engineers at the Simpson Strong-Tie Riverside, Calif., branch. Keith graduated with a degree in Architectural Engineering from Cal Poly San Luis Obispo and worked for an engineering consulting firm in Orange County designing commercial structures in steel, concrete and masonry, and multi- and single-family residential structures in cold-formed steel and wood. Prior to joining Simpson Strong-Tie in 2012, he worked for a steel deck manufacturer performing R&D and providing product technical support and promotion. He is a LEED Accredited Professional (AP) and a registered Professional Engineer in the State of California. Here is Keith’s post:

I bet you’d be shocked if someone told you the epicenter for structural engineering was located in Stockton, California. Well, for two days in late October this year, it was. That’s where Simpson Strong-Tie held its 2013 Light-Frame Engineering Symposium.

More than 150 industry professionals attended, including principals and project managers from the top engineering and architectural firms throughout the United States as well as local policy makers, researchers and a number of Simpson Strong-Tie engineers.

The event included several informative presentations by leading experts on topics such as design and analysis of diaphragms and multi-story shear walls, designing high-rise structures with wood, podium deck anchorage, soft-story retrofit testing, code reports and the future direction of building codes.

Steve Pryor gives an overview of the lab's testing capabilities. — Steve Pryor gives an overview of the lab’s testing capabilities.

In addition, the group was given a sneak peek into the testing done at Simpson Strong-Tie’s Tyrell Gilb Research Laboratory.

Wings or No Wings?

Guest blogger Jeff Ellis, engineering manager

While the title of this blog post might remind you of the tasty turkey dinner you enjoyed on Thanksgiving, it’s actually a question regarding a shear wall component’s effect on performance. What type of fastener do you use to attach wood structural panel sheathing to cold-formed steel (CFS) framing, and what is the effect on a shear wall assembly?

Wood Structural Panel Sheathed CFS Framed Shear Walls.( Image credit: Don Allen, DSi Engineering)

Structural sheathing is most commonly attached to CFS framing with self-piercing or self-drilling tapping screws, power driven pins, and adhesives.

The AISI North American Standard for Cold-Formed Steel Framing – Lateral Design standard (S213) specifies using either #8 or #10 self-tapping screws (depending on the assembly) that comply with ASTM C1513, and have a minimum head diameter of 0.285” or 0.333”, respectively.

It’s worth noting that you cannot verify ASTM C1513 compliance by simple inspection. While screw dimensions are easy to measure, other features such as hardness, ductility, torsional strength, drill drive, and thread tapping cannot be evaluated in the field or by visual inspection. It’s prudent that a Designer and jurisdiction expect a screw manufacturer to validate its product’s compliance with ASTM C1513. This can be done through test reports by an accredited test lab and evaluation data, or by an evaluation report published by an ANSI-accredited product certification entity such as ICC-ES or IAPMO UES.Continue Reading

Steel Roof Decking

This week’s post comes from Bryan Wert,one of our engineers at the Simpson Strong-Tie McKinney, TX branch. Bryan provides technical product support, new product R&D, and customer education/training for the Southeast U.S. territory. Before starting his career with Simpson Strong-Tie early in 2007, he worked as a structural engineer at a large consulting firm in Las Vegas, NV. Bryan’s design experience ranges from single-family tract and custom homes, to retail centers, to hotel and condo projects. Bryan graduated from USC with a B.S. in Civil Engineering (Building Science emphasis) and from Stanford University with a M.S. in Civil Engineering (Structural emphasis). Here is Bryan’s post:

My wife, Kristin, sometimes gets angry with me while grocery shopping. It’s understandable. She’s asked me to grab some tomatoes or a loaf of bread and instead I’m just standing there looking up at the ceiling. Technically, it’s not a ceiling, but the underside of the roof, and I’m looking up to see the connection detailing, including whether or not the steel roof deck I’m looking at was welded, pinned, or screwed down to the steel joist, beam and angle supports.

If you’re a structural engineer, you might also do this inside your local supermarket, Target, Walmart or The Home Depot. Many of these “big box” stores are typically constructed of tilt-up concrete perimeter walls, tube steel interior columns, and roofs built of steel joists, girders and decking. Though Simpson Strong-Tie is well known in the light-frame wood construction industry, some may not know that we’ve long been developing and selling anchors and fasteners for commercial construction.

Outside of a few dips into a Verco or ASC steel decking catalog from my consulting days in Las Vegas, my first real foray into the steel decking industry was about two years ago. I was asked to assist in representing Simpson Strong-Tie as an associate member at the Steel Deck Institute’s (SDI) quarterly meeting held just down the road in Dallas in November 2011. Since joining SDI, my main focus has been to find out what the industry needs, both from the installer’s and designer’s standpoint for steel deck attachment. Though we’ve had a screw attachment offering for years, my colleagues and I have worked to develop a better overall system which now includes: