Earlier this week, we were busy finishing these tapered glulam beams. This project called for us to add coverboards (shown in this first picture) to cover up the glue lines that show when the angled cut is made.
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Tapered #glulam beams with coverboard
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Lag Screw: Wednesday's Word(s) Of The Week
Lag screws do require special pre-drilling, equal to the unthreaded body diameter and a fraction of the threaded diameter for the unthreaded and threaded lengths of the screw, respectively. This pre-drilling is typically done during shop fabrication, or clearly described if done in the field.
The unthreaded portion of lag screws can be "full-body diameter" (equal the lag size), or "reduced body diameter." This has an impact on the screw shear capacity and drilling requirements. Unalam only supplies full-body diameter lags on our projects. Screws come in ½" increments up to 6" long, 1" increments up to 12" long, and 2" increments beyond 12". Standard thread length is half the fastener length + ½", up to 6" of thread total.
You may have heard the term "lag bolt" before. This is sometimes used to describe a lag screw because the diameters and hex heads of lag screws are similar to bolts. To avoid any confusion, the term lag bolt should be avoided.
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Fully Threaded Lag Screw: Wednesday's Word(s) Of The Week
Although not standard, it is possible to special order lags which are threaded their entire lengths. Lead times and cost are significantly higher than standard lags. They are typically used as reinforcing within a beam, rather than for connecting parts. A common example is radial tension reinforcing of pitched and tapered beams made of species other than southern yellow pine.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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Glulam Can Be Rough, Too
We have a large rough-sawn project going through our plant right now. We added a rough finish to the exposed sides of these beams before staining them. This gives the glulam the look of old, hand-hewn timber.
Why wouldn't you just use solid timber? Glulam can be manufactured to larger sizes and it can be curved to more complex shapes. From a distance, you really can't tell the difference.
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Carriage Bolts: Wednesday's Word(s) Of The Week
The rounded head can't be gripped by a wrench, so a special feature of carriage bolts is a square profile just under the head. As the bolt is seated, this grips the wood and prevents the bolt from spinning as the nut is tightened.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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Moment Connection: Wednesday's Word(s) Of The Week
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| Installing a Moment Connection |
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| Moment Splices are highlighted in this photo |
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| The finished arena |
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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Washers: Wednesday's Word Of The Week
Another basic type of hardware that most people are familiar with is the washer. Washers are used in glulam construction whenever a bolt head or nut would bear directly against the wood surface. They protect the finished wood surface from bolt head scratches and crushing.
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The most common type of washer used is a "standard cut washer." For a ¾"ø bolt, standard cut washers are 2" outside diameter (O.D.). This is sufficient when bolts are loaded in shear or lightly loaded in tension, the majority of conditions.
If a bolt or rod is highly loaded in tension, crushing of wood under the 2"ø washer will control design, so larger washers are available to increase capacity. The simplest are New York Dock Department (NYDD) washers, which are simply 3" O.D. washers cut from ¼" steel plate. Malleable iron washers are also 3" O.D. with a shaped profile that is ½" thick overall - they are very strong with good corrosion resistance. Either of these will increase area (and therefore total compression capacity) of wood under the washer by about 2.5 times.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
The most common type of washer used is a "standard cut washer." For a ¾"ø bolt, standard cut washers are 2" outside diameter (O.D.). This is sufficient when bolts are loaded in shear or lightly loaded in tension, the majority of conditions.If a bolt or rod is highly loaded in tension, crushing of wood under the 2"ø washer will control design, so larger washers are available to increase capacity. The simplest are New York Dock Department (NYDD) washers, which are simply 3" O.D. washers cut from ¼" steel plate. Malleable iron washers are also 3" O.D. with a shaped profile that is ½" thick overall - they are very strong with good corrosion resistance. Either of these will increase area (and therefore total compression capacity) of wood under the washer by about 2.5 times.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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Throwback Thursday: Jersey Devil
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We found this interesting article featuring the firm, Jersey Devil, that we worked with in the '70s. If you scroll down you can read more about the Silo House from 1975.↧
A Retirement Celebration
This afternoon, we celebrated Duane Lowe's retirement after 21 years of service with Unalam. Duane actually has a lot more experience with our glulam, having installed it with Payne's Cranes for several years before joining our team in 1995. We wish Duane the best in his retirement!
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Combination Layup: Wednesday's Word(s) Of The Week
Glulam is produced using standard lumber as the raw material, which is supplied in nominal sizes between 1x4 and 2x12 and up to 20' long. In all glulam beams, the wide faces of lumber are glued together to build up the beam depth, for example 16 layers of nominal 2x lumber are used to make a 22" deep glulam. And, in almost all glulam members, lumber is finger jointed to create glulam beams which are longer than the raw material or to efficiently use the material when creating odd lengths.
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However, in the third dimension (glulam beam width), it is not typically necessary to add to the raw material. The width of a 2x6 is used for a 5" wide glulam, and a 2x12 is used for a 10½" glulam. Beyond 10½" (or sometimes 10¾") wide, it does become necessary to build up the glulam beam in all three dimensions. There are two ways to do this.
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The first, and simplest, method is the Combination Layup. Here, two different sizes of lumber are used side by side to increase the beam width (a 2x6 & 2x12 are combined to make a 16" wide glulam), and their locations alternate to stagger the joint between them. This joint between the edges of lumber is not glued, so there are continuous voids inside the glulam and on the face. For architectural appearance, the void on the face is routed and plugged. The internal voids do reduce the weak axis shear strength of the member, which is accounted for in footnote 3 of NDS Table 5A (and footnote 2 of NDS Table 5B.)
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
The first, and simplest, method is the Combination Layup. Here, two different sizes of lumber are used side by side to increase the beam width (a 2x6 & 2x12 are combined to make a 16" wide glulam), and their locations alternate to stagger the joint between them. This joint between the edges of lumber is not glued, so there are continuous voids inside the glulam and on the face. For architectural appearance, the void on the face is routed and plugged. The internal voids do reduce the weak axis shear strength of the member, which is accounted for in footnote 3 of NDS Table 5A (and footnote 2 of NDS Table 5B.)
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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#TBT Walt Whitman Birthplace Interpretive Center
It's really hard to believe that nearly 20 years have passed since we completed glulam trusses for the Interpretive Center at Walt Whitman's birthplace in Huntington Station, NY. Liz, our sales associate, recently gave a presentation nearby and stopped in to see the building in person.
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These are really interesting trusses; all of the tension members are steel rods (pictured more clearly below.) Because of the overall roof shape with the clerestory windows, you end up with an interesting truss geometry. Without that diagonal steel, the remaining truss members wouldn't all make triangles. As we've already mentioned in an earlier Wednesday's Word of the Week, trusses should be formed of a series of triangles.
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Manufactured Ply: Wednesday's Word(s) Of The Week
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| Manufactured plies cover the wide members of this pergola |
pieces. Each piece is 1½" thick, 22" wide, and 40' long… and can be used as a single ply in a wide glulam beam.
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| End cut of glulam made entirely with manufactured plies |
There is more work and waste involved in making a beam from manufactured plies than a combination layup, so it is only occasionally used. Sometimes a single manufactured ply is added to the face of a combination layup to avoid plugging the face. Or, for complicated parts like a spiral, manufactured plies are easier to handle than the multiple boards in a combination layup. Note that when you use a manufactured ply there will be glue lines on all sides of the glulam made from manufactured plies.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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Beautiful (and Unique) Glulam
Back in January we told you about some unique glulam frames going into a new building and shared a couple of photos. Here are some more pictures of the building as it is being completed.
The outside of the building combines timber and stone, and conceals spectacular beauty within.
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The roof inside is framed with glulam, complete with concealed connections.The outside of the building combines timber and stone, and conceals spectacular beauty within.
Here's the steel for one of those connections, to give some perspective.
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Unalam Takes Manhattan
Last night, several members of the Unalam team descended upon Manhattan for the opening of Martin Puryear's Big Bling at Madison Square Park. We were so excited to see the sculpture fully assembled in the park. It was also wonderful to see the artist again, as well as our friends from the Madison Square Park Conservancy.
We'll leave you to view the rest of our photos. Because, as you can see, we think Big Bling speaks for itself.
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Stress Combination: Wednesday's Word(s) Of The Week
Stress combination refers to the specific composition of lumber in a glulam beam and the associated material properties of the finished glulam member. Specific stress combinations are designated with a Combination Symbol. A table of industry standard Combination Symbols is available in Table 5A Expanded and Table 5B of the NDS.
Because the Combination Symbols listed in the NDS are industry standards, the allowable stresses and other properties can be used for design regardless of who produces the glulam.
These tables in the NDS are actually copies of tables in ANSI 117 "Standard Specification for Structural Glued Laminated Timber of Softwood Species." ANSI 117 also includes the lay-up requirements for each combination - where and how much of different wood grades are required in the finished beam.
We will have more information on what the different Stress Combinations mean in upcoming weeks.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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#Glulam Trellis At Long Island Transit Plaza
We manufactured a glulam trellis for the new Transit Plaza in the hamlet of Wyandanch, NY on Long Island. The trellis is made of curved glulam that has been pressure treated to better withstand the elements. Additionally, these were glued using a combination layup to achieve an overall beam width greater than 10½". In this case, the "width" is actually the height as installed because these are horizontal curves.
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Bending Layups: Wednesday's Word(s) Of The Week
16F-V2, 16F-V3, 16F-V5
20F-V2, 20F-V3, 20F-V5
24F-V1, 24F-V3, 24F-V4, 24F-V5, 24F-V8
26F-V1, 26F-V2, 26F-V3, 26F-V4, 26F-V5
The first numbers represent the allowable bending stress (1600 psi to 2600 psi), 2400 psi is the most common. Of the five combinations listed, 24F-V4 has a footnote explaining that it contains wane, so that combination should be ignored. So, four combinations left to choose from:
24F-V1, 24F-V3
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| Unbalanced (left) and Balanced (right) glulam layup |
The next choice is whether a balanced or unbalanced layup is required. Unbalanced is for simple span beams (high tension stresses only expected at bottom of beam.) Check the allowable Fbx- value, for tension stress at the top of beam. In balanced layups Fbx+ equals Fbx-, which is true for 24F-V5 and 24F-V8. The remaining difference between these two grades is their modulus of elasticity (E); 24F-V8 is slightly more rigid than 24F-V5.
The most common bending layups used for southern yellow pine are 24F-V3 and 24F-V5.
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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Tapered #Glulam Beams Are In
You might remember the post we did back in March about the tapered beams with coverboards. We received some photos of the beams installed in the field, giving you a good picture of their final end use.
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Uniform Layups: Wednesday's Word Of The Week
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| Bending (left) vs. Uniform (right) glulam layup |
The presence of knots (N1 has fewest knots, N2 has more knots)
The spacing of growth rings (Dense/D lumber has tighter spaced growth rings than Medium/M)
The slope of grain (1:16 slope of grain is very close to straight, 1:8 is more angled)
An example SYP Combination Symbol is #49/1:12.
The first number represents the knots and density and the second half indicates the maximum allowable slope of grain.
47/48/49/50 indicate N2M/N2D/N1M/N1D material, respectively.
1:12 would require grain to be at no more than a 1:12 slope compared to the ply axis.
Common uniform layups are:
#47/1:8 for members which are not highly stressed.
#49/1:12 for members requiring higher allowable stresses.
#50/1:12 for maximum capacity (and maximum cost)
*Wednesday's Word Of The Week is a feature on Unalam's Wood Times Blog. Each Wednesday our structural engineer, Rik Vandermeulen, will discuss a new term associated with glulam manufacturing. He will do this until we run out of words. If there is a timber or glulam term that you have heard of and want to know more about, let us know in the comments.
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#TBT #Glulam From 1974
There's a lot of talk recently about a resurgence in timber construction. We've been manufacturing timber used to build beautiful and durable buildings for over 50 years. Here's an example of a job from the early 70s that is now over 40 years old. It's from Casey Park in Auburn, NY.
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Like any building, with normal upkeep the wood can last for many, many years.
Like any building, with normal upkeep the wood can last for many, many years.
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