Monday, February 27, 2012
wood panel sheathing example ...
... here is an example of specifying roof sheathing for a heavily loaded roof (our `ski-lodge' example in class). Note that I split up the Dead load ... assuming only 10 psf of the 20 total is carried by the roof sheathing ... with the other 10 psf being the trusses themselves and the ceiling, etc. Also, since the sheathing is over the attic space, and NOT attached to sheetrock, I relax the deflection requirement to L/240. For the trusses themselves, which will have sheetrock attached, I would hold to the L/360.
Friday, February 24, 2012
Tall (LONG) Wood Studs ....
...
So, in class we were talking about tall stud walls ... in our example, 20 ft. We found out that the deflection under wind load was 2.88 in. for the 2 x 6 @ 16 in. o.c., blah, blah ... and this was excessive with regard to a limit of L/180. I may have remembered wrong. The appropriate deflection limit for our example should be L/120 = 2.0 in. Which means we're still a bit excessive.
Options ...
1. 2 x 8 studs?
2. closer spacing? ... 12 in. o.c., or less? (yikes, that ends up being a lot of woood, ... and nails, and ...)
3. `plant shelf' or some other lateral support
4. `counting' the stiffness of the wall sheathing
5. (we didn't mention) ENGINEERED LUMBER
I didn't mention Engineered Lumber for two reasons: 1) I forgot, and 2) Engineered studs aren't much stiffer than the dim. lumber ones (even though they are stronger).
ONE ADVANTAGE, however, of the engineered lumber, is that it is more amiable to longer lengths than the dim. lumber.
...
I found some cool stuff on using ENGINEERED LUMBER for wall studs ... the Boise Cascade Versa Stud ...
I can't seem to paste a link - but simply Google "western versa stud 1.7 wall guide" or something similar. You should land on the Boise Cascade stuff.
The ` ... Guide' has a lot of the same stuff we were talking about in class ...
Interestingly, it show we can get the 2 x 6 (1.5 x 5.5) up to 20 ft @ 16 in. o.c. ... with one side of wall sheathed, 20 psf wind pressure, L/120 deflection limit.
SWEET.
The Trus-Joist people manufacture a `Timberstrand' Engineered Lumber stud, which I am sure is similar.
....
ALSO NOTE: ... the long engineered lumber studs are very useful in construction where we have `open to above' type situations ... where `platform' framing adjacent to the opening ... DOESN'T WORK.
Doc
...
So, in class we were talking about tall stud walls ... in our example, 20 ft. We found out that the deflection under wind load was 2.88 in. for the 2 x 6 @ 16 in. o.c., blah, blah ... and this was excessive with regard to a limit of L/180. I may have remembered wrong. The appropriate deflection limit for our example should be L/120 = 2.0 in. Which means we're still a bit excessive.
Options ...
1. 2 x 8 studs?
2. closer spacing? ... 12 in. o.c., or less? (yikes, that ends up being a lot of woood, ... and nails, and ...)
3. `plant shelf' or some other lateral support
4. `counting' the stiffness of the wall sheathing
5. (we didn't mention) ENGINEERED LUMBER
I didn't mention Engineered Lumber for two reasons: 1) I forgot, and 2) Engineered studs aren't much stiffer than the dim. lumber ones (even though they are stronger).
ONE ADVANTAGE, however, of the engineered lumber, is that it is more amiable to longer lengths than the dim. lumber.
...
I found some cool stuff on using ENGINEERED LUMBER for wall studs ... the Boise Cascade Versa Stud ...
I can't seem to paste a link - but simply Google "western versa stud 1.7 wall guide" or something similar. You should land on the Boise Cascade stuff.
The ` ... Guide' has a lot of the same stuff we were talking about in class ...
Interestingly, it show we can get the 2 x 6 (1.5 x 5.5) up to 20 ft @ 16 in. o.c. ... with one side of wall sheathed, 20 psf wind pressure, L/120 deflection limit.
SWEET.
The Trus-Joist people manufacture a `Timberstrand' Engineered Lumber stud, which I am sure is similar.
....
ALSO NOTE: ... the long engineered lumber studs are very useful in construction where we have `open to above' type situations ... where `platform' framing adjacent to the opening ... DOESN'T WORK.
Doc
...
Friday, February 17, 2012
Column Capacities ...
...
... the following embellishes (and maybe better explains) the column capacity stuff we were covering in class today.
On the board I wrote our design check as being ... is f_c = P / A < = F_c' ...?
When we use a capacity table our design check is essentially the same thing - except the whole `equation' is multiplied by the member cross section area.
Thus, our check is ... is P (applied load) < = P (published allowable capacity).
As I pointed out in class, and below ... the published allowable capacities already incorporate the Column Stability factor.
Doc
... the following embellishes (and maybe better explains) the column capacity stuff we were covering in class today.
On the board I wrote our design check as being ... is f_c = P / A < = F_c' ...?
When we use a capacity table our design check is essentially the same thing - except the whole `equation' is multiplied by the member cross section area.
Thus, our check is ... is P (applied load) < = P (published allowable capacity).
As I pointed out in class, and below ... the published allowable capacities already incorporate the Column Stability factor.
Doc
Monday, February 13, 2012
CURVED BEAMS ...
...
WHAT I WANT YOU TO KNOW ABOUT CURVED BEAMS ...
1. We can make all kinds of curved shapes ... circular, `S’ shaped, whatever.
Curved beams can have a constant radius, or changing radius ... and can be constant depth, or changing depth (tapered).
2. But! ... there is a minimum radius of curvature we need to deal with.
3. Minimum radius of curvature depends primarily on the lamination thickness.
4. Curved beams will have a `thrust’ (`push-out’) component to the Reactions.
5. Get an Engineer on board with curved beams – and maybe the Manufacturer.
Here are some curved roof beams for the Anatek Labs over in Moscow. (Only the ends are shown here. They actually carry the roof via a ridge beam line over to the right (out of sight) that load the curved beams with concentrated loads at center span (as I recall). I designed the beams as a consultant to Design West Architects (Pullman).
To deal with the push-out we use steel rods that tie the ends together and thus get the push-out to `cancel-out'.
In that regard then, the beam-cable system simply bears down vertically on the supporting columns.
As mentioned in class most of the columns are hidden within the wall spaces.
...
WHAT I WANT YOU TO KNOW ABOUT CURVED BEAMS ...
1. We can make all kinds of curved shapes ... circular, `S’ shaped, whatever.
Curved beams can have a constant radius, or changing radius ... and can be constant depth, or changing depth (tapered).
2. But! ... there is a minimum radius of curvature we need to deal with.
3. Minimum radius of curvature depends primarily on the lamination thickness.
4. Curved beams will have a `thrust’ (`push-out’) component to the Reactions.
5. Get an Engineer on board with curved beams – and maybe the Manufacturer.
Here are some curved roof beams for the Anatek Labs over in Moscow. (Only the ends are shown here. They actually carry the roof via a ridge beam line over to the right (out of sight) that load the curved beams with concentrated loads at center span (as I recall). I designed the beams as a consultant to Design West Architects (Pullman).
To deal with the push-out we use steel rods that tie the ends together and thus get the push-out to `cancel-out'.
In that regard then, the beam-cable system simply bears down vertically on the supporting columns.
As mentioned in class most of the columns are hidden within the wall spaces.
...
Glulam Roof Beam ... Total Load Deflection Check
... here is the deflection check for Total load for the example we have been doing in class.
... yeah, it's a bit blurry. Taken by my cell phone and uploaded just for your benefit. Creep is NOT considered in the calculation.
See if you can get your mind around the comments I make at the end.
... I also give a hint to the question I posted on the 351 - 352 FB page.
Doc
...
Friday, February 10, 2012
Study Outline, 1, GLULAM
...
SO, here is what I want you to understand about glulam ... (particularly BEAMS)
1. It (GLULAM) is stronger and stiffer (for the most part) than sawn lumber.
2. It is a very efficient use of our lumber resource (now that glulam is highly evolved – as is here in America).
3. It can be made for use in either beams or columns.
4. A member intended for use as a beam can be used as a column ... just make sure that it isn’t cambered.
5. A member that is intended for use as a column can be used as a beam – and there are Design Values for such.
6. A beam can be loaded in the strong (x-) or weak (y-) direction (and there are Design Values for such).
7. It’s nice when the compression zone of a beam is laterally supported – as is by the floor or roof system it is supporting – as is most often the case for simple beams.
8. For cantilever beams, beams with overhangs, and continuous beams, where the compression zone of the beam is NOT laterally supported, we need to deal with the Beam Stability factor, CL (which is not much fun).
9. For columns we need to consider how there are braced, and in what directions.
10. We should also consider how columns are loaded (centrically, or not necessarily centrically).
11. Glulams may be loaded as beams and columns at the same time! (Contact your local engineer – I am in the phone book, I think.)
12. Glulams intended for use as beams have higher grade laminations on top and bottom.
13. Glulams intended for use as columns generally have uniform `layups’.
14. Glulams intended for use as beams fall into two categories:
... 1) Unbalanced
... 2) Balanced or Reversible
15. Unbalanced Beams are intended for use as simple spanning members
16. Unbalanced Beams are often `cambered’
17. If unbalanced beams are installed upside down or in continuous spanning conditions or with cantilever spans ... they theoretically have less `capacity’
18. Stock beams are generally unbalanced and have camber
19. Balanced beams are intended for use in continuous spanning and cantilever/overhang conditions
20. Balanced beams are generally manufactured straight (no camber)
21. Glulam may be made into curved shapes, tapered shapes, curved and tapered, etc.
22. Curved and tapered beams are `custom’, and the designer should interface directly with the manufacture on their design, etc.
23. Glulam beams made be made into a nearly unlimited variety of lengths, depths, shapes (curved, tapered, etc.) ...
24. The main limitations on glulam size and shape (curved, etc.) are imposed by transportation issues.
25. Generally we don’t splice wood members – but due to transportation issues we have come up with a `moment splice’ for glulam.
26. You should specify glulam in accordance with what is available.
27. Glulam specifications should include stress and appearance grades.
28. For simple drop-in-place and prop-in-place members (beams and columns) there is a lot of `design guide’ type information.
29. For custom stuff, like curved beams, get an engineer and the manufacturer on board.
30. Manufacturers of `stock’ glulam generally do not provide engineering assistance.
31. Manufacturers of `custom’ glulam, or glulam systems (trusses, etc.) ... might provide design assistance, even a `stamp’.
32. The American Institute of Timber Construction (AITC) and the American Plywood Association – Engineered Wood Systems (APA-EWS) are the main trade organizations with glulam – and they provide a lot of useful information.
THAT’S IT FOR NOW ... MORE TO FOLLOW!
...
SO, here is what I want you to understand about glulam ... (particularly BEAMS)
1. It (GLULAM) is stronger and stiffer (for the most part) than sawn lumber.
2. It is a very efficient use of our lumber resource (now that glulam is highly evolved – as is here in America).
3. It can be made for use in either beams or columns.
4. A member intended for use as a beam can be used as a column ... just make sure that it isn’t cambered.
5. A member that is intended for use as a column can be used as a beam – and there are Design Values for such.
6. A beam can be loaded in the strong (x-) or weak (y-) direction (and there are Design Values for such).
7. It’s nice when the compression zone of a beam is laterally supported – as is by the floor or roof system it is supporting – as is most often the case for simple beams.
8. For cantilever beams, beams with overhangs, and continuous beams, where the compression zone of the beam is NOT laterally supported, we need to deal with the Beam Stability factor, CL (which is not much fun).
9. For columns we need to consider how there are braced, and in what directions.
10. We should also consider how columns are loaded (centrically, or not necessarily centrically).
11. Glulams may be loaded as beams and columns at the same time! (Contact your local engineer – I am in the phone book, I think.)
12. Glulams intended for use as beams have higher grade laminations on top and bottom.
13. Glulams intended for use as columns generally have uniform `layups’.
14. Glulams intended for use as beams fall into two categories:
... 1) Unbalanced
... 2) Balanced or Reversible
15. Unbalanced Beams are intended for use as simple spanning members
16. Unbalanced Beams are often `cambered’
17. If unbalanced beams are installed upside down or in continuous spanning conditions or with cantilever spans ... they theoretically have less `capacity’
18. Stock beams are generally unbalanced and have camber
19. Balanced beams are intended for use in continuous spanning and cantilever/overhang conditions
20. Balanced beams are generally manufactured straight (no camber)
21. Glulam may be made into curved shapes, tapered shapes, curved and tapered, etc.
22. Curved and tapered beams are `custom’, and the designer should interface directly with the manufacture on their design, etc.
23. Glulam beams made be made into a nearly unlimited variety of lengths, depths, shapes (curved, tapered, etc.) ...
24. The main limitations on glulam size and shape (curved, etc.) are imposed by transportation issues.
25. Generally we don’t splice wood members – but due to transportation issues we have come up with a `moment splice’ for glulam.
26. You should specify glulam in accordance with what is available.
27. Glulam specifications should include stress and appearance grades.
28. For simple drop-in-place and prop-in-place members (beams and columns) there is a lot of `design guide’ type information.
29. For custom stuff, like curved beams, get an engineer and the manufacturer on board.
30. Manufacturers of `stock’ glulam generally do not provide engineering assistance.
31. Manufacturers of `custom’ glulam, or glulam systems (trusses, etc.) ... might provide design assistance, even a `stamp’.
32. The American Institute of Timber Construction (AITC) and the American Plywood Association – Engineered Wood Systems (APA-EWS) are the main trade organizations with glulam – and they provide a lot of useful information.
THAT’S IT FOR NOW ... MORE TO FOLLOW!
...
Tuesday, February 7, 2012
GLULAM
... here are some industry publications on Glulam.
APA's thing: http://www.apawood.org/pdfs/download_pdf.cfm?PDFFilename=managed/E30_Glulam.pdf (you have to register, free, if you haven't already, to see their stuff)
AITC's stuff:
General: http://www.aitc-glulam.org/glulam.asp
Span Table for 24F-V4 DF for FLOOR OCCUPANCY LIVE LOAD ... here
Span Table for 24F-V4 DF for ROOF SNOW LOAD ... here
Span Table for 24F-V4 DF for ROOF CONSTRUCTION LOAD ... here
Enjoy!
APA's thing: http://www.apawood.org/pdfs/download_pdf.cfm?PDFFilename=managed/E30_Glulam.pdf (you have to register, free, if you haven't already, to see their stuff)
AITC's stuff:
General: http://www.aitc-glulam.org/glulam.asp
Span Table for 24F-V4 DF for FLOOR OCCUPANCY LIVE LOAD ... here
Span Table for 24F-V4 DF for ROOF SNOW LOAD ... here
Span Table for 24F-V4 DF for ROOF CONSTRUCTION LOAD ... here
Enjoy!
TOTALLY COOL EXAMPLE PROBLEM - WOOD I-JOISTS
This example references the TrusJoist TJ-4000 Specifier's Guide and the NDS Beam Design Formulas ...
Links are:
TJ-4000 ... http://www.woodbywy.com/literature/TJ-4000.pdf
NDS Beam stuff ... http://www.awc.org/pdf/DA6-BeamFormulas.pdf
Monday, February 6, 2012
Rest of Example Problem ...
...
So, yeah, here is the rest of that example problem.
Recall we found that to satisfy the Live load deflection criterion we needed EI = 320 million lb-sq.in. ... we got it with the TJI-110 14" EI = 392 million ... good! ... and the TJI 210 16" 629 million ... WAY GOOD!
( ... whoa, there isn't a 110 series joist in the 16")
The we checked Moment (`flexure') ...
area load = 40 psf Live + 45 psf Dead ... the Dead being 15 psf from framing and 30 psf for 3 in. lightweight conc.
w = area load x spacing = (40 + 45 psf) x 16/12 ft = 113.3 plf
M = 113.3 lb/ft (17 ft) squared / 8 = 4094 lb-ft ... NEEDED!!!
p. 3 of the brochure (http://www.woodbywy.com/literature/TJ-4000.pdf) ...
TJI 110 14" M = 3740 ... NOT GOOD!
TJI 210 14" M = 4490 ... OKAY!
TJI 16" 210 Series ... M = 5140 GOOD! BABY!
... now ... SHEAR!!!
V = wL/2 = 113 lb/ft (17 ft) / 2 = 960 lb.
p. 3 of the brochure ...
TJI 210 14" ... V = 1945 lb ... GOOD!
TJI 210 16" ... V = 2190 lb ... GOOD!
So, the 210 Series works, in both the 14 in. and 16 in. depths.
BEARING ...
R = V = 960 lb
End ... p. 3 ... 14" 210 Series ... 1005 lb for 1-3/4 in. of bearing.
Assuming 2 x 6 walls that will have 5-1/2 in. top plates ... and that the rim will take up about 1-1/4 of the 5-1/2, leaving over 4 in. ... good!
We'd be good even if we dropped down to 2 x 4 framing ... 3.5 in. minus 1-1/4 gives 2-1/4 ... good.
FOR THE INTERMEDIATE BEARING - INT. BEARING WALL ...
... we'd probably have a 2 x 4 wall, at least ...
... if the joists end/start over the wall ... they need 1-3/4 in. each ... 2 x 1-3/4 = 3.5 ... perfect!
16" ... same ... good!
If the joists span continuously over the interior support ... we'll address that on another post! (or in class)
ANSWER: TJI 210 SERIES JOISTS IN EITHER 14 IN. OR 16 IN. DEPTHS ... WILL DO IT!
So, yeah, here is the rest of that example problem.
Recall we found that to satisfy the Live load deflection criterion we needed EI = 320 million lb-sq.in. ... we got it with the TJI-110 14" EI = 392 million ... good! ... and the TJI 210 16" 629 million ... WAY GOOD!
( ... whoa, there isn't a 110 series joist in the 16")
The we checked Moment (`flexure') ...
area load = 40 psf Live + 45 psf Dead ... the Dead being 15 psf from framing and 30 psf for 3 in. lightweight conc.
w = area load x spacing = (40 + 45 psf) x 16/12 ft = 113.3 plf
M = 113.3 lb/ft (17 ft) squared / 8 = 4094 lb-ft ... NEEDED!!!
p. 3 of the brochure (http://www.woodbywy.com/literature/TJ-4000.pdf) ...
TJI 110 14" M = 3740 ... NOT GOOD!
TJI 210 14" M = 4490 ... OKAY!
TJI 16" 210 Series ... M = 5140 GOOD! BABY!
... now ... SHEAR!!!
V = wL/2 = 113 lb/ft (17 ft) / 2 = 960 lb.
p. 3 of the brochure ...
TJI 210 14" ... V = 1945 lb ... GOOD!
TJI 210 16" ... V = 2190 lb ... GOOD!
So, the 210 Series works, in both the 14 in. and 16 in. depths.
BEARING ...
R = V = 960 lb
End ... p. 3 ... 14" 210 Series ... 1005 lb for 1-3/4 in. of bearing.
Assuming 2 x 6 walls that will have 5-1/2 in. top plates ... and that the rim will take up about 1-1/4 of the 5-1/2, leaving over 4 in. ... good!
We'd be good even if we dropped down to 2 x 4 framing ... 3.5 in. minus 1-1/4 gives 2-1/4 ... good.
FOR THE INTERMEDIATE BEARING - INT. BEARING WALL ...
... we'd probably have a 2 x 4 wall, at least ...
... if the joists end/start over the wall ... they need 1-3/4 in. each ... 2 x 1-3/4 = 3.5 ... perfect!
16" ... same ... good!
If the joists span continuously over the interior support ... we'll address that on another post! (or in class)
ANSWER: TJI 210 SERIES JOISTS IN EITHER 14 IN. OR 16 IN. DEPTHS ... WILL DO IT!
Saturday, February 4, 2012
Manufactured Floor Systems ..
...
Print this out (link below), maybe take a look at beforehand, and bring to class on Monday.
Good stuff! Where possible I let the Manufacturer `design' the floor system.
Much of what is in it should be making more and more sense ...
`Uniform and Predictable' ...
Design Properties, p. 3 ... Allowable Moment, Shear, and End Reaction ... these are basically like Allowable stresses multiplied by section properties (or contact area, for bearing).
Note the 100% load duration ... this is like our C_D for `Normal' Load duration (Occupancy Live load) ...
Note that design values CANNOT be increased by the repetitive use factor (footnote 1 to table on p. 3). (Anyone wanna take a shot at why?!!!)
Note the 2-term deflection equations I told you about ... the second term being for shear deflection.
Note that deflection equations are units-dependent.
Note that S and I are NOT published. :)
p. 4 ... and beyond ... Span Tables ...
Live load ... deflection limits, etc.
Cool Material Weights info on right side of p. 4 ...
p. 5 ... Load Table ...
p. 6 ... What a `System' looks like ... and the `ingredients' ...
p. 7, and beyond ... Details
p. 9 Allowable HOLES ... woohoo!
Other stuff ...
Roof framing, starting p. 13 ...
And then connectors ...
http://www.woodbywy.com/literature/TJ-4000.pdf
Enjoy the Super Bowl. (Who is playing?)
Doc
Print this out (link below), maybe take a look at beforehand, and bring to class on Monday.
Good stuff! Where possible I let the Manufacturer `design' the floor system.
Much of what is in it should be making more and more sense ...
`Uniform and Predictable' ...
Design Properties, p. 3 ... Allowable Moment, Shear, and End Reaction ... these are basically like Allowable stresses multiplied by section properties (or contact area, for bearing).
Note the 100% load duration ... this is like our C_D for `Normal' Load duration (Occupancy Live load) ...
Note that design values CANNOT be increased by the repetitive use factor (footnote 1 to table on p. 3). (Anyone wanna take a shot at why?!!!)
Note the 2-term deflection equations I told you about ... the second term being for shear deflection.
Note that deflection equations are units-dependent.
Note that S and I are NOT published. :)
p. 4 ... and beyond ... Span Tables ...
Live load ... deflection limits, etc.
Cool Material Weights info on right side of p. 4 ...
p. 5 ... Load Table ...
p. 6 ... What a `System' looks like ... and the `ingredients' ...
p. 7, and beyond ... Details
p. 9 Allowable HOLES ... woohoo!
Other stuff ...
Roof framing, starting p. 13 ...
And then connectors ...
http://www.woodbywy.com/literature/TJ-4000.pdf
Enjoy the Super Bowl. (Who is playing?)
Doc
Wednesday, February 1, 2012
Manufactured Wood Floor System
Okay, now our conversation will focus on `manufactured' wood systems.
Download, print, and bring to class: http://www.woodbywy.com/literature/TJ-4000.pdf
(Only 20 pages!)
Download, print, and bring to class: http://www.woodbywy.com/literature/TJ-4000.pdf
(Only 20 pages!)
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