Wood Beam Design Example Using NDS! (Part 1 of 2)
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- Опубліковано 29 чер 2024
- The steps a Professional Engineer would take to properly design a wood beam, using the NDS manual,to adequate support specified loading criteria. Talking about deflection, shear, and bending moment and the checks needed to determine a wood beams size requirements.
I really appreciate your work on the videos!
Glad you like them!
Could you do a video where you do a simple building? Example: Show a small shed, or home, with a roof slope, 4 to 12 or something of that manner, in a location, and show where/how you got the loads? I feel this could be beneficial and to help others understand when a distributed load is in place, when there is a point load, etc?
I think d for 2x10 is 9.25" and not 9.5". Can someone correct me if I am wrong.
shoot... you're right MOE! 1 1/2 x 9 1/4. great catch!
Moe & Kestava: I'm only watching this video now on October 2nd, 2022 but I said wait a minute, once you get past a 2x6 your widest dimension goes to 7.25 for an 8-inch dimension, 9.25 for the 10-inch dimension, etc. Anyway great video and you do a nice job!!
@@Kestava_Engineering Moe & Kestava: I'm only watching this video now on October 2nd, 2022 but I said wait a minute, once you get past a 2x6 your widest dimension goes to 7.25 for an 8-inch dimension, 9.25 for the 10-inch dimension, etc. Anyway great video and you do a nice job!!
sorry everyone, the video has now been oriented correctly! part 2 coming soon!
Thank you @kestava. Great video. Hope to have more videos from you.
@@nabindahal8043 thank you! are there any problems you would like to see for my next video??
@@Kestava_Engineering Steel column design. Finding moment and reaction for Indeterminate structures (statics). More tips and tricks AISC steel manual, IBC 2015, ACI 318
@@Kestava_Engineering hi thank you for your helpful videos. what about commercial wood decking span trib width 14 feet, LL =100 psf, DLl 10 psf, span of beam 14 feet....
It appears that your application of the calculation for Cf (size adjustment) was maybe misinterpreted . Per AWC 4.3.6.1 you would use that equation if the member was 5" or thicker and more than 12" in depth. It would then imply that you should use the Size Factor table in the AWC Supplement page 32 which in this case results in the same value of 1.0. I only noticed this because I had been using your method for a nominal 3" thk x6" depth beam which resulted in a fairly large adjustment to Fb, Ft & Fc. Thanks for your work and any feedback.
I stand corrected only to say that since you were using a nominal 2x10 I believe your Cf value should have been 1.1 applied to Fb anf Ft (not 1.0 as I stated above). Thanks.
Hello, could you please provide clarification regarding the Cfu factor Table 4D in the NDS supplement? It appears that there are different values specified for beam and stringers. I'd like to inquire further about this matter. Thank you.
Would it be necessary to use load combinations for a simply supported pedestrian bridge?
Daniela, yes you always need load combinations. for a pedestrian bridge you would need to design using load combinations per the AASHTO pedestrian bridge design manual in the united states. I hope this helped!
Do the bending and shear values change by doubling the beam, or do the double beam apply to 2"-4" thick materials?
the bending and shear capacity of the beam definitely increases!
I apologize for the ignorance, I'm not a engineer. My question is: You decided to use 2x10 and then extracted the factors. However, what led you to select the size? Could you make a video regarding the factors that lead to select the size of the beam?
I designed the problems loading criteria to be relatively close to what a 2x10 could handle. the more you do it the better you get at giving a rough estimate of what size member is needed. I think a video on engineering judgment is a really great idea!
Thanks!
thank you so much! your support means a lot
For deflection check, shouldn't we use E' instead of E? Thanks a lot for the nice videos.
we do use E' but you should find that all the adjustment factors come out at 1.0 so it doesnt change
I'm not an engineer so this may be a dumb question. In your example, was the Trib Width of 24" simple an assumed figure or was it calculated from the information you presented? If calculated, how was the calculation made. If assumed, how would Trib Width normally be calculated? From what I understand, if a beam is supporting a 10'X10' ceiling, the trib width would be 5' so the trib width would have been 120" in your example.
Correction, Trib Width would be 60"?
@@junk4bh565 my bad I didn't respond earlier! The trib. width was an assumed distance. Basically I assumed that this beam would be similar to a wood floor joist which are usually 12" to 24" O.C. so the trib for each "beam" would be that spacing. trib width is the dimension perpendicular to the beam span, it does not have anything to do with the dimension of the beam span. so the beam is 10ft long and supporting a trib width of floor of 24" or 12" each side of the beam along the length of the beam for a total supported area of 24" x 10ft = 20sqft. I hope this helped. let me know if youd like a short vid on this for a visual junk!
best
Rich
@@Kestava_Engineering Thank you, I get it now I think. I was confused by dividing 24 by 12 and where the 24 came from. In essence, if the trib load is 50 plf and the trib width is 2' (24"), you simply multiply the plf by 2. So if the trib width in your example was 36", the plf would be 150 plf correct (36/12 or 50 x 3)? But to be sure, the trib width as used in your example doesn't have anything to do with, the joists I'll say, being 24" oc. In other words, if the joists resting on the bean were 16" oc, it would not change the plf of 100 in your example? If I'm still off perhaps a short vid might be helpful.
Would it be possible to calculate timber beam in Limit State Design as Allowable State Design is not followed in Eurocodes?
Jose,LSD or otherwise known as LRFD design can be done when designing wood. I can do another video using LRFD!
@@Kestava_Engineering Thanks a lot for replying.
And yes a video would be very very helpful as we have to design a glulam beam and column using LSD (LRFD).
@@josesibi check out my latest video - design of a glulam beam using LRFD!
Why is there a difference in the NDS values between "Bending" strength Fb and "Tension parallel to grain" strength Ft? Bending stress is tensile stress, no?
hmmm I see where you're coming from. ive never thought about it before. im thinking they did so much testing with wood beams that they found there was a big enough difference between tensile failure from bending vs tensile failure from pulling on a board.
Gracias
denada
2x10 is 1.5x9.25 heads up
yes sir! great catch!