LRFD vs ADS Wood design 2

[erik1938]

I am just curious as to how many people use ASD or LRFD for wood design. I am a new graduate and I have learned ASD wood design, but I think that LRFD may be more efficient as well as less cumbersome.

Any thought?

 

[SacreBleu]

There's already enough absurdity in the IBC Code, let's not add wood LRFD to it!

 

[CraigICE]

I've shown young engineers how to simplify LRFD loads to ASD for concrete design and their answer has often been "not necessary -- LRFD is no problem if you learned it first."

It only takes them about three years to shed the LRFD.

sduggan's comment about designing to the nearest in-lb is a good point. I showed a youg graduate how to sum up the weight of the steel framing in the 200' x 200' second floor in a central utilities building and then reduce the roughly 12 sizes to three or four by changing the size not before an 8 lb to 12 lb/ft spread in weights occurred. The difference in framing techniques amounted to about 300 lbs for a 40,000 sf floor. At $1 /lb installed, that $300 spent would have saved thousands in detailing expense and waste due to drop-off in the fabrication shop.

This project had been "value engineered" by the contractor's estimater (sp?). To add insult to injury, they decided not to use the 12" concrete slab as originally designed but went with 4" of concrete over metal deck.

The contractor must have made thousands off of this careful design and I made tens of thousands reinforcing the floor so that my customers could install the tanks that everyone new would be placed there.

Even for concrete design, LRFD is relatively meaningless. It's the Whitney's stress block that makes the difference. And you'll notice that over the last 60 years, concrete shear has gotten more and more conservative and that didn't involve LRFD.

Again, shouldn't this discussion be taken mainstream? How many people would like to read our collective comments and add their voices?

Also, forget about that other improvement to engineering called SI units. The code writing people and government agencies are dropping this elegant system of units in favor of our barbaric imperial system. That means no mks (meters, kilograms, seconds) for awhile either.

The distance between the tips of my thumb and little finger is about 20 cm. That's easy -- Newtons and Pascals, that's not.