Illbay
Structural
- May 22, 2001
- 54
Performing this design calculation, I was struck by the strange "murkiness" of the requirements for shear capacity of the beam web. The pertinent explanatory paragraph of the Design Guide 4 (Second Edition, published March 2015) is as follows:
"Only the web to end plate weld between the mid-depth of the beam and the inside face of the beam compression flange may be used to resist the beam shear. This assumption is based on engineering judgment; literature is not available to substantiate or contradict this assumption." [Paragraph 2.1.8]
I was struck by the incongruity of this phrase in comparison to most modern design literature. "Back in the day," when I was getting started in the profession - and so much of research had yet to be done - one frequently encountered such statements. However, in the decades since (yes, I'm old), the burgeoning amount of research not to mention the availability of sophisticated computer modeling techniques and products, has reduced much of the uncertainty one used to encounter in recommended design practice. I actually studied as an undergraduate with the late Prof. Krishnamurthy, who originated the end-plate moment connection research, and I recall that these types of "unsubstantiated assumptions" existed then - but that was in the late 1970s! Surely we have dissipated some of that fog by now!
Does anyone know of any research-based recommendations on this topic? As it is, I'm having a very tough time with this design, and it simply makes no sense that there is a shear failure at this point given the practical sizes of the members I'm coming up with based on the other criteria. And failing that, I am minded to add a doubler plate to the web in the "compression zone" of the web, to deal with the ASSUMED required shear capacity. Any opinion on that?
"No one is completely useless. He can always serve as a bad example." --My Dad ca. 1975
"Only the web to end plate weld between the mid-depth of the beam and the inside face of the beam compression flange may be used to resist the beam shear. This assumption is based on engineering judgment; literature is not available to substantiate or contradict this assumption." [Paragraph 2.1.8]
I was struck by the incongruity of this phrase in comparison to most modern design literature. "Back in the day," when I was getting started in the profession - and so much of research had yet to be done - one frequently encountered such statements. However, in the decades since (yes, I'm old), the burgeoning amount of research not to mention the availability of sophisticated computer modeling techniques and products, has reduced much of the uncertainty one used to encounter in recommended design practice. I actually studied as an undergraduate with the late Prof. Krishnamurthy, who originated the end-plate moment connection research, and I recall that these types of "unsubstantiated assumptions" existed then - but that was in the late 1970s! Surely we have dissipated some of that fog by now!
Does anyone know of any research-based recommendations on this topic? As it is, I'm having a very tough time with this design, and it simply makes no sense that there is a shear failure at this point given the practical sizes of the members I'm coming up with based on the other criteria. And failing that, I am minded to add a doubler plate to the web in the "compression zone" of the web, to deal with the ASSUMED required shear capacity. Any opinion on that?
"No one is completely useless. He can always serve as a bad example." --My Dad ca. 1975