Bolted Connection is or is not a moment resisting connection?

[NearBeer]

Thank you for your time. Please bear with my lack of knowledge on structures; I just separated from the military after 10 yrs flying helos and haven't had to use my CE degree till now with my new company. I am in the process of designing/estimating a shelving system to be used in an automated retrival system. I am attempting to make this system a bolt together vice welded since it would save about $80,000 in materials and shipping. However, my boss think that we will have to make it a welded system. I disagree with her. Our point of contention is the connection of the horizontal shelves to the vertical uprights. I contend that if we use 2 or 4 bolts in the equal leg structural angle horizontal beam/stringer and connect it to the vertical equal leg, then it becomes a moment resisting connection; she says "not necessarily" and tells me that it is a pinned connection. If I have the bolts separated by 90 deg so that they will bolt into both legs of the angle, how can such a connection not resist a moment? Our loads are light--370# distrubted over a span of 54" and seismic forces are nil. Any help, flames, comments, sneers, or jest is greatly appreciated. Thank you for your time.

In search of my next cold one,
NearBeer

 

[RARWOOD]

Purchase off of Ebay a used copy of a structural steel design book. If you have single angles which your shelf attaches to then basically you have a angle beam seat. the beam seat carrys vertical load and the only moment resistance you have is in the bending stiffness of the angle. If you have two angles one on top and one on the bottom of your shelf you can develop a moment.

Another approach would be to weld an end plate on your shelf and design a bolted end plate moment connection.

 

[civilperson]

Not a moment connected unless the connection is slip critical. The over sized holes, the bending available in one leg connection and lack of moment transfer into the vertical member all describe a simple,(hinge), connection. The design of selves is RARELY flexural stress driven, but rather deflection criteria will determine the members.

 

[NearBeer]

okay...thanks for the info so far. I left out one piece of info that is critical. I will weld a roll formed angle tab with holes in it to the underside (at the end) of one of the horizontal angles and then bolt it into the corner of the vertical angle. Thus, there will be a way to have the bolts connect through the horizontally running angle legs to the vertical angle. In response to civilperson's comments, if I were to have bolts going through each leg, would that count as bending NOT available in both connections?

Still haven't found my cold one,

NearBeer

 

[Dinosaur]

My vision of shelving is that it is comparatively slender and deflects easily. This agrees with the above observation. A slender member in the very best circumstances would form a plastic hinge at each end and then behave as a simply supported member. However, it is difficult for me to envision a slender member such as shelving having the capacity to form a plastic hinge without substantial diagonal braces to the verticals.

Good luck.

 

[dik]

Just to add to the confusion... it's possible to design a moment connection without using slip critical fasteners (although it's nice - moment resisting col base plates come to mind).

The critical thing is the fasteners used...

Dik

 

[strider6]

just a suggestion..have a look at this two publications from Lincoln

Mixing Welds and Bolts, Part 1

http://www.jflf.org/pdfs/papers/design_file201.pdf

Mixing Welds and Bolts, Part 2

http://www.jflf.org/pdfs/papers/design_file202.pdf

hope this help

S.

Corrosion Prevention & Corrosion Control