Shear resistance with standard base plate 2

[FeSE]

When a base plate sees more shear than available friction, what actually happens? Certaintly the anchors go into bending. After some deformation would it not be reasonable that a concrete wedge forms as shown in the following sketch? Wouldn't that in turn add to the friction available?

Does anyone know of research or designs based on something like this?

On my current project, I have I have the following;
rxns;
.6D+.7E 97k uplift & 57k shear
D+L+.7E 337k down & 57k shear
W12x79 column.

So, I need to pretension the anchor rods in order to overcome the 97k uplift. AISC doesn't recommend that either... wouldn't that be pretty simple though?

 

[Tmoose]

Nuts under the base plate are an attractive feature for leveling, but they effectively defeat ANY useful pretensioning of that anchor. If all the anchor bolts have leveling nuts underneath, Depending on how much the grout expands, (1 % at most, which compares pitifully to several percent of a pretensioned much longer anchor bolt) the entire structure can be left resting on the anchor bolts. Kind of like a hair brush resting on its bristles.

http://www.zteam.com/images/A0512a.jpg

Probably Ok for a light pole in parking lot, but hardly a structural connection suitable for a machinery base. Having fought to keep many lively machines attached to their bases I hate those leveling nuts.

The maintenance of pretensioning versus applied load depends on the fastener appearing stretchy, and that requires something much stiffer surrounding the fastener and being clamped by the fastener.

Maintaining the preload makes the bolt fatigue strength essentially a non-issue by chopping the range stress by 90% or so. That is very handy and practically free.
Maintaining the preload makes stress corrosion cracking a real issue sometimes even in nice environments.

 

[Lion06]

nutte-
Thanks for the reference for me to read. That's worth a star.