Framing Connection

[LSPSCAT]

See attached sketch of simple frame in a single plane. No other support is provided out of plane. Frame is part of machine equipment with force applied to the horizontal framing member that acts bidirectional in the vertical direction. Magnitude is 100,000 lbs. Now for basic analysis in analyzing frame it is assumed as a non-rigid to determine loads in the main horizontal member and columns. Beam is designed as a simply supported member. The beam is connected to the frame with a 4-bolt fastener group and fasteners are designed based on loading in pure tension.

Now, for stability the frame is checked as a semi-rigid frame and the connections are then check based on the applied moments at the joints. The connection from the vertical column to the horizontal framing member is then checked for the tensile loading from the applied vertical load and for the moment that is developed from any out-of-plane applied forces. For stability loading, between 2% and 5% of the vertical load is applied both in plane and out of plane to the top horizontal member in conjunction with the vertical live load.

Bolting is required for assembly and disassembly. No welding allowed. Bracing is not really an option due to overall configuration.

Second question:

If the 4-bolt fastener group was replaced by a single line of fasteners should it be assumed that no moment can be transferred or would I be able to base the fastener loading on prying action based the geometry of the faying surfaces.
Just working through this and I am mainly concerned about the stability of the frame out of plane.

 

[Lion06]

I believe that if you are going to use a partially restrained connection IBC requires testing to determine the moment-rotation characteristics.

How are you planning to determine the moment-rotation characteristics of the connection?

If you believe there will be moment there, then you need to check the beam for it (unless it's completely unbraced for both positive and negative bending).

I'm not sure how assuming some rotational spring will help with out of plane stability.

 

[LSPSCAT]

Structural EIT,

I am trying to stay away from building codes as this is a frame for a machine, not that I want to ignore the guidelines but I intend to give myself some leeway. I do want the basics of the structural analysis to be correct. I am in a niche market with basic ASD design guidelines to go by. SF of 5 to ultimate and 3 to yield.

The beam is designed as simply supported in the initial check. When stability is checked with the lateral load case the moments from the horizontal force in plane will be superimposed on this load case. I will then have end moments and an additional moment at center span to add in.

 

[paddingtongreen]

Is this a reversing load? if so, how many lifetime reversals? (fatigue)

Is the load applied concentric to the frame? if not, the tolerance needs to be in the design as an eccentric, perhaps moment inducing, loading.

Is the load strictly up and/or down, or might it have a horizontal component? if so that effect should be in the design.

The only way for the frame to resist out of plane forces is for the baseplate to be fixed in that direction.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[LSPSCAT]

The load is reversing. Fatigue is not an issue for the design cycles. All fasteners are preloaded with a SF of 2 against separation.

The load is applied concentric to the frame, center span of the main horizontal member.

The load does not have a horizontal component, however, we do include as stated a 2% to 5% load applied horizontal to the frame at the top horizontal member both in plane (sidesway) and out of plane. This is a placed in order to simulate any potential "shock" loads during operation. There is no wind load or applied horizontal - but we need to place some reasonable load to check stability of the frame.

So typically, I place sidesway load into the frame and check the bolted connection for its abiilty to transfer the moment along with the applied tensile loading. The baseplate would then also be designed to resist these forces.

 

[paddingtongreen]

LSPSCAT that sounds reasonable to me. I assumed that the 100k included any impact load.

Michael.
Timing has a lot to do with the outcome of a rain dance.