connection design

[PowerRanger]

Hi fellows
For the portal frame design, some times the case is the rafter weld to the end plate and bolt to the column. But how about if the case is the column weld to the plate and bolt to the rafter, can i just rotate it and do the same design as the first case?

Thank you for you time

 

[jike]

If this is a symmetrical portal frame, symmetrical loading with two same size, non tapered, vertical columns and a horizontal, non tapered, beam, no overhangs and you have used the forces derived at the intersecting centerline of the members (not the faces of the members), then the moments would be the same but the shear would become the axial force and the axial force would become the shear force.

It is possble the connection may be adequate for both but you should definitely run thru the numbers to be certain.

 

[pba]

It's not clear if you are trying to design the joint or the pertal frame.

Jike is correct. Note also that the rafter is usually bolted to the column as the extra depth of the beam haunch assists in the bolt lever arm. To do the same at the top of a column is possible but the haunch orientation is not so good for the design on the rafter.

 

[J1D]

PowerRanger,

To my understanding, you question is whether the bolting interface can be at column side OR at top of column. Both exist as I observed. “At Top” is good to prevent clash of purlin to connection plates and save the concern of shear at the connection. “At Side” is better for connection (as pba indicates) if the rafter is haunched but not the column. In industrial frames, columns usually to go through since the column extension is required from time to time.

 

[dbuzz]

Are you talking about: (i) a column cap plate, where the beam runs over the top of the column; and (ii) a bolted moment end plate, where the beam runs to the side of the column?

 

[PowerRanger]

dbuzz

yes, that is true. So how should I design a column cap plate? Any example to follow?

Thx very much

 

[dbuzz]

The design procedure will be very similar to that for a bolted moment end plate. If you resolve the bending moment and shear force into design forces on the elements in the connection (stiffeners, end plates, bolts and welds) you can't go wrong.