Moment Connection vs Continuous Beam

[Sanira]

Suppose you have two bay frame in which the two beams are connected to column in the middle through moment connection. The beans are also connected to end colums through moment connection. Do you analyze this beak as a simple continuous beam? Does the moment connection makes the beam continuous? Also what forces are transferred to the centre column from the beams on both sides OR the moments get cancelled out from either sides?

 

[msquared48]

The structure you are describing is a two span moment frame with three columns, one continuous beam, and moment connections at the three beam-column joints.

The beam is not simple continuous, but continuous as no vertical deflection will be present at the center column, only rotation.

The center column will see both vertical and lateral reactions, plus moments, with the amount of the reactions dependent on all the column and beam sizes, the size and location of the vertical loads, and the size and nature of the lateral loads to mention a few factors.

No simple answer here... You need to run through the numbers...

Mike McCann, PE, SE (WA, HI)

 

[Sanira]

Thanks Mike for the reply. What if the there are no two beams, but just one beam running on the top of middle column and connected to it? Does it still transfer moment to column?

 

[mtu1972]

Depends on your connection. Continuous beam over cap plate with only two bolts (no moment transfer) then it’s a “pinned” connection to the middle column.

From your original description, you would have to design the beams and the columns as a frame. Moments will be transferred through the connections depending on relative stiffness of the members, unbalanced loads, etc. Can be done by hand with Moment-Distribution.

gjc

 

[KootK]

What if the there are no two beams, but just one beam running on the top of middle column and connected to it? Does it still transfer moment to column?

What's your goal here? Do you want the moment in the column or are you seeking to avoid it? New structure or existing?

 

[msquared48]

If you have lateral loads to resist and you either do not want to use shear walls or do not have them available in the same line as the frame you describe, then you will need a moment frame.

However, if all you are supporting is gravity (vertical) loads, then the connections you mention do not have to be moment connections unless you want them to be.

Mike McCann, PE, SE (WA, HI)