Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations KootK on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Columns Moments Transferring

Status
Not open for further replies.

concrete12

Structural
Apr 26, 2023
3
Hi All,

I’m trying to understand how moments in an insitu RC column transfers to the column below.

For example, on L5, the column above is loading the column below eccentrically (200mm). The load from the column above is N* = 5000kN, so the column below takes a moment of 5000kN * 0.2m = 1000kNm as well as an axial compression force of 6000kN (assuming the load increases by 1000kN each floor). Column below L5 can be designed for this combined compression and moment.

Assuming that all columns are fixed, and the column below L4 is concentric to the column below L5 and it takes an axial compression force of 7000kN. However, I’m trying to see how the moments in the column below L5 will transfer to the moments in the column below L4. Will the column below L4 also take a moment of 1000kNm, or, can you resolve the moment from the column below L5 into a push/pull and combine us with the 7000kN force that acts uniformly over the column cross section so that the resultant force is eccentric to the column below L4 (but the eccentricity is less than 200mm) and design that column for combined bending and axial force?

For simplicity in this example, let’s assume all columns are 1000x1000. Also, for simplicity, I haven’t taken into consideration any additional moments from the slabs/beams.
 
Replies continue below

Recommended for you

Capture_jljuct.jpg


Boundary conditions are all important. If you say all columns are fixed, the moment stops at L5.
If columns are permitted to rotate but not translate, the applied moment M is shared equally by column L5-6 i.e. M/2 each. Then M/2 carries over M/4 to L4 and continues distributing half of the carry-over moment to the next floor below.

If columns are permitted to rotate and translate, then a correction must be made to the moment distribution to restore equilibrium to the system. And any other effects, such as wind forces must be included in the analysis.
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor