Please help! lapping joggle falls on beam column joint while making plinth beam. 1

[akgtm]

My five story public building is situated in earthquake prone area.The contractor placed joggle at beam column joint. And 50 percent of laps fall at beam column joint while constructing plinth beam. Would it be ideal to construct the plinth beam at that joggled region? Please provide me some suggestions. I have attached photo also of joint.

 

[HTURKAK]

Is the contractor free to choose the rebar splice location ? Doesn't the contractor have rebar details?
Apparently, the perimeter grade beams are located on brick walls and will be cast together with SOG slab after the soil fill completed. What is the situation for the interior frames? Do the grade /tie beams extent to the plinth level ?

I suspect, you should worry about the dirt at connection and short column risk ..

Provide more info to get better responds..

 

[akgtm]

Actually the height of plinth was increased to get to road level and the half of the splice location fall on the plinth height. The lapping position was in alternate so these joggle fall at plinth beam and column joint. We had rebar detail's and client told to change the original height of plinth to meet above road level. I was worried whether the bending moment will be dangerous if there is joggle at beam column joint. It basically happened because we didn't plan for increasing the foundation height. They have also provided engough lapping length for all the columns. But the half of the laps joggle at beam column joint now. As you can see in picture.

 

[HTURKAK]

Let me express my concern,
- The tie beams are for only perimeter to provide threshold and there are no tie beams at interior frames..
- The ground floor slab plain concrete and does not provide diaphragm for the columns at GFL..

If not, pls provide some details ,structural plan and some sections to get the full picture.

 

[akgtm]

I have attached the drawing and shown the the shifted plinth height from original location as you can see cross mark there. I hope you understand.

 

[HTURKAK]

Dear akgtm ,

I understand but i am afraid you did not understand the consequences of the site revisions ..
I strongly advise you to go to EOR or designer and ask the revision of the full structural drawings..
Apparently,the base tie beam rebar should change. The analysis shall be revised for the elevated GFL, the column splice locations shall be revised acc. to new floor levels..

 

[akgtm]

Thanks HTURKAK, for your help. The drawings will be revised and recalcuated. But the main problem is how critical can we take plinth beam and column joint incase of eq loading.The site condition cannot be altered and column has already been casted and its time for plinth beam construction. I clearly need to figure it out whether the lapping cause problem in joint or not.

 

[HTURKAK]

IMO, The lapping at new plinth beam -column connection is not critical except congestion. The max. moment region for the column will also change and will be above plinth level.
The picture shows some column rebars having different heights. Make sure the existing column rebars will not have lap splices at critical zones of the columns.
You are saying 50 % of laps fall at beam column joint . In this case, the column bar lengths shall be (21'+ 60d) so column reinforcement will be spliced every other floor to reduce congestion.

I will suggest to provide min mesh reinf. for sog / ground slab to provide diaphragm at GFL. The total soil back fill ht is around 2.5 m .. The dynamic active soil load should be considered for new analysis.

The following doc. is useful to see the splice locations, beam-column joint details .

 

[akgtm]

Thanks HTURKAK, for your valuable suggestions. I was in alot of stress and now I got something to plan for future. I also appreciate your time and effort to explain in details.