Expansion joint in hig rise building

[sag04]

I'm working on a 35 storey twin tower with combined ground &parking floors (P1, P2 ,P3) in which expansion joints are located both in X & Y direction. At each expansion joints there is two columns 2 cm apart resting on pile foundation with pile cap.The pile cap is combined one for both the column. The problem is our client engineer insists for expansion joint must start from pile foundation itself . ie, seperate pile cap for each coulmn set apart 2 cm spacing at expansion joints. But design engineer says expansion joints starts from column only and no need to provide expansion joints in pile cap. Who is correct client engineer or design engineer? please comment and save me from this dilemma...
thanks a lot
regards

 

[haynewp]

2cm is pretty small. Are you in a seismic area?

 

[MotorCity]

sag04,

If you are in a seismic zone or an area heavy with frost action, expansion joints in the foundation will allow for lateral expansion. However if wind is the only consideration you probably don't need expansion joints in the foundation. This is especially true for tall structures. Generally, the largest deflections are at the top of a building and decrease as you go down toward the foundation. Therefore, expansion joints are more critical the higher you go as there is more movement. In other words, the foundation will not sway in the wind like the top of the building will, so expansion joints in the foundation are a good idea but not necessary based only on wind forces.

 

[JAE]

I guess I've always seen expansion joints start just above the foundation, with the footing system tied together. In fact, in seismic areas, the code requires ties between piling/pier foundations.

Expansions joints are added to offset the effects of thermal movements in the building. For foundations, the temperature range is very small, if not zero, so the thermal movements aren't there. For a very large footprint building, yes, you might consider separating the foundation areas with joints as there could be build-up in stresses in gradewalls, etc., due to foundation settlements or heaving. But generally, the expansion joints start at the base of the building columns and walls.

 

[haynewp]

Is the horinzontal expansion joints just in the parking floors?

 

[sag04]

Thanks all
hi haynewp
The project is in Dubai UAE. So out of seismic area. Here the temperature variation is very high (Average temperature 40 C and max 50 C).Up to the parking floor expansion joints is in both direction X & Y, after that only in Y direction.
Regards

 

[haynewp]

The reason I was asking is because when I put in expansion joints, the first thing I think of is to make sure there will not be a problem with accomodating the drift due to lateral loads. You don't want your separate structures banging together. It may not be a problem in this case.