Expert: Arshad Khan - 4/25/2007

Question
QUESTION: Could I analyze a tall building in United Arab of Emirates for Temperature Effects using ETABS program? Let me know the Temperature Value and the exposed Elements.
ANSWER: Hi Mohamed,

Yes you can, but you need to know the cladding/insulation details and how hot the exterior can get- both during construction and during operation. The temperature can go as high as 60-70 degress C if it is not insulated!

I hope that helps!

Kind regards,

Arshad

---------- FOLLOW-UP ----------

QUESTION: Many thanks for your reply
1. In case the tall building is externally insulated
  (using cladding), Is it right to apply temperature to
  the roof slab only?
2. In case the exterior columns and shear walls are
  exposed (not insulated), Is it right to apply
  temperature to the exterior columns and shear walls and
  roof slab?
3. How can I apply temperature during construction?
4. In UAE designers apply +25C and -25C to the roof slab
  of tall building (during analysis using ETABS), Is it
  right?
ANSWER: Hi Mohamed,

1. Yes.
2. Yes, and les to interior members, so you will get differential elongation.
3. You will need to do a laod case with say 1/4 height, then with half height, then 3/4 height.
4. No, I would say +50C to +10C.

Hope that helps!

Kind regards,

Arshad

---------- FOLLOW-UP ----------

QUESTION: Many thanks for your second reply. I need to ask you about:
1. In your appreciated reply (Answer 2), What is meant by
  "less to interior members", In such a case, Could you  
  let me know the values of temperature that can I apply
  to exterior columns, interior columns, roof slab and
  floor slabs?
2. In case for a tall building (40m by 100m in plan)and
  both the external surface and roof are insulated, Could
  I neglect the adding of an expansion joint?
3. Now (in ETABS) two types of Diaphragm (Rigid and
  Semi-Rigid) are given, Which one Could I use to model
  flat plate slabs (in Tall Buildings) having thiknesses  
  ranging for example from 180mm to 350mm?
4. During construction and upon using a load case with
  say 1/4 height, then with 1/2 height, and so on, Which
  members Could I apply temperature to them and the
  corresponding value of temperature in each load case?
5. What are the load combinations that can be used (inc.
  temperature efffects), BS 8110?
6. The earthquake loads are not included in the BS 8110
  Load Combinations, How can I add them?

Answer
Hi Mohammed,

Answers:

1. For final state, take interiors as 20 degC and exterior 30-50 deg C depending on amount of insulation. Ditto for roof- could be 30-50 Deg C

2. For seismic zone, it is best to avoid expansion joint otherwise you will have pounding problems- will need a wide gap! Just take care of horizontal temperature stresses by adding addition rebar.

3. Use semi-rigid diaphragm.

4. Use say 50 deg C for external vertical members and 30-40 deg C for internals not subjected to direct sunlight.

5. For temperature, just use 1.2 DL + 1.2 LL + 1.2 Wind- but check this in EC8 (see below).

6.Use the eurocode EC8, for load combinations with Eq.

Hope that helps1

Kind regards,

Arshad