Following the request of our fellow Ismaiel, who replied to our newsletter email asking to clarify how to compute the temperature loading in slabs desigm, here below I’ll try to explain it step by step. You may request the next article of StepbyStep by sending an email to firstname.lastname@example.org
In case you missed the Step by Step series, Check it up below. It’s a MUST !
- [Part 1] Step by Step Analysis Procedure of Seismic Loads Based on IBC2012/ASCE7-10
- [Part 2] Step by Step Analysis Procedure of Seismic Loads Based on IBC2012/ASCE7-10
- Step by Step – Deflection Analysis Using CSI SAFE
- Step by Step – How to Compute P-Delta effect using ETABS according to ASCE 7-10
Actually, the temperature loading evaluation when designing a slab using CSI SAFE is not that much complicated, as it could be considered as a normal load pattern like the super imposed dead load, live load, etc. But We shall not forget to introduce the temperature load case in the load combination related to the adopted standard.
Here below, we will consider a typical square slab of 10m span supported on a continuous wall from all sides.
From Define menu, load patterns We design a load case having name of Temperature and We choose its type “Temperature”
After that We will assign the Temperature load on the slab. Here I have to mention that In SAFE, two types of temperature loads can be applied to slab elements: an overall change in temperature or a temperature gradient across the slab thickness.
I’ll press right click on the slab, press on Loads then Assign Loads, Temperature Loads.
Here we have to choose the difference of temperature in accordance to the local instructions for the location of our project. We will choose here in this example just a random assumption. At the top of slab 80C and at the bottom of Slab 20C.
After that, I will go to the Define menu, Load Combinations to define the strength load combination having the Temperature load case into it. I will adopt in this example the load combination from ACI318 §9.2: 1.2D+1.6L+1.2T and I will define the regular strength load combination 1.2D+1.6L, just to compare the results and check out how the temperature will affect the stresses in the slab.
After that We make sure from Design menu, Design Combos that the requested load combinations are taken into consideration in the design of slab.
Now We will run the model and check out the difference of the moment along axis 2 under both load combination
As We can notice that the moment along axis 2 increased from around 9t/m2 to 25t/m2.
Now I will post a verification made by CSI company itself proofing how SAFE results when computing the Temperature loading are the same as hand-Calculated results.
Hopefully we could clarify properly how to compute the long term cracked analysis. If you have any question please do not hesitate to drop it by comment below.
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