Thermal Design

[mhdhamood]

Senior Engineers;

Can you provide us by the procedure for thermal design of buildings. Such as what to do in ETABS and SAFE, and what to do about modifiers of elements.

regards

[WR1]

There is no such thing as thermal design in ETABS. You have to use other softwares for finite element analysis for thermal stresses.

 

For the usual design to take into account the temperature loading, don't use rigid diaphragm or it will take all the forces from T.

 

Use usual modifiers and make a load case of T. Then you can always use minus and plus sign in combinations.

 

Use load combinations as per ACI. T comes with 1.2 factor like dead load.

 

Just make sure put reinforcement in beams like in columns. Equal on all faces.

 

And the fun part, let me know how you calculate the crackwidth with P and M-M at service level. If you can't find let me know then.

 

Good luck!

[mhdhamood]

Thanks Waseem; let me say what we ordinary do then if wront then please coorrect 

What we do in ETABS is :

1. We use ETABS for the effect of temperature on columns and walls and foundations.

2. In ETABS model the modifiers will be : 0.35 beams, 0.7 columns and walls (0.35 if cracked), and m11=m22=m12=f11=f22=f12=0.25 for slabs. 

3. we assign temperature to all elements(columns beams slabs).

4. In addition to load combinations.

 

Now in Safe for slabs design :

1. the modifiers we enter are 0.35 beams, 0.7 columns and walls (0.35 if cracked), and m11=m22=m12=f11=f22=f12=0.25 for slabs.

  So here because we put modifiers to elements, we need another file for slab other than the one we use for deflection and earthquake +gravity laods design .

2. the temperature is assigned to slab.

3. In addition to load combinations.

 

The fun part that you mentioned I dont know , so please help!!

regards our great engineer

[Dik]

In these environs, only if a building is unheated (eg. some warehouses, parkades, etc.) nearly all buildings are heated in the winter and cooled in the summer. Thermal change in dimensions is normally accommodated by construction details at the time of construction. Once a building is enclosed, there is very little thermal movement.

[kalielianna]

1. Define the Building's Thermal Loads in ETABS:

   • Start by defining the thermal loads that your building will encounter. These include solar radiation, internal heat gains, and external temperature variations.
   • In ETABS, go to Define > Load Patterns, and create new load patterns for each type of thermal load (e.g., solar, internal).

2. Assign Thermal Loads to Elements:

   • Assign these thermal loads to relevant structural elements (walls, floors, roofs) by going to Assign > Loads > Surface Loads or Assign > Loads > Frame Loads.

3. Adjust Material Properties for Thermal Analysis:

   • Ensure that the material properties reflect thermal characteristics. This involves setting thermal expansion coefficients and heat capacities. Go to Define > Material Properties, and adjust these settings accordingly.

4. Element Modifiers for Accurate Analysis:

   • Adjust the element stiffness and strength modifiers to account for the effects of thermal loads. This is crucial for an accurate representation of how the structure behaves under thermal stress.
   • In ETABS, use Assign > Frame > Frame Property Modifiers or Assign > Shell > Shell Property Modifiers to tweak these values.

5. Thermal Load Combinations:

   • Create load combinations that include thermal loads. Go to Define > Load Combinations, and include the thermal load patterns you defined earlier. This helps in evaluating the structure under combined load effects.

6. Run the Analysis:

   • Perform the analysis in ETABS to understand the thermal effects on your structure. Review the results for any significant stresses or deformations caused by thermal loads.

7. Thermal Effects on Foundation - SAFE:

   • Export the thermal load effects to SAFE for foundation analysis if needed. This is particularly important for understanding how thermal expansion and contraction affect the foundation.
   • In SAFE, apply the thermal load effects to the foundation elements and run the analysis to ensure stability and performance.

Remember, precise Construction Estimating must consider thermal loads to ensure the building's safety and comfort. This approach not only enhances the building's performance but also provides a comprehensive cost estimation.

Feel free to reach out if you need more detailed steps or examples. Happy designing!