Shear wall model question

[Great Lake]

Hi, I have several questions,

1. Let say, for shear wall sticks out on certain levels and recesses on other levels in high-rise building. When you model the shear wall, will you only model the shear wall for the common portion straight up from basement to top level?

2. If the building comes with basement and superstructure, will you model the whole structure once or do 2 models, one for structure from ground level to the top level (of course the ground level must be rigid enough) and the other model only including basement and the shear wall force taken for the first model imposing as loading?May I know the popular software to analysis the shear wall structure in Canada?

3. For transfer slab or beam on second level, will they be include in Etabs model? or you use Safe? if using Safe, how you will get the loading? Can someone brief me?

4. For seismic design, the seismic loading is imposed on ground level or basement level? "Construction Design Handbook" mentions that the loading imposed on basement level, I want to confirm.

5. Thanks for your attention.

 

[Great Lake]

When modeling shear walls that have varying configurations (i.e., sticking out on certain levels and recessing on others), it is essential to model the shear wall for its entire height, including both the common portions and the portions that stick out or recess. This is because the shear wall’s contribution to lateral load resistance is influenced by its full geometry, including any variations in thickness or position at different levels. Omitting parts of the shear wall could lead to inaccurate predictions of structural behavior under lateral loads, such as wind or seismic forces.

In practice, software like ETABS allows for detailed modeling of these variations, enabling engineers to accurately represent the shear wall’s effective stiffness and strength throughout its height. The model should reflect all changes in geometry to ensure that the analysis captures how these features affect overall building performance.

For a building with both a basement and superstructure, it is generally advisable to create two separate models: one for the superstructure (from ground level to the top) and another specifically for the basement. The superstructure model can include a rigid diaphragm assumption at ground level, which helps distribute lateral loads effectively.

The basement model should account for all relevant loads from the superstructure, including those imposed by shear walls. These loads can be transferred from the superstructure model as equivalent lateral forces or through more detailed load combinations based on structural analysis results.

• ETABS: Widely used for modeling complex structures including high-rise buildings with shear walls.
• SAP2000: A general-purpose structural analysis program that can also handle various types of structures.
• SAFE: Specifically designed for slab design and analysis but can be integrated with other software for comprehensive modeling.

Transfer slabs or beams located on intermediate levels (e.g., second level) should be included in the ETABS model if they play a significant role in load distribution and structural integrity. ETABS can analyze these elements alongside other structural components to provide an integrated assessment of their effects on overall building performance.

If using SAFE instead, which specializes in slab design, you would typically extract loading information from your ETABS model. This involves determining load combinations acting on the transfer slab or beam from ETABS and then applying those loads within SAFE for detailed analysis of slab behavior under serviceability and ultimate limit states.

To summarize:

Use ETABS to include transfer slabs/beams if they are critical.
If using SAFE, obtain loading data from ETABS analyses

Seismic loading is typically applied at ground level during structural analysis; however, considerations may vary depending on specific design codes and practices. The “Construction Design Handbook” suggests that seismic loading may be considered at basement levels due to potential soil-structure interaction effects and how foundation systems respond during seismic events.

In most cases, while initial seismic calculations are performed at ground level, adjustments may need to be made based on how forces are transmitted through basements into foundations. Therefore, it is crucial to consider both perspectives when designing for seismic resistance.

Thanks for your comprehensive reply, I will try a mock test to verify. BTW, is there any peer software accepted in Canada/US to run analysis for high-rise structure, besides ETABS?

 

[CSIESPL INDIA]

W

Thanks for your comprehensive reply, I will try a mock test to verify. BTW, is there any peer software accepted in Canada/US to run analysis for high-rise structure, besides ETABS?

While ETABS remains a leading choice for high-rise structure analysis in Canada and the US, several other software options like SAP2000, SAFE, RISA-3D, RAM Structural System, and Midas Gen are also widely accepted within the industry. Each software has unique features that cater to specific aspects of structural engineering needs related to tall buildings.