Dear all, please clarify, why in case of seismic analysis (static or dynamic analysis) of building, the slab are not model and only frames containing columns and beams are modeled.
Actually, the slab act as lateral force resisting system, then why no one model it along beam and columns, in staad pro or etabs etc.
If i want to model a soft storey, probably at the bottom floor (which has no walls, so lowest stiffness),then how i distinguish the softstorey floor and other floors, because all the floors are modelled without a slab.
Thank you all.
Pandi Mani
In seismic analysis, the focus is typically on the frames (beams and columns) since they are the primary elements resisting lateral forces. Although slabs do contribute to the overall stiffness of a structure, they are often not modeled explicitly in software like STAAD Pro or ETABS. Instead, slabs are treated as in-plane elements that distribute loads to the beams, and their lateral load resistance is considered indirectly through the stiffness of the beams. Including slabs in the model can complicate the analysis without significantly improving accuracy, especially for regular structures.
When it comes to modeling a soft story, you can still capture its unique vulnerabilities without explicitly modeling the slabs. By adjusting the stiffness properties of the columns and beams in the soft story, either by reducing their stiffness or by adding specific elements like shear walls in the other stories, you can effectively distinguish the soft story from the rest of the structure. This approach highlights the potential weaknesses of the soft story during seismic events, ensuring a more accurate and meaningful analysis.
Please tell how can i reduce beam and column stiffness in staad pro to model soft storey (with modeling slab)
Thank you
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