Dynamics and Earthquakes

Question 1

What are the 3 assumptions for the table

Answer 1

1. The slab is rigid in its plane
2. The slab is rigid in bending
3. The torsional stiffness on the columns is negligible

Question 2

The slab is rigid in its plane
What is this assumptions, when is it appropriate

Answer 2

The structure is not expected to experience significant flexural deformations in the plane of the slab

Its only appropriate for stiff slabs with low frequency dynamic laods

Releasing this assumption could equal additional modes of vibration in the slab

Question 3

The slab is rigid in bending
What is this assumption, when is it appropriate

Answer 3

The structure is not expected to experience significant bending deformations

Assumes there are no rotations at the top of the columns so the stiffness matrix can be calculated by hand

Releasing it could alter the mode shapes and frequencies of vibration

Question 4

Torsional stiffness of the columns is negligable

Answer 4

Assumes the columns are stiff and so won’t twist

Appropriate when there are no significant torsional loads applied to the structure

If released you would need to consider torsional modes of vibration