## Question

**In the case of spectral analysis, is the base shear force the sum of the inertia force of each layer or the shear force of the layer? Which is correct?**

## Answer

**The bottom shear force is the shear force of the layer corresponding to the bottom.**

In the case of wind load, which is a static load, it is equal to the sum of the story shear force and the load (wind load) from the upper floor to the floor, but in the case of Response Spectrum Analysis, the sum of the inertia force and the base shear force are not the same because the mode results are combined by SRSS or CQC method.