h $($m$)=3\mathrm{.}5$

I $($m$4)=0\mathrm{.}0001$

E $($MPa$)=240000$

m$1($t$)=25$

m$2($t$)=10$

A two story shear frame with lumped masses has the mass and

story stiffness properties shown in figure. The beams are rigid and the flexural

rigidities of the columns are defined in terms of EI$.$ Neglect axial deformations

in all elements. Determine the natural frequencies and modes of the system.

Sketch the modes.