The size of this sdf model is 61.0 cm high and a 43.0 cm span. the columns and girder are made of manufactured thin rectangular shaped steel. the dimensions are 28 mm wide and .85 mm thick. for a good visual observation effect, the columns of the frame are oriented such that columns bend about the weak axis when the earthquake force is supplied in the plane of frame. for the purpose of dynamic analysis of the frame, the column is considered massless with a weight of 4.5 n lumped at the beam level. required: determine the frequency of the sdf system analytically and experimentally.