The shear frame shown in Fig. 6.21 is constructed of rigid girder and flexible columns. The frame supports uniformly distributed load of total weight of 120kN and the frame is subjected to step force with a ramp as shown in Fig. 6.21 at the girder level. Determine the horizontal displacement at t = 0.75s. E = 200 GPa and damping can be assumed as zero. Moment of inertia of end columns and centre column are 3.4465e 5mm* and 7.07e 5mm respectively. IT 6.21 Portal frame. V t = 0.5s 80 kN