Select the lightest
available w14 section for column tosupport the axial
compression loads pd=150k and pl=200 k if kl =14ft and a572 grade
50 steel is used. column is assumed to be inframe that is braced
against side-sway. use trial and error methodin which a kl/r value
is estimated. solution should have requiredareas calculated, trial
section selected checked revised ifnecessary.

Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.