Elasto-plastic frame under horizontal and vertical Gaussian excitation

Taking geometric non-linearity into account anoscillator of the form as aportal frame with a rigid traverse and with ideal-elastic ideal-plasticclamped-in columns behaves under horizontalexcitation as an ideal-elastic hardening / softening-plastic oscilator given that the columns carry atension/compression axial force.

Assuming that the horizontal excitationof the traverse is Gaussian white noise, statistics related to the plastic displacement response are determinedby use of simulation based on the Slepian modelprocess method combined with envelope excursion properties. Besidesgiving physical insight the method givesgood approximations to results obtained by slow direct simulation of thetotal response.

Moreover, the influence of a randomly varying axial column force isinvestigated by direct response simulation. This case corresponds to parametric excitation as generated by the vertical acceleration component in a quake.