The OpenSees Community

Hi I've modeled a 2D frame, with beams and columns. Is it possible to reduce the mass of a beam after 3.23 second? this is the beam: element nonlinearBeamColumn 1 1 6 10 14 1 5 which means the mass is 5 how is it possible to reduce %30 of it after 3.23 second? and what about to add %30 of mass after...