Eccentric bridge model

[Sanjeema]

Dear fmk,

I am trying to model an eccentric 3D bridge (and compare the results with an experiment). I have a diagonal mass matrix with masses along local x-and y-directions and a rotational mass about the local z-axis. How can I model this rotational mass? Is it enough to assigned masses at deck level along x- and y- directions and rotational mass about z at the center of mass, which is offset from center of stiffness?

[fmk]

if mx and my at the nodes are such that there is an eccentricity, that should be taken into account .. you could test by building a symmetric bridge, unsymmetric mass and see if it twists under a motion in 1 direction