you may use...
DEFINE MATERIAL START
ISOTROPIC VERYRIGID
E 3.19e+015
POISSON 0.17
DENSITY 0
ALPHA 1e-005
DAMP 0.02
END DEFINE MATERIAL
DEFINE MATERIAL START
ISOTROPIC VERYRIGID
E 3.19e+015
POISSON 0.17
DENSITY 0
ALPHA 1e-005
DAMP 0.02
END DEFINE MATERIAL