Time Dependent Distributed (Consistent) Mass Mstrix Calculation in FEM

Dear All

I am working on large deformation finite element analysis for my research work. To consider the self-weight I need to calculate the distributed (consistent) mass matrix. So my question that how calculate time (for static analysis time will be representing only load steps) dependent distributed mass matrix in new configurations. 

Any comment will be appreciated 

Thanks

Vasudeo Chaudhari