hi saranam
the difference lies in the approach to obtain each. cosistent mass matrix is obtained using same shape function used for obtaining stiffness matrix while lumped mass matrix is obtained ususally by inspection. consistent mass matrix involved much effort and computer cost but gives more...
i was just browsing by when i read denniro's reply to herry's query which attracted my cuoriousity! is it realy possible to interact with sap2000 to the extent that you can create your own element subroutine and run it within the main program. that would be marvelous!
some recent elements developed, to my knowledge, in 1990 by Zienciewich and others (journal of computer and structures)namely the element by the name 'DRM' will work fine for both situations and you don't have to diferentiate. please also see the book by zienciewicz and taylor 'finite element...
you must also consider wheather the soil is expansive or not because if it is then it is better to isolate the beam's sofit than to support it directly on soil