This study rebuilds the computer model of combination building for preparations to enhance the seismic design of nuclear power plants. The lumped mass stick model is used to generate the natural frequency and floor response spectrum, and this paper conducts a comparison of the variations between the original and rebuilt model before an evaluation. The analysis results indicate that the natural frequency and floor response spectrum provided by the novel lumped mass stick model represent the overall building responses in a reasonable fashion. The results generated by the lumped mass model fit those generated by the previous calculations in 1986. The lumped mass model is suitable for performing the safe evaluation of combination building after an occurrence of earthquakes and tsunamis.