Plot the elastic and inelastic acceleration response spectra $($ductility $=2$ and

$=4)$ for the $1994$ Northridge $($California$)$ earthquake, Newhall Fire Station and

the $1995$ Hyogo$-$ken Nanbu $($Japan$)$ earthquake, Kobe University Station. Also,

calculate the inelastic spectra for a record comprising the same records as

above, applied twice in series in the same analysis. Comment on the

difference in results if any between the two earthquake records and between

the single and double application of the same record. For both elastic and

inelastic spectra, assume a viscous damping of $1\%.$