Table 5: Dependence of modal frequencies on PRA. 
 Mode  Direction  Model type  Modal frequency (y)–PRA (x) relationship^{(*)}  
 Building A 
 1st  X  P/flexible base^{(**)}   0.80  Flexible base   0.59  Y  P/flexible base   0.53  Flexible base   0.40  2nd  X  P/flexible base   0.59  Flexible base   0.34  Y  P/flexible base   0.47  Flexible base   0.33  3rd  X  P/flexible base   0.63  Flexible base   0.65  Y  P/flexible base   0.51  Flexible base   0.52 
 Building B 
 1st  X  P/flexible base   0.57  Flexible base   0.55  Y  P/flexible base   0.60  Flexible base   0.59  2nd  X  P/flexible base   0.69  Flexible base   0.43  Y  P/flexible base   0.69  Flexible base   0.43  3rd  X  P/flexible base   0.51  Flexible base   0.58  Y  P/flexible base   0.51  Flexible base   0.56 


^{(*)}Modal frequency in units of Hz, PRA in units of g. ^{(**)}P/flexible base = pseudoflexible base.
