RE: fundamentals period T

Thanks so much, Sye.  I almost clea up my confusing.

Some questions:

  Q1: Where did you get the T= 4.583 in Rayleigh method?  

  Q2: Based on the calculations you showed, does the T in x and z shall be the same?   I cannot figure out what the differences are in Table 12.8-2 as for X or Z directions?

  Q3: This is a bridge.  Is STAAD Pro followed the AASHTO C4.7.4.3.2c?

I appreciate your help.

Sincerely,