I was very Engineerly
![[bigsmile] [bigsmile] [bigsmile]](/data/assets/smilies/bigsmile.gif)
delighted to read the whole comments.
Now let me tell you why brought this question:-
First I have a pedestrian bridge as shown in the attached that I needed to check for vibration and I have the following problem:-
1) I can't check it according to the ordinary procedures of DG11 due to the huge opening in the middle of the bridge
2) if I conservatively check it as two girders only , you need to take a look on the bridge, it will be unsatisfactory for vibration
3) I could not go for the Aashto requirement as I did not if it is based on the 1.5% or 5% frequency criteria for indoor and out door bridges. Moreover because of what listed in point 1 I could not be sure that the aashto requirement will apply
therefore I went to:-
1) the FRF, which strangely yielded a safe Vibration design
2)I went to Time history equivalent to that FRF obtained the same value of FRF (both FRF and TH are equal actually)
3)Used the procedure JoshplumSE described in the video it yielded a very different value the 1 and 2 and a more safer design
4)Used ETABs walking vibration check yielded the same values as 3
5) Changed the ETABS walking frequency to that of the Modal frequency provided a reslts a tittle bit close to 1 and 2
and now I've to read more investigate and read more