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Time Period in design softwares
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Aatif
SEFI Regulars
SEFI Regulars


Joined: 26 Jul 2016
Posts: 35

PostPosted: Tue Dec 01, 2020 9:19 am    Post subject: Re: Time Period in design softwares Reply with quote

va wrote:
It is always better to calculate the time period as per code provided empirical formula and provide the value in STAAD, so that , there is no confusion. Otherwise software will try to calculate the time period based on the data of height and base width as it understands.

Regards.
Hemant Vadalkar
Consulting Engineer Mumbai.


Thank you Hemant sir for sharing your views!!

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sakumar79
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Joined: 18 Apr 2008
Posts: 692

PostPosted: Sat Dec 19, 2020 11:50 am    Post subject: Reply with quote

aditya wrote:
Dear Sefian,
In Staad.Pro, one needs to define "Seismic Definition" for auto-seismic load generation. It can be done through graphical user interface screen or directly as command line parameter in an input file which is a text file.
For time period calculation, one needs to define the parameter named "ST" which means "Structure Type" whose value may be from 1 to 5 depending upon the type of structural system. Values of ST for different structural system are shown below:
Structure type of the seismic-resisting system. The program will calculate natural period as per Clause 7.6.2 of IS:1893(Part 1)-2016.

1 = RC moment-resisting frame building
2 = RC-Steel composite moment-resisting frame building
3 = Steel moment-resisting frame building
4 = Building with RC structural walls*
5 = All other buildings
Note: *ST 4 requires that wall data be entered in order to determine the natural period.
Another option would be to directly give the values of time periods as "PX" and "PZ" values in seconds from the empirical time period formulas given in the code. If PX and PZ are defined, program will not use the value of ST in the calculation of the time period.
Detailed syntax of STAAD input for seismic load definition is given in the attached file. You may also refer the inbuilt help in STAAD.
with regards,
Aditya


Dear Sirs,
   With reference to the above post, I would like to post one clarification which I think STAAD has been neglecting from the beginning. The values of ST 1 to 3 refer to RC/Composite/Steel MRF WITH NO MASONRY INFILLS. IT IS NOT APPLICABLE TO OUR NORMAL BUILDINGS WHICH HAVE BRICK WALLS. For such buildings, ST should be given as 5 to take the correct formula.

    IMHO, it is better to calculate and enter the PX and PZ values to avoid any confusion in STAAD's assumptions. For ETABS also, it is better to enter the value rather than ask the software to make an internal calculation.

Yours sincerely
S Arunkumar
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