STAAD Pro. v8i ~ Auto Seismic Loads Combination & Dead Loads in Seismic Load Case

Q: STAAD Pro. v8i ~ Auto Seismic Loads Combination & Dead Loads in Seismic Load Case by Waqar

Hi All,

Auto Seismic Loads Combination

I have question related to auto seismic load combination as per seismic load definition defined in STAAD program, putting the values of S1 and Ss, Importance and Response modification factor, I have concerns that will STAAD program calculate automatically the seismic forces both in horizontal and vertical direction as per below email extracted from the code;

E = (Rho) x Q_E (+/-) 0.2 x S_DS x D

If STAAD not calculates the forces automatically in seismic forces used in load combination, then we will have to calculate manually and then applied on the structure. Reply with some technical reference will be satisfactory.

Dead Loads in Seismic Load Case

Now this question is very basic but important for me as I am learner in STAAD, even if I defined the repeat loads cases in reference load definition, and again I recalled my loads (dead loads for seismic force calculation) in seismic loads definition, will I have to defined the dead loads in seismic load cases like in LC Seismic X and LC seismic Z? If Yes, then what are the function/ reason for defining the dead loads in seismic loads definition menu?

Keep sharing and thanks in advance.

W Haider

A: Re: STAAD Pro. v8i ~ Auto Seismic Loads Combination & Dead Loads in Seismic Load Case by Sye

The seismic load generation in STAAD only calculates the horizontal portion Qe. The factors like Rho or the vertical effect factors like 0.2SDS has to be calculated manually and applied as factors to the appropriate loads when defining load combinations.

To answer your second question, the best way to consider dead/live loads in seismic weight calculation is to define these as reference load of type MASS. Then there is no need to define these loads as part of the seismic load again as STAAD would automatically get the data from the MASS type reference load data.  

A: Re: STAAD Pro. v8i ~ Auto Seismic Loads Combination & Dead Loads in Seismic Load Case by Sye

Hi Waqar,

RAM Structural System can automatically account for the vertical seismic effects through generated load combinations. In RAM Elements you have to define the factor manually in combinations you have to for STAAD.Pro.

STAAD.Offshore is generally used for calculating wave loads on a structure or for calculating inertia forces due to transportation and so you may not be using it for seismic analysis of structures. I am not conversant with SACS but as far as I know, it is also a product that is used for analysis of offshore type structures and not for seismic analysis of buildings.

Hope this helps.

Thanks,

Sye  

Q: Re: STAAD Pro. v8i ~ Auto Seismic Loads Combination & Dead Loads in Seismic Load Case by Waqar

Hi Sye,

Thanks for your reply. I think STAAD new release should consider this vertical component of seismic forces. By putting manually is time consuming work. I hope that new release will definitely account this effect.

Warm regards,

W Haider

Q: Re: STAAD Pro. v8i ~ Auto Seismic Loads Combination & Dead Loads in Seismic Load Case by Waqar

Hi Sye

Thanks for your reply...what about other Bentley structure software like STAAD Offshore, SACS and RAM family, I am asking about my first concern related to vertical seismic forces, either I will have to calculate the vertical component of seismic forces same like in STAAD Pro. v8i?

Warm regards,

W Haider