Hello to everyone

I want to make seismic calculation in a code which is not included in the code list in PVElite, So i´m entering the seismis spectrum in the option Res. Spectrum but i have a doubt: the program ask for a combination method but the code that i´m actually using does not contemplate a combination of modes for static calculation, but only for dynamic calculation. My question is does PVElite make dynamic calculation? There any recommendation about literature in the selection of the method?
Thanks for yours answers

On the other hand i haven´t been able to put the data os the spectrum. The program say that data points shall be in ascending order, but already is in ascending order.
Thanks

Hi Jose,

When you specify the response spectrum analysis option, this is the true dynamic analysis calculation. You will note this when you review the Earthquake Analysis report. In it you will find mass participation factors, natural frequencies etc. So yes this is a dynamic analysis. If the program is not accepting your input and you believe it is correct, please send us your input file (.pvi) for evaluation.

Thanks a lot for yours answer.
I solved the problem, just putting the first point of the period as 0.0005, instead of the 0.0000 that i have in my spectrum graphics.

Please i have another two question, I have noted that for horizontal vessels, the seismic calculations consider only one vibration mode, and in consequence only one natural frecuency, and in my case, the mass percentage in Y is just 30.11 percent, and zero in X. So my question is why is this?

in the other hand what is the "Include Missing Mass Components"? I note that when this checkmark is selected, the program adds some masses that i haven´t been able to identify. What the program takes into account when this option is selected?

Thanks a lot for your help

Best Regards

Jose,

Usually because horizontal vessels are not tall and flexible (like vertical vessels) and since they have more than one support, they usually have high modes of vibration. During an earthquake event, they typically would shake right along with the foundation and the strata beneath them.

Here are some notes on "Missing Mass" that may help you.

During spectrum (either seismic or force spectrum) or time history analyses, the response of a system under a dynamic load is determined by superposition of modal results. One of the advantages of this type of modal analysis is that usually only a limited number of modes are excited and need to be included in the analysis. The drawback to this method is that although displacements may be obtained with good accuracy using only a few of the lowest frequency modes, the force, reaction, and stress results may require extraction of far more modes (possibly far into the rigid range) before acceptable accuracy is attained.

PVElite provides a feature, called the "Missing Mass Correction", which helps solve these problems. This feature offers the ability to include a correction which represents the contribution of the higher order modes not explicitly extracted for the modal/dynamic response, thus providing greater accuracy without additional calculation time. When this option is activated (by checking this parameter), the program automatically calculates the net (in-phase) contribution of all non-extracted modes and combines it with the modal contributions - avoiding the long calculation time associated with the extraction of the high order modes and the possible excessive conservativism of the summation methods.