Hi,
I have made a dynamic time history analysis for a 3story rc building.i use time history load curve named artificial that is present in seismostruct accelogram file. the results show 12cm reletive displacement between base and top of the structure and the absolute displacement in the base is 45 cm. though you had explained in help menu i realy coudnt understand the reason for this high displacement in the restrained node of structure, i had made some diffrent models and the relative displacements was so small but the absolute displacement in the restrained node was 60cm. please guide me how can i trust to my results?
absolute displacement in time history analysis
Re: absolute displacement in time history analysis
mortymory,
The artificial time history has an integrated displacement that is quite high at the end of the record.
If you download SeismoSpect and look at the analysis of the record you will see this. This is typically not a problem in relative results for structures with periods less than say, 10 seconds or so. So it is seldom a problem in most of the results.
It can be a nuisance in presenting results however. The solution is to use SeismoSpect (or SeismoSignal) to baseline correct to time hstory and use the modified version in your analysis.
The artificial time history has an integrated displacement that is quite high at the end of the record.
If you download SeismoSpect and look at the analysis of the record you will see this. This is typically not a problem in relative results for structures with periods less than say, 10 seconds or so. So it is seldom a problem in most of the results.
It can be a nuisance in presenting results however. The solution is to use SeismoSpect (or SeismoSignal) to baseline correct to time hstory and use the modified version in your analysis.
Tim Huff
Re: absolute displacement in time history analysis
thank you very much dear huffte...
Re: absolute displacement in time history analysis
hi
i used seismosignal for correction of accelograms. i had tried many frames with diffrent time history curves and the displacements in base restrained nodes are not zero, the relative displacements are very small. i think the earthquake forces dont transmit to the structure. only the ground moves. where did i do wrong?
i used seismosignal for correction of accelograms. i had tried many frames with diffrent time history curves and the displacements in base restrained nodes are not zero, the relative displacements are very small. i think the earthquake forces dont transmit to the structure. only the ground moves. where did i do wrong?
Re: absolute displacement in time history analysis
Mortymory, are you looking at response history plots of the displacements of various nodes, or just the final time step?
Did you properly scale your input time history by gravity (9.81 m/s or 32.2 ft/s) when you applied the time history to the structure base nodes?
My initial thought is that you might be well served by creating a model or two with the wizard for the type of analysis you wish to run. This can be of great help in determining modeling errors or misunderstandings.
Best of luck mortymory.
Did you properly scale your input time history by gravity (9.81 m/s or 32.2 ft/s) when you applied the time history to the structure base nodes?
My initial thought is that you might be well served by creating a model or two with the wizard for the type of analysis you wish to run. This can be of great help in determining modeling errors or misunderstandings.
Best of luck mortymory.
Tim Huff
Re: absolute displacement in time history analysis
Im looking for the maximum relative displacement at the top floor.
i have created some models with the wizard. for example Ive created a 2d frame with one bay(5m length) and one story(3m height)and Ive used Corralitos accelogram. I didnt change any other parameters. then the results show that the maximum relative displacement is 7.5mm and the maximum displacement at restrained node is 16cm. is it realy true?
i have created some models with the wizard. for example Ive created a 2d frame with one bay(5m length) and one story(3m height)and Ive used Corralitos accelogram. I didnt change any other parameters. then the results show that the maximum relative displacement is 7.5mm and the maximum displacement at restrained node is 16cm. is it realy true?
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seismosoft
- Posts: 1272
- Joined: 06 Jul 2007, 04:55
Re: absolute displacement in time history analysis
Dear mortymory,
Yes, when subjected to earthquake action, the foundation/restrained nodes of a structure do displace (otherwise, the structure would not move at all), and such absolute displacements can indeed be much larger than the relative deformations experienced by the structure.
Seismosoft Support
Yes, when subjected to earthquake action, the foundation/restrained nodes of a structure do displace (otherwise, the structure would not move at all), and such absolute displacements can indeed be much larger than the relative deformations experienced by the structure.
Seismosoft Support