In my project model of etabs consist unit are (m , kN , C). I got different time history from various sources. some of time history are in (g) unit, some of time history are in (m/sec2) unit and some of time history are in (cm/sec2) unit so that my question is "which scale factor should be used in scale factor dialogue box"?
https://www.sefindia.org/forum/download.php?id=8941&sid=56d6611a750f6780c6e7c2c8a7487988
Dear @Dhaval Parekh
The mentioned scale factor that needs in time history analysis, calculated based on the spectrum of records and design spectrum.
The calculation procedure of this scale factor usually defined in the design code such as UBC.
Hello Dhaval Parekh
Like Sina Shirgir said, a scale factor is usually required to match a predefined design spectrum. So, first you need to choose which design/analysis code is more suitable for your project. There are some differences between them when defining the selecting and scaling procedure of ground motions. Generally speaking: ASCE7/16 defines the minimum design loads for buildings (take a look at Chapter 16 for time history analysis), FEMA P58 is about seismic assessment analysis (check Chapter 4), FEMA 356/2000 is for seismic rehabilitation analysis, FEMA P695/2009 defines some seismic factors, and the list goes on.
Now, if you just want to make the units consistent your first need to check in your model what is the unit selected for acceleration, like Al Mouayed Bellah Nafeh beautifully explained (go Options
Firstly, you have to do matching with a specific spectrum that your country depended on it then the scale factor could b estimated by dividing g over R whereas g represented ground acceleration and R behavior Factor who depended on your structural system. Finally and after running your model you have to compare and match base shear who come from spectrum and static equivalent method analysis
- Load pattern. When load type is set to load pattern, the values of the time-history function are multiplied by the scale factor to produce unitless terms. Here, the record should describe the variation in loading over time, as applied in the load pattern.
- Accel. When load type is set to Accel, the scale factor should be specified such that it multiplies with the values of the time-history function to produce the acceleration desired in the current units. If the values of the time-history function are given in the current units, the scale factor should be set to 1.0. Otherwise, the scale factor should reflect the conversion from the units of the time-history function to the current units. For example, if time-history data is in cm/sec/sec, and current units are ft/sec/sec, then a scale factor of 1ft / 30.48cm = 0.0328 should be used.
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