How can we scale an earthquake record and use it to create IDA curves.
For instance, If I would have a record with a PGA of 0.3g, I can scale this record by multiplying it by some arbitrary values such as 0.5, 0.75, 1.25 and 1.5, and then apply these record to the structure and run a nonlinear time history analysis and obtain my Demand Measure, and finally draw my IDA curve(using different scales we can cover the behavior of structure from elastic response to collapse) . BUT now what is the role of for example the Sa(T1,5%). How this variable is used to obtain these scales?
I know how to scale records based on ASCE, but in that case we obtain only ONE scale,multiply it to our records and then use the scaled records for analysis. But by using Sa(T1,5%) or even PGA how can we obtain different scales to be used in our IDA analysis?
Please assume that we are not going to use advanced algorithms such as hunt and fill.