Seismosoft | Earthquake Engineering Solutions

hi
Please help me about define spectrum (from file) for matching and scaling.
should I multiply values of spectrum by 1.4 before matching as UBC cobe said
" (SRSS) Of The Two Horizontal Components Should Not Be Less Than 1.4 The Design Spectrum Ordinates In The Range From 0.2T To 1.5T (UBC 1997 )"

If you are strictly bound to use the UBC SRSS criteria, then there are a number of ways to go. This SRSS-method of modification is not the preferred method using the current science however. It is critical that you know the nature of the target spectrum - is it a geometric mean spectrum, or is it a maximum direction spectrum? For guidance on preferred modification methods, see NIST GCR 11-917-15, Selecting and Scaling Ground Motions for Performing Response-History Analyses. It is freely available online.

If you are bound to the SRSS scaling/matching, then you could match each component to the target (not 1.4 times the target). Then the SRSS of the components would be SQRT(2) times the target = 1.414 times the target. In doing this, however, you lose the relative intensity variation of the two components. Another way would be to assume some value - say y - for the ratio of the maximum component to the minimum component. Then, to make the SRSS of the two components equal to 1.4 times the target:

SQRT[(H1)^2 + (H2)^2] = 1.4TARGET
SQRT[(H1)^2 + (yH1)^2] = 1.4TARGET
..
..
H1 = 1.4TARGET(1/SQRT[1+y^2])
H2 = 1.4TARGET(y/SQRT[1+y^2])

Using, as an example, y=1.2 gives:
H1 = 0.8963TARGET
H2 = 1.0755TARGET

You would match one component to 0.8963 times the target and the second component to 1.0755 times the target.

thanks so much for nice reply