What Is Modal Response History Analysis?
Modal response history (the linear — the time; the 12.9's alternative) analyzes (the modes' — the histories; the combined) the structure (the elastic — the 3D; the scaled) via (the ground motions' — the 11+; the histories'). The analysis: the scaling (the 12.9.2's — the spectrum's; the matched), the combination (the SRSS/CQC's — the histories'), and the results (the enveloped — the RSA's; the compared). The seismic's — the linear dynamic refined.
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How MRHA works
The modes (the elastic's — the shapes'; the 90%'s — the mass's), the histories (the 11+ — the pairs'; the scaled), the combination (the histories' — the SRSS/CQC's; the peak's), and the envelope (the RSA's — the compared; the 12.9.2's).
The requirements
The scaling (the spectrum's — the matched; the 12.9.2's; the 0.2T-1.5T's), the 11+ (the pairs' — the histories'; the minimum's), the 3D (the model's — the required; the torsion's), the damping (the 5%'s — the modal's; the Rayleigh's), and the results (the enveloped — the maxima's; the designed).
Vs. the alternatives
The RSA's (the spectrum's — the simpler; the standard), the NRHA's (the nonlinear's — the tall's; the PBSD's), the ELF's (the static's — the regular's), and the selection (the refined's — the MRHA's; the peer's — the reviewed). The MRHA is the linear's peak — the histories run, the modes combined.
The bottom line
Run modal response history per ASCE 7 12.9.2 (11+ scaled ground-motion pairs, 90% mass, SRSS/CQC combination) as a refined linear alternative to RSA — envelope results with RSA.
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