NEHRP Clearinghouse
- Title
- Accuracy of Modal Superposition for One-Dimensional Soil Amplification Analysis.
- File
- PB293050.pdf
- Author(s)
- Whitman, R. V.; Roesset, J. M.; Dobry, R.; Ayestaran, L.
- Source
- National Science Foundation, Washington, DC. Applied Science and Research Applications., October 1972, 19 p.
- Identifying Number(s)
- STRUCTURES PUB-352
- Abstract
- The nature and possible magnitude of the errors involved in the determination of soil amplification effects, using modal analysis of a discrete lumped mass system, are discussed. These errors are mainly due to the treatment of damping and arise from the nature of the damping (hysteretic rather than viscous), the possible lack of normal modes in the classical sense, and the radiation effect in the underlying rock. It is shown that in many cases these errors are either negligible or they can be accounted for by relatively simple procedures (use of weighted modal damping and an additional term corresponding to the radiation effect). There are cases, however, where these corrections do not yield satisfactory results (in particular when the stiffness and damping of two layers are very different). It is then advisable to use the continuous solution in the frequency domain instead of the lumped mass model.
- Keywords
- Damping; Earth movements; Ground motion; Earthquake engineering; Soil dynamics; Soil properties; Soil profiles; Earthquakes