## Abstract

Wave parameter (typically denoted by 1/σ) is a dimensionless factor introduced by Veletsos and co-workers, to describe inertial Soil-Structure Interaction (SSI) effects on simple structures founded on soft ground. For a simple oscillator of height h and fixed-base natural period T resting on a rigid footing of radius r underlain by compliant soil having shear wave propagation velocity V_{s} and Poisson's ratio ν_{s}, the wave parameter is defined as (1/σ) = (h /T V_{s}). This factor was introduced in classical equations for period elongation and damping shift due to SSI, so that both could be expressed in terms of familiar parameters such as the fundamental structural period, soil shear wave propagation velocity and structural slenderness. Values of (1/σ) greater than 10^{-1} indicate significant SSI effects and vice versa. This article focuses on a certain weakness of the wave parameter leading to a previously unsuspected difficulty in carrying out parametric investigations with (1/σ) being an independent variable. Specifically, to employ (1/σ) one needs to introduce a mass ratio [usually γ= m/(π ρ_{s} r^{2} h)] to balance the effect of mass introduced via the natural period. It is shown that by introducing γ, it is difficult to alter (1/σ) in a parametric analysis without altering the values of the other governing variables, including γ and (h/r). In other words, (1/σ) is coupled with the other problem parameters and being such, it cannot be used as an independent variable in SSI investigations in (1/σ, h/r, γ, ν_{s}) space. A second difficulty associated with the use of (1/σ) lies on the apparent increase in period elongation due to SSI with structural height, a trait which is not supported by experimental and analytical evidence. Ways to overcome these difficulties by introducing alternative parameters are discussed.

Original language | British English |
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Title of host publication | COMPDYN 2019 - 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, Proceedings |

Editors | Manolis Papadrakakis, Michalis Fragiadakis |

Publisher | National Technical University of Athens |

Pages | 1924-1932 |

Number of pages | 9 |

ISBN (Electronic) | 9786188284463 |

DOIs | |

State | Published - 2019 |

Event | 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, COMPDYN 2019 - Crete, Greece Duration: 24 Jun 2019 → 26 Jun 2019 |

### Publication series

Name | COMPDYN Proceedings |
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Volume | 1 |

ISSN (Print) | 2623-3347 |

### Conference

Conference | 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, COMPDYN 2019 |
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Country/Territory | Greece |

City | Crete |

Period | 24/06/19 → 26/06/19 |

## Keywords

- Dimensional Analysis
- Period Elongation
- Soil-Structure-Interaction
- Wave Parameter