Lateral free-field responses and kinematic interaction of monopiles to obliquely incident seismic waves in offshore engineering

2021 ◽  
Vol 132 ◽  
pp. 103956
Author(s):  
Rui He ◽  
Amir M. Kaynia ◽  
Jisheng Zhang
Keyword(s):  
Seismic Waves ◽  
Free Field ◽  
Kinematic Interaction ◽  
Obliquely Incident ◽  
Offshore Engineering

The Beneficial Role of Piles on the Seismic Loading of Structures

2019 ◽  
Vol 35 (3) ◽  
pp. 1141-1162 ◽  
Author(s):  
Maria Iovino ◽  
Raffaele Di Laora ◽  
Emmanouil Rovithis ◽  
Luca de Sanctis
Keyword(s):  
Seismic Waves ◽  
Rapid Assessment ◽  
Free Field ◽  
Dimensionless Frequency ◽  
Fe Model ◽  
Soil Stiffness ◽  
Interaction Factor ◽  
Power Law Function ◽  
Pile Length

We examine the kinematic response of fixed-head vertical floating piles embedded in continuously nonhomogeneous soils and subjected to upward propagating seismic waves. The problem is explored numerically by means of a rigorous finite element (FE) model of the soil-pile system to quantify the kinematically induced reduction of the horizontal free-field spectral acceleration. Soil stiffness varies continuously with depth according to a generalized power law function. We show that kinematic pile response in the harmonic regime is controlled by a unique dimensionless frequency parameter involving the active pile length in a generalized nonhomogeneous soil. A new, simplified expression for the horizontal kinematic interaction factor Iu is proposed for practical time-domain applications while a novel physical interpretation of the filtering action of piles is reported by introducing the role of pile stiffness in averaging soil motion over an effective pile length. Following a parametric study under transient motion, we propose a set of novel, ready-to-use formulae for a rapid assessment of the pile-induced filtering action. An application of the proposed formulae to clayey soils is finally presented, leading to useful indications for the selection of the pile diameter associated with the maximum filtering potential.

SEISMIC DECOUPLING FOR EXPLOSIONS IN SPHERICAL UNDERGROUND CAVITIES

Geophysics ◽  
1961 ◽  
Vol 26 (6) ◽  
pp. 772-799 ◽  
Author(s):  
William M. Adams ◽  
DeWitt C. Allen
Keyword(s):  
Spherical Cavity ◽  
Seismic Waves ◽  
Free Field ◽  
Salt Mine ◽  
Cavity Pressure ◽  
Frequency Range ◽  
Overburden Pressure ◽  
Underground Cavities ◽  
Order Of Magnitude ◽  
Surface Measurements

A series of paired explosions in a salt mine near Winnfield, Louisiana, has been conducted to test a theory by A. L. Latter concerning seismic decoupling by underground cavities. The theory predicted a decoupling of 130. Free‐field and surface measurements from an explosion in either a 6‐ft‐ or a 15‐ft‐radius spherical cavity were compared with similar measurements from a completely tamped explosion of equal size. Shot sizes were from 20 pounds to a ton. Surface measurements were made out to 100 km and covered the frequency range from 0.05 to 100 cps. The experiment confirmed that decoupling does occur. For explosions that produce an average cavity pressure up to one‐fifth and possibly more of the lithostatic overburden pressure, seismic waves were decoupled by more than 100, i.e., two orders of magnitude. Even for explosions producing an average cavity pressure of six times the lithostatic overburden pressure, the seismic waves were decoupled by 20—more than a full order of magnitude. Minimum decoupling factors as a function of frequency are presented.

Evaluation of the effect of depth to bedrock on seismic amplification phenomena

2020 ◽  
Author(s):  
gaetano falcone ◽  
giuseppe naso ◽  
stefania fabozzi ◽  
federico mori ◽  
massimiliano moscatelli ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Site Response ◽  
Soft Soil ◽  
Free Field ◽  
Response Spectra ◽  
Maximum Depth ◽  
Response Analysis ◽  
Local Conditions ◽  
Seismic Amplification ◽  
Bedrock Depth

<p>When an earthquake occurs, the propagation of the seismic waves is conditioned by local conditions, e.g., depth to seismic bedrock and impedance ratio between soft soil and seismic bedrock. Bearing in mind that the maximum depth of site prospections generally does not extend up to seismic bedrock depth, a parametric study was carried out with reference to ideal case studies in order to investigate the effect on local seismic amplification of the depth to bedrock.</p><p>The results are presented in terms of charts of amplification factors (i.e., ratio of integral quantities referred to free-field and reference response spectra) and minimum depth to investigate vs building type. These charts will allow defining the thickness of the cover deposit that should be characterised in terms of geophysical and geotechnical parameters in order to perform seismic site response analysis according to a precautionary approach, in areas where depth to seismic bedrock is higher than conventional maximum depth of site surveys.</p>

scholarly journals Fragility Analysis of RC Frame Structures Subjected to Obliquely Incident Seismic Waves

2021 ◽  
Vol 13 (3) ◽  
pp. 1108
Author(s):  
Bo Huang ◽  
Jiachen Guo ◽  
Kailong Liao ◽  
Yu Zhao
Keyword(s):  
Structural Damage ◽  
Seismic Waves ◽  
Incident Angle ◽  
Structural Characteristics ◽  
Frame Structure ◽  
Fragility Analysis ◽  
Exceedance Probability ◽  
Rc Frame ◽  
Foundation Soil ◽  
Obliquely Incident

Obliquely incident seismic waves have been habitually overlooked in fragility analysis. In this paper, a new approach to solving the equivalent loads on the infinite element boundary due to obliquely incident seismic waves is proposed. Based on the site conditions and structural characteristics in the Jiaxing area, the seismic response of a multi-story reinforced concrete (RC) frame structure has been fully investigated through the finite element method. Under obliquely incident SV waves (shear wave in the vertical x-z plane), the distribution of internal forces on the structure in the case of homogeneous foundation soil is significantly asymmetrical. Among the 3 obliquely incident angles investigated in this paper, the maximum inter-story displacement is smallest when the incident angle is 20° and largest when the angle equals 30°. For the structural fragility, the exceedance probability at each structural damage level is smallest when the incident reflection angle is 20° and largest when the angle equals 30°. When the structure is located in the silty valley, the influence of oblique incidence is attenuated and there is no obvious stress asymmetry on the structure due to the refraction of seismic waves on the interface.

Numerical Analysis of Free Field under Horizontal Seismic Excitations

2012 ◽  
Vol 166-169 ◽  
pp. 2005-2008
Author(s):  
Shou Long Chen ◽  
Chun Yi Cui ◽  
Zhong Tao Wang
Keyword(s):  
Seismic Waves ◽  
Soil Depth ◽  
Soft Soil ◽  
Free Field ◽  
Low Frequency ◽  
Seismic Excitations ◽  
Finite Element Program ◽  
Element Program ◽  
Frequency Components ◽  
Free Bank

Based on Newmark-β gradual integration method and elastic-plastic mechanical theory, numerical analyses of the effects of soft soil depth and thickness on the characteristics of seismic response of free bank field with soft soil layers are conducted by using finite element program Midas/GTS. The numerical results show that the high frequency components of seismic excitations can be filtered and the low frequency components are amplified correspondingly when seismic waves are transmitted through the free bank field from the bedrock.

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