Effects of Structural Material Damping on Nonlinear Seismic Response of Offshore Piles

2008 ◽  
Author(s):  
Mehrdad Kimiaei
Keyword(s):  
Structural Material ◽  
Nonlinear Response ◽  
Free Field ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Material Damping ◽  
Nonlinear Seismic Response ◽  
Lateral Response ◽  
Foundation Model ◽  
Offshore Piles

Nonlinear response of pile foundations is the most important part of potential nonlinear response of pile supported offshore platforms to seismic excitations. Soil nonlinearity, soil radiation damping and structural material damping are the main sources of energy dissipation in seismic behavior of offshore piles. In this study, a practical BNWF (Beam on Nonlinear Winkler foundation) model is used to compute the nonlinear lateral response of piles, embedded in layered soil deposits, subjected to seismic loading. The results of equivalent linear and nonlinear earthquake free field ground motion analyses are used as the input excitations at support nodes of the model. Sensitivity of the pile seismic responses to structural material damping ratios are discussed and addressed in this paper. Numerical results are compared with centrifuge test results.

Simplified BNWF model for nonlinear seismic response analysis of offshore piles with nonlinear input ground motion analysis

2005 ◽  
Vol 42 (2) ◽  
pp. 365-380 ◽  
Author(s):  
M Hesham El Naggar ◽  
Mohsen Ali Shayanfar ◽  
Mehrdad Kimiaei ◽  
Ali Akbar Aghakouchak
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Motion Analysis ◽  
Nonlinear Response ◽  
Free Field ◽  
Response Analysis ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Nonlinear Seismic Response ◽  
Offshore Piles

The seismic response of pile-supported offshore structures is strongly affected by the nonlinear behavior of the supporting piles. Nonlinear response of the pile foundation is the most important source of potential nonlinearity in the dynamic response of offshore platforms to earthquake excitations. It is often necessary to perform a dynamic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity conditions at pile–soil interfaces, energy dissipation through soil radiation damping, and structural nonlinear behaviors of piles. In this paper, an attempt is made to develop an inexpensive and practical procedure, compatible with readily available structural analysis software, for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. In the proposed model a beam on nonlinear Winkler foundation (BNWF) approach, consisting of simple nonlinear springs, dashpots, and contact elements, is used. This model was incorporated into a finite element program, ANSYS, which was used to compute the response of laterally excited piles. A nonlinear approach was used for seismic free-field ground motion analysis. The computed responses compared well with the centrifuge test results. This paper deals with the effects of free-field ground motion analysis on nonlinear seismic behavior of embedded piles. Different parts of a BNWF model, together with quantitative and qualitative findings and conclusions for dynamic nonlinear response of offshore piles, are discussed and addressed in detail.Key words: nonlinear, seismic response, offshore piles, seismic pile–soil interaction, BNWF models.

A Practical Model for Nonlinear Seismic Response Analysis of Jacket Type Fixed Offshore Platforms

2006 ◽  
Author(s):  
Mehrdad Kimiaei ◽  
Ali Akbar Aghakouchak ◽  
Mohsen Ali Shayanfar ◽  
M. Hesham El Naggar
Keyword(s):  
Seismic Response ◽  
Response Analysis ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Seismic Response Analysis ◽  
Practical Procedure ◽  
Nonlinear Seismic Response ◽  
Lateral Response ◽  
Proposed Model ◽  
Soil Structures

Offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. In seismic design of offshore platforms, it is often necessary to perform a dynamic analysis that accounts for nonlinear pile soil structures interaction effects. This paper summarizes an inexpensive and practical procedure compatible with readily available structural analysis software (ANSYS) for estimating the nonlinear lateral response of fixed offshore platforms resting on flexible piles subjected to seismic loading. In the proposed model, piles and jacket members are modeled using BNWF (Beam on Nonlinear Winkler Foundation) and FE (Finite Element) approaches respectively in an integrated model. In this paper, nonlinear seismic response analysis of an existing sample offshore platform has been performed and sensitivity of the results to the model main parameters is investigated.

The Effects of Free Field Ground Motion Analysis on Seismic Response of Offshore Piles

2005 ◽  
Author(s):  
Mehrdad Kimiaei ◽  
Mohsen Ali Shayandar ◽  
M. Hesham El Naggar ◽  
Ali Akbar Aghakouchak
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Free Field ◽  
Nonlinear Behavior ◽  
Winkler Foundation ◽  
Main Concern ◽  
Offshore Platforms ◽  
Seismic Excitations ◽  
Earthquake Design ◽  
Offshore Piles

Nonlinear response of piles is the most important source of potentially nonlinear behavior of pile-supported offshore platforms due to earthquake excitations. Earthquake design of offshore platforms is one of the main parts in offshore platforms design on which seismic soil pile structure interaction could be the main concern. In this paper, seismic response of offshore piles embedded in layered soil deposits is determined using a BNWF model (Beam on Nonlinear Winkler Foundation). Results of the free field ground motion analyses using equivalent-linear or nonlinear approaches are applied as input seismic excitations to the support nodes of BNWF model. Sensitivity of the results to input ground motions are discussed and addressed in this paper. Computed responses are also compared with centrifuge test results.

Incremental Dynamic Analysis Considering Pile-Soil-Structure Interaction for the Jacket Type Offshore Platforms

2008 ◽  
Author(s):  
Behrouz Asgarian ◽  
Alireza Fiouz ◽  
Ali Shakeri Talarposhti
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Response ◽  
Limit State ◽  
Nonlinear Behavior ◽  
Incremental Dynamic Analysis ◽  
Layered Soil ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Structure Interaction ◽  
Soil Deposits

Nonlinear response of piles is the most important source of potentially nonlinear behavior of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviors of the piles. Incremental dynamic analysis is an analysis method that has recently emerged as a promising tool for thoroughly evaluating the seismic performance of structures. It involves subjecting a structural model to a suite of ground motion records, each scaled to several intensities and recording the responses at each level to form IDA curves of response versus intensity. In this paper, jacket and soil-pile system is modeled and the effects of Soil-Pile-Structure Interaction (SPSI) are considered, and the Incremental Dynamic Analysis (IDA) is used to investigate nonlinear behavior of offshore platforms. An attempt is made to introduce a practical BNWF (Beam on Nonlinear Winkler Foundation) model for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. This model was incorporated into a Finite Element program (OpenSees). All the analyses are performed in two directions and the results are compared with each others. A computer program for Nonlinear Earthquake site Response Analyses of layered soil deposits (NERA) is used for analysis nonlinear response of soil layers. Limit state of the jacket is calculated from incremental dynamic analysis of the jacket using fiber elements for the nonlinear modeling of the system.

Non Linear Seismic Pile Soil Structure Interaction Analysis of Piles in Offshore Platforms

2004 ◽  
Author(s):  
Mehrdad Kimiaei ◽  
Mohsen Ali Shayanfar ◽  
M. Hesham El Naggar ◽  
Ali Akbar Aghakouchak
Keyword(s):  
Soil Structure ◽  
Seismic Analysis ◽  
Interaction Analysis ◽  
Site Response ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Model Parameters ◽  
Winkler Foundation ◽  
Offshore Platforms ◽  
Structure Interaction

Pile supported offshore platforms in seismically active areas should be designed to survive severe earthquake excitations with no global structural failure. It is often required to perform nonlinear seismic analysis of offshore platforms that accounts for soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural nonlinear behaviours of the piles. In this study a BNWF (Beam on Nonlinear Winkler Foundation) model is incorporated into a finite element program (ANSYS) and it is used to compute the lateral response of piles subjected to seismic loading. The soil stiffness is established using the P-Y curve. The results of equivalent linear earthquake free field ground motion analyses are used as the input excitations at support nodes of the model. The components and advantages of this practical ANSYS model in seismic pile soil structure interaction analyses are discussed and addressed in detail. Computed responses compared well with the experimental test results. Sensitivity of the results to model parameters and site response calculations are evaluated.

Mechanics-Based Interactive Modeling for Medical Flexible Needle Insertion in Consideration of Nonlinear Factors

2016 ◽  
Vol 11 (1) ◽  
Author(s):  
Shan Jiang ◽  
Xingji Wang
Keyword(s):  
Soft Tissue ◽  
Kinematic Model ◽  
Needle Insertion ◽  
Winkler Foundation ◽  
Nonlinear Characteristics ◽  
Deformation Control ◽  
Needle Deflection ◽  
Iteration Cycle ◽  
Foundation Model ◽  
Sensitivity Studies

A mechanics-based model of flexible needle insertion into soft tissue is presented in this paper. Different from the existing kinematic model, a new model has been established based on the quasi-static principle, which also incorporates the dynamics of needle motions. In order to increase the accuracy of the model, nonlinear characteristics of the flexible needle and the soft tissue are both taken into account. The nonlinear Winkler foundation model and the modified Euler–Bernoulli theory are applied in this study, providing a theoretical framework to study insertion and deformation of needles. Galerkin method and iteration cycle analysis are applied in solving a series of deformation control equations to obtain the needle deflection. The parameters used in the mechanics-based model are obtained from the needle force and needle insertion experiment. Sensitivity studies show that the model can respond reasonably to changes in response to variations in different parameters. A 50 mm needle insertion simulation and a 50 mm corresponding needle insertion experiment are conducted to prove the validity of the model. At last, a study on different needle tip bevel demonstrates that the mechanics-based model can precisely predict the needle deflection when more than one parameter is changed. The solution can also be used in optimizing trajectory of the needle tip, enabling the needle to reach the target without touching important physiological structures such as blood vessels with the help of dynamic trajectory planning.

Curling Stress Equation for Transverse Joint Edge of a Concrete Pavement Slab Based on Finite-Element Method Analysis

1996 ◽  
Vol 1525 (1) ◽  
pp. 35-43 ◽  
Author(s):  
Tatsuo Nishizawa ◽  
Tadashi Fukuda ◽  
Saburo Matsuno ◽  
Kenji Himeno
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fem Analysis ◽  
Concrete Pavement ◽  
Winkler Foundation ◽  
Stress Equation ◽  
The Past ◽  
Transverse Joint ◽  
Foundation Model ◽  
Element Method

In the design of concrete pavement, curling stresses caused by the temperature difference between the top and bottom surfaces of the slab should be calculated at the transverse joint edge in some cases. However, no such equation has been developed in the past. Accordingly, a curling stress equation was developed based on stress analysis using the finite-element method (FEM). In this FEM analysis, a concrete pavement and its transverse joint were expressed by means of a thin plate–Winkler foundation model and a spring joint model, respectively. Multiregression analysis was applied to the results of the FEM numerical calculation and, consequently, a curling stress equation was obtained. After comparing the calculated results of the equation with curling stress equations developed in the past, it was confirmed that the equation was valid and practical.

Study on a New Foundation Stiffness Calculation Model

2012 ◽  
Vol 166-169 ◽  
pp. 1258-1261
Author(s):  
Yan Jun Ma ◽  
Bin Yan ◽  
Jing Zhang
Keyword(s):  
Calculation Model ◽  
Summation Method ◽  
Winkler Foundation ◽  
Foundation Soil ◽  
Foundation Model

This paper combined the feature of Winkler foundation model and base model of limited compressible layer based on the layer-wise summation method, on condition that considering the feature of foundation soil, to derived from a newly foundation stiffness calculation model and to verify it.

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