Analytical expression between the impact damping ratio and the coefficient of restitution in the non-linear viscoelastic model of structural pounding

In this paper a non linear viscoelastic model governed by fractional derivatives is presented for modeling the in-service behavior of polyester mooring lines. In the formulation an iterative approach utilizing the Gauss-Newton minimization algorithm in conjunction with the catenary equations used to determine the static modulus of elasticity and the effective length of polyester mooring lines corresponding to calm sea conditions. Upon establishing the accuracy of the static modulus via comparison with field data, the catenary equations and the offshore platform’s position versus time are used to identify the polyester strain under developed-sea conditions. In this manner, time histories of stress and strain for polyester ropes in service conditions are obtained. Then, a non linear viscoelastic model involving fractional derivative terms is used to capture the in service polyester line behavior. For this, the tension of the proposed model corresponding to the actual polyester strain is compared at each time step to the tension obtained from the field data. Finally, the parameters of the proposed model are derived by minimizing the error in the least-squares sense over a large number of data points using the Levenberg-Marquardt algorithm. The numerically derived force-strain relationship is found to be in reasonable agreement with supplementary field and laboratory experimental data, the field data pertain to an offshore structure moored in position using polyester mooring lines operated in the Gulf of Mexico during Hurricane Katrina (August of 2005).

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A Non-linear Viscoelastic Model of the Incudostapedial Joint

Journal of the Association for Research in Otolaryngology ◽

10.1007/s10162-019-00736-0 ◽

2019 ◽

Vol 21 (1) ◽

pp. 21-32 ◽

Cited By ~ 1

Author(s):

Majid Soleimani ◽

W. Robert J. Funnell ◽

Willem F. Decraemer

Keyword(s):

Viscoelastic Model ◽

Non Linear ◽

Linear Viscoelastic ◽

Incudostapedial Joint ◽

Linear Viscoelastic Model

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Effective Formula for Impact Damping Ratio for Simulation of Earthquake-induced Structural Pounding

Geosciences ◽

10.3390/geosciences9080347 ◽

2019 ◽

Vol 9 (8) ◽

pp. 347 ◽

Cited By ~ 5

Author(s):

Seyed Mohammad Khatami ◽

Hosein Naderpour ◽

Rui Carneiro Barros ◽

Anna Jakubczyk-Gałczyńska ◽

Robert Jankowski

Keyword(s):

Kinetic Energy ◽

Impact Force ◽

Damping Ratio ◽

Dissipated Energy ◽

Force Model ◽

Single Collision ◽

Structural Pounding ◽

Impact Forces ◽

The Impact ◽

Impact Damping

Structural pounding during earthquakes may cause substantial damage to colliding structures. The phenomenon is numerically studied using different models of collisions. The aim of the present paper is to propose an effective formula for the impact damping ratio, as a parameter of the impact force model used to study different problems of structural pounding under seismic excitations. Its accuracy has been verified by four various approaches. Firstly, for the case of collisions between two structural elements, the dissipated energy during impact has been compared to the loss of kinetic energy. In the second stage of verifications, the peak impact forces during single collision have been analyzed. Then, the accuracy of different equations have been verified by comparing the impact force time histories for the situation when a concrete ball is dropped on a rigid concrete surface. Finally, pounding between two structures during earthquakes has been studied. The results of the analysis focused on comparison between dissipated and kinetic energy show relatively low errors between calculated and assumed values of the coefficient of restitution when the proposed equation is used. In addition, the results of the comparison between experimentally and numerically determined peak impact forces during single collision confirm the effectiveness of the approach. The same conclusion has been obtained for the whole impact time history for collision between a ball and a rigid surface. Finally, the results of the comparative analysis, conducted for pounding between two structures during an earthquake, confirm the simulation accuracy when the proposed approach is used. The above conclusions indicate that the proposed formula for impact damping ratio, as a parameter of impact force model for simulation of earthquake-induced structural pounding, is very effective and accurate in numerical simulations in the case of different scenarios.

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