scholarly journals Nonlinear Dynamic Analysis of Seismically Base-Isolated Structures by a Novel OpenSees Hysteretic Material Model

2021 ◽  
Vol 11 (3) ◽  
pp. 900
Author(s):  
Nicoló Vaiana ◽  
Raffaele Capuano ◽  
Salvatore Sessa ◽  
Francesco Marmo ◽  
Luciano Rosati
Keyword(s):  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Material Model ◽  
Model Parameters ◽  
Hysteretic Model ◽  
Restoring Force ◽  
Nonlinear Dynamic Response ◽  
Elastomeric Bearings ◽  
Software Products ◽  
Proposed Model

The complex response characterizing elastomeric isolation bearings is reproduced by employing a novel uniaxial hysteretic model that has been recently formulated and successfully implemented in OpenSees. Such a novel OpenSees material model offers several advantages with respect to differential models typically available in commercial software products for structural analysis, such as 3D-BASIS and CSi programs. Firstly, it is based on a set of only five model parameters that have a clear mechanical significance; such a property not only allows one to drastically simplify the parameters identification process, but it also allows the model to be used in practice. In addition, the model does not require numerical methods for the evaluation of the restoring force since the latter is computed by solving an algebraic equation. To encourage researchers and designers to adopt the proposed model for research and practical purposes, we demonstrate its accuracy by performing some numerical tests in OpenSees. In particular, we first employ the recently implemented model to compute the nonlinear dynamic response of a seismically base-isolated structure with elastomeric bearings and, subsequently, we compare the results with those obtained by modeling the seismic isolators with the OpenSees BoucWen uniaxial material model, that is one of the most popular and accurate hysteretic models currently available in OpenSees.

scholarly journals Flexural behavior of composite structural insulated panels with magnesium oxide board facings

2020 ◽  
Vol 20 (4) ◽  
Author(s):  
Łukasz Smakosz ◽  
Ireneusz Kreja ◽  
Zbigniew Pozorski
Keyword(s):  
Magnesium Oxide ◽  
Material Model ◽  
Expanded Polystyrene ◽  
Flexural Behavior ◽  
Joint Analysis ◽  
Model Parameters ◽  
Fe Model ◽  
Computational Results ◽  
Four Point Bending ◽  
Proposed Model

Abstract The current report is devoted to the flexural analysis of a composite structural insulated panel (CSIP) with magnesium oxide board facings and expanded polystyrene (EPS) core, that was recently introduced to the building industry. An advanced nonlinear FE model was created in the ABAQUS environment, able to simulate the CSIP’s flexural behavior in great detail. An original custom code procedure was developed, which allowed to include material bimodularity to significantly improve the accuracy of computational results and failure mode predictions. Material model parameters describing the nonlinear range were identified in a joint analysis of laboratory tests and their numerical simulations performed on CSIP beams of three different lengths subjected to three- and four-point bending. The model was validated by confronting computational results with experimental results for natural scale panels; a good correlation between the two results proved that the proposed model could effectively support the CSIP design process.

scholarly journals Nonlinear Dynamic Analysis of a Masonry Arch Bridge Accounting for Damage Evolution

Geosciences ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 343
Author(s):  
Daniela Addessi ◽  
Cristina Gatta ◽  
Mariacarla Nocera ◽  
Domenico Liberatore
Keyword(s):  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
Damage Index ◽  
Nonlinear Dynamic Analysis ◽  
Time History ◽  
Damage Variable ◽  
Constitutive Law ◽  
Masonry Arch ◽  
Nonlinear Dynamic Response ◽  
History Of

This study investigates the nonlinear dynamic response of the masonry bridge ‘Ponte delle Torri’ in Spoleto, aiming at assessing the seismic performance of the structure and evaluating the occurring damaging mechanisms. A 3D Finite Element (FE) macromechanical procedure implemented in the FE program FEAP is adopted to model the bridge. To reproduce the typical nonlinear microcracking process evolving in masonry material when subjected to external loads, an isotropic damage model is used. This is based on a scalar damage variable introduced in the stress-strain constitutive law and equally degrading all the components of the elastic constitutive operator. A nonlocal integral definition of the damage associated variable, that is the equivalent strain measure governing its evolution, is adopted to overcome the mesh dependency problems of the FE solution typically occurring in the presence of strain softening behavior. Based on the results of a recent study by some of the authors, a single equivalent pier is analyzed, whose geometry and boundary conditions are selected so that its response can provide useful information on the out-of-plane dynamic behavior of the overall bridge. To perform the seismic assessment, a set of recorded accelerograms is properly selected to simulate the seismic history of the Spoleto site. The nonlinear dynamic response of the structure is evaluated and monitored in terms of top displacement time history, evolution of the global damage index, and distribution of the damage variable. First, a set of analyses is performed by imposing the selected ground motions one by one on the initial undamaged configuration for the structure with the aim of emphasizing the damaging effects on its dynamic response. Then, the accelerograms are arranged in sequence to reproduce the seismic history of the site and analyze the influence of accumulated damage on the dynamic amplification of the response. A critical comparison of the bridge response to the sequence of accelerograms and the single records is made, and the interaction between the damaged structure dynamic response and the signal characteristic is highlighted, as well.

Modelling of Mechanical Systems With Friction Interfaces Considering Variable Normal Contact Load and Tangential Micro/Macro Slip

2016 ◽  
Author(s):  
Dongwu Li ◽  
Chao Xu
Keyword(s):  
Normal Load ◽  
Friction Model ◽  
Hysteretic Model ◽  
Friction Contact ◽  
Restoring Force ◽  
Normal Contact ◽  
Load Variation ◽  
Proposed Model ◽  
Frictional Damping ◽  
Microslip Friction

Mechanical structures with frictionally constrained interfaces often involve complex contact kinematics induced by tangential and normal relative motions. The tangential motion induces stick-micro/macro slip friction and causes energy dissipation. The normal motion induces normal load variation and possible separation of the joint interfaces. For effective analysis of dynamics of jointed structures, a reduced friction contact model is needed to characterize the nonlinear, coupled normal and tangential contact behaviors precisely. However, most developed microslip friction contact models considers only constant normal load. In this paper, an improved microslip friction model with normal load variation induced by normal motion is proposed. The tangential stick-micro/macro slip friction is modeled by continuous Iwan hysteretic model. This model is characterized by a slippage uniform distribution density function and a linear stiffness at stick state. The coupling relationship between tangential nonlinear restoring force and normal load variation is built. This leads to generalization of the original Iwan hysteretic friction model to consider the effect of variable normal load. The proposed model is applied to model a 7-dofs frictional damping experimental system. The results show that normal load variation and tangential microslip motion exert an important effect on prediction of friction contact behaviors. The proposed model is capable of generating asymmetric hysteresis loops and intermittent normal separation. The numerical simulation fit well with the experimental results for the 7-dofs frictional damping system, which validates the effectiveness and accuracy of the proposed model.

Parametric Identification of Carbon Nanotube Nanocomposites Constitutive Response

2019 ◽  
Vol 86 (4) ◽  
Author(s):  
Giovanni Formica ◽  
Michela Taló ◽  
Giulia Lanzara ◽  
Walter Lacarbonara
Keyword(s):  
Carbon Nanotube ◽  
Mesoscale Model ◽  
Differential Evolution Algorithm ◽  
Material Design ◽  
Fine Tuning ◽  
Model Parameters ◽  
Restoring Force ◽  
Stick Slip ◽  
Proposed Model ◽  
Constitutive Parameters

Hysteresis due to stick-slip energy dissipation in carbon nanotube (CNT) nanocomposites is experimentally observed, measured, and identified through a one-dimensional (1D) phenomenological model obtained via reduction of a three-dimensional (3D) mesoscale model. The proposed model is shown to describe the nanocomposite hysteretic response, which features the transition from the purely elastic to the post-stick-slip behavior characterized by the interfacial frictional sliding motion between the polymer chains and the CNTs. Parametric analyses shed light onto the physical meaning of each model parameter and the influence on the material response. The model parameters are determined by fitting the experimentally acquired force–displacement curves of CNT/polymer nanocomposites using a differential evolution algorithm. Nanocomposite beam-like samples made of a high performance engineering polymer and high-aspect-ratio CNTs are fabricated and tested in a bending mode at increasing deflection amplitudes. The entire time histories of the restoring force are fitted by the model through a unique set of parameters. The parameter identification is carried out for nanocomposites with various CNT weight fractions, so as to highlight the model capability to identify a wide variety of nanocomposite hysteretic behaviors through a fine tuning of its constitutive parameters. By exploiting the proposed model, a nanostructured material design and its optimization are made possible toward the exploitation of these promising materials for engineering applications.

scholarly journals A nonlinear dynamic model of magnetorheological elastomers in magnetic fields based on fractional viscoelasticity

2020 ◽  
pp. 1045389X2095361
Author(s):  
Guanghong Zhu ◽  
Yeping Xiong ◽  
Zigang Li ◽  
Ling Xiao ◽  
Ming Li ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Dynamic Model ◽  
Nonlinear Dynamic ◽  
Experimental Results ◽  
Model Parameters ◽  
Nonlinear Dynamic Model ◽  
Dynamic Moduli ◽  
Magnetorheological Elastomers ◽  
Proposed Model ◽  
Wide Range

As smart materials, magnetorheological elastomers (MREs) have been broadly applied in the field of intelligent structures and devices. In order to mathematically represent the dynamic behavior in a wide range of strain amplitude, excitation frequency and magnetic field; a nonlinear model with a fractional element was developed for MREs in a linear viscoelastic regime. The identification of model parameters was realized through fitting experimental data of dynamic moduli measured in shear mode, and the identified parameters exhibited good repeatability and consistency to reflect the rationality of this nonlinear dynamic model. Considering material elasticity and viscosity, the dependence of model parameters on strain amplitudes and magnetic fields was analyzed to interpret the dynamics of MREs. The fitted results displayed an excellent agreement with the experimental results on the dependence of dynamic moduli on strain amplitudes and magnetic fields. Using the predictor-corrector approach, predicted results on the stress-strain hysteresis loop were calculated based on identified parameters to further validate the proposed model by comparing with experimental results and predicted results of the revised Bouc-Wen model. This proposed model is expected to facilitate the dynamic analysis and simulation of MRE based vibration systems with a high precision accuracy.

Nonlinear Dynamic Response Analysis of the Braced Steel Frame with Wedge Devices

2011 ◽  
Vol 368-373 ◽  
pp. 685-689
Author(s):  
Jin Song Lei ◽  
Yin Sheng Zou ◽  
Ya Li Wang ◽  
Qing Ma
Keyword(s):  
Plastic Deformation ◽  
Dynamic Response ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Steel Frame ◽  
Structural Deformation ◽  
Response Analysis ◽  
Lateral Stiffness ◽  
Earthquake Intensity ◽  
Nonlinear Dynamic Response

In order to research the nonlinear dynamic respond analysis of a new braced steel frame with wedge devices under the action of earthquake, its damping mechanism is analyzed, and the computational model is obtained. Based on the mechanism of multiple resistant lateral system, the explicit nonlinear dynamic analysis and dynamic contact algorithm are adopted to separately analyze the steel frame with no brace, with centric and eccentric brace, and with the new braced wedge block. During the analysis, in order to take the material and geometrical bi-nonlinear into account, the material model is chosen as the bilinear equivalent strength, and the explicit centered difference algorithm is adopted. It can be obtained from structural deformation and energy and so on. The results show that the stiffness of structure decays after plastic deformation in the earthquake effect, and the hysteresis energy consumption and system dumping appear. The nonlinear dynamic response of steel frame is affected by resistant lateral stiffness, plastic deformation, and system damping. The braced steel frame with wedge block regulates the displacement and acceleration response with yield energy dissipation of brace, as it provides resistance lateral stiffness to control the deformation. This kind of structure has strong adaptability to earthquake intensity and good seismic performance.

scholarly journals Nonlinear Dynamic Analysis of Plates Stiffened by Parallel Beams with Deformable Connection

2014 ◽  
Vol 2014 ◽  
pp. 1-22 ◽  
Author(s):  
J. A. Dourakopoulos ◽  
E. J. Sapountzakis
Keyword(s):  
Dynamic Analysis ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Practical Interest ◽  
Geometrically Nonlinear ◽  
Analog Equation Method ◽  
Transverse Vibrations ◽  
Proposed Model ◽  
Great Practical Interest ◽  
Analog Equation

In this paper a general solution to the geometrically nonlinear dynamic analysis of plates stiffened by arbitrarily placed parallel beams of arbitrary doubly symmetric cross-section, subjected to dynamic loading, is presented. The plate-beam structure is assumed to undergo moderate large deflections and the nonlinear analysis is carried out by retaining nonlinear terms in the kinematical relations. According to the proposed model, the arbitrarily placed parallel stiffening beams are isolated from the plate by sections in the lower outer surface of the plate, making the hypothesis that the plate and the beams can slip in all directions of the connection without separation and taking into account the arising tractions in all directions at the fictitious interfaces. These tractions are integrated with respect to each half of the interface width resulting in two interface lines, along which the loading of the beams and the additional loading of the plate are defined. Six boundary value problems are formulated and solved using the analog equation method (AEM), a BEM-based method. Both free and forced transverse vibrations are considered and numerical examples with great practical interest are presented demonstrating the effectiveness, wherever possible, the accuracy, and the range of applications of the proposed method.

In-Plane Flexible Ring Tire Model—Part 1: Modeling and Parameter Identification

2018 ◽  
Vol 46 (3) ◽  
pp. 174-219 ◽  
Author(s):  
Bin Li ◽  
Xiaobo Yang ◽  
James Yang ◽  
Yunqing Zhang ◽  
Zeyu Ma
Keyword(s):  
Static Load ◽  
Model Parameters ◽  
Tire Model ◽  
Test Results ◽  
Lumped Mass ◽  
Virtual Test ◽  
Proposed Model ◽  
Particle Swarm Method ◽  
Vehicle Dynamic Simulation ◽  
Flexible Ring

ABSTRACT The tire model is essential for accurate and efficient vehicle dynamic simulation. In this article, an in-plane flexible ring tire model is proposed, in which the tire is composed of a rigid rim, a number of discretized lumped mass belt points, and numerous massless tread blocks attached on the belt. One set of tire model parameters is identified by approaching the predicted results with ADAMS® FTire virtual test results for one particular cleat test through the particle swarm method using MATLAB®. Based on the identified parameters, the tire model is further validated by comparing the predicted results with FTire for the static load-deflection tests and other cleat tests. Finally, several important aspects regarding the proposed model are discussed.

EXPONENTIATED HALF-LOGISTIC LOMAX DISTRIBUTION WITH PROPERTIES AND APPLICATION

2019 ◽  
Vol XVI (2) ◽  
pp. 1-11
Author(s):  
Farrukh Jamal ◽  
Hesham Mohammed Reyad ◽  
Soha Othman Ahmed ◽  
Muhammad Akbar Ali Shah ◽  
Emrah Altun
Keyword(s):  
Real Data ◽  
Continuous Model ◽  
Model Parameters ◽  
Data Set ◽  
Lomax Distribution ◽  
Mathematical Properties ◽  
Proposed Model ◽  
Probability Weighted Moment ◽  
Record Statistics ◽  
Maximum Likelihood Criterion

A new three-parameter continuous model called the exponentiated half-logistic Lomax distribution is introduced in this paper. Basic mathematical properties for the proposed model were investigated which include raw and incomplete moments, skewness, kurtosis, generating functions, Rényi entropy, Lorenz, Bonferroni and Zenga curves, probability weighted moment, stress strength model, order statistics, and record statistics. The model parameters were estimated by using the maximum likelihood criterion and the behaviours of these estimates were examined by conducting a simulation study. The applicability of the new model is illustrated by applying it on a real data set.

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