Rafael Omar Ruiz

University of Michigan-Dearborn | UM-Dearborn

The assessment of the effectiveness of mass dampers for the Chilean region within a multi-objective decision framework utilizing life-cycle performance criteria is considered in this paper. The implementation of this framework focuses here on the evaluation of the potential as a cost-effective protection device of a recently proposed liquid damper,...

A recently proposed new type of liquid mass damper, called Tuned Liquid Damper with Floating Roof (TLD-FR), is the focus of this paper. The TLD-FR consists of a traditional TLD (tank filled with liquid) with the addition of a floating roof. The sloshing of the liquid within the tank counteracts the motion of the primary structure it is placed on, o...

This paper introduces a new type of tuned liquid damper (TLD) having a relatively simple, easy-to-model behavior and high effectiveness in controlling structural vibrations. It consists of a traditional TLD with addition of a floating roof. Since the roof is much stiffer than water, it prevents wave breaking, hence making the response linear even a...

A computationally efficient numerical model is developed in this study for evaluating the dynamic behavior of liquid storage tanks. This model has higher complexity than the Housner model (which corresponds to the simplest and most popular approach for approximating the behavior of rectangular and circular tanks) but still enjoys high computational...

The study of dynamic whirl behavior of air bearings is fundamental for an adequate rotordynamic analysis and future validation of numerical predictions. This work shows the dynamic response of the air film on a three lobe bearing under non-synchronous whirl motion. One-dimensional multifrequency orbits are used to characterize the bearing rotordyna...

Piezoelectric energy harvesters (PEHs) can be used as an additional power supply for a Structural Health Monitoring (SHM) system. Its design can be optimised for the best performance , however, optimal design depends on the input vibration, e.g. an acceleration of a bridge due to wind loads and passing traffic. In the previous studies, we have show...

With the rapid development of Internet of Things (IoT) technology, worldwide efforts to seek continuous energy sources for various information sensing devices remains critical. A meritable pathway to mitigating environmental degradation is to investigate and innovate more effective renewable energy solutions that capitalise on the natural phenomena...

This work proposes a hierarchical Bayesian framework to identify electromechanical properties of Piezoelectric Energy Harvesters (PEHs) and associated uncertainties based on experimental frequency response functions (FRFs). The framework allows the use of experimental data from multiple devices, potentially defined by different electromechanical pr...

Chile presents a high seismicity and very particular characteristics due to its subductive environment and high convergence rate of the interacting plates. In this paper, ground motion models (GMM) for Arias Intensity and strong ground motion duration are developed based on recently compiled Chilean earthquakes records. The Chilean derived GMM are...

The use of Piezoelectric Energy Harvesters (PEHs) on bridges is explored in this work. First, a PEH model based on Isogeometric Analysis (IGA) is extended to estimate the harvested energy from induced vibration in bridges using a modal reduction and an efficient time integration method. The model is also coupled with the Particle Swarm Optimisation...

This work proposes a mathematical framework to identify the relationship between the manufacturing tolerance of a component and the expected variations on its mechanical performance with focus on journal bearing applications. The manufacturing tolerance is described through probability density functions, while its effect on performance is addressed...

A framework that allows the use of well-known dynamic estimators to infer the electromechanical properties in Piezoelectric Energy Harvesters (PEHs) is presented here. The framework is based on Bayesian inference applied over experimental results obtained from Frequency Response Functions (FRFs). The posterior probability density function is approx...

Recently, a model of a piezoelectric energy harvester (PEH), based on bimorph Kirchhoff–Love plate of variable shape and constant thickness was developed and subsequently discretized using isogeometric analysis (IGA). The model describes a wide class of non-conventional PEH configurations and can be paired with an optimization algorithm to identify...

The dynamic behavior of piezoelectric energy harvesters has been widely studied in the last decade. Different deterministic modeling techniques and simplifications have been adopted to describe their electromechanical coupling effect in order to increase the accuracy on the output power estimation. Although it is a common practice to use determinis...

The development of custom cellular materials has been driven by recent advances in additive manufacturing and structural topological optimization. These contemporary materials with complex topologies have better structural efficiency than traditional materials. Particularly, truss-like cellular structures exhibit considerable potential for applicat...

In the structural design of shear wall buildings, the initial process requires the interaction between the architecture and engineering teams to define the appropriate distribution of the walls, a stage typically carried out through a trial-and-error procedure, without any consideration of previous similar projects. In previous work, a database of...

The vibrational behavior of composite structures has been demonstrated as a useful feature for identifying debonding damage. The precision of the damage localization can be greatly improved by the addition of more measuring points. Therefore, full-field vibration measurements, such as those obtained using high-speed digital image correlation (DIC)...

The present work proposes a baseline‐free method to assess debonding on composite panels. The method is based on regressive Gaussian processes (GP) used to obtain vibration modes free of noise. A Bayesian scheme is implemented to allow the automatic determination of the model hyperparameters. The estimation of the undamaged vibration modes is carri...

Abstract of the online presentation in the World Congress of Computational Mechanics (WCCM), covering the topic “Isogeometric shape optimization of piezoelectric energy harvesters.”

A framework that allows for the use of well-known dynamic estimators in piezoelectric harvesters (PEHs) (i.e., deterministic performance estimators) and that accounts for the random error associated with the mathematical model and the uncertainties of model parameters is described presented here. This framework may be employed for Posterior Robust...

This paper develops a record-based stochastic ground motion model for the Chilean Subduction zone that generates ground motions compatible with the seismic hazard (represented by a local Ground Motion Predictive Equation GMPE) for both interplate and intraslab mechanism and considering rock soil conditions. The stochastic ground motion is obtained...

The model updating of the electro-mechanical properties of Piezoelectric Energy Harvesters (PEHs) using experimental data within a Bayesian inference setting is discussed. The implementation requires: a predictive model for the harvester response; an assumption for its prediction error; a prior multivariate probabilistic density function for the el...

In this work, we propose new packing algorithm designed for the generation of polygon meshes to be used for modeling of rock and porous media based on the virtual element method. The packing problem to be solved corresponds to a two-dimensional packing of convex-shape polygons and is based on the locus operation used for the advancing front approac...

Piezo-electric energy harvesters (PEHs) are widely used to recycle waste vibrations for powering small electronic devices. In this work, we study the performance of PEHs of non-conventional shapes with the aim to optimize their design. A PEH is modeled as a bimorph cantilever Kirchhoff-Love plate subjected to base acceleration. The shape is describ...

In this work, we propose to leverage the advantages of both the Artificial Neural Network (ANN) based Second Order Reliability Method (SORM) and Importance sampling to yield an Adaptive Importance Sampling based ANN, with specific application towards failure probability and sensitivity estimates of Variable Stiffness Composite Laminate (VSCL) plate...

In this work, we propose to leverage the advantages of both the Artificial Neural Network (ANN) based Second Order Reliability Method (SORM) and Importance sampling to yield an Adaptive Importance Sampling based ANN, with specific application towards failure probability and sensitivity estimates of Variable Stiffness Composite Laminate (VSCL) plate...

In this work, we propose to leverage the advantages of both the Artificial Neural Network (ANN) based Second Order Reliability Method (SORM) and Importance sampling to yield an Adaptive Importance Sampling based ANN, with specific application towards failure probability and sensitivity estimates of Variable Stiffness Composite Laminate (VSCL) plate...

A general numerical framework to estimate the stress range versus number of cycles curves experienced by a cable due to wind-induced vibrations is presented in this paper. The algorithm associated to the proposed numerical framework relies on a probabilistic approach to account for the uncertainties in the cable properties, initial conditions, damp...

Sandwich structures are subjected to imperfect bonding or debonding caused by defects during the manufacturing process, by fatigue, or by impact loads. In this context, their safety and functionality can be improved with the implementation of vibration‐based structural damage assessment methodologies. These methodologies involve the computation of...

Resumen Producto de la alta sismicidad que caracteriza a Chile se hace necesario desarrollar herramientas para el estudio de peligro sísmico. Para lo anterior se utilizan algunos parámetros que permiten estimar la respuesta del suelo frente a eventos sísmicos y los daños que podrían provocar en las estructuras. Dentro del marco anterior, para la es...

In this paper a novel and efficient computational framework to estimate the stress range versus number of cycles curves experienced by a cable due to external excitations (e.g., seismic excitations, traffic and wind-induced vibrations, among others) is proposed. This study is limited to the wind-cable interaction governed by the Vortex Shedding mec...

The tuned mass-damper-inerter (TMDI) is a recently proposed passive vibration suppression device that couples the classical tuned mass-damper (TMD), comprising a secondary mass attached to the structure via a spring and dashpot, with an inerter. The latter is a two-terminal mechanical device developing a resisting force proportional to the relative...

A probabilistic framework for the cost-effective design of supplemental seismic protective devices considering multiple criteria related to their life-cycle performance is reviewed in this contribution. The framework relies on time-history analysis for describing structural behavior, on an assembly-based vulnerability approach for quantifying earth...

The interest of this work is to describe a framework that allows the use of the well-known dynamic estimators in piezoelectric harvester (deterministic performance estimators) but taking into account the random error associated to the mathematical model and the uncertainties on the model parameters. The framework presented could be employed to perf...

In the last decade, several numerical and analytic procedures have been proposed to predict the dynamic behavior of piezoelectric energy har- vesters (PEHs). Nevertheless, PEHs present characteristics that are di ffi cult to control in their manufacturing process, for example the electromechanical properties of the materials present variations up to...

A beam-like and a plate-like piezoelectric energy harvesters are studied, both modeled through a plate-based finite element procedure (FEM) and the well-known Analytic Distributed Parameter Solution (ADPS) proposed by Erturk and Inman in 2008. Uncertainties related to the model parameters are also included and propagated to obtain a more robust pre...

The goal of this work is to describe a framework to propagate uncertainties in piezoelectric energy harvesters (PEHs). These uncertainties are related to the incomplete knowledge of the model parameters. The framework presented could be employed to conduct prior robust stochastic predictions. The prior analysis assumes a known probability density f...

In recent decades, the concept of the passive linear tuned mass-damper (TMD) has been considered as a valid option for vibration suppression of dynamically excited building structures due to its relatively simple design and practical implementation. Conceptually, the TMD comprises a mass attached to the structure whose vibration motion is to be con...

It has been identified that small variations in the pad clearance and preload of a Tilting Pad Journal Bearing lead to important variations in their dynamic coefficients. Although this variation trend is already identified, a more robust statistical analysis is required in order to identify more general tendencies and quantify it. This work present...

The interest of this work is to describe a framework to propagate uncertainties in piezoelectric energy harvesters (PEHs). The uncertainties are related to the random error associated to the mathematical model adopted, incomplete knowledge of the model parameters and the randomness nature of the excitation. The framework presented could be employed...

The design of a new liquid damper device is considered in this paper based on life-cycle criteria. This new device, called Tuned Liquid Damper with Floating Roof (TLD-FR) maintains the advantages of traditional Tuned Liquid Dampers (low cost, easy tuning, alternative use of water) while establishing a linear and generally more robust/predictable da...

This paper introduces a new type of Tuned Sloshing Damper (TSD) having a relatively simple, easy-to-model behavior and capable of effectively controlling earthquake vibrations. It consists of a traditional TSD with the addition of a floating roof. Since the roof is much stiffer than water, it prevents wave breaking, hence making the response linear...

This paper introduces a new type of Tuned Sloshing Damper (TSD) having a relatively simple, easy-to-model behavior and capable of effectively controlling earthquake vibrations. It consists of a traditional TSD with addition of a floating roof. Since the roof is much stiffer than water, it prevents wave breaking, hence making the response linear eve...

The purpose of the present work consists on improving the understanding of the energy dissipation mechanism in the structure of a gas foil bearing. The analysis is based on an analytical model capable of predicting bumps deformation due to a load on the top coupled with dry friction forces at the top and bump ends. Models of mass-individual bump an...

The majority of rotordynamic studies concerned with bearing properties identification estimate rotordynamic coefficients without addressing the issue of parameter uncertainties. Uncertainty quantification is required to establish the accuracy and therefore the robustness of the identified parameters. Accuracy on the identification methodology is ha...

This work presents direct experimental measurements of air film rotordynamic coefficients on a three lobe bearing. The test rig uses two magnetic bearing actuators to impose desired test orbits to the journal. Tests are conducted at several rotating speeds up to 12,000rpm. Journal whirling excitation is independent of the rotating speed, thus allow...

This paper describes the design and operation of an experimental facility for measurement of equivalent stiffness and damping of air bearings. The rig uses two magnetic bearings to impose any given orbit to the journal, including displacement in two perpendicular directions on the rotation plane and tilting on the conical mode. Dynamic forces are m...