Effects of soil-structure interaction in seismic analysis of buildings with multiple pressurized tuned liquid column dampers

In this paper soil-structure interaction (SSI) effects are investigated while an array of Pressurized Tuned Liquid Column Dampers (PTLCD) is employed for seismic vibration control of buildings. This device represents the most general case of a passive damper, with different reduction options to other control devices obtained by simplifying the involved parameters. Soil conditions considerably affect the control device functioning, because dynamic parameters such as natural frequency, damping factor, and natural modes depend on the soil properties. A simplified mathematical model is developed for the building with multiple degrees of freedom connected to a flexible base. For the time-domain analysis, a computational routine is developed for the linearization of the equilibrium equations of the PTLCD, as well as details for the reduction to the other types of passive dampers. Several numerical examples are selected for the analysis of the damper efficiency in reducing seismic vibration considering SSI. These simulations include Kobe earthquake data, which is applied to the model to evaluate the device performance under different scenarios. It is verified the influence of SSI in the natural frequency and structural response, which is related to the earthquake frequency components. Results confirm that the array of PTLCD’s can reduce the vibration amplitudes, being more effective for soils with higher stiffness values

Growth of nanostructured zinc oxide on flexible conductive substrate: a review

In this paper, a review on the structural and morphological of nanostructured zinc oxide (ZnO) fabricated on flexible conductive substrate, mainly indium tin oxide coated on polyethylene terephthalate (ITO/PET) via various fabrication method is reported. Besides fabrication method, the effect of fabrication condition such as immersion time of ZnO-ITO/PET via hydrothermal method, concentration of modification material of precursor solution via sol-gel method, value of applied cathodic voltage and value of current densities via electrochemical deposition are also discussed. XRD analysis showed that the growth of ZnO-ITO/PET are preferred on (002) or (101) planes. SEM analysis revealed various type of nanostructured ZnO when prepared by sol-gel, spin coating, HWT and hydrothermal method, highlighting ZnO nanorods as the main morphology of ZnO�ITO/PET. The diameter of ZnO nanorods ranges from 10 nm to 830 nm

Response Modification and Seismic Protection of Yielding Structures Equipped with Inerters and Hysteretic Dampers

This study investigates the seismic response of structures with sustainable, long-stroke response modification devices. The main thrust of the dissertation is the investigation of the seismic response of yielding structures equipped with supplemental rotational inertia, or inerters. The last chapter of this dissertation investigates the seismic response of multistory yielding steel structures equipped with pressurized sand dampers. Inerters are mechanical devices with resisting force proportional to the relative acceleration of their end nodes. This class of response modification devices complements the traditional fluid viscous damping devices with resisting force proportional to the relative velocity at their end-nodes. Mass-amplification is the main benefit of inerter-based devices, which provide a high level of vibration control with a small amount of actual mass. This study first reviews the seismic response of elastic structures equipped with supplemental rotational inertia. The generalized equations of motion of structures equipped with inerters in any arbitrary story derived. The best seismic performance, obtained when inerter-devices are installed in the bottom story. A time-domain formulation for the response analysis of a single-degee-of-freedom structure and a two-degree-of-freedom 2DOF structure equipped with inerters are developed. The seismic performance of supplemental rotational inertia system compared to traditional energy dissipation mechanism. Both a single inerter and a pair of clutching inerters that can only resist the motion of the structure are examined. The nonlinear behavior of structures equipped with supplemental rotational inertia is investigated by using the Bouc-Wen hysteretic model. The effect of rigid and compliant inerters supports are examined. The post-yielding behavior of the system is investigated, and the advantages and challenges associated with using supplemental rotational inertia are discussed. The seismic performance of high-rise yielding structures equipped with the novel response-modification strategy, the outrigger-inerter system, is studied. The proposed seismic control mechanism uses inerters vertically within a conventional core-to-external column outrigger system. To study the seismic behavior of the outrigger-inerter system, a new material developed in C++. This new material is used to represent the behavior of inerters in the OpenSees platform. Both single inerter and a pair of clutching inerters are examined. This research concludes that supplemental rotational inertia effectively controls the seismic response of structures and could emerge as an attractive response modification strategy with the potential to replace the traditional energy dissipation systems in building structures. The last chapter of this dissertation studies the seismic response analysis of the 9-story SAC building equipped with pressurized sand dampers. Sand dampers are low-cost energy dissipation devices wherein the material enclosed within the damper housing is pressurized sand. The strength of the pressurized sand damper is proportional to the externally exerted pressure on the sand via prestressed steel rods. The strong pinching behavior of the pressurized sand dampers is characterized by a previously developed 3-parameter Bouc-Wen hysteretic model. The model was implemented in the open-source code OpenSees with a C++ algorithm and used to analyze the seismic response of a 9-story SAC steel building subjected to several strong ground motions

7th International Conference on Nonlinear Vibrations, Localization and Energy Transfer: Extended Abstracts

International audienceThe purpose of our conference is more than ever to promote exchange and discussions between scientists from all around the world about the latest research developments in the area of nonlinear vibrations, with a particular emphasis on the concept of nonlinear normal modes and targeted energytransfer

Embodied neuromechanical chaos through homeostatic regulation

In this paper, we present detailed analyses of the dynamics of a number of embodied neuromechanical systems of a class that has been shown to efficiently exploit chaos in the development and learning of motor behaviors for bodies of arbitrary morphology. This class of systems has been successfully used in robotics, as well as to model biological systems. At the heart of these systems are neural central pattern generating (CPG) units connected to actuators which return proprioceptive information via an adaptive homeostatic mechanism. Detailed dynamical analyses of example systems, using high resolution largest Lyapunov exponent maps, demonstrate the existence of chaotic regimes within a particular region of parameter space, as well as the striking similarity of the maps for systems of varying size. Thanks to the homeostatic sensory mechanisms, any single CPG “views” the whole of the rest of the system as if it was another CPG in a two coupled system, allowing a scale invariant conceptualization of such embodied neuromechanical systems. The analysis reveals chaos at all levels of the systems; the entire brain-body-environment system exhibits chaotic dynamics which can be exploited to power an exploration of possible motor behaviors. The crucial influence of the adaptive homeostatic mechanisms on the system dynamics is examined in detail, revealing chaotic behavior characterized by mixed mode oscillations (MMOs). An analysis of the mechanism of the MMO concludes that they stems from dynamic Hopf bifurcation, where a number of slow variables act as “moving” bifurcation parameters for the remaining part of the system

Index to NASA Tech Briefs, 1975

This index contains abstracts and four indexes--subject, personal author, originating Center, and Tech Brief number--for 1975 Tech Briefs

Energy-based monitoring and correction to enhance the accuracy and stability of explicit co-simulation

[Abstract] The simulation of complex engineering applications often requires the consideration of component-level dynamics whose nature and time-scale differ across the elements of which the system is composed. Co-simulation offers an effective approach to deal with the modelling and numerical integration of such assemblies by assigning adequate description and solution methods to each component. Explicit co-simulation, in particular, is frequently used when efficient code execution is a requirement, for instance in real-time setups. Using explicit schemes, however, can lead to the introduction of energy artifacts at the discrete-time interface between subsystems. The resulting energy errors deteriorate the accuracy of the co-simulation results and may in some cases develop into the instability of the numerical integration process. This paper discusses the factors that influence the severity of the energy errors generated at the interface in explicit co-simulation applications, and presents a monitoring and correction methodology to detect and remove them. The method uses only the information carried by the variables exchanged between the subsystems and the co-simulation manager. The performance of this energy-correction technique was evaluated in multi-rate co-simulation of mechanical and multiphysics benchmark examples.Xunta de Galicia; ED431B2016/031Xunta de Galicia; ED431F2021/04Ministerio de Economía, Industria y Competitividad; RYC-2016-20222Ministerio de Economía, Industria y Competitividad; TRA2017-86488-