Observations on the vibration of axially-tensioned elastomeric pipes conveying fluids

A study of the effect of axial tension on the vibration of a single-span elastomeric pipe clamped at both ends conveying fluid has been carried out both experimentally and theoretically. A new mathematical model using a penalty function technique and the method of kinematic correction and fictitious loads has been developed. The influence of flowing fluid and axial tension on natural frequencies and mode shapes of the system has been described using this model and compared with experimental observations. Linear and non-linear dynamic response of the harmonically excited pipe has also been investigated for varying flow velocities and initial axial tensions

Interaction of Two Adjacent Structures Coupled by Inerter-based System considering Soil Conditions

The inerter-based systems have proven to be effective for vibration control of adjacent structures. The interaction through the soil medium between adjacent structures in urban areas is generally accepted. However, existing studies concerning the inerter-based adjacent structures are primarily based on the assumption of a fixed base, without considering the inevitable interaction. To address this issue, this study incorporated the soil effects into the theoretical analysis of adjacent structures interconnected by an inerter system, and correspondingly develops an optimal design framework for such system. Employing a classic discrete model for structures and soil, the interaction behavior between inerter-based adjacent structures and soil was extensively studied in a comparative analysis. Based on the revealed interaction phenomena, the need for considering the soil condition in the design of an inerter system for adjacent structures was addressed, and a performance-demand-based optimal design framework was developed. The results indicated that for inerter-based adjacent structures spaced closely, the coupled interaction effect of soil and structure requires careful consideration, especially in soft soil conditions. Owing to the soil effects, the inerter system exhibited a weakened effectiveness for displacement reduction. A larger inner deformation of the inerter system is required to meet the demand for energy dissipation. With consideration of the soil condition, the proposed design method can satisfy the pre-specified target displacement demands for adjacent structures, simultaneously optimizing the control cost as an economical solution

A Finite Element Computation of the Gravitational Radiation emitted by a Point-like object orbiting a Non-rotating Black Hole

The description of extreme-mass-ratio binary systems in the inspiral phase is a challenging problem in gravitational wave physics with significant relevance for the space interferometer LISA. The main difficulty lies in the evaluation of the effects of the small body's gravitational field on itself. To that end, an accurate computation of the perturbations produced by the small body with respect the background geometry of the large object, a massive black hole, is required. In this paper we present a new computational approach based on Finite Element Methods to solve the master equations describing perturbations of non-rotating black holes due to an orbiting point-like object. The numerical computations are carried out in the time domain by using evolution algorithms for wave-type equations. We show the accuracy of the method by comparing our calculations with previous results in the literature. Finally, we discuss the relevance of this method for achieving accurate descriptions of extreme-mass-ratio binaries.Comment: RevTeX 4. 18 pages, 8 figure

Design of a thin-plate based tunable high-quality narrow passband filter for elastic transverse waves propagate in metals

For the elastic SV (transverse) waves in metals, a high-quality narrow passband filter that consists of aligned parallel thin plates with small gaps is designed. In order to obtain a good performance, the thin plates should be constituted by materials with a smaller mass density and Young’s modulus, such as polymethylmethacrylate (PMMA), compared to the embedded materials in which the elastic SV waves propagate. Both the theoretical model and the full numerical simulation show that the transmission spectrum of the designed filter demonstrates several peaks with flawless transmission within 0 KHz ∼20 KHz frequency range. The peaks can be readily tuned by manipulating the geometrical parameters of the plates. Therefore, the current design works well for both low and high frequencies with a controllable size. Even for low frequencies on the order of kilohertz, the size of this filter can be still limited to the order of centimeters, which significantly benefits the real applications. The investigation also finds that the same filter is valid when using different metals and the reason behind this is explained theoretically. Additionally, the effect of bonding conditions of interfaces between thin plates and the base material is investigated using a spring model

Pseudo-dynamic method for structural analysis of automobile seats

This work describes the application of a pseudo-dynamic (PsD) method to the dynamic analysis of passenger seats for the automotive industry. The project of such components involves a structural test considering the action of dynamic forces arising from a crash scenario. The laboratory certification of these automotive components consists essentially on the inspection of the propagation and extension of plastic deformations zones in metallic members of the seat structure as consequence of the mutual action between the seat and the passenger fastened to the seat via seat belt anchorages. This work presents a relatively simple experiment using PsD techniques as a novel method to performa test equivalent to the dynamic model of a dummy-seat pair subjected to impulsive loads from a car crash. Essentially, the PsD test method is a hybrid and hierarchic computer-driven testing procedure where a numerical algorithm and experimental step are used and combined on-line in order to solve a problem in the scope of structural dynamics. The implementation of the method is not expensive and has the leading advantage of offering the operator a total control of any intermediate structure state during the test still keeping the realism of a real dynamic testing.Project: NDT-AUTO Ref 13-02-2003-FDR-01281 (Agencia de Inovação

Application of reliability-based robustness assessment of steel moment resisting frame structures under post-mainshock cascading events

This paper proposes a reliability-based framework for quantifying structural robustness considering the occurrence of a major earthquake (mainshock) and subsequent cascading hazard events, such as aftershocks that are triggered by the mainshock. These events can significantly increase the probability of failure of buildings, especially for structures that are damaged during the mainshock. The application of the proposed framework is exemplified through three numerical case studies. The case studies correspond to three SAC steel moment frame buildings of three, nine, and 20 stories, which were designed to pre-Northridge codes and standards. Two-dimensional nonlinear finite-element models of the buildings are developed with the Open System for Earthquake Engineering Simulation framework (OpenSees), using a finite length plastic hinge beam model and a bilinear constitutive law with deterioration, and are subjected to multiple mainshock-aftershock seismic sequences. For the three buildings analyzed herein, it is shown that the structural reliability under a single seismic event can be significantly different from that under a sequence of seismic events. The reliability based robustness indicator shows that the structural robustness is influenced by the extent to which a structure can distribute damage

Finite Element Simulation of Dense Wire Packings

A finite element program is presented to simulate the process of packing and coiling elastic wires in two- and three-dimensional confining cavities. The wire is represented by third order beam elements and embedded into a corotational formulation to capture the geometric nonlinearity resulting from large rotations and deformations. The hyperbolic equations of motion are integrated in time using two different integration methods from the Newmark family: an implicit iterative Newton-Raphson line search solver, and an explicit predictor-corrector scheme, both with adaptive time stepping. These two approaches reveal fundamentally different suitability for the problem of strongly self-interacting bodies found in densely packed cavities. Generalizing the spherical confinement symmetry investigated in recent studies, the packing of a wire in hard ellipsoidal cavities is simulated in the frictionless elastic limit. Evidence is given that packings in oblate spheroids and scalene ellipsoids are energetically preferred to spheres.Comment: 17 pages, 7 figures, 1 tabl

Assessing Security Needs of the multifaceted relationships of Energy and Water Providers

In the near future, the United States will be facing constraints on energy availability due to the heightened demand for both energy and water, especially during droughts and summers. Increasing stress on the inextricably linked resource availability of both water and energy can be mitigated with integrated planning. Exchanging data is an important component to current and future mitigation approaches within the Energy-Water Nexus. We describe the types of relationships that are formed in the United States EWN, and address the data sharing obstacles within. Approaches to removing the obstacles of data sharing are presented, based on case studies