Elastic Connection Research Articles

Study on seismic response control of a single-tower self-anchored suspension bridge with elastic-plastic steel damper

Elastic-plastic steel damper (EPSD) is a new device controlling seismic responses. The mechanical principle of EPSD was presented and a comparison was conducted between the theoretical formulas and finite element (FE) simulation of damper units. The verified force-displacement hysteretic curve of the damper system was obtained with reference to tests. The Nanjing Jiangxinzhou Bridge (NJB) was subsequently taken as the case to investigate the seismic response control effect of EPSDs on single-tower self-anchored suspension bridges. A 3-dimensional FE model of the bridge was established in ANSYS and the dynamic and static analyses of the bridge were conducted, the control effect of EPSDs under different seismic waves was further investigated through nonlinear time-history analysis based on the validated model. Results showed that both the simplified theoretical and FE simulation methods can preferable reflect the mechanical performance of EPSD, and that seismic responses of NJB with EPSDs are better than those with elastic connection device or fluid viscous damper. However, the control effect of EPSDs is influenced by seismic wave characteristics.

Pseudomonas aeruginosa Attachment on QCM-D Sensors: The Role of Cell and Surface Hydrophobicities

While biofilms are ubiquitous in nature, the mechanism by which they form is still poorly understood. This study investigated the process by which bacteria deposit and, shortly after, attach irreversibly to surfaces by reorienting to create a stronger interaction, which leads to biofilm formation. A model for attachment of Pseudomonas aeruginosa was developed using a quartz crystal microbalance with dissipation monitoring (QCM-D) technology, along with a fluorescent microscope and camera to monitor kinetics of adherence of the cells over time. In this model, the interaction differs depending on the force that dominates between the viscous, inertial, and elastic loads. P. aeruginosa, grown to the midexponential growth phase (hydrophilic) and stationary phase (hydrophobic) and two different surfaces, silica (SiO(2)) and polyvinylidene fluoride (PVDF), which are hydrophilic and hydrophobic, respectively, were used to test the model. The bacteria deposited on both of the sensor surfaces, though on the silica surface the cells reached a steady state where there was no net increase in deposition of bacteria, while the quantity of cells depositing on the PVDF surface continued to increase until the end of the experiments. The change in frequency and dissipation per cell were both positive for each overtone (n), except when the cells and surface are both hydrophilic. In the model three factors, specifically, viscous, inertial, and elastic loads, contribute to the change in frequency and dissipation at each overtone when a cell deposits on a sensor. On the basis of the model, hydrophobic cells were shown to form an elastic connection to either surface, with an increase of elasticity at higher overtones. At lower overtones, hydrophilic cells depositing on the hydrophobic surface were shown to also be elastic, but as the overtone increases the connection between the cells and sensor becomes more viscoelastic. In the case of hydrophilic cells interacting with the hydrophilic surface, the connection is viscous at each overtone measured. It could be inferred that the transformation of the viscoelasticity of the cell-surface connection is due to changes in the orientation of the cells to the surface, which allow the bacteria to attach irreversibly and begin biofilm formation.

Elastic connection disk subjected to periodically fluctuating transmitted torque and rotational speed

Involving the intrinsic power transmission torque/speed coupling characteristics of prime-movers, a rotating elastic connection disk subjected to periodically fluctuating transmitted torque and rotational speed generated by the fluctuation of external loads is investigated. Using Galerkin's method, the rotating elastic connection disk is modeled as a parametrically excited gyroscopic system. The effects of the torque/speed coupling, transmitted torque fluctuation amplitude and frequency, and constant parts of the transmitted torque and the rotational speed on the system dynamic stability are explored for the disk modes possessing different nodal diameters. The rotational speed, transmitted torque and their fluctuations can all result in system instability of the elastic connection disk. The instability can be suppressed or avoided by operating at small amplitude and low frequency of the transmitted torque fluctuation, and by operating in the weakly coupled torque/speed regime of the prime-movers. Low rotational speed avoids the instability in the case of a small transmitted torque, but medium rotational speed operation is valuable to suppress the instability induced by a large transmitted torque and its fluctuation. Instability parameter regions for the positive and negative torque/speed coupling coefficient are roughly similar in shape, but there are some differences in the value of the instability coefficient.

Synthesis of Adequate Mathematical Description of Rolling Mill Motion

AbstractSynthesis of adequate mathematical description of the main mechanical line of rolling mill are considered. The four‐mass model with weightless elastic connections is chosen as mathematical model of dynamic system of the main mechanical line of the rolling mill. The problem was reduced to solution of integral equation of the first kind (to unsteady problem). The methods of obtaining of the steady solutions are suggested. Synthesis of the adequate mathematical descriptions with unitary model of external load are suggested. The metal rolling was executed with using of real experimental measurements as an example. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Vibration of rotating elastic connection disc

Vibration of a rotating elastic connection disc subjected to a transmitted torque is investigated by including the initial unstressed transverse runout of the disc, the axial displacement, and deflection angles between the inner and outer clamped edges due to machining and installation errors in real discs. The governing equation of the connection disc is discretized by Galerkin's method, and natural frequency, dynamic stability, resonance condition, and steady-state deflections are calculated. Excluding the parameters causing the dynamic instability and system resonance, an available parameter region in the parameter plane of the disc rotating speed – the transmitted torque is presented for the engineering application. Amplitudes of the steady-state deflections induced by the initial transverse runout, the prescribed axial displacement, and deflection angles are obtained for each disc mode, and effects of the disc rotating speed and the transmitted torque on them are discussed.

Divalent Counterions Tether Membrane-Bound Carbohydrates To Promote the Cohesion of Auditory Hair Bundles

The cell membranes in the hair bundle of an auditory hair cell confront a difficult task as the bundle oscillates in response to sound: for efficient mechanotransduction, all the component stereocilia of the hair bundle must move essentially in unison, shearing at their tips yet maintaining contact without membrane fusion. One mechanism by which this cohesion might occur is counterion-mediated attachment between glycan components of apposed stereociliary membranes. Using capillary electrophoresis, we showed that the stereociliary glycocalyx acts as a negatively charged polymer brush. We found by force-sensing photomicrometry that the stereocilia formed elastic connections with one another to various degrees depending on the surrounding ionic environment and the presence of N-linked sugars. Mg2+ was a more potent mediator of attachment than was Ca2+. The forces between stereocilia produced chaotic stick-slip behavior. These results indicate that counterion-mediated interactions in the glycocalyx contribute to the stereociliary coherence that is essential for hearing.

탄성 조인트로 연결된 이중 꼬리 지느러미 오스트라키폼 물고기 로봇의 추진력 해석 및 조인트 위치가 추력에 미치는 영향

A simplified linearized dynamic equation for the propulsion force generation of an Ostraciiform fish robot with elastically jointed double caudal fins is derived in this paper. The caudal fin is divided into two segments and connected using an elastic joint. The second part of the caudal fin is actuated passively via the elastic joint connection by the actuation of the first part of it. It is demonstrated that the derived equation can be utilized for the design of effective caudal fins because the equation is given as an explicit form with several physical parameters. A simple Ostraciiform fish robot was designed and fabricated using a microprocessor, a servo motor, and acrylic plastics. Through the experiment with the fish robot, it is demonstrated that the propulsion force generated in the experiment matches well with the proposed equation, and the propulsion speed can be greatly improved using the elastically jointed double fins, improving the average speed more than 80%. Through numerical simulation and frequency domain analysis of the derived dynamic equations, it is concluded that the main reason of the performance improvement is resonance between two parts of the caudal fins.

Nonlinear elasto-dynamic analysis of bi-material composite members subjected to explosion

Composite members that are composed of two or more elements connected together by elastic shear connection are frequently found in many areas of engineering practice. Evaluation and subsequent strengthening of new and existing types of these members for extreme loading cases, such as explosion or blast, require a realistic and pragmatic design approach to be formulated and for which there is a significant dearth of scientific data in the literature. This paper therefore addresses, in generic form, an innovative mechanical-based formulation for the nonlinear elasto-dynamic response of an isolated bi-material composite element under a blast loading, which importantly incorporates the partial shear interaction which occurs at the interface of the two components. The formulation is based on a non-discretisation semi-analytical method, in which the second order effects in the strain-displacement field are taken into account so that the axial force developed is quantified correctly. The bi-material composite member is restrained at its ends by translational and rotational springs, which simulate a semi-rigid connection in a steel-concrete composite frame. The generic technique that is developed is shown to agree with solutions obtained from the finite element method, and it provides a structural model for the dynamic response of bi-material composite members with the potential for inclusion in prescriptive code rules.

Solution of free vibration equation of elastically supported Timoshenko columns with a tip mass by differential transform method

► We investigate analytical and DTM solutions of free vibration of a Timoshenko column. ► We examine the variations in free vibration natural frequencies of the column. ► We observe good agreement in the results of DTM with the results of analytical method. In this study free vibration analysis of a Timoshenko column with a tip mass having rotary inertia is carried out by both exact solution and differential transform method (DTM). The support of the system is modeled by an elastic spring against rotation. Fixity factor is used to define the relative stiffness of the elastic connection and the column. The governing equation of the column is solved by the separation of variables method including the rotatory inertia to get the exact solution. The same problem is also solved by DTM algorithm and the results are compared with the ones of exact solution. The comparison tables are presented in numerical analysis to show that a very good agreement is observed for DTM.

Optimal impulse characteristics for devices protecting elastic objects from shocks

We consider the problem of shock-protection-device optimization in the case when the protected object is a deformable body described by multibody models with linear elastic connections. The power characteristics of shock-protection devices were constructed with minimal motion under the condition of deformation limitation. It was shown that the solutions to the problem formulated include as terms momentum functions such as the Dirac delta function and its weak derivative. A numerical method to solve these problems was designed and implemented with software.

Comprehensive optimal control on seismic response of a single-tower self-anchored suspension bridge

Earthquake may cause severe damage to all kinds of bridge such as the falling down of the girder; therefore, effective measures should be employed to control the seismic displacement. In this paper, the method of comprehensive optimal control, combined with analytic hierarchy process, is employed to investigate the seismic response control of the Nanjing Jiangxinzhou Bridge, which is a single-tower self-anchored suspension bridge (SSSB). Also, 3-dimensional nonlinear seismic response analyses are conducted. Three types of practical connection measures for seismic response control of SSSB are investigated, and the optimal parameters of the connection devices are achieved by this method. Results show that both the elastic connection devices and the dampers with rational parameters can reduce the seismic displacement of the bridge effectively, but the elastic connection devices will increase the seismic force of the tower. When all factors are considered, the optimal measure is by using the elastic connection devices and the dampers together. These results can provide references for seismic response control of SSSBs.

Analysis of connection element classes and locations and of some structural requirements for the mounting of different superstructure types on transport vehicles

Analysis of connection element classes and locations and of some structural requirements for the mounting of different superstructure types on transport vehicles

On the Interaction of Partial Interaction and Shrinkage in Composite Steel-Concrete T-Beams

The use of composite beams of steel and concrete joined by shear connectors goes back well over half a century, and they are now ubiquitous civil engineering structures. Their populaarity and efficiency derive from the fact that the concrete carries compression and the steel carries tension, thereby making best use of the two materials to enhance the strength and stiffness of the beam when the concrete slab is joined mechanically to the steel girder. Without considering long-term shrinkage and creep effects in the concrete, Newmark, Siess and Viest deriived the classic partial interaction solution in 1951, quantifying the increase in beam's stiffness as the stiffness of the mechanical shear connection increases; the solution being represented with hyperbolic trigonometric functions. With no shear connection between the concrete and steel, the deflection of the beam is based on the flexural stiffness of the two materials alone and any uniform shrinkage deformations of the slab will have no effect on the lateral deflection of the beam. On the other hand, if the shear connection between tthe concrete and steel is infinitely stiff, uniform shrinkage of the slab whose lever arm is eccentric the centroid of the transformed cross-section may lead to considerable shrinkage-based deformations, thereby negating the stiffening effects of the fully-composite action. In theory, a fully-composite beam may deflect more than one without any composite action because of shrinkage-based slab deformations. Using a rational technique based on virtual work, the paper presents a solution for a composite beam with elastic shear connection subjected to slab shrinkage deformations. Its focus is on identifying the competing and coupled influences of stiff partial interaction in reducing deformations, and high shrinkage deformations in causing beam deformations. The solutions may be used to optimise beam deformations, being suitable for deesign.

Parametric oscillations of wings excited during nonuniform fluid flow

The mechanism of excitation of rotary parametric oscillations during nonuniform fluid flow in a partially filled wing with a pivotal bearing and elastic connections is examined. It is experimentally revealed that at a certain flow velocity, intensive wing oscillations are excited with an eigenfrequency approximately twice as high as rotary oscillations alone. When the air cushion is removed and the wing is filled completely by the liquid, these oscillations stop. It is shown that significant modulation of the mass moment of inertia with a period equal to the half-period of self-oscillations appear due to significant displacements of the air cushion and liquid displacement towards the peripheral segments of an incompletely filled wing during rotary oscillations. Therefore, the parametric intensification of rotary oscillations of a wing in nonuniform liquid flow at a frequency approximately twice as high as the eigenfrequency can take place. The intensive rotary oscillations of an incompletely filled wing, which are excited by a nonuniform liquid flow, can be efficiently used for driving the different mechanisms in machine manufacturing, power engineering and the shipbuilding industry

On the stability of the upper airways system

Simple models for upper pharyngeal obstruction, describing the sleep apnea syndrome are proposed. Stability is discussed, of two and three individualized elements, with and without elastic connections, interacting with the steady flow. Considering the flow as the controlling parameter, critical steady state flows are located and their post-critical behavior is discussed for various models. It is pointed out that non-linear constitutive elastic laws are necessary contrary to the linear ones introduced by Fodil (1998) [15]. Finally the three element model will be presented and studied with non-linear constitutive relations and side connections. Applications of the theory will be performed and discussion for the three models will be presented. It is pointed out that the sleep apnea syndrome is due to the instability of the upper pharyngeal region.

Viscoelastic locally resonant double negative metamaterials with controllable effective density and elasticity

A metamaterial that is composed of solid viscoelastic elements with controllable properties is proposed in this Letter. This enables an adaptable and general acoustic metamaterial to be practically realised. An array of masses with a single elastic connection to a supporting viscoelastic structure, such as one that is dynamically equivalent to an array of Helmholtz resonators, only provides a system with negative effective mass. A local active control scheme applied to each of these masses can emulate additional elastic connections to the supporting structure. An array of masses with a suitable local control scheme can provide both the negative effective stiffness and mass required for negative refraction. The tuneable feedback control parameters determine the characteristics of the region of double negativity.

Nonlinear thermoelastic analysis of composite steel–concrete arches including partial interaction and elevated temperature loading

Composite structural elements containing two materials joined by means of an elastic shear connection find widespread use in both traditional and innovative structural engineering applications. The most common of these are steel–concrete members, joined by headed mechanical stud shear connectors. Despite their popularity and ubiquity, a thorough understanding of the behaviour of composite elements has yet to be fully developed, especially in an environment when they are subjected to elevated temperatures. This paper presents a somewhat generic model for the nonlinear elastic behaviour of composite arches subjected to sustained loading at elevated temperatures. The effect of partial interaction between the steel and concrete components in the tangential direction, as well as the variation of internal axial compressive forces along the member, is taken into account. Based on the governing differential equation obtained from the longitudinal equilibrium of an element of the concrete component, exact solutions for the displacement field are presented. The generic technique that is developed is shown to agree with solutions obtained from ABAQUS, and has a potential for inclusion in prescriptive design recommendations. The scope of the formulation is illustrated by presenting a parametric study of a steel–concrete composite arch at elevated temperatures, which indicates the variation of the displacements, axial force and internal bending moment with respect to both the thermal profile and the degree of partial interaction between the concrete slab and steel component.

Variations in Sound Insulation in Nominally Identical Prefabricated Lightweight Timber Constructions

Variations in sound insulation necessitate higher safety margins to the legal requirements, which results in higher production costs. Increased knowledge about variations leads to lowered costs and better sound quality. In-situ measurements of 30 nominally identical apartments of a lightweight timber construction were performed, to assess and quantify the variations in airborne sound reduction and impact sound pressure level. The construction is an industrially prefabricated system of complete volumes. Different sound insulation was found between floor numbers as the apartments on the highest floor achieved significantly better sound insulation. This difference was assumed to be due to the extra weight on lower floors affecting the elastic connections used to structurally connect the apartments. The variation between apartments on the same floor was therefore evaluated using the Root Mean Square Error, resulting in a standard deviation of 0,9 dB and 1,4 dB for the airborne and impact sound insulation, respectively. The measurement variance was subtracted from the total variance. The remaining, unexplainable, variation of 0,8 dB in airborne sound insulation can be attributed to workmanship.

Transverse vibration of a multiple-Timoshenko beam system with intermediate elastic connections due to a moving load

Based on Timoshenko beam theory, the dynamic response of an elastically connected multiple-beam system is investigated. The identical prismatic beams are assumed to be parallel and connected by a finite number of springs. Assuming n parallel Timoshenko beams, the motion of the system is described by a coupled set of 2n partial differential equations. The method involves a change of variables and modal analysis to decouple and to solve the governing differential equations, respectively. A case study is solved in detail to demonstrate the methodology and several plots of the midpoint deflections of beams are given and investigated for different values of moving load velocity and the stiffness of elastic connections. From the numerical results it is observed that the maximum deflection of the multiple Timoshenko beam system is always smaller than one of a single beam.

Shape and Flexibility in the Titin 11-Domain Super-Repeat

Titin is a giant protein of striated muscle with important roles in the assembly, intracellular signalling and passive mechanical properties of sarcomeres. The molecule consists principally of ∼ 300 immunoglobulin and fibronectin domains arranged in a chain more than 1 μm long. The isoform-dependent N-terminal part of the molecule forms an elastic connection between the end of the thick filament and the Z-line. The larger, constitutively expressed C-terminal part is bound to the thick filament. Through most of the thick filament part, the immunoglobulin and fibronectin domains are arranged in a repeating pattern of 11 domains termed the ‘large super-repeat’. There are 11 contiguous copies of the large super-repeat making up a segment of the molecule nearly 0.5 μm long. We have studied a set of two-domain and three-domain recombinant fragments from the large super-repeat region by electron microscopy, synchrotron X-ray solution scattering and analytical ultracentrifugation, with the goal of reconstructing the overall structure of this part of titin. The data illustrate different average conformations in different domain pairs, which correlate with differences in interdomain linker lengths. They also illustrate interdomain bending and flexibility around average conformations. Overall, the data favour a helical conformation in the super-repeat. They also suggest that this region of titin is dimerised when bound to the thick filament.