Type Of Energy Dissipation Research Articles

Reduction of a fan vibration activity in a life support system of oil and gas stations

Relevance. Electromechanical fans are widely used in life support systems of oil and gas stations, operate in conditions of vibration, high rotational speeds and loads. Design, technological and operational reasons influence vibration activity of an electromechanical device. The greatest "contribution" to the existing vibrations, according to the frequency spectrum, is made by the imperfection of the design elements of the ball bearing. They are: separator movement, variable stiffness under the action of radial load, interaction of micro-dimensions of working surfaces, facet and waviness of working surfaces of rings and balls. In addition, the resulting vibrations negatively affect both the reliability and durability of the fan. Since it is technically impossible to completely eliminate the vibration activity of an electromechanical device, it is advisable to reduce it with the help of a technical solution by introducing a damping element into a kinematic circuit of the vibration source. In this regard, the development of a damping device is an integral technical task that helps to reduce the vibration activity of technical life support systems of oil and gas stations, as well as to improve the quality of environmental conditions of human life. To reduce vibration activity, a damper design is proposed that takes into account various types of energy dissipation. However, given the dense spectrum of vibration frequencies from ball bearings, a viscous friction element is introduced into the damper design. To determine the effectiveness of reducing vibration activity, a model of the damper in question was made based on the developed 3D model. For tests in determining the effectiveness of applying a viscous friction element, two variants of the damper design were used. In the first version of the damper design, there was no viscous friction element, and in the second version there was one. According to the test results of the damper layouts, it can be seen that the developed technical solution to reduce the vibration activity of the electromechanical device has practical confirmation. The studies underlying the developed design of the damper with a viscous friction element allows for reduction in the vibration amplitude. Object. Electromechanical device in operating mode. Aim. To describe the vibration activity in the operating mode of an electromechanical device in the entire spectrum of disturbing effects acting along the axes, taking into account the imperfect geometry of ball bearing parts; to develop a damper for reducing the vibration activity level in the electromechanical device. Methods. Vibration diagnostics, computational mathematics, measuring instruments, software "Vibration recorder-F", "Vibration Recorder-M2", "Logger"-recorder and "Bearing". Results. The paper demonstrated the effectiveness of the proposed technical solution to reduce the vibration amplitude in the operating frequency range of the electromechanical device rotor up to 4 times compared with the corresponding maximum amplitude value without its use.

Characterization and Simulation of Nanoscale Catastrophic Failure of Metal/Ceramic Interfaces.

The catastrophic failure of metal/ceramic interfaces is a complex process involving the energy transfer between accumulated elastic strain energy and many types of energy dissipation. To quantify the contribution of bulk and interface cohesive energy to the interface cleavage fracture without global plastic deformation, we characterized the quasi-static fracture process of both coherent and semi-coherent fcc-metal/MgO(001) interface systems using a spring series model and molecular static simulations. Our results show that the theoretical catastrophe point and spring-back length by the spring series model are basically consistent with the simulation results of the coherent interface systems. For defect interfaces with misfit dislocations, atomistic simulations revealed an obvious interface weakening effect in terms of reduced tensile strength and work of adhesion. As the model thickness increases, the tensile failure behaviors show significant scale effects-thick models tend to catastrophic failure with abrupt stress drop and obvious spring-back phenomenon. This work provides insight into the origin of catastrophic failure at metal/ceramic interfaces, which highlights a pathway by combining the material and structure design to improve the reliability of layered metal-ceramic composites.

Comparative study of buckling restrained braces and fluid viscous damper applied in an RCC structure following pushover analysis

Energy dissipators are widely used to enhance structural performance against wind and seismic activities. Since India is an earthquake-prone country, displacement-dependent (an example: buckling restrained bracing), and velocity-dependent (an example: fluid viscous damper) both types of energy dissipators are becoming more well-known and widely used to lessen the effects of seismic occurrences. Although most of the study about the application and performance evaluation of energy dissipators like buckling restrained braces (BRB) and fluid viscous damper (FVD) were based on steel and composite structure, reinforced cement concrete (RCC) building makes up the majority of structures in India, and a large number of RCC building structure are not capable to resist damage due to seismic activity. Additionally, nonlinear static analysis-based comparative information concerning BRB and FVD is very few. This study focused on a comparison of two energy dissipators- a) buckling restrained bracing (BRB) and b) fluid viscous damper (FVD) used in an RCC structure following pushover analysis to produce a pushover curve and evaluate structural performance. Four Ground floor + 14 (G + 14) storey RCC structures were created according to Indian Standard (IS) provisions in Extended Three-Dimensional Analysis of Building System (ETABS) software and applied BRB and FVD separately in diagonal and inverted V shapes. To compare structural responses with BRB and FVD independently, the results of the diagonal and inverted V systems have been explored. All the data were acquired by utilizing response spectrum sources developed under IS 1893:2016 following ASCE 41–13 NSP graphical display for static pushover curve in ETABS. It has been determined that the sample BRB has performed more admirably than FVD in both circumstances while using a diagonal and inverted V bracing system. But in large displacement FVD tends to increase performance. BRB is stiffer than FVD, allowing it to be used to raise the structure's stiffness as needed. It is essential to consider the seismic weight of BRB and FVD while designing a new building or retrofitting and restoring a structure.

Design Method of Core-Separated Assembled Buckling Restrained Braces Confined by Two Lightweight Concrete-Infilled Tubes

This paper introduces a novel type of buckling restrained braces (BRBs) called core-separated assembled BRBs (CSA-BRBs). These braces are comprised of two single BRBs that are confined by lightweight concrete-infilled tubes, which are longitudinally connected by two continuous webs. The CSA-BRBs utilize materials more efficiently by increasing the height of the webs to create a large inner cavity, leading to an economical design. This paper predicts the threshold of the restraint ratio of CSA-BRBs approximately. This is achieved by assuming that the maximum moment resulting from applied loads at mid-height is less than the moment-bearing resistance that is conducted according to the outermost fiber of the external restraining section reading yielding. Elastic-plastic numerical analysis is conducted using FEM with beam elements for CSA-BRBs that are subjected to both monotonic and cyclic axial loads. The load resistance, hysteretic performance, and failure mechanism of CSA-BRBs are investigated by varying their restraining ratios. It is recommended that the restraint ratio threshold of CSA-BRBs under monotonic axial compression is used as a bearing type and the restraint ratio threshold of CSA-BRBs under axially compressive-tensile cyclic loads as an energy-dissipation type. This method provides a complete design for CSA-BRBs.

Efficiency of energy dissipators in the seismic response of buildings

This paper aims to study the efficiency of energy dissipators, both fluid viscous and hysteretic, to improve the seismic responses of buildings. To quantify the ability of energy dissipators to reduce seismic responses, a series of time history analyzes were carried out on simplified models of buildings. Said simplified models consist of masses and springs with linear and elastic behavior whose properties are obtained from a shear beam model, joined by link elements with non-linear behavior to simulate energy dissipators. The main study parameters that were considered are the fundamental period of the structure without seismic control devices and the objective reduction factor. Likewise, a procedure is proposed for the dimensioning of the hysteretic dampers that will be incorporated into a building. On the other hand, the main building of the Lima airport was used as a case study, for which two alternatives are proposed, each one with a different type of energy dissipator, but both designed to have similar performance. Finally, the reductions obtained by both the simplified models and three-dimensional models are compared. It is concluded that the simplified models allow a fast and acceptable prediction of the levels of reduction of the seismic response in buildings that incorporate energy dissipators.

Spontaneous Collapse Mechanism of World Trade Center Twin Towers and Progressive Collapse in General

The collapse of the World Trade Center (WTC) Towers during the terrorist attacks on September 11, 2001, remains one of the most tragic catastrophes in the field of structural engineering. This paper first reviews a mathematical model that explains the process of the total collapse of the Twin Towers and shows that the downward collapse progression below the impacted floors was spontaneous. The model is based on a continuum description of the motion of the crush front and captures various types of energy dissipation during the collapse. The predictions of this model match all the observations, including the video records of the first few seconds of motion of both towers, the seismic records of the collapse durations for both towers, the mass and size distributions of comminuted concrete particles, and the fast expansion of dust clouds during collapse with the booms generated. This catastrophe provoked general interest in other types of progressive collapse of buildings. This is the subject of the second part of this paper, in which a three-dimensional stochastic computational model for the collapse of RC frame buildings is presented. The occurrence probabilities of different collapse patterns are predicted. The model is further extended to investigate the delayed collapse behavior of RC frames. The results of the analysis shed light on the emerging trend of probabilistic analysis and design of structures against progressive collapse.

Optimal Location of Energy Dissipation Box in Long Distance and High Drop Gravitational Water Supply System

In the long-distance and high-drop gravitational water supply systems, the water level difference between the upstream and downstream is large. Thus, it is necessary to ensure energy dissipation and pressure head reduction to reduce the pipeline pressure head. The energy dissipation box is a new type of energy dissipation and pressure head reduction device, which is widely used in the gravitational flow transition systems. At present, there is still a dearth of systematic knowledge about the performance of energy dissipation boxes. In this paper, a relationship between the location of the energy dissipation box and the pressure head amplitude is established, a theoretical optimal location equation of the energy dissipation box is derived, and numerical simulations using an engineering example are carried out for verification. The protective effects of an energy dissipation box placed at the theoretical optimal location and an upstream location are compared. The results indicate that for the same valve action time, the optimal position allows effectively reducing the total volume of energy dissipation box. The oscillation amplitudes of the water level in the box and the pressure head behind the box are markedly reduced. Under the condition that the water level oscillation of the energy dissipation box is almost the same, the optimal location offers better pressure head reduction protection performance than the upstream location.

Material-based models for post-tensioned shear wall system with energy dissipators

The Prestressed-Laminated timber system, Pres-Lam, developed in New Zealand, is a low damage innovative wood-hybrid system that utilizes post-tensioned (PT) mass timber components along with various types of energy dissipators. In addition to testing, numerical modelling is another important approach used to investigate the structural performance of Pres-Lam system. In this study, a material-based modelling method was proposed to investigate the seismic performance of Pres-Lam cross-laminated timber (CLT) wall system. Correspondingly, specific material-based numerical models were developed for PT-only and Pres-Lam CLT walls in general purpose finite element software package, ABAQUS. Only the material and geometrical properties of panels, connections and energy dissipators are required as inputs for the material-based models. These models are different from other current simplified numerical models by the fact that they can eliminate the time- and resource-consuming wall tests for the models’ calibration, and also can predict the structural performance of the Pres-Lam CLT wall system to complete failure which is challenging to obtain by testing. The response of the developed models agreed well with the experimental results of all tested wall configurations. The influence of PT force level, aspect ratio of the wall panel, and spacing and number of energy dissipating devices on the response of the system was investigated using the developed models. The material-based models provide structural engineers and researchers with a cost-effective method for the analysis and design of the Pres-Lam CLT shear walls. The analysis results will form the basis for developing future design guidelines for PT-only and Pres-Lam mass timber systems under in-plane lateral loads.

The Damping Effect on Critical Values of Nonconservative Loads

A systematic study of the effect of energy dissipation on critical nonconservative loads within the stability calculation is carried out. Some classical nonconservative elastic stability problems are considered: the stability of a linear form of equilibrium of a double pendulum under the action of a follower force, the stability of a cantilever beam compressed by a follower force (Beck’s problem), and the stability of a flat panel in a supersonic gas flow. The dependences of critical loads on the damping parameters are built, and the conditions of mechanical system stabilization and destabilization are determined for the cases when damping coefficients vary over a wide range and for various ratios. The external and internal frictions (according to the Voigt model) are considered for the distributed parameter systems. Conclusions about the effect of various types of energy dissipation on the critical values of nonconservative load parameters and about the conditions of nonconservative system destabilization due to the energy dissipation are formulated.

Roughened bed stilling basin and its hydraulic jump characteristics

The roughened-bed stilling basin, serving as one new type of energy dissipator, has been analyzed both theoretically and experimentally in the literature. This study deduces the calculation formula of the length of the curve C0 between the flow-depth contraction section (i.e. hc) and the section just before the hydraulic jump (i.e. h1) when the same elevation is employed for both the bottom of roughened-bed stilling basin and the river-bed surface in the downstream. Further, by approximately assuming the equation of the resistance force exerted on the flow and caused by the bed roughness, this study obtains the expression of the ratio between the flow depth before the hydraulic jump and that behind the hydraulic jump, namely h1/h2. With the aid of the experimental results in the existing literature, it can be concluded that, when compared with the traditional smooth-bed hydraulic jump, the sequent depth and the length of the rolling hydraulic jump can be reduced by about 20∼30% and 20∼50%, respectively, in the condition of the chopping roughness riverbed. Additionally, by combining with the hydraulic model tests, this study indicates that adding the bed-roughness can eliminate the secondary hydraulic jump, improve the flow regime and (under the circumstance of the sill-roughness stilling basin) decrease the length of the stilling basin up to about 40%∼50%. Keywords: Stilling Basin; Hydraulic Jump; Hydraulic Characteristics; Roughened Bed; Sequent Depth; Energy Dissipation

Theoretical and experimental studies of battened buckling-restrained braces

A new type of core-separated buckling-restrained braces, namely a core-separated battened buckling-restrained brace (B-BRB) has been proposed. Its load-carrying capacity and hysteretic response are investigated theoretically and experimentally in this paper. The B-BRB has a remarkable advantage over a common buckling-restrained brace (BRB), in which the newly formed cross-section of the B-BRB is spread outwards by spacing two cores, hence resulting in higher material utilization efficiency in its structural design. In addition, the two independent all-steel BRBs, each having a single plate core simply in-filled in a narrow hollow section, are connected by longitudinally distributed battens rather than continuous plates. Based on the elastic-plastic FE analysis of a B-BRB under monotonic compressive load, its ultimate resistance and failure modes are investigated numerically, considering the effect of its overall initial geometric imperfection. An interaction formula between normalized slenderness ratio and buckling factor of the B-BRB is proposed for predicting its ultimate load-carrying capacity. Consequently, the hysteretic response of the B-BRB is explored through elastic-plastic FE analysis. The maximum normalized slenderness ratios of the B-BRBs required for a load-bearing type and an energy-dissipation type are proposed in their strength designs, respectively. Ultimately, hysteretic responses of five B-BRB specimens have been experimentally investigated. The experimental results are compared with the FE numerical analysis, which considers plate local buckling of all components of the B-BRBs. The comparison has verified the rationality of the proposed design method.

Study on Hydraulic Characteristic of Submerged Jet with Depression Angle Dived into Plunge Pool from the Underwater Surface

Experiment research on submerged jet with depression angle dived into plunge pool from near-surface was carried out. The results showed that this type of energy dissipation type has good effect in improving the energy dissipation rate, reducing the surface fluctuation and reducing near-bed velocity and so on. Calculation formulas of conjugate depth and energy dissipation were obtained through theory analysis of submerged hydraulic jump in water cushion. Formula analysis showed that for high Froude number flow at a certain downstream depth, to obtain stable submerge hydraulic jump through adjusting size of jet exit, by decreasing its width is better way than by increasing height. When flow Froude number is larger sudden expansion ratio is more sensitive to energy dissipation, therefor to improving effect of energy dissipation by decreasing jet exit’s width or increasing plunge pool’s width can be used.

Local ground effects in near-field and far-field areas on seismically protected buildings

This paper presents a 2-D numerical study on the nonlinear seismic response of buildings equipped with two types of energy dissipators, which dissipate energy activating two different mechanisms. Three types of reinforced concrete buildings with 3, 7 and 15 stories, respectively representative of short, medium and long period ranges, are considered. Dissipators are placed on steel diagonal braces at all the floors; their sliding threshold (or yielding) forces are taken as 100% of those generated by the equivalent static lateral forces recommended by EC8 for a ductile moment resisting frame. The input consists of six recorded earthquakes, 3 representatives of near-field earthquakes and 3 representatives of far-field earthquakes. Each input is considered once from the bedrock and once filtered by a common ground with several layers of different thicknesses. The responses of the buildings are discussed and compared emphasizing the filtering effects produced by the ground.

Anelastic acoustic impedance and the correspondence principle

A general definition of seismic wave impedance is proposed as a matrix differential operator transforming the displacement boundary conditions into traction ones. This impedance is proportional to the standard acoustic impedance at all incidence angles and allows extensions to attenuative media and to the full elastic case. In all cases, reflection amplitudes at the contact of two media are uniquely described by the ratios of their impedances. Here, the anelastic acoustic impedance is studied in detail and attenuation contrasts are shown to produce phase-shifted reflections. Notably, the correspondence principle (i.e., the approach based on complex-valued elastic modules in the frequency domain) leads to incorrect phase shifts of the impedance due to attenuation and consequently to wrong waveforms reflected from attenuation contrasts. Boundary conditions and the Lagrange formulation of elastodynamics suggest that elastic constants should remain real in the presence of attenuation and the various types of energy dissipation should be described by their specific mechanisms. The correspondence principle and complex-valued elastic moduli appear to be applicable only to homogeneous media and therefore they should be used with caution when applied to heterogeneous cases.

HYDRAULIC MODEL STUDIES FOR TUNNEL SPILLWAY AND ENERGY DISSIPATOR OF PARBATI H.E. PROJECT, STAGE-III, HIMACHAL PRADESH

ABSTRACT Hydraulic design of tunnel spillway is complex and site specific. The diversion structures in the form of upstream and downstream cofferdams and diversion tunnels/channels are needed to divert the river during construction stage. Once the construction is over, these tunnels can be plugged or utilized for various purposes such as power tunnels, silt flushing tunnels, irrigation outlets and spillway tunnel. Various parameters such as approach flow conditions, depth of submergence, inlet and outlet shape, length and slope etc. are considered in design of tunnel spillway. Type of energy dissipator to be provided at the outlet mainly depends on site conditions, orientation of river course with respect to alignment of the tunnels, depth and velocity at the exit portal and tail water level in the river. This paper describes the hydraulic model studies conducted for tunnel spillway of Parbati H.E. Project, stage-Ill, Himachal Pradesh.

Thresholds in small rivers? Hypotheses developed from fluvial morphological research in western Germany

The objective of this study was the formulation of fluvial morphological regularities for small rivers with a wide range of morphological and geological characteristics in North-Rhine-Westphalia (Germany) based on a statistical research methodology. Such empirical quantitative information on reference conditions is required for the restoration of small rivers in the former highly industrialised Ruhr-Area. Following the approach of some classic empirical works in fluvial morphology of the last century, several natural reference rivers in the entire research area have been observed in order to provide a statistical correlation between independent and dependent morphological variables. Regressions between valley-floor slope, bankfull discharge and stream power on the one hand and several variables describing the longitudinal profile and river planform on the other hand have shown some significant results. The regularities found are a quantitative contribution to the establishment of reference conditions as well as a useful tool for the restoration of small rivers, if the specific properties and values of the underlying random sampling are taken into account. In addition, the relation between stream power and sinuosity shows the likely existence of a threshold: Exceeding a stream power of 100 W/m, the sinuosity decreases after an increase for lower stream power values. Comparable thresholds were found for the relation between stream power and pool depth as well as stream power and step steepness. The thresholds could be explained by a change in the type of energy dissipation, due to different physio-geographical settings in highland rivers within forested v-shaped valleys. Here, large-woody debris seems to increase the channel roughness and possibly replaces the significance of coarse-grained bed material, pool depth and step steepness as contributors to energy dissipation.

Decoupling of viscous dissipation and damage dissipation in particulate-reinforced polymeric materials

Under the assumption of small deformation, the dissipation of energy in particle-filled polymeric materials can be roughly divided into viscous dissipation and damage dissipation. Decoupling of these two types of energy dissipation is important in order to design the particle size and the weight ratio of particles to the matrix that the particles are filled in the particle-filled polymeric composite materials. This paper presents a study on the calculations of dissipation energy and the investigation of the influence of the average strain of matrix, interfacial adhesive energy, particle size dispersion, initial volume fraction of particles, average radius of particles and relaxation time of matrix on both the viscosity dissipation energy and damage dissipation energy.

Alvin Peterka—Hydraulic Engineer

An energy dissipator is a hydraulic structure used to convert hydraulic energy mainly into heat. These dissipators have a relatively short history because they were developed only after damage had occurred at the toe of overflow structures. The German Theodor Rehbock ~1864–1950! conducted the first detailed research into these structures, although hydraulic jumps had received attention as early as the 1820s by the Italian Giorgio Bidone ~1781–1839! by imposing constant energy head across the hydraulic jump. In 1838, Jean-Baptiste Belanger ~1790–1874! correctly applied the momentum equation for the prediction of sequent depths, and Henry Bazin ~1829–1917! verified this concept with limited observations. Nothing much happened until around 1910–1920 when Arnold Gibson ~1878–1959!, the successor of Osborne Reynolds at Manchester University, presented experiments that corroborated the predictions of Belanger. That concept obtained final acceptance by the 1916 paper of the American Karl R. Kennison ~1886–1977!, whose closure verified data of various sources ~Hager 1990!. At about the same time, Rehbock proposed his ‘‘dentated sill.’’ It was later realized that this device mainly deflects remaining bottom currents to the free surface and thus inhibits scour downstream of the end of the stilling basin. The development of stilling basins was then continued mainly by the Austrian Armin Schoklitsch ~1888–1969! with his two books ~Schoklitsch 1930, 1935! and by Hunter Rouse ~1906–1996! from the conceptual side by introducing the Froude number as the significant parameter for all quantities of that phenomenon ~Rouse 1934!. In 1933, the International Commission of Large Dams ICOLD was founded with exponents such as Andre Coyne ~1891–1960!, who in the late 1930s proposed the ski jump type dissipator as an alternative to the conventional hydraulic jump dissipators. The latter continued to be a standard design mainly for relatively small velocities up to a maximum of about 20 m/s and inflow Froude numbers essentially between three and six. A number of elements had been proposed to reduce the length of the stilling basin but without a definite consideration of the various pros and cons. By the end of World War II, hundreds of different types of energy dissipators were available, partly developed for particular site conditions and partly presented as an engineer’s design from the office table. What was definitely missing was a thorough scientific consideration of energy dissipators under a wide variety of flow conditions and proposals relating to engineering applications. Here, Peterka has contributed significantly and was even able to come up with a series of standard designs to be applied under well-defined flow conditions without the need for additional observations. The engineering community thus derived a great benefit from his services. For completeness, the contributions to that subject by Fred W. Blaisdell ~1911–1998!, of the Saint Anthony Falls Hydraulic Laboratory should also be mentioned.

Performance Comparison of Passive Energy Dissipation Systems in Structural Applications – I: Linear Reference System

In this paper, an analysis is presented for the performance comparison of representative passive energy dissipation systems which have been developed and implemented in structures in recent years. They include viscous fluid dampers, viscoelastic solid dampers, metallic dampers, friction dampers, tuned mass dampers and tuned liquid dampers. A single-degree-of-freedom linear structural system is used as a standard reference system where ground excitations are simulated either as a white noise or a filtered white noise. The performance criteria are first established, followed by the formulation of computational models for each of the energy dissipators considered. For those exhibiting inherent nonlinear behavior, statistically equivalent linearized models are used for analyzing their modified dynamical properties, such as additional mass, stiffness and damping coefficients due to addition of the energy dissipators to the reference system. Finally, representative numerical models of the above six types of energy dissipators are used to make quantitative comparisons of their performances when added to the reference system by calculating their equivalent additional dynamical properties and their effectiveness in alleviating key response quantities of the system.

Numerical efficiency assessment of energy dissipators for seismic protection of buildings

SUMMARY This paper presents a two-dimensional numerical study on the nonlinear seismic response of buildings equipped with two types of energy dissipators: Constant Friction Slip Braces (CFSB) and Adding Damping and Sti⁄ness (ADAS). Three types of reinforced concrete buildings with 3, 7 and 15 storeys, representatives of the short-medium- and long-period ranges, are considered. Dissipators are placed in steel diagonal braces in all the floors. The sliding threshold (or yielding) forces for each mechanism are selected using two di⁄erent criteria: (i) they are taken as 50, 75 and 100 per cent of those generated by the equivalent static lateral forces recommended by the UBC-91 for a ductile moment resisting frame and (ii) they are constant in the whole building (this constant value is chosen equal to the maximum forces obtained with the previous criterion). The input consists of ten recorded earthquakes (normalized with respect to their Housner intensity) corresponding to medium and sti⁄ local soil conditions. Average values on the ten registers are given for the maximum horizontal displacement, the base shear, the energy dissipated and the interstorey drift. The possibility of failure in some devices has been numerically simulated to assess the robustness of the system. The obtained results show that both devices are useful to reduce the response compared to the bare frame and that CFSB is more eƒcient than ADAS; for 7and 15-storey frames the lateral displacement with CFSB is even smaller than the one for the braced frame (rigid connections instead of dissipators). The conclusions are expected to provide simple design guidelines. ( 1998 John Wiley & Sons, Ltd.