Energy Dissipation Coefficient Research Articles

Predicting landslide sliding distance based on energy dissipation and mass point kinematics

Based on classical mechanics and the law of energy conservation, we present a model for predicting landslide sliding distance. We conceptualize landslide movement as the movement of a mass point and divide the sliding surface into two sections—an upper sliding surface where the slip is accelerating, and a lower section where deceleration occurs. Energy dissipation and landslide deformation during the sliding process are also considered as we constructed a coefficient of energy dissipation η and a factor of length ratio. Furthermore, different types of landslides which correspond to the energy dissipation coefficient η and L ratio are explored. The established sliding distance prediction model is verified using two cases—the Chonghetang landslide and the Zaoshugou #2 landslide, both in Lanzhou, China. The sliding surface parameters are derived using Bishop’s method. The predicted landslide distances are quite close to the field measurements (error levels are 1.9% for the Chonghetang landslide and − 6.6% for the Zaoshugou #2 landslide). We conclude that our model provides an easy and widely applicable method for predicting loess landslide sliding distance.

Size effect on seismic performance of high-strength reinforced concrete columns subjected to monotonic and cyclic loading

It has been shown that as concrete strength increases, the size effect becomes more pronounced in both samples and members. However, the effect of section size on the seismic performance of high-strength reinforced concrete columns requires further confirmation. For this purpose, six high-strength reinforced concrete columns were subjected to monotonic and cyclic loading in this study. The experimental results indicate that the relative nominal flexural strength, average energy dissipation coefficient, factor of safety, and local factor of safety all exhibited a strong size effect by decreasing as the column size increased. Moreover, the size effect on the factor of safety was stronger for high-strength columns than for conventional columns. The observed changes in the factor of safety were in good agreement with the Type 2 size effect model proposed by Bažant; so, using the local factor of safety and Bažant’s Type 2 model, the code equation for moment capacity was modified to provide a constant factor of safety regardless of column size.

Performance of the Cold‐Bending Channel‐Angle Buckling‐Restrained Brace under Cyclic Loading

In this study, three restricted cold‐bending channel‐angle buckling‐restrained brace (CCA‐BRB) specimens were experimentally characterised by a low‐reversed cyclic loading test. Three specimens had steel cores with cruciform cross section. Two restraining units were assembled to form an external constraint member, each of which was composed of an equilateral cold‐bending channel and two equilateral cold‐bending angles via welding. A gap or a thin silica gel plate was set between the internal core and the external constraint member to form an unbonded layer. Several evaluation parameters on the seismic performance, hysteretic behaviour, and energy dissipation capability of the CCA‐BRB was investigated, including hysteresis curve, skeleton curve, compression strength adjustment factor, measured and computed stiffness, energy dissipation coefficient, equivalent viscous damping ratio, ductility coefficient, and cumulative plastic deformation. The test results and evaluation indices demonstrated that the hysteretic performance of braces with a rigid connection was stable. A Ramberg–Osgood model and two model parameters were calibrated to predict, with fidelity, the skeleton curve of CCA‐BRB under cyclic load. The initial elastic stiffness of the brace used in practice should contain overall portions of the brace instead of the yielding portion of the brace. Finally, all the tested CCA‐BRBs exhibited a stable energy absorption performance and verified the specimens’ construction was rational.

Study on the Damping Effect of Particle Dampers considering Different Surface Properties

Particle dampers are nonlinear vibration control devices. The surface property has a great influence on the performance of the particle damper, but it is difficult to be considered and analyzed. This paper firstly gives a view of how to establish a theoretic model of the particle damper. The dynamic equation and energy dissipation coefficient of collision are revised from the Hertz contact theory in the proposed theoretic model, considering the friction of particles. Then, a contrastive collision model relying on the finite element method is established to verify the reasonability of the theoretic model. The effects of different factors which will have an influence on the performance of the particle damper are discussed, and several conclusions on how to optimize the particle damper are proposed. Except for the aforementioned dynamic analysis, this paper also presents a particle damping index to evaluate the capability of energy dissipation of different materials, in order to facilitate the material selection in the practical design. Finally, an experiment is developed to verify the character of the collision and energy dissipation. The feasibility of the proposed method to estimate the surface property of different particles is validated by the free vibration experiment.

Effect of Structure Parameters on Polycal Wire Rope Isolator Stiffness‐Damping Characteristics

Wire rope isolators are mainly used to isolate vibration and protect precise equipment. However, the issue of regulation of vibration isolators taking into account the nonlinearity of their characteristics was poorly understood in the modern literature. In this paper, the influence of structural parameters (diameter ratio and lay pitch of the single strand, and lay pitch and bending radius of the wire rope) on stiffness‐damping characteristics of the Polycal WRI was investigated by the simplified finite element analysis method. The stiffness and damping prediction models including structural parameters and material properties were established. The results showed that the stiffness‐damping characteristics were the best; when the diameter ratio of wire strand was 1.1, the inside layer wire pitch length was 6 times the diameter of the wire strand, the outside layer wire pitch length was 11 times the diameter of the wire strand, the pitch length of the wire rope was 7.5 times its diameter, and the bending radius was equal to 46.5 mm. The errors of the prediction for prestiffness and softened stiffness were within 5%, and the errors of prediction for the energy dissipation coefficient were within 10%.

Seismic Performance of Full‐Scale Joints Composed by Concrete‐Filled Steel Tube Column and Reinforced Concrete Beam with Steel Plate‐Stud Connections

A concrete‐filled steel tube (CFST) column has the advantages of high bearing capacity, high stiffness, and good ductility, while reinforced concrete (RC) structure systems are familiar to engineers. The combinational usage of CFST and RC components is playing an important role in contemporary projects. However, existing CFST column‐RC beam joints are either too complex or have insufficient stiffness at the interface, so their practical engineering application has been limited. In this study, the results of a practical engineering project were used to develop two kinds of CFST column‐RC beam joints that are connected by vertical or U‐shaped steel plates and studs. The seismic performance of full‐scale column‐beam joints with a shear span ratio of 4 was examined when they were subjected to a low‐cyclic reversed loading test. The results showed a plump load‐displacement curve for the CFST column‐RC beam joint connected by steel plates and studs, and the connection performance satisfied the building code. The beam showed a bending failure mode similar to that of traditional RC joints. The failure area was mainly concentrated outside the steel plate, and the plastic hinge moved outward from the ends of the beam. When the calculated cross section was set at the ends of the beam, the bending capacity of joints with the vertical or U‐shaped steel plates and studs increased compared to the RC joint. However, when the calculated cross section was set to the failure area, the capacity was similar to that of the RC joint. The proposed joints showed increases in the energy dissipation, average energy dissipation coefficient, and ductility coefficient compared to the RC joint.

Stiffness test in lateral direction of temporary wooden building supports

Temporary supports consisting of a jack, a stack of wooden cubic elements and a iron plate are used during the removal of buildings deflections by uneven raising. Where the weight of a building is rested on temporary supports with a considerable length, unintentional displacements of buildings in the horizontal direction are seen. The displacements are connected with supports deformations caused by horizontal forces acting on the building part being raised. Non-vertically installed jacks, being part of the supports, are the most frequent reason for the occurrence of such forces. The jacks are not vertical due to deformations in the stack of wooden elements, upon which they are rested. In such case, the stiffness of temporary supports is essential for the safety of the deflection removal process. Laboratory tests of temporary supports were carried out and they showed that their stiffness, understood as a horizontal force divided by a displacement in the acting direction of the force, is not constant. The stiffness of supports is decreasing as the displacement amplitude grows. A considerable decrease in supports stiffness was experienced when positive longitudinal deformations occurred in the cross section of the support elements. As a result, the unconnected elements of the supports were unable to transmit positive stresses of this number. For the investigated range of loads, the deformations of the material of the supports elements were elastic. Inelastic forces were however generated along the contact points of the elements forming part of the supports, and such forces were responsible for creating a hysteresis loop and energy dissipation by the supports. The system, when a full load-unload cycle was applied, was returning to the initial position. Higher values of the energy dissipation coefficient correspond to higher values of a displacement amplitude.

Size Effect on the Seismic Performance of High-Strength Reinforced Concrete Columns with Different Shear Span-to-Depth Ratios

The size effect on the seismic performance of conventional reinforced concrete columns has been observed in terms of flexural failure and shear failure. Under earthquake loading, slender columns experience flexural failure, and short columns experience flexure-shear failure and shear failure. However, the effect of section size on the seismic performance of high-strength reinforced concrete columns under the conditions of different shear span-to-depth ratios requires further confirmation. For this purpose, six high-strength reinforced concrete columns with shear span-to-depth ratios of 2 and 4 were subjected to cyclic loading in this study. The experimental results indicated that relative nominal flexural strength, energy dissipation coefficient, factor of safety, and local factor of safety all exhibited a strong size effect by decreasing with increasing column size. Furthermore, the size effect became stronger as the shear span-to-depth ratio was increased, except for average energy dissipation coefficient. The observed changes in the factor of safety were in good agreement with the Type 2 size effect model proposed by Bažant. Thus, based on the local factor of safety and Bažant’s Type 2 model, the code equation for moment capacity of different shear span-to-depth ratios was modified to provide a consistent factor of safety regardless of column size.

Numerical investigation of slip and fracture instability mechanism of coal- rock parting-coal structure (CRCS)

Based on theoretical analysis and numerical simulations, the factors that influence the slip and fracture instability of coal-rock parting -coal structure (CRCS) were investigated. Stress, coefficient of friction and energy dissipation during slip and fracture instability were analysed individually. The macro- and microscopic mechanical behaviours, especially acoustic emission (AE) characteristics, were determined. According to the variations in stress, energy and b-value of AE events, the precursors of CRCS slip and fracture instability were summarized. Finally, the instability mechanism was proposed. This work is relevant for early warning coal-rock dynamic disasters that are triggered by slip and fracture instability of CRCS in coal mines.

Response of UHPFRC Columns Submitted to Combined Axial and Alternate Flexural Loads

This paper deals with the experimental determination of ductility of ultra-high-performance fiber-reinforced concrete (UHPFRC) columns with longitudinal passive reinforcement, tested under combined axial and alternate flexural load. The influence of axial load has been studied, as well as the presence or not of a reduced shear reinforcement. One companion column made of ordinary concrete and with a high shear reinforcement ratio has also been tested for comparison. The ductility has been assessed with energy dissipation and ductility coefficient calculations. In addition, the maximum bending moment has been compared with theoretical calculation, using the material characteristics determined from characterization tests. The paper concludes that UHPFRC columns with a longitudinal reinforcement which have not been specifically designed for seismic resistance do display a ductility coefficient higher than 2 and a noticeable ability to protect the rebars from buckling, but have a rather high decrease of bending moment under the succession of series of alternate flexural load cycles.

Experimental and numerical study of the seismic performance of an all-steel assembled Q195 low-yield buckling-restrained brace

A new type of buckling-restrained brace (BRB), namely, an all-steel assembled Q195 low-yield-point buckling-restrained brace (LYBRB), is proposed in this paper. The difference between the LYBRB and a traditional BRB is that Q195 low-yield point steel with an in-line cross-section (which can better absorb seismic energy) of the core material is adopted. A Q235 steel core is used for the comparative analysis. Additionally, to prevent residual stress, water cutting is performed to cut the core plate. A quasi-static low-cycle reciprocating load test is conducted to determine its failure mode, hysteretic response and restoring force model. The seismic behavior of the LYBRB is evaluated according to the following performance indices: the hysteresis curve, skeleton curve, tension and compression nonuniform coefficient, energy dissipation coefficient, equivalent viscous damping ratio, plastic deformation performance, and in-plane and out-of-plane lateral displacements of the external restraining plate of the LYBRB. The failure mode of the LYBRB is tension-controlled; its hysteresis curve shows good symmetry, stability and fullness; and its energy dissipation capacity support is better. Combined with the restoring force model obtained via an experiment, the bilinear kinematic hardening model is adopted to conduct finite element (FE) numerical simulation analysis of the core plate. Comparison with the test results shows that both the failure mode and the hysteretic response are in good agreement. The influence factors (such as the gap-thickness ratio between the core plate and external restraining plate, width-thickness ratio, core material properties and slenderness ratio of the core plate in the weak-axis direction for the LYBRB) are then used to carry out a parametric analysis to provide better insight into the LYBRB.

Particle swarm optimization-based LS-SVM for hydraulic performance of stepped spillway

ABSTRACT Accurate estimation of energy dissipation and discharge coeffichine (LS-SVM) to recognize the factors affecting the discharge coefficient and energy dissipation. To this end, all data was extracted from physical models and original experiments. Particle swarm optimization (PSO) was also applied to optimize the hyper-parameters of the LS-SVM model. The results indicated that the applied methods had a high capability in modeling energy dissipation and discharge coefficient of stepped spillways. Additionally, the results of sensitivity analysis of both proposed methods showed that the Fr 1 and the W/y 1 parameters had the highest and the lowest important influence in modeling of the discharge coefficient, respectively. Besides, the role of parameter was very highlighted; and also had the lowest impact on estimating energy dissipation over stepped spillways.

Nonlinear analysis of sloshing and floating body coupled motion in the time-domain

The aim of this paper is to develop a coupled nonlinear time-domain simulation scheme for nonlinear interactions among sloshing flows and floating body motion for both regular and irregular wave excitation. The contributions of a variety of nonlinear factors, outside waves and inside sloshing induced forces, as well as their influences on body coupled sway and roll motion were investigated. The induced forces are due to the changes in the transient wet surface of the floating body and full nonlinear sloshing. The effects of tank fill ratio and excitation wave height on the nonlinear coupled motion, as well as the relationship between sloshing and floating body nonlinear coupled motion under large wave amplitudes and severe sea conditions were also investigated and the results are presented. Finally, the numerical solutions are compared with existing experimental result. The fully nonlinear sloshing and floating body coupled motion are simulated based on the potential flow theory, with the transient position hydrodynamic assumption. The boundary value problem is solved by the B-spline higher-order panel method. The ISITIMFB (iterative semi-implicit time integration method for floating bodies) is applied to solve for the body's velocity and displacements. The sloshing energy dissipation is modeled by changing the boundary condition on the tank's solid boundaries. An extended principle to determine the energy dissipation coefficient for both regular and irregular cases is extracted. Then, the sloshing and floating body nonlinear coupled motion under large wave amplitudes and severe sea conditions are investigated, and the numerical solutions are compared with existing experimental results. The effects of tank fill ratio and excitation wave height on the nonlinear coupled motion is also investigated.

Surface gravity wave interaction with a submerged horizontal flexible porous plate

An analytical study for surface gravity wave interaction with submerged flexible porous plate based on small amplitude water wave theory and structural response is presented. The flexible porous plate is modeled based on the thin elastic plate theory and wave past porous plate is using generalized Darcy's law to incorporate both frictional force and inertia force. The dispersion relation is analyzed to determine the wave motion characteristics of two propagating wave modes in the presence of free surface and flexural waves at the submerged horizontal porous plate in specific cases. Further, the linearized long wave equation under shallow water approximation is derived in a direct manner and the limiting cases are compared. The integral forms of Green’s functions are derived using the fundamental solution associated with the two-dimensional Laplace equation. Using Green’s identity, the generalized expansion formulae for the wave-maker problem associated with the surface wave interaction with the submerged flexible porous plate are obtained in both the cases of finite and infinite water depths. The usefulness of the expansion formula is demonstrated by analyzing a physical problem associated with the surface gravity wave interaction with a moored finite submerged horizontal elastic porous plate in finite water depth. In the numerical results, the accuracy of the numerical computations are checked and the combined effect of mooring stiffness and porous-effect parameter are analyzed on the reflection coefficients, wave energy dissipation coefficients, and vertical forces. It is observed that the wave energy dissipation/absorption depends significantly on the mooring stiffness, porous-effect parameter, and suitable positing of the submerged plate.

Hydraulic spillways using the effect of interacting circulation currents

The paper is devoted to study of hydraulic characteristics of flow energy dissipators on hydraulic spillways. Transfer to high-head structures requires unconventional approaches to studying the phenomena associated with high-velocity flows and development of fundamentally new kinds of currents and flow energy dissipation designs forming new technological solutions in hydraulic engineering. Considered here is flow energy dissipation with the aid of counter-vortex dissipators based on interacting circulation currents. The objective of the paper consists in justification of effectiveness of operation flow energy dissipator discharged by hydraulic spillways. The analysis was based on physical modeling method. The described flow energy dissipation method based on the work of viscous friction forces allows for excess flow energy to be dissipated in a very short portion of the spillway water conveyance system. The results of the analysis made it possible to state that with counter-cortex flow the energy dissipation coefficient can be very high. It is shown that the proposed approach favorably differs from the known methods of energy dissipation. In the conclusions it is noted that: efficiency of flow energy dissipation at the counter-vortex dissipators can reach 90-98% of the operating head at a length of 6-8 diameters of the mixing chamber.

High dimensional stability and low viscous response solid propellant binder based on graphene oxide nanosheets and dual cross-linked polyurethane

This work describes the fabrication, characterization, and deformation behavior of graphene oxide (GO) filled dual cross-linked polyurethane (PU) nanocomposites serving as solid propellant binder. The composites were synthesized through attaching isophorone diisocyanate onto GO nanosheets and cross-linking the modified GO (MGO) with PU chains. This methodology leads to uniform dispersion of MGO and its strong interface adhesion with matrix. The coefficient of thermal expansion (CTE) of the composites is tuned to the value of 150 ppm/°C, and reduced by 38.8% compared to neat PU. Moreover, both coefficient of energy dissipation and residual strain are linearly reduced, and the deformation recovery capability is specifically increased. Loss tangent (tan δ) shows the low dynamic viscous behavior, suggesting strong dependence on MGO content. Besides, the composite with 1.0 wt% MGO exhibits a critical point, where the transition from solid-like to liquid-like behavior nearly disappears. This study provides an achievable and important way to prepare the high-performance polymeric composite with prominent deformation properties.

Estimation of friction coefficient for double walled permeable vertical breakwater

The present study deals with the derivation of an empirical formula for determining the friction coefficient of a double walled permeable vertical breakwater. The formulation is achieved in terms of variables representing the porosities of seaward side and shoreward side vertical walls, gap between the walls and depth of water. This formula is derived based on the results of experimental and theoretical studies carried out on a structure consisting of two vertical porous walls separated by some space. The theoretical model is developed by employing the method of eigenfunction expansion, which aids the prediction of such hydrodynamic coefficients as transmission, reflection, and energy dissipation coefficients. The values of friction coefficient are calculated by means of a best fit between the predicted and experimental values of hydrodynamic coefficients. The validity of the proposed formula is evaluated by conducting experiments and by comparing with published results. The results indicate that the proposed empirical formula can be effectively applied for the direct estimation of the friction coefficient of a double walled permeable vertical breakwater within the specified range.

Development and Analysis of the Control Effect of a Reid Damper with Self‐Centering Characteristics

To improve the recoverability of structures following an earthquake, a Reid friction damper with self‐centering characteristics is proposed and its hysteretic behavior is studied by theoretical analysis and experimental research. The main parameters of the damper are the equivalent stiffness and energy dissipation coefficient. Based on a 10‐story steel frame structure, 10 energy dissipation design schemes using the proposed Reid damper are proposed. The additional equivalent damping ratios of the 10 schemes are equal, whereas the energy dissipation coefficients of the dampers are different. The vibration control effects of the energy dissipation structures are analytically investigated under four earthquake loads. The experimental results of the friction damper are in good agreement with the theoretical results, and the hysteretic behavior of the damper follows that of a typical Reid model. The seismic response and structural damage can be reduced using any of the 10 design schemes; however, the effects are different. When the energy dissipation coefficient is in the range of 0.1–0.3, the control effect on the interstory drift is better; however, the structural acceleration response and damping force of the dampers increase. When the energy dissipation coefficient is in the range of 0.6–1.0, the energy dissipation effect of the dampers is good; however, the self‐centering ability is poor. Therefore, the optimum range of the energy dissipation coefficient of a Reid damper intended for energy dissipation structures should be 0.3–0.6.

Experiment on Behavior of a New Connector Used in Bamboo (Timber) Frame Structure under Cyclic Loading

Connection is an important part of the bamboo and timber structure, and it directly influences the overall structural performance and safety. Based on a comprehensive analysis of the mechanical performance of several wood connections, a new connector for the bamboo (timber) frame joint was proposed in this paper. Three full‐scale T‐type joint specimens were designed to study the mechanical performance under cyclic loading. The thickness of the hollow steel column was different among three specimens. The specimens were loaded under displacement control with a rate of 10 mm per minute until the specimens reach failure. It was observed that the failures of three specimens were caused by the buckling of flanges in the compression and that the steel of connections does not yield. The load‐displacement hysteretic curve for three specimens is relatively plump, and the stiffness of connection degenerates with the increasing of cyclic load. The maximum rotation is 0.049 rad, and the energy dissipation coefficient is 1.77. The thickness of the hollow steel column of the connector has significant impact on the energy dissipation capacity and the strength of the connection. A simplified moment‐rotation hysteresis model for the joint was proposed.

Nonlinear Numerical Analyses of a Fabricated Connection of Concrete-Filled Steel Column to Steel Beam Under Low-Reversed Cyclic Loading

Introduction: Based on FEM program ABAQUS, three-dimensional numerical models of a fabricated connection of concrete-filled steel column to steel beam under low-reversed cyclic loading were established by considering both nonlinearity of material and geometry. Effects of stiffen ring plate, axial compression ratio and backing plate on the hysteresis curves, skeleton curves, ductility coefficient and energy dissipation coefficient were analyzed respectively. Methods: Furthermore, parametric analyses with comparison were also conducted to discuss the mechanical characteristics and damage mechanism of the fabricated connection. Results: The results show that there are clear stress concentrations near the area of bolt holes in beam flange. The increase in width of ring plate and the shape change of ring plate from square to circle can both improve the ductility and the characteristics of hysteretic behavior. Besides, the backing plates have positive effects on the hysteretic characteristics, ductility and energy dissipation of the CFST column connections. Oppositely, the increase in axial compression ratio contributes negatively to both the bearing capacity and deformation performance of the connection specimens. Conclucion: It can be concluded that the fabricated connection displays good working performance relating to hysteretic characteristics, energy dissipation and ductility, which can be hopefully applied and provide reference to engineering practice.