Effect Of Dynamic Loading Research Articles

Magnetothermoelastic vibrations on a viscoelastic microbeam subjected to a laser heat source

The linear theory of viscoelasticity remains an important field of research like most solids and polymer materials when exposed to a vicious dynamic loading effect. This article introduces a new model for describing the behavior of thermoviscoelastic microbeams considering the effects of temperature change and the longitudinal magnetic field. The governing equations in this model are derived based on the Euler–Bernoulli beam theory, Kelvin–Voigt model of viscosity, the generalized thermoelasticity, and the classical Maxwell equations. The two ends of the microbeam are clamped and subjected to the influence of a laser pulse with a temporal intensity profile. The analytical solutions to the physical fields are evaluated using the Laplace transform and its inversion transforms are performed numerically. The thermo-viscoelastic responses of the microbeam are calculated numerically and investigated graphically. The effect of different parameters such as viscosity, laser intensity, and the magnitude of the magnetic field are studied in detail.

Mode of bond failure between 3D-printed denture teeth and printed resin base material: effect of fabrication technique and dynamic loading. An in-vitro study.

To evaluate the failure load of 3D-printed denture resin material and teeth before and after dynamic loading. A total of 40 specimens were fabricated following ISO/TS 19736 and were divided into two equal groups. In the test group, the cylindrical base and denture teeth were 3D printed separately and then luted together. In the control group, the specimens were fabricated from conventional heat-cured polymethyl methacrylate (PMMA) and commercially available denture teeth using the compression-molding technique. Ten specimens from each group were subjected to dynamic load of 50 N for 250,000 cycles in a chewing simulator. All specimens were subjected to static load of 50 N using Instron machine with a crosshead speed of 1 mm/minute until fracture. The fractured surfaces were analyzed using field emission scanning electron microscopy. The failure loads were calculated and compared using analysis of variance (P < .05). All specimens survived the loading, undergoing 250,000 cycles without fracture. The mean failure load was influenced by fabrication technique and was significantly higher for the 3D-printed test group (P = .028). 3D-printed teeth showed a mixed mode of fracture, whereas in the control group, the specimens showed cohesive fracture within the teeth. The fabrication technique has an influence on the mode of failure between acrylic teeth and resin base material. Cohesive failure in teeth was predominant in the conventional group, suggesting possibly higher bond strength between the teeth and resin base in this group. The observed failure modes reveal that both fabrication techniques exhibited satisfactory bond strength. Chewing simulation did not significantly influence the bond strength of any of the tested groups.

Measurements of bridge dynamic amplification factor using bridge weigh-in-motion data

The dynamic component of bridge traffic loading is commonly taken into account with a Dynamic Amplification Factor (DAF)—the ratio between the dynamic and static load effects on a bridge. In the design codes, this factor is generally more conservative than in reality. Recently a new method of calculation of this factor had been developed. Data from 15 different bridges have been analysed since then and this paper presents the results of the analyses. The background for Bridge Weigh-in-Motion is given, and the most recent method for DAF calculation is described. The sites from which the data originated are presented, and the selection of data discussed. The results of the analyses are presented and discussed and some examples of DAF calculations are shown. Data from the considered sites have invariably demonstrated a DAF decrease with increasing axle load. This is a significant result, especially for assessment of existing structures, since it is beneficial to use measured structural parameters to optimise structural analysis.

Accurate physical modeling and synchronization control of dual-linear-motor-driven gantry with dynamic load

To achieve high-accuracy tracking of a dual-linear-motor-driven (DLMD) gantry, high-level synchronization between redundant actuators becomes a non-negligible factor and also a difficult issue to be solved priorly. Especially, when both X and Y axes are simultaneously operating to accomplish complex tasks efficiently, additional coupling effects will be generated by the dynamic load presented on the crossbeam, which makes the synchronization issue more complicated than the case with static load. However, due to the absence of an accurate model to fully reveal the complete coupling characteristics, existing approaches to this issue still have inherent limitations. Therefore, this paper focuses on the systematic physical modeling and synchronization control of a DLMD gantry with a dynamic load presented on the crossbeam. A complete coupling mathematical model is established first, by fully considering two linear motions (X-axis and Y-axis) and also including the additional rotational motion of the crossbeam. Built upon the effective model information, corresponding solutions by compensating the dynamic load effects and actively controlling the rotational dynamics to regulate the internal forces have been proposed, leading to a novel adaptive robust synchronization control method. The results of comparative experiments verify the effectiveness and superiority of the proposed method in dealing with the synchronization issue subjected to dynamic load effects.

Investigation of Nonlinear Behaviour of Semiburied Cylindrical Concrete Reservoir without Dynamic Load Effect

This study aimed to examine the effect of rigid and flexible foundations on the response by a semiburied water storage reservoir. In this study, the reservoir support conditions of both flexible and inflexible states were studied. The seismic behaviour of reinforced and prestressed concrete reservoirs was compared based on their support conditions. The powerful numerical method FEM was used to study about the nonlinear behaviour of cylindrical reservoirs using static and dynamic nonlinear analysis. The values of the results correcting factor in the design codes and standards were evaluated. Moreover, the response correcting behaviour (R) was evaluated based on the findings from a push-over and nonlinear dynamic analysis. This research finding indicated that the reservoir shapes and support types affect the deformability of the reservoirs. Reservoirs with prestressed concrete show less flexibility compared to reinforced concrete reservoir. Finally, it is resulted that displacement, base shear, and wave height obtained from time history analysis are more than those of response spectrum analysis, indicating insufficiency of response spectrum analysis.

Maximum Probabilistic and Dynamic Traffic Load Effects on Short-to-Medium Span Bridges

The steadily growing traffic load has resulted in lots of bridge collapse events over the past decades, especially for short-to-medium span bridges. This study investigated probabilistic and dynamic traffic load effects on short-to-medium span bridges using practical heavy traffic data in China. Mathematical formulations for traffic-bridge coupled vibration and probabilistic extrapolation were derived. A framework for extrapolating probabilistic and dynamic traffic load effect was presented to conduct an efficient and accurate extrapolation. An equivalent dynamic wheel load model was demonstrated to be feasible for short-to-medium span bridges. Numerical studies of two types of simply-supported bridges were conducted based on site-specific traffic monitoring data. Numerical results show that the simulated samples and fitting lines follow a curve line in the Gumbel distribution coordinate system. It can be assumed that dynamic traffic load effects follow Gaussian distribution and the extreme value follows Gumbel distribution. The equivalent probabilistic amplification factor is smaller than the individual dynamic amplification factor, which might be due to the variability of individual samples. Eurocode 1 is the most conservative specification on vehicle load models, followed by the BS5400 specification. The D60-2015 specification in China and ASSHTO specification provide lower conservative traffic load models.

The effect of dynamic loading on bacterial microleakage of the dental implant fixture-abutment interface: An in vitro study.

Aim:Bacterial micro leakage at implant-abutment interface under functional loading is an important factor, may lead to crestal bone loss and affect the long term success of dental implants. Due to the limited studies about the implant systems with a connection of Slip joint design, this study aimed to evaluate the effect of dynamic loading on bacterial leakage at the implant-abutment interface with slip joint connection.Settings and Design:In vitro- comparative study.Materials and Methods:A total of 20 implants and abutments with slip joint connections (Tapered Screw-Vent, 3.7 mm ×10 mm, Zimmer Dental, USA) was examined and depends on using functional loading were divided into two groups; loaded and unloaded. Initially, 10 μl of Brain Heart Infusion (BHI) culture broth was pipetted to the internal lumen of each implant, then the abutments were tightened to the fixtures and crowns were cemented. In the unloaded group, samples were immersed in E-Coli suspension for 5 days. In the loaded group, samples were immersed in microbial suspension under 500000 cycles using a cyclic load device. Following disconnection of fixtures and abutments, microbial samples were taken from the internal lumen of implants and colonies were counted. Data were analyzed using.Statistical Analysis Used:Mann-Whitney statistical test, SPSS version 24.Results:The mean rate of micro leakage in unloaded and loaded groups was 4000 CFU/ml and 27000 ± 31640 CFU/ml respectively. Bacterial colonies grew in 10% of unloaded samples and 50% of loaded samples. This difference was statistically significant. (P < 0.05)Conclusions:Microbial micro leakage at the implant-abutment interface with slip joint design increased significantly after functional loading.

Effect of dynamic loading on hip implant using finite element method

Hip joint is the primary joint which provides stability to the human body. Ageing of human, disease and accidental circumstances are the focal point for hip replacement surgery. Hip Arthroplasty is a surgical procedure for replacing the disease or fractured hip joint. Present analysis consists of Charnley’s femoral stem with three metallic materials i.e. CoCrMo, Ti-6Al-4 V and Ti-6Al-7Nb, undergoing to the realistic dynamic loading i.e. average walking load condition. These three materials demonstrate excellent biocompatibility. The aim of this paper is to analyze the mechanical parameters i.e. stress, deformation and strain of the femoral stem for walking, based on in vivo loading conditions obtained from patient’s practical activities, in order to find out the most suitable implant material. The final outcome demonstrates that CoCrMo is the best suited material because this metallic material demonstrates maximum stress with minimum deformation and strain as compared to other two.

Dynamic Loading Effect on Fault Current and Arc Flash for a Coordinated Substation

Due to load growth and various load types within the service territory, utilities need to enhance the utilization of substations. In any case, towards the coordinated substation design, the utilization of the transformers' most total capacity cannot be reduced just because there is a lack of proper coordination between transmission and distribution systems. The transmission and distribution systems' stability and safe operability must be investigated in a coordinated substation. The critical issues are the asymmetric fault currents on the high voltage and arc-related safety issues on the distribution switchgear at different dynamic loading scenarios. We found that when one 138 kV transmission line and two transformers are energized, with increased dynamic loading, from 40% and above, the substation, as a whole, gets gradually more stressed. Because of the highest amount of fault currents on the 138 kV bus, to avoid CT saturation, we need to consider that three transmission lines are connected, and all three transformers are running at 100% dynamic loading. At this value of dynamic loading, in the 13.2 kV switchgear, the incident energy is 2 cal/cm2, and the arc flash boundary is four feet, which ensures that all workers need to wear the proper arc-rated clothes to work on any de-energized cubicle of the switchgear.

Применение алгоритма обнаружения изменения сигнала в системе контроля гидроамортизаторов

During nuclear power plant (NPP) operation, the reactor plant main equipment can show displacements when subjected to the effect of various external and internal loads. These displacements are mainly caused by thermal expansion of the metal and seismic loads. To cope with these phenomena, the reactor plant components that are most susceptible to these types of loads are fastened with hydraulic shock absorbers (HSAs) to limit their displacements under the effect of seismic or accident dynamic loads, as well as to ensure thermal displacements in increasing or decreasing the power unit output. For monitoring the HSA operation and indirectly monitoring the displacements of the reactor plant equipment items fastened with hydraulic shock absorbers, the dedicated hydraulic shock absorber monitoring system (HSAMS) is used, which is equipped with linear displacement sensors installed directly on the HSAs. If the displacements go beyond the predetermined limits, the HSAMs algorithms produce an appropriate alarm. The information from the HSAMS is also used by the automated residual lifetime monitoring system (ARLMS) to calculate the steam generator connection pipe displacement criteria parameters. However, during the operation of a number of NPP power units, a problem associated with numerous failures of the HSAMS linear displacement sensors has been faced. These failures manifested themselves in that the sensor signals went beyond the valid range or frozen under the effect of external influencing factors. As a result, the HSAMS and ARLMS operation was complicated by a large number of unreliable measurements and the functions of these systems were not performed in a proper way. To solve this problem, it has been proposed to use an algorithm for tracking signal changes, which can improve the credibility of HSAMS indications by determining unreliable data in the online mode and by performing statistical processing of the already available array of indications.

Flexible‐Rigid Wheelset Introduced Dynamic Effects due to Wheel Tread Flat

The widespread faults that occur in railway wheels and can cause a massive dynamic impact are the wheel tread flat. The current work considered changes in vehicle speed or wheel radius deviation and studied the dynamic impact load. The modal technique for the impact evaluation induced by the wheel flat was proposed via the finite element analysis (FEA) software package ANSYS, integrated into a multibody dynamics model of the high‐speed train CRH2A (EMU) through SIMPACK. The irregularity track line has developed and depends on the selected simulation data points. Additionally, a statistical approach is designed to analyze the dynamic impact load response and effect and consider different wheel flat lengths and vehicle speeds. The train speed influence on the flat size of the vertical wheel‐rail impact response and the statistical approach are discussed based on flexible, rigid wheelsets. The results show that the rigid wheel flat has the highest vertical wheel impact load and is more significant than the flexible wheel flat force. The consequences suggest that the wheelset flexibility can significantly improve vertical acceleration comparably to the rigid wheel flats. In addition, the rendering of the statistical approach shows that the hazard rate, PDF, and CDF influence increase when the flat wheel length increases.

ФАКТОРЫ, ВЛИЯЮЩИЕ НА ПРОЦЕСС РАЗРУШЕНИЯ ГРУНТОВОГО И ГОРНОГО МАССИВА

The article is devoted to the analysis of the process of impact destruction of solid and frozen soils and rocks. The classification of factors influencing the energy efficiency of excavation and mining is presented. The main attention in the study is paid to the analysis of rock mass destruction by single and double percussion tools. The schemes of the deformations development in the massif as a result of the impact on it with one or two indenters under impact action are considered. The schemes of the destruction phases’ development of soil and rock massif, both with single and paired impact of percussion instruments, are considered step by step. It is noted that when a double percussion tool is applied to a destructible medium, the efficiency of rock mass destruction increases due to the intensive formation of a general stress field between the indenters, which leads to the formation of a compaction core in this zone with the subsequent destruction of the monolith. It was found that the optimal distance between indenters operating in pairs is a constant value for each rock and does not depend on the indenter diameter. The schemes of dynamic loads propagation from the sources to the operator with the rigid connection of the working body and the working body equipped with an additional connection are presented. Analysis of rock mass destruction by percussion tools made it possible to propose constructive solutions for the executive bodies of earth-moving machines that ensure the redistribution of the reactive forces arising from the impact into the zone of destruction of the soil or rock mass, which significantly reduces the effect of dynamic loads on the base machine and the operator. On the example of a percussion ripper with a balancing weight, an analytical dependence is presented in which the impact energy is redistributed to the zone of destruction of the massif

STRUCTURAL ANALYSIS OF JACKET FOUNDATIONS FOR OFFSHORE WIND TURBINES IN TRANSITIONAL WATER

Most of the offshore wind turbines (OWT) recently installed in Europe, China and North America are in shallow water. However, unlocking the full potential of OWT lies in deeper waters. Jacket substructures have presented themselves as a reliable foundation concept for transitional water depth. This study focuses on the structural static and dynamic analysis of the traditional jacket substructures (with X and K bracing) and the recently patented three-legged twisted jackets (with a twisted angle of 30 and 60 degrees) for deployment in transitional water (beyond 60 m). To facilitate comparison, the dimensions of all the jackets remain the same, while, the geometric configurations are distinct. Static analysis was implemented to better understand the global load bearing behaviour of the jackets. First, the global displacement patterns at the tower top are compared. The individual reactions at mud-line were investigated, followed by the evaluation of the maximum von Mises stress. Subsequently, this research went on to investigate the effect of dynamic loading. In this dynamic analysis, three main critical points were considered, including the wave point (67 m), the platform and the tower top. A modal analysis was performed to compute the mode shapes and natural frequencies for all the jackets. The first five modes of all the jackets were also checked against the results available for the OC4 project. A similar analytical approach was adopted for the structural design of monopile or tripod foundations for offshore wind turbines. The results showed that in the static analysis both the traditional jackets and the twisted jackets were safe under the provided load combination. The twisted jacket proved to possess excellent structural behaviour compared to the traditional four-legged jackets, while maintaining the merits of lower material usage with fewer nodes. Analysing the von Mises stress revealed that the maximum stress occurred at the transition piece and close to the working platform. The modal analysis results of the jackets demonstrated that the twisted jackets (30 and 60 degrees) with the first natural frequency of 0.29 and 0.31 Hz fell under the soft-stiff design category whereas the traditional four-legged jackets were classified as stiff-stiff designs. The discovered structural performance of OWTs equipped with various jacket foundations contributes to the preliminary structural selection and optimal design of foundations of OWTs to be installed in transitional water.

Dynamic Load Effects of Wheeled and Tracked Military Vehicles on a Steel Girder Composite Bridge

Abstract The perceived and observed differences in the dynamic behavior between wheeled and tracked military vehicles should be accounted for in the application of appropriate dynamic load effect v...

Study on effect of dynamic load on rail joint bar by finite element method (FEM)

ABSTRACT The effects of vertical dynamic wheel loading and bolt conditions on rail-end joint bar by using the finite element method (FEM) in terms of vertical displacement, principal and shear stress are investigated. Preliminary results of dynamic load show that variation of either tight/loose-bolted joint bar has the response of rail-end joint varies, the joint bar vertical displacement, principal and shear stresses on the joint bar also vary. The test results show that contact force at the wheel-rail joint bar interface would not change monotonically with the variable train speed and the shear stresses calculated at joint bar significantly lower than the principal stress and stresses of the joint bar for a given speed. The tightly bolted joint bar is strongly recommended because of its high stiffness causing smaller deflection and smaller principal and shear stress on the joint bar can reduce initiation of failure around the joint.

Dynamic Loading Effect Testing of a Modular Truss Bridge: Procedures and Resultant Data Set

Abstract Experimental bridge testing often produces large data sets that may have applicability to many analysis goals within bridge engineering. To ensure the persistence of these records for futu...

Dynamic Reliability of Continuous Rigid-Frame Bridges under Stochastic Moving Vehicle Loads

The current volume of freight traffic has increased significantly during the past decades, impacted by the fast development of the national transportation market. As a result, the phenomena of truck overloading and traffic congestion emerge, which have resulted in numerous bridge collapse events or damage due to truck overloading. Thus, it is an urgent task to evaluate bridge safety under actual traffic loads. This study evaluated probabilistic dynamic load effects on rigid-frame bridges under highway traffic monitoring loads. The site-specific traffic monitoring data of a highway in China were utilized to establish stochastic traffic models. The dynamic effect was considered in a vehicle-bridge coupled vibration model, and the probability estimation was conducted based on the first-passage criterion of the girder deflection. The prototype bridge is a continuous rigid-frame bridge with a midspan length of 200 m and a pier height of 182 m. It is demonstrated that the dynamic traffic load effect follows Gaussian distribution, which can be treated as a stationary random process. The mean value and standard deviation of the deflections are 0.071 m and 0.088 m, respectively. The dynamic reliability index for the first passage of girder deflection is 6.45 for the current traffic condition. However, the reliability index decreases to 5.60 in the bridge lifetime, accounting for an average traffic volume growth ratio of 3.6%.

Analysis of Aqueducts Subjected to Hydrostatic and Dynamic Loads Using 3D - Solid Modeling

In many areas of developing countries, the access to fresh water is limited even today. Aqueducts are the major structures in water supply and diversion schemes when carrying the water over natural and artificial obstacles such as valleys, rivers, roads, railway lines, canals etc. During an earthquake, the effect of water sloshing on the walls of aqueduct and the resulting hydrodynamic forces is often neglected. In this study, the analysis is carried out for a single span elevated aqueduct using finite element analysis, in which the structure is discretized into smaller elements. The structure is modelled using solid elements in Staad Pro V8i software for different loads. The behavioral response of aqueduct structure subjected to hydrostatic loads and dynamic loads due to seismic ground excitation has been analyzed. It has been observed that the structure is more vulnerable to dynamic loads compared to hydrostatic loads. The effect of dynamic loads due to sloshing of water under seismic forces is predominant. The stresses induced by hydrodynamic loads are observed to be 2.4 times more than hydrostatic loads.

The vibroacoustic analogies method

The article deals with the main problem of computational dynamic modeling of building structures, which is associated with the computational modeling of dynamic parameters of structural elements. The methods and schemes of construction of dual analogies between such dynamic properties of designs elements as inertia, rigidity and pliability to dynamic loadings are presented. The Vibroacoustic analogies for Ohm’s law, Kirchhoff’s laws, Hooke and Newton and the mathematical analogies between acoustic and electrical impedances for the elements of building structures are considered. The patterns of Vibroacoustic analogies for the resonance properties simulation of structural elements are examined. It is shown that the elements of the design have a multi-mode acoustic impedance. It is shown that correct modal analysis of structural elements dynamic reaction is a necessary condition for the correct simulation dynamic reaction schemes of buildings and structures to the effects of dynamic loads as complex mechanical systems. The article shows the convenience of using vibroacoustic analogies both in calculations of dynamic load distribution on building structures elements and in dynamic monitoring data interpretation of buildings and structures technical condition. The dynamic models of design are analyzed taking into account their vibroacoustic interaction in the acoustically coupled system of structural elements. The article presents equivalent schemes and systems of equations calculation modeling of the distribution of dynamic stress and strain in the building structure space. As an example, the computational modeling principles of dynamically indeterminate mechanical systems of buildings and structures is considered.

Seismic Response of Multi Story Structure Strengthened with Micropiles

Micropiles are reinforced grouted piles that have small diameters commonly not higher than 30 cm. They are widely used for slope stabilization, controlling structural settlement, and in some cases, as retaining structures. Also, they are used for resisting dynamic uplift loads, seismic retrofit mainly in restrictive and low headroom areas, and retrofitting of historical monuments. The main goal of this research is to develop a finite element model that can capture the different aspects of seismic behavior of multi-story structure supported with deep foundation via using of micropiles. Also, a main target for the executing numerical modelling is to show the influence of the surrounding soil on this system and vice versa. Firstly, a representative two-dimensional finite element model is conducted to represent the soil-structure interaction system under seismic excitation supported with proper boundary conditions in PLAXIS 2D V20 for dynamic analysis based on previous recommendations considering the nonlinear soil behavior. The behavior of micropiles is studied and verified using previous results. Based on these models, the effect of lateral dynamic loads on the response of a structure with different foundation types is investigated. Also, a wide range of parametric studies, considering structure properties, earthquake magnitude, micropile diameter, micropile length, and the number of micropiles, have been carried out in order to investigate the actual interaction between soil, substructure, and superstructures. The study results showed that the seismic response of the structure is highly affected by the properties of the sub-surface soil layer. Consequently and similarly, analysis results established that underpinning using micropiles is an efficient technique for controlling the seismic response of existing structures.