Theory Of Dynamic Interactions Research Articles

Modified connection mode of rack system on super-slope bridge under extreme temperature load in rack railway

The construction of rack railways is widely planned across the mountainous areas of Southwest China. However, the huge differences in the daytime and nighttime temperatures in these areas easily lead to deformation mismatch between rack and bridge structures and subsequently result in unpredictable phenomena, such as connection failures in the rack system. This article then explores the vehicle-track (rack)-bridge system (VTRBS) interaction problem caused by extreme temperature loads. Guided by train-track-bridge dynamic interaction theory and considering the meshing behavior of the gear-rack and wheel-rail contact, a dynamic model for investigating the VTRBS interaction under extreme temperature load is constructed. The reliability of the rack system on a super-slope bridge under different rack and sleeper connection modes is studied using this model, and the modified connection mode is proposed. Under an extreme temperature load of –45 ℃, the reliability of the rack system is greatly affected by the rack and sleeper connection modes. When traditional fixed connections are used, the maximum stresses in the rack and fixed connection bolts are 1095 MPa and 1980 MPa, respectively, both exceeding the material strength. When using traditional fasteners, the maximum stresses in the rack and fastener bolts are 203 MPa and 38 MPa, which do not exceed the material strength. However, the elastic displacement between the rack and sleeper exceeds the allowable range of traditional fasteners. When using longitudinal resistance modified fasteners, the stresses in the rack system do not exceed the material strength, but the elastic displacement exceeds the maximum allowable range. When using elastic displacement modified fasteners, the modified elastic displacement ranges between 16 mm and 24 mm, which is within the normal working range. When using longitudinal resistance and elastic displacement modified fasteners, the modified elastic displacement ranges between 12 mm and 24 mm, which is also within the normal working range. These results provide theoretical basis for the early design and later operation and maintenance of rack railways.

Damage Model of Bridge Bearing and Its Influence on Train-Track-Bridge Dynamic System

Bridge bearing damage is unavoidable in railway engineering. This work presents an investigation on the damage model of bridge bearing and its influence on the dynamic responses of the high-speed train-track-bridge system. Primarily, the mathematical description of bridge bearing damage model is explained in detail, which is then compared with the traditional linear model. Then a 3D train-track-bridge dynamic model considering bearing damage is established based on the train-track-bridge dynamic interaction theory. Adopting the model, the influences of single-point-damage and multi-point-damage on the dynamic behaviors of the coupled system are deeply investigated. Results show that the calculated obtained by the proposed model and the traditional linear model are different, especially in frequency-domain. Compared to results of traditional linear model, the results obtained by the proposed model are smaller due to the additional damping effect. Bridge bearing damage has almost no influence on the train vibrations, while has great effect on bridge vibrations. The damage in z-direction mainly affects the vertical vibrations, while damage in y-direction mainly influences the lateral vibrations. Among all the damaged bearings in this work, the influence of damage in x-direction has the least influence on the system. The damage in the fixed bearing is larger than that in other bearings, indicating that more attentions should be paid to the health monitoring of fixed bearings in railway engineering.

Experimental and numerical study on vibration and structure-borne noise of high-speed railway composite bridge

In order to investigate the characteristics of train-induced vibration and structure-borne noise of high-speed railway steel–concrete composite bridge, a 5 × 50 m continuous steel–concrete composite bridge is adopted and tested in this paper. The vibration acceleration response and radiated noise of the bridge are measured during the test. The prediction model of vibration and structure-borne noise is further established to explore the radiation spectrum characteristics of the composite bridge. Firstly, the train-track-bridge dynamic interaction theory is applied to calculate the vibration response of the bridge under high-speed train loading. The boundary element method (BEM) and Statistical Energy Analysis (SEA) are subsequently combined to predict the full-frequency band noise of the structure. The accuracy of the model is verified through comparison with the measured data. Based on the field test and numerical study, it is found that the dominant frequency range of vibration and structure-borne noise is 20 ∼ 1000 Hz. The root mean square (RMS) accelerations of vertical and transverse vibration are lower than 0.5 m/s2, while local vibration of the steel web can reach 1.0 ∼ 2.5 m/s2. As a result, the acoustical contribution of the web at far-field site can reach 80% of the structure-borne noise. In addition, the setting of the bottom concrete reduces the acceleration level of the bottom plate by 10.75 dB and the radiated noise by 7.16 dB, showing a good effect of vibration and noise reduction.

Violation of the Taylor relation under high-energy external influences

The motion of an edge dislocation ensemble in a binary alloy under high strain rate deformation is theoretically analyzed. Within the framework of the theory of dynamic interaction of defects (DID) an analytical expression for the dependence of the dynamic yield stress on the dislocation density is obtained. The conditions for the violation of the Taylor relation under high-energy external influences are determined. The experimentally observed nonmonotonic dependence of the dynamic yield strength on the dislocation density is explained. The minimum of this dependence is due to the competition between the influence of various structural defects on moving dislocations. This minimum takes place during the transition from the dominance of dynamic drag by one type of defects to the dominance of another type defects. Keywords: dislocations, high strain rate deformation, defects, Guinier-Preston zones, alloys.

Нарушение соотношения Тейлора в условиях высокоэнергетических внешних воздействий

The motion of an edge dislocation ensemble in a binary alloy under high strain rate deformation is theoretically analyzed. Within the framework of the theory of dynamic interaction of defects (DID) an analytical expression for the dependence of the dynamic yield stress on the dislocation density is obtained. The conditions for the violation of the Taylor relation under high-energy external influences are determined. The experimentally observed nonmonotonic dependence of the dynamic yield strength on the dislocation density is explained. The minimum of this dependence is due to the competition between the influence of various structural defects on moving dislocations. This minimum takes place during the transition from the dominance of dynamic drag by one type of defects to the dominance of another type defects.

The effect of hydrogen on the mechanical properties of metals under conditions of high-speed deformation

The movement of an ensemble of edge dislocations in metals with a high hydrogen content under conditions of high-speed deformation (high strain rate deformation) is theoretically analyzed. Within the framework of the theory of dynamic interaction of defects (DVD) (DID), an analytical expression is obtained for the dependence of the dynamic yield strength on the concentration of hydrogen atoms. Keywords: dislocations, hydrogen, high-speed deformation, metals.

Train-Bridge Dynamic Behaviour of Long-Span Asymmetrical-Stiffness Cable-Stayed Bridge

Long-span cable-stayed bridge (LCB) with unequal-height towers is being designed and constructed in metro lines due to its better adaptability to environment and terrain conditions compared to traditional cable-stayed bridge with equal-height towers. However, the asymmetrical arrangement of towers leads to obvious nonuniformity of the structural stiffness along the longitudinal direction, which intensifies the wheel-rail coupled vibration behaviour, and affects the running safety of operating trains and ride comfort. Therefore, train-bridge dynamic behaviour of long-span asymmetrical-stiffness cable-stayed bridge is deeply investigated in this work. Primarily, considering the comprehensive index of frequency difference and modal assurance criterion (MAC), a nonlinear model updating technique (NMUT) based on penalty function theory is proposed, which can be used to optimize the bridge numerical model. Secondly, on the basis of the train-track-bridge dynamic interaction theory (TDIT), a train-track-bridge coupled dynamic model (TCDM) is established. Finally, a LCB with unequal-height towers is applied as a case to illustrate the influence of asymmetrical stiffness on the train-track-bridge dynamic characteristics. Results show that the proposed NMUT is efficacious and practical. For the LCB with unequal-height towers, a significant difference between the bridge vibration at low tower location and that at high tower location appears. The vertical displacement difference of the main beam on both sides of the bridge increases with the distance from the observation point to the bridge tower increasing. The variation of acceleration difference on both sides of the bridge is influenced by the speed of the train and the position of the observation point simultaneously. In general, vibrations of the main beam at low tower location are larger than those at high tower location.

Relationship between track stiffness and dynamic performance of vehicle–track–bridge system

Track stiffness irregularity is superficially invisible on rail surface, while causes dynamical impact and track deformation when trains running through. Aiming at this issue, this work presents an investigation on the influence of track stiffness on dynamic behaviours of the high-speed vehicle–track–bridge dynamic system. Primarily, a determination method of track stiffness irregularity is analytically deduced, in which a novel solution of deformation of free beam is proposed. Then a high-speed vehicle–track–bridge dynamic interaction model is established based on the vehicle–track–bridge dynamic interaction theory. On this basis, the influence of track stiffness on the dynamic behaviours of the coupled system is investigated both in time domain and in frequency domain. Results show that the distribution of track stiffness in longitudinal direction indeed affects the vibrations of the system. More vibration details of system in full frequency bands can be revealed by considering track elasticity. The most sensitive indicator to different track types is the pitch acceleration of bogie. The wave amplitude caused by length of slab is very small, however its influence on vehicle vibrations is great, indicating that tiny track stiffness change caused by length of slab cannot be ignored in dynamic investigations.

Method for Determining Longitudinal Stiffness of Combined Double Thin-Walled Pier Based on Train-Track-Bridge Interaction

Combined double thin-walled pier is a new kind of pier adopted in the urban transit system in China, whose longitudinal stiffness cannot be determined by adopting traditional methods. Aiming at this practical issue, this work proposed an alternative method for determining the longitudinal stiffness of the combined double thin-walled pier based on the train-track-bridge interaction. Primarily, the relationship between longitudinal stiffness of the pier and rail stress is underlined, based on which the proposed methodology is described in detail. Finally, a case study is conducted to validate the effectiveness of the proposed method. Results show that the train-track-bridge dynamic interaction theory is effective in determining the longitudinal stiffness of the newly designed and special pier. Rail stress and longitudinal displacement of pier top exceed their limit values with the change of pier longitudinal stiffness. The dynamic stress and thermal stress of rail are the two most important indicators in determining pier longitudinal stiffness, which should be paid attention to in practical engineering.

Influence of Pier Settlement on Structural Stress of Longitudinal Connected Track in High-Speed Railways

Pier settlement is unavoidable in the construction and operation of high-speed railways. This paper presents a work on the influence of pier settlement on additional structural stress of longitudinal connected track (LCT). First of all, the generation mechanism of additional structural stress of LCT caused by pier settlement is described in detail. On this basis, the deformation of LCT caused by pier settlement is analytically deduced and a dynamic model of high-speed train-LCT-bridge coupled system considering pier settlement is established based on the train-track-bridge dynamic interaction theory, adopting which the additional structural stresses of LCT are discussed from static and dynamic perspectives. Results show that pier settlement has a great influence on the stability of LCT. Additional tensile stresses of LCT appear at settlement pier location and two adjacent pier locations. Tensile stresses on top surface of slab and on bottom surface of base should be paid attention to. The behaviors of LCT at adjacent pier locations cannot be ignored in studying the influence of pier settlement on the system. To ensure the stability of LCT and running performance of train, the control value of pier settlement is suggested to be 10.5 mm from the static and dynamic perspectives in practical engineering.

Theoretical method of determining pier settlement limit value for China’s high-speed railway bridges considering complete factors

Reasonable pier settlement is an extremely important limit value in the design of high-speed railway bridges, which directly affects the service performance of bridges and the running safety of trains. Comprehensively considering complete factors affecting the determination of pier settlement limit value (PSLV), this paper presents a method to investigate PSLV for simply supported girder bridges in China’s high-speed railways. First of all, an investigation on PSLV written in China’s current codes is conducted to explain the necessity of this present work. Then based on the train-track-bridge dynamic interaction theory, the methodology for determining PSLV for China’s high-speed railway bridges is proposed, in which the complete factors affecting the determination of PSLV are emphatically discussed and summarized. Adopting the established model, the bridge deformations caused by different factors are calculated, and the PSLV for China’s high-speed railway bridges is then obtained according to the running safety and ride comfort of high-speed trains. Results show that important factors written in codes, including self-weight, prestress, creep, shrinkage, temperature and rail random irregularity, should be fully considered in determining PSLV due to these factors greatly affect bridge deformations and dynamic behaviors of running trains. According to the running safety and ride comfort of high-speed trains, the PSLV for simply supported girder bridges in China’s high-speed railways is suggested to 12.7 mm.

Train–track–bridge dynamic interaction: a state-of-the-art review

ABSTRACTTrain–track–bridge dynamic interaction is a fundamental concern in the field of railway engineering, which plays an extremely important role in the optimal design of railway bridges, especially in high-speed railways and heavy-haul railways. This paper systematically presents a state-of-the-art review of train–track–bridge dynamic interaction. The evolution process of train–bridge dynamic interaction model is described briefly, from the simplest moving constant force model to the sophisticated train–track–bridge dynamic interaction model (TTBDIM). The modelling methodology of the key elements in the TTBDIM is systematically reviewed, including the train, the track, the bridge, the wheel–rail contact, the track–bridge interaction, the system excitation and the solution algorithm. The significance of detailed track modelling in the whole system is highlighted. The experimental research and filed test focusing on modelling validation, safety assessment and long-term performance investigation of the train–track–bridge system are briefly presented. The practical applications of train–track–bridge dynamic interaction theory are comprehensively discussed in terms of the system dynamic performance evaluation, the system safety assessment and train-induced environmental vibration and noise prediction. The guidance is provided on further improvement of the train–track–bridge dynamic interaction model and the challenging research topics in the future.

A New Celestial Mechanics Dynamics of Accelerated Systems

We present in this text the research carried out on the dynamic behavior of non-inertial systems, proposing new keys to better understand the mechanics of the universe. Applying the field theory to the dynamic magnitudes circumscribed to a body, our research has achieved a new conception of the coupling of these magnitudes, to better understand the behavior of solid rigid bodies, when subjected to multiple simultaneous, non-coaxial rotations. The results of the research are consistent with Einstein’s theories on rotation; however, we propose a different mechanics and complementary to classical mechanics, specifically for systems accelerated by rotations. These new concepts define the Theory of Dynamic Interactions (TDI), a new dynamic model for non-inertial systems with axial symmetry, which is based on the principles of conservation of measurable quantities: the notion of quantity, total mass and total energy. This theory deduces a general equation of motion for bodies endowed with angular momentum, when they are subjected to successive non-coaxial torques.

Dynamic Effects in a Defective System of Crystal

Works devoted to studying the interaction between dislocations and structural defects in a crystal lattice in the dynamic region of velocities are considered. Analytic expressions for the force of dynamic drag and the dynamic yield stress for a wide range of problems of dislocation dynamics are obtained using the theory of dynamic interaction between structural defects.

Running safety of high-speed train on rigid frame bridge subjected to earthquakes

To research the running safety when high-speed train running over a high-pier rigid frame bridge subjected to earthquakes, a coupling vibration model is set up based on the traintrack-bridge dynamic interaction theory. In this model, the seismic action is solved by the relative motion method and the ballast track is simulated by the elastic point support model with three layers. As an example, a high-pier rigid frame bridge with spans of (88+168+88) m is modelled, and the dynamic responses of vehicle and bridge system under El Centro seismic wave are calculated. The analysis results show that the dynamic responses of the high-pier rigid frame bridge present weakly coupled in plane and out plane, moreover the running safety of the train is decreased along with the increase of seismic amplitude and train speed. In addition, the most threat direction to the running safety of the train on bridge is transverse, and the running safety threshold of ICE3 subjected to 7 degree, 8 degree and 9 degree frequent seismic is 275, 250 and 225 km/h.

Study on the safe value of multi-pier settlement for simply supported girder bridges in high-speed railways

This paper presents a method to analyse the influence of multi-pier settlement on the train–track–bridge coupled dynamic system, and to determine the safe value of the continuous multi-pier settlement for simply supported girder bridges in Chinese high-speed railways. Firstly, the mapping relationship between the multi-pier settlement and the rail deformation is derived theoretically. Then, taking the superposition of the rail deformation and the track random irregularity as excitation, the variations of vehicle dynamic indices are analysed based on the train–track–bridge dynamic interaction theory. Further, the relationships between the pier settlement and the change amounts of vehicle dynamic indices are obtained. The multi-pier settlement safe value is determined according to the limits of vehicle dynamic indices. Results show that the rail deformation caused by multi-pier settlement agrees well with the settlement data. When passing through the 32.6 m-long simply supported girder bridge with multi-pier settlement, the train suffers a low-frequency excitation. Only considering the influence of pier settlement, the settlement value difference between two adjacent piers should be less than 26.3 mm at China’s highest operation speed of 350 km/h from the perspective of dynamics, which is much larger than the pier settlement limit in the current code for Chinese high-speed railways.

Rolling Over into the Age of Algorithm

This paper is an extract of the prologue to the book: New Paradigm in Physics—Theory of Dynamic Interactions [1], published by Gabriel Barceló. This summary describes the elements that constitute the characteristics of the Theory of Dynamic Interactions, and certain circumstances of it. The author recalls that the Theory of Dynamic Interactions arrives at unheard of conclusions which, even with the level of dissemination reached by this theory over recent years, have not been scientifically refuted.

Theory of Dynamic Interactions: Innovations

The theory of dynamic interactions suggests a new paradigm of mechanics and initiates us into a new area of knowledge, hitherto undeveloped. In this paper, we describe the innovations that this theory brings to physics, and in particular, the ideas expressed on new book by Doctor Barceló: New paradigm in physics. It is necessary to analyse the incorporation into mechanics not only of knowledge about bodies with inertial movement, but also that of non-inertial systems. It is necessary a new structure of knowledge that can incorporate both inertial and accelerated systems. On this paper we referred to the main innovations and novel ideas proposed by Doctor Barceló on his new book, in relation to the rotational dynamics.

Physico-Mathematical Models in Rotational Motions

This paper was the prologue to the first book published by Gabriel Barcelo on the Theory of Dynamic Interactions, entitled: The Flight of the Boomerang. However, this text, is fully current, as well as the book itself. The book described mainly the initial historical analysis made by Dr. Barcelo on the rotational dynamics. For Professor Garcia Moliner, the book contains an extremely positive message. It shows us that scientific research consists of constantly questioning hitherto accepted theories and seeing if they can always be applied to new situations.

The Works and Days of Gabriel Barceló

This paper is a commentary to the book: New Paradigm in Physics—Theory of Dynamic Interactions, published by Gabriel Barceló. The paper describes the origins of the Theory of Dynamic Interactions, his contents and certain circumstances of it. He remembers certain conclusions of the researcher. For example, howa free, unrestrained body in space, can initiate an orbit that has no need for the existence of a central force.