Papers by Keyword: Moving Load

Abstract: The dynamic free and forced axial vibrations subjected to moving exponential and harmonic axial forces of a single-walled carbon nanotube (SWCNT) embedded in an elastic medium, are studied in this paper. Two different boundary conditions of SWCNT, including clamped-clamped and clamped-free, are taken into account. Eringen’s nonlocal elasticity theory is used to show the nonlocality for the model. The constitutive equations and their boundary conditions are derived by Hamilton’s principle. Employing the general solution, the derived equations are analytically solved to obtain two items. Firstly, the axial natural frequencies, secondly, the time-domain axial displacements at the middle of the carbon nanotube (CNT), and then the maximum axial displacements. The responses are validated with previous works, and the results demonstrates good agreement to them to verify the influence of the nonlocal parameter on the nondimensional natural frequencies for three various mode numbers. In the time-domain section, the effects of the nonlocal parameter, length, nondimensional stiffness of the elastic medium, and velocity of the moving load on the axial displacement are investigated. Also, the influences of the excitation frequency to natural frequency for the harmonic moving load, as well as the time constant for the exponential moving load on the axial displacement, are illustrated. Finally, the effect of the nonlocal parameter on the maximum axial deflection versus velocity parameter is schematically indicated.

Abstract: A railway bridge over several decades will be degraded due to localized corrosion. As a result, the load capacity of the bridge decreases, especially under the live load caused by trains. This paper examines the residual load capacity of a bridge deteriorated by localized corrosion by using the multibody dynamics approach. This approach allows an accurate description of the interaction between trains and bridges. At the same time, it allows the formation of corrosion marks on each structural member of the bridge in a numerical model precisely based on actual measured data. In order to describe accurately the remaining load of the bridge under the moving load of the train, a dynamic testing and finite element modeling of a steel bridge are conducted and compared. At the same time, the results are also compared with the simulation results of the bridge model before being corroded. In addition, the paper also tests the reliability of the numerical model for assessments of similar bridges without actual measurement results that are costly and time-consuming.

Abstract: This article is presents a finite element formulation for the dynamic response of a rotating simply supported shaft subjected to a moving load. The Timoshenko beam theory is used to model the rotating shaft. The assumed modes method and Finite Element method are employed in this study. The equations are solved with numerical method. The influence of parameters moving load speed and rotational speed are discussed for rotating simply supported shaft model. The results show that the maximum displacement occurs in the direction of the load at the midpoint of the simply supported shaft. The gyroscopic effect occurs only in the direction perpendicular to the load and is dependent on rotational speed of the shaft.

Abstract: The influence of the moving load on suspended monorail was studied. During the movement of suspended carriages were established inertial forces, which lead to the additional monorail curvature. Found the dependence of the maximum dynamic load of the trucks speed along the monorail. Established speed of truck at which load of the monorail is practically static. The dependence of the bending section of the monorail under the influence of moving dynamic forces and the value of dynamic coefficient for suspended monorail track were found.

Abstract: In order to analyze the dynamic response of asphalt pavement under vehicle load, the random characteristic of pavement roughness was considered and the vehicle was simplified into 1/2 model with four freedom degrees when establishing the dynamic load model. Then the sequence of the random dynamic load coefficient was obtained by developing a MATLAB program based on the incremental Newmark-β method. Based on the plane strain assumption, a two-dimensional layered finite element model of asphalt pavement was established by ABAQUS software. Then the dynamic load coefficient was used to modify tire pressure that would be applied on the ABAQUS model. Then dynamic response rule of the model and how it was effected by vehicle speed were studied under random load. The results show that under the condition of random load, dynamic response of the pavement structure exhibiting a fluctuation trend as vehicle speed increases and the dynamic response characteristics of each point is different.

Abstract: Based on the theoretical analysis on the coupled vehicle-bridge vibration, this paper simulates the action of the moving vehicle load on a bridge structure with a sprung mass model, and obtains the dynamic response of the simply-supported bridge structure under the moving vehicle load through computation by finite element method (FEM). Through checking computations of classic examples, this paper proves the applicability of this computation method.

Abstract: In this paper, a novel method is proposed to address the non-linear dynamic response of a beam-like structure supported by a tensionless foundation due to moving loads. A lattice spring model (LSM) is developed to describe the structure as a discrete assembly of particles interacting via shear and rotational springs while the tensionless foundation is simulated using a chain of one-way normal springs connecting the particles to the ground. The total time for the travelling load to traverse the beam is divided into a number of steps and the generalised explicit matrix equation can be solved for each time step to obtain the time-history response of the structure. An iterative procedure is adopted to obtain the correct sign of lateral displacement for all particles at each time step, which determines the lift-off regions throughout the beam.

Abstract: Pavements represent the transport structures subjected to dynamic effect of moving vehicles. The real transport load is needed for the assessment of pavements. Such data can be obtained by numerical or experimental way. Various computing models can be used for the analysis of concrete pavements. Some possibilities are presented in this contribution.

Abstract: Subgrade stress under static vehicle load is different from that under moving load. In order to study the law of subgrade dynamic stress under moving vehicle load, the paper established the three-dimensional analysis model with finite element software and calculated the subgrade dynamic stress of different depth. It is concluded that subgrade dynamic stress decreases with the increase of depth and the smaller the depth is, the faster the degradation is. To a certain depth, subgrade dynamic stress changes a little. Meanwhile, the paper analyzed the effect of surface layer modulus and thickness, roadbase modulus and the thickness, subgrade modulus on subgrade dynamic stress. It is concluded that surface layer modulus and thickness have little effect on subgrade dynamic stress , subgrade dynamic stress decreases when roadbase modulus and the thickness increase, especially for the depth of the subgrade is relatively small. Subgrade dynamic stress increases with the increase of subgrade modulus. Increase trend is more obvious when the depth is small.

Abstract: A new damage identification method for arch bridge structures under a moving load based on the difference of deflection is presented. The function of the deflection at the mid span of the arch with the changing positions of the moving load is derived using the Moore integral method. It can be concluded from the results that when the moving load is in the area without damage, this target indicates to be linear functions with the cosine of an angle (θ) between moving load and horizontal. Nevertheless, this target is multinomial with the change of cosθ in the damage area. In order to validate the proposed damage detection algorithm, a steel arch modal is simulated, which is proved to be practicable in projects. The results indicate that the location and degree of single damage can be identified accurately.