Manicka Dhanasekar

A dynamic model for the vertical interaction of the rail track and wagon system

Abstract With the advent of high-speed trains, there is a renewed interest in the rail track–vehicle interaction studies. As part of an ongoing investigation of the track system optimisation and fatigue of the track components, a dynamic model is developed to examine the vertical interaction of the rail track and the wagon system. Wagon with four wheelsets representing two bogies is modelled as a 10 degree of freedom subsystem, the track is modelled as a four-layer subsystem and the two subsystems are coupled together via the non-linear Hertz contact mechanism. The current model is validated using several field test data and other numerical models reported in the literature by other researchers.

A THREE-DIMENSIONAL MODEL FOR THE LATERAL AND VERTICAL DYNAMICS OF WAGON-TRACK SYSTEMS

Abstract Lateral and vertical dynamics of the wagon and track affects the maintenance and safety of the heavy haul railway operation. With a view to understanding this aspect comprehensively, a three-dimensional wagon-track system dynamics (WTSD) model is developed and presented. The model consists of a full wagon with 37 degrees of freedom (DOF), a four-layer track with discretely supported rails and a wheel-rail interface representing Kalkers creep and Hertzian contact parameters. The model has been validated using two sets of field data: one dealing with vertical impact due to the flat wheel and the other dealing with lateral hunting. The effect of detailed track modelling on lateral hunting is discussed, and the capability of the three-dimensional WTSD model in predicting lateral impact is demonstrated.

Coupling of FE and EFG using collocation approach

A collocation approach is introduced to couple the finite element (FE) and the element-free Galerkin (EFG) methods. The basic idea is to evaluate the real value of nodes at the interface between the FE and the EFG regions using the moving least square interpolant for EFG and then assign this value to the FE nodal set. This method appears versatile for coupling of FE and EFG and other meshless methods. It satisfies the linear consistency exactly. Numerical tests show that this method gives reasonably accurate results consistent with the theory. Numerical studies on the sensitivity of the results to the shape of integration cells and the size of the domain of influence are also carried out.

Performance of square and inclined insulated rail joints based on field strain measurements

Insulated rail joints (IRJs) possess lower bending stiffness across the gap containing insulating endpost and hence are subjected to wheel impact. IRJs are either square cut or inclined cut to the longitudinal axis of the rails in a vertical plane. It is generally claimed that the inclined cut IRJs outperform the square cut IRJs; however, there is a paucity of literature with regard to the relative structural merits of these two designs. This article presents comparative studies of the structural response of these two IRJs to the passage of wheels based on continuously acquired field data from joints strain-gauged closer to the source of impact. Strain signatures are presented in time, frequency, and wavelet domains and the peak vertical and shear strains are systematically employed to examine the relative structural merits of the two IRJs subjected to similar real-life loading. It is shown that the inclined IRJs resist the wheel load with higher peak shear strains and lower peak vertical strains than that of the square IRJs.

Detection of Rail Wheel Flats using Wavelet Approaches

Sudden application of heavy traction/braking torque induces flats in rail wagon wheelsets. Flat wheels generate high frequency impact forces sufficient to cause severe damage to the rail head surface. Early detection of flats would facilitate re-profiling the wheels before they cause serious damage to critical rail components, such as switches, crossings, and insulated rail joints. Although there are many sensors available in the market to detect/record wagon accelerations, there are no powerful signal processing tools readily available to detect the presence of wheel flats from the recorded acceleration signatures. This study presents two wavelet approaches to overcome the difficulties in the on-board monitoring and detection systems of rail wheel flats using vibration signals. Signal average techniques, wavelet local energy average concept, and wavelet decomposition are employed in this study. A Matlab-Simulink based dynamic simulation system capable of modeling the wheel flats and track irregularities is also developed for predicting the wheelset/bogie frame acceleration time series. An analysis of the numerical simulation results demonstrates that the methods proposed in this study are effective for the on-board monitoring of wheel flats of sizes smaller than the condemning limits.

Flexural behaviour of bonded-bolted butt joints due to bolt looseness

Butt joints containing glued cover plates and bolts are used in structures subjected to severe loading with a view to maximising the structural integrity. The behaviour of such joints is not well understood due to the complex interaction of a large number of components as well as material nonlinearities. This paper presents an analysis of bonded-bolted steel butt joints with particular attention to the effect of the loss of bolt tightness to the structural behaviour. Bonded-bolted butt joints subjected to biaxial stress field have been investigated using three-dimensional finite element modelling subjected to two-step loading, the first involving pre-stressing of the bolts followed by application of inplane bending. Effect of looseness of the bolts to the inplane deformation characteristics of the joint has been particularly examined.

Effect of Spacing of Reinforcement on the Behaviour of Partially Grouted Masonry Shear Walls

Partially Grouted Reinforced Masonry (PGRM) shear walls perform well in places where the cyclonic wind pressure dominates the design. Their out-of-plane flexural performance is better understood than their inplane shear behaviour; in particular, it is not clear whether the PGRM shear walls act as unreinforced masonry (URM) walls embedded with discrete reinforced grouted cores or as integral systems of reinforced masonry (RM) with wider spacing of reinforcement. With a view to understanding the inplane response of PGRM shear walls, ten full scale single leaf, clay block walls were constructed and tested under monotonic and cyclic inplane loading cases. It has been shown that where the spacing of the vertical reinforcement is less than 2000 mm, the walls behave as an integral system of RM; for spacing greater than 2000 mm, the walls behave similar to URM with no significant benefit from the reinforced cores based on the displacement ductility and stiffness degradation factors derived from the complete lateral load – lateral displacement curves.

Plane hybrid stress element method for 3D hollow bodies of uniform thickness

Abstract A semi-analytical plane hybrid stress element method is developed from the 3D Hellinger–Reissner principle for hollow bodies of moderate thickness that possess symmetry of geometry, material properties, loading and constraint conditions to its middle plane. Exact elastic plane stress solution is extended to the assumed distribution of stress and displacement fields. Traction free conditions on the external and internal surfaces that are perpendicular to the axis passing through the thickness direction are satisfied precisely. The element possesses good convergence characteristics and its results can be compared well with the results of simple and complex engineering problems reported in the literature.

Effects of joint thickness, adhesion and web shells to the face shell bedded concrete masonry loaded in compression

The Australian masonry standard allows either prism tests or correction factors based on the block height and mortar thickness to evaluate masonry compressive strength. The correction factor helps the taller units with conventional 10 mm mortar being not disadvantaged due to size effect. In recent times, 2-4 mm thick, high-adhesive mortars and H blocks with only the mid-web shell are used in masonry construction. H blocks and thinner and higher adhesive mortars have renewed interest of the compression behaviour of hollow concrete masonry and hence is revisited in this paper. This paper presents an experimental study carried out to examine the effects of the thickness of mortar joints, the type of mortar adhesives and the presence of web shells in the hollow concrete masonry prisms under axial compression. A non-contact digital image correlation technique was used to measure the deformation of the prisms and was found adequate for the determination of strain field of the loaded face shells subjected to axial compression. It is found that the absence of end web shells lowers the compressive strength and stiffness of the prisms and the thinner and higher adhesive mortars increase the compressive strength and stiffness, while lowering the Poissons ratio.

Dynamic simulation of train–truck collision at level crossings

ABSTRACT Trains crashing onto heavy road vehicles stuck across rail tracks are more likely occurrences at level crossings due to ongoing increase in the registration of heavy vehicles and these long heavy vehicles getting caught in traffic after partly crossing the boom gate; these incidents lead to significant financial losses and societal costs. This paper presents an investigation of the dynamic responses of trains under frontal collision on road trucks obliquely stuck on rail tracks at level crossings. This study builds a nonlinear three-dimensional multi-body dynamic model of a passenger train colliding with an obliquely stuck road truck on a ballasted track. The model is first benchmarked against several train dynamics packages and its predictions of the dynamic response and derailment potential are shown rational. A geometry-based derailment assessment criterion is applied to evaluate the derailment behaviour of the frontal obliquely impacted trains under different conditions. Sensitivities of several key influencing parameters, such as the train impact speed, the truck mass, the friction at truck tyres, the train–truck impact angle, the contact friction at the collision zone, the wheel/rail friction and the train suspension are reported.