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• Polymer cement matrix (PCM) with and without fabric overlays/inserts characterised. • Benefits of carbon fibre (CF) and auxetic fabrics (AF) to PCM investigated. • CF overlayed/inserted specimens exhibited debonding and high peak load. • AF overlayed/inserted specimens exhibited no debonding and high energy absorption. • An elastic FE with contact nonlinearity predicted debonding in CF but not in AF. An experimental investigation on the flexural response of polymer cement mortar matrix overlayed or inserted with carbon fibre or auxetic fabric layers subject to four levels of rates of loading (1–150 mm/min) is reported. Seventy-two specimens made from plain polymer cement mortar, composites with auxetic and carbon fibre fabric layers overlayed at the bottom and inserted at the mid-depth of the specimens were prepared and tested under four point bending. The failure mode including debonding, peak load, load-deflection behaviour, longitudinal strain at peak load, ultimate stage and energy dissipation are reported. All composite specimens exhibited higher peak load, longitudinal strain and energy dissipation in comparison to the plain polymer mortar specimens. Auxetic fabric composites exhibited increased energy dissipation and longitudinal strain at peak load without any sign of debonding. Carbon fibre composites, on the other hand, failed due to debonding at a lower longitudinal strain. A finite element model is presented to demonstrate the debonding tendencies observed in the experiments. Increase in rate of loading improved the performance of the auxetic fabric composites but reduced the energy dissipation of carbon fibre composites. [ABSTRACT FROM AUTHOR]

Train derailment on bridges is an infrequent event, yet when it occurs, it's usually catastrophic. These incidents can toss-out part of the derailed train from the bridge deck and collapse whole or a part of the bridge. Understanding the derailment mechanisms of trains on bridges and identifying the dynamic characteristics of bridges subjected to the impact of the derailed train is fundamental to minimising severities of these incidents. This paper presents the formulation of a train-track-bridge interaction model for predicting the response of bridges under in-service operation and post-derailment behaviour. The model is used to illustrate the collision induced derailment mechanisms of a passenger train travelling on a box girder bridge; the effect of impact due to the derailed train to the dynamic response of the bridge is also narrated. The nonlinear behaviour of the train-track-bridge system under derailment impacts is detailed through the sensitivity of the wheel/rail contact and the suspension components of the train as well as the parameters of the slab-track. It is shown that the risk of the derailed vehicles being tossed out of the slab-track bridge is high although the bridge deformation and bending moment are low. • Train crashing onto obstacle on bridge deck and subsequent derailment investigated. • Rail bridge containing slab-track and passenger train were considered. • Explicit displacement method was used to assess derailment of wheelset from rail. • Post derailment response of trains and bridge deck investigated. • Derailment impact vibration is larger in slab-track than the ballast track bridges. [ABSTRACT FROM AUTHOR]

Periodic deviation of the diameter of wheel across its circumference is referred to as the out-of-round (OOR) defect that can cause significant damages to wheel – rail interface, affect the service life of various components of the vehicle/track system and the safety of trains. Under braking, OOR defect may exacerbate these damages; to uncover such exacerbation, a multi-body dynamic simulation model in a fixed coordinate system for wagons containing new/ defect free or OOR wheels subject to braking torques has been formulated and validated using a dataset in the literature. Using the validated model, the effects of the repetition order (single or multiple deviations of diameter) of OOR defect and the severity of application of braking torques to wheel wear has been examined. It has been found that under constant speed, the normal contact force increased with the repetition order. The OOR defect dominated the normal contact force with a dynamic impact force factor of 1.48, whilst the new/ defect free wheels exhibited negligible impact force. It is shown that the effect of OOR defect is significant for wear of wheels under normal braking whist under wheel skid, braking torque dominates wear. Wheel unloading ratio is shown to be a better indicator for the determination of risk to derailment, than the commonly used Nadal's derailment quotient where the wheel contains OOR defect. • Out-of-round wheels under normal, severe and emergency braking investigated. • A fixed coordinate model was formulated to investigate wheel skid under braking. • Wheel-rail contact frictional power was used to determine wear depths. • Wear under skid was significantly large irrespective of presence or absence of OOR. • Unloading of OOR wheels better predict wagon derailment than Nadal's Criterion. [ABSTRACT FROM AUTHOR]

Abstract A raised crossing (RC), as an alternate to the current form of level crossings to minimise risks of wheel-rail contact failure under frontal collision of trains onto stuck trucks, has been recently formulated by the authors (Engineering Failure Analysis, 80 (2017) 403–415) to mitigate the severity of accidents at road-rail crossings. The aim of the present paper is to assess the effectiveness of the profile of the RC to minimise the risk of speeding through and minimise the peak vertical acceleration of the passing road vehicle below the threshold level for discomfort and safety of its occupants. For this purpose, a simplified two-dimensional multibody dynamic simulation modelling method has been formulated and validated using a detailed three-dimensional industry standard model. The validated model has then been used to optimise the geometric profile of the RC by minimising the peak vertical accelerations of the occupants below the safety threshold of 0.7 g. It is shown that the optimised profile of the RC increases the peak acceleration with the increase in speed of travel of the road vehicles whilst the LC does the opposite. This finding confirms that the RC has the potential to reduce the risk of speeding, which is vital to the safety of the train and road vehicles at rail – road crossings. Highlights • A raised road – rail crossing is proposed to mitigate the severity of crashes. • Safety of heavy vehicles crossing the raised crossing simulated • The raised crossing is shown to deter road vehicles speeding through. • The slopes and gaps were optimised to minimise vertical acceleration of road vehicles. • Optimised crossing is shown to improve safety significantly than the level crossing. [ABSTRACT FROM AUTHOR]

Highlights • Unreinforced masonry (URM) under multiaxial loading examined. • In-plane and out-of-plane loading combined with precompression considered. • Three edges supported URM walls analysed and interaction curves established. • Interaction curves are affected by the type of support condition. • In-plane resistance increases with increase in precompression. • In-plane resistance sharply reduces with the increase in out-of-plane loading. Abstract Interaction curves for masonry walls supported on all four edges subject to multi-directional loading has recently been reported by the authors (Noor-E-Khuda et al., 2018). Load bearing URM walls are generally detailed with vertical control joints (which are structural end where the normal stress vanishes), and non-load bearing walls are likely to have unsupported top horizontal edge. Therefore, three sides supported URM walls are examined in this study. An explicit finite element macro model based on a layered shell element is used in the investigation. A series of interaction curves approximately resembling bilinear domain is developed to represent the response of the one vertical edge unsupported URM walls under multi-directional loading. The interaction curves for the top horizontal edge free walls showed a trilinear approximation. Influence of the boundary conditions and the level of out-of-plane loading to the shape of the interaction curve have been examined. It is shown that the in-plane capacity reduces rapidly beyond a critical out-of-plane load level; therefore, disregarding the multi-directional loading interaction could be unsafe. A simplified non-dimensional expression proposed by the authors for the interaction curves of four sides supported walls is extended for the three sides supported walls in this paper. [ABSTRACT FROM AUTHOR]

Contact surface unevenness of the dry-stackable, interlocking blocks adversely affects the constructability of the drystack system. This paper presents the contact surface characteristics of these blocks and strategies for mitigating the unevenness through systematic experimental and numerical studies. First, the contact surface characteristics of the dry-stackable blocks have been examined experimentally using matrix based tactile surface sensors (MBTSS). High peak pressure locations on the contacting interfaces have been identified; these locations have remained unaffected by the level of the applied load in the experiment. A micro finite element modelling method incorporating the uneven contact surface has been formulated and the parameters calibrated using the experimental data. Two strategies for minimising the contact surface unevenness are then proposed (1) grinding of the surfaces of the blocks and (2) embedding a packing material between the surfaces. Both strategies have been analysed through the finite element model. The peak contact pressure is shown to have reduced considerably for the grinding strategy and when an auxetic fabric is used as an insert between the contacting surfaces of the blocks. [ABSTRACT FROM AUTHOR]

Derailments on bridges, although not frequent, when occurs due to a complex dynamic interaction of the train–track–bridge structural system, are very severe. Furthermore, the forced vibration induced by the post-derailment impacts can toss out the derailed wagons from the bridge deck with severe consequences to the traffic underneath and the safety of the occupants of the wagons. This paper presents a study of the train–track–bridge interaction during a heavy freight train crossing a concrete box girder bridge from a normal operation to a derailed state. A numerical model that considers the bridge vibration, train–track interaction and the train post-derailment behaviour is formulated based on a coupled finite-element – multi-body dynamics (FE-MBD) theory. The model is applied to predict the post-derailment behaviour of a freight train composed of one locomotive and several wagons, as well as the dynamic response of a straight single-span simply supported bridge containing ballast track subjected to derailment impacts. For this purpose, a typical derailment scenario of a heavy freight train passing over a severe track geometry defect is introduced. The dynamic derailment behaviour of the heavy freight train and the dynamic responses of the rail bridge are illustrated through numerical examples. The results exhibit the potential for tossing out of the derailed trains from the unstable increase in the yaw angle signature and a lower rate of increase of the bridge deck bending moment compared to the increase in the static axle load of the derailed wheelset. [ABSTRACT FROM AUTHOR]

The safety of cars and trucks crossing gapped road surfaces can be affected by their operational speed, mass, and the tire and road surface characteristics. As part of a research on the safety of road vehicles crossing discontinuous road surfaces, the dynamic behavior of a single tire passing a gap has been examined as reported in this paper. First, the kinematics of a tire crossing the gap in the road surface is analytically formulated. The formulation has shown that the tire exhibits three distinct (single-point, two-point, and flying) modes of travel depending on its operational speed. The dynamics of the tire are larger in single-point mode that exhibits two critical velocities, which have been validated using a nonlinear arbitrary Lagrangian Eulerian method in the finite-element framework. The validated analytical model has shown that the critical velocity is mainly affected by the mass of the overburden. [ABSTRACT FROM AUTHOR]

Derailments of trains often occur due to the wheel-rail contact failure caused by the impact of the trains with road vehicles at road-rail crossings. Frontal collisions of passenger trains onto stuck road vehicles occur frequently at such road-rail crossings even where active warning systems are installed. Such collisions are often fatal and cause significant damages to vehicles and the infrastructure especially when they incur derailments. Innovations in passive railway infrastructure designs for mitigating the severity of collision induced derailments are rare. This paper presents a formulation for a passive road-rail crossing involving stiffened edges of the raised road pavement to minimise the risk of failure of wheel–rail contact using a nonlinear three-dimensional multibody dynamics model. Severe derailment scenarios of trains passing through the passive and normal road-rail crossings have been analysed and presented. The innovative design of the road-rail crossing with passive track structure presented in the paper is shown to reduce the failure of the wheel-rail contact and hence the train-truck frontal collision derailment potential. [ABSTRACT FROM AUTHOR]

Application of auxetic materials in automobile and biomedical engineering is widely reported and their usage in civil engineering is emerging. This paper reports the manufacturing and characterising of cementitious polymer mortar – auxetic foam composites suitable for wall rendering. The deformation behaviour of the composites with the high negative Poisson’s ratio (NPR) auxetic foam embedded in polymer cement mortar matrix has been experimentally evaluated and compared to the commonly used mortar composites containing fiberglass mesh layers (that exhibits positive Poisson’s ratio). It is shown that the auxetic embedded polymer cement composite outperformed other composites through elimination of delamination and minimisation of brittleness. The auxetic foams used in this research were manufactured from the inexpensive open cell polyurethane foam through a thermo-mechanical process and characterised through lab tests; the maximum Poisson’s ratio determined was −1.5. Sixty composite specimens tested under axial compression exhibited a maximum NPR of −0.11. The results were validated numerically. The numerical model was then used to examine the effectiveness of the relative thickness of the auxetic foam layers and the polymer cement matrix for maximising the NPR of the composites. The results show that through auxetic material embedment, delamination and brittleness suffered by the cementitious composites could be eliminated. [ABSTRACT FROM AUTHOR]

Insulated rail joints (IRJs) identify broken rails and train locations in railway signalling circuitry, which are critical to the rail safety operation. Unfortunately, IRJs exhibit several failure modes due to complex interaction between their components, the load spectra and the support conditions. A novel idea of simplifying the design of the IRJs consisting of only two pieces of insulated rails embedded into a concrete sleeper in such a way that the free ends of the rails at the gap attain stiffness commensurate to that of the current designs where the gapped rails are connected with two joint bars (also known as fishplates) one on each side of the rail web with the assembly resting on top of sleepers. The advantages of the new design are that it exhibits stability levels comparable to the current designs with fewer components and hence fewer failure modes. A multi-objective optimisation framework was used for the development of the new design that enables safe passage of train wheels across the gap between the rails embedded in concrete sleepers. Feasibility of the sleeper embedded gapped insulated rails under traffic loading is demonstrated through a dynamic analysis of a rail wheel rolling on top of a selected optimal design from the Pareto front. The deformation components of the rail edge at the gap of the new design are shown to be lower than that of the classical insulated rail joints. [ABSTRACT FROM AUTHOR]

Collision incidents involving trains and road vehicles at road-rail crossings are common occurrences, which are fatal and incur significant economic and societal costs. The existing studies of train collision derailments mainly focus on the rail vehicles running on straight tracks, while the derailments induced by train-truck collision at a road-rail crossing in curved tracks are rarely investigated, although such crossings are more common. This paper presents a study of the derailment assessment of passenger trains due to the collision with heavy road trucks stuck across the curved road-rail crossing by means of train-track dynamics simulations. For this purpose, a nonlinear three-dimensional model of a passenger train impacting a road truck stuck on curved tracks is developed based on the multi-body dynamics theory. Sensitivity of key design parameters such as the curve radius, the collision point at the curved track section, and the impact direction between the train and the truck, and their effects on the derailment behaviour of colliding trains are reported. The results show that the derailment potential is higher at smaller radius track and at the circular curves. [ABSTRACT FROM PUBLISHER]

Road trucks stuck obliquely across rail tracks in level crossings and collided by trains are common occurrences; such scenarios are used in the assessment of crashworthiness of locomotives. With the ongoing increase in mass of the road trucks, these incidents can lead to derailment without fully exhausting the crush zones of the locomotives, especially in light passenger trains. Understanding the derailment mechanism of trains due to frontal collisions on stuck road trucks is fundamental for the development of advanced devices and/or technologies that can prevent these derailments. This paper presents a study of the dynamic responses and derailment mechanisms of trains for this scenario using a multi-body dynamics simulation method. A fully nonlinear three-dimensional dynamic model to simulate the frontal collision of a passenger train onto an obliquely stuck road truck on a ballasted track is formulated. This nonlinear model is capable of predicting the dynamic response as well as the derailment mechanism of trains. It is shown that the large lateral shift and yaw motion of the longitudinally coupled train vehicle bodies caused by the frontal impact force is the root cause of the derailments. [ABSTRACT FROM AUTHOR]

Lateral collisions between heavy road vehicles and passenger trains at level crossings and the associated derailments are serious safety issues. This paper presents a detailed investigation of the dynamic responses and derailment mechanisms of trains under lateral impact using a multi-body dynamics simulation method. Formulation of a three-dimensional dynamic model of a passenger train running on a ballasted track subject to lateral impact caused by a road truck is presented. This model is shown to predict derailment due to wheel climb and car body overturning mechanisms through numerical examples. Sensitivities of the truck speed and mass, wheel/rail friction and the train suspension to the lateral stability and derailment of the train are reported. It is shown that improvements to the design of train suspensions, including secondary and inter-vehicle lateral dampers have higher potential to mitigate the severity of the collision-induced derailments. [ABSTRACT FROM AUTHOR]

A generalised model based on damage mechanics for predicting the response of masonry subjected to compression is presented. The model accounts for the behaviour of the constituents of the masonry, viz., the units, the mortar and the unit–mortar interfaces; in this paper, the unit–mortar interfaces and the mortar layers have been treated as a homogenised continuum. The principles of damage mechanics coupled with limiting damage surfaces have been used to simulate the behaviour of the masonry constituents. The novelty is the use of a non-linear, progressively stiffening stress–strain curve to simulate the viscoelastic behaviour of the homogenised mortar–interface (for conventional masonry) or dry surface–interface (for dry-stack masonry) layers until a threshold strain is reached. Beyond the threshold strain, their behaviour is assumed to have changed to progressive softening common for concrete like materials. The damage model for compression and tension due to progressive stiffening and softening criteria respectively have been formulated for the masonry constituents. The parameters which characterise the tensile and compressive behaviours, the volumetric change and the damage behaviour of the masonry constituents have been calibrated using some available experimental data in the literature. The model is shown to predict the average compressive strength and stress–strain behaviour of the masonry prisms appropriately. The model is capable of capturing the behaviour including appropriate stiffness degradation and post peak softening that are comparable to the experimental predictions reported in the literature for various types of masonry. [ABSTRACT FROM AUTHOR]

This paper provides critical analyses of the presence of the reinforced grout cores within the masonry walls with particular reference to the existing in-plane shear design expressions in several national standards; these expressions comprise terms which define the shear strength of masonry, the vertical load and the area of reinforcement. These expressions treat the wall height to length ratio (termed as wall aspect ratio) as a prime factor in their respective masonry strength terms. The consideration of the wall aspect ratio in these design expressions implies existence of a compression strut along the wall diagonal, although such a phenomenon is not established in the literature. In this paper, through an extensive analyses of partially grouted reinforced masonry shear walls using a validated nonlinear finite element model, it is shown that the aspect ratio of the unreinforced masonry panels inscribed within the vertical and the horizontal reinforced grouted cores has profound effect on the in-plane shear capacity of the walls. It is also shown that the horizontal and the vertical reinforcements do never yield and hence their inclusion in the in-plane shear capacity expressions is not justified. A recently reported expression by the authors is also reviewed and compared with the other international design expressions. [ABSTRACT FROM PUBLISHER]

Derailments due to lateral collisions between heavy road vehicles and passenger trains at level crossings (LCs) are serious safety issues. A variety of countermeasures in terms of traffic laws, communication technology and warning devices are used for minimising LC accidents; however, innovative civil infrastructure solution is rare. This paper presents a study of the efficacy of guard rail system (GRS) to minimise the derailment potential of trains laterally collided by heavy road vehicles at LCs. For this purpose, a three-dimensional dynamic model of a passenger train running on a ballasted track fitted with guard rail subject to lateral impact caused by a road truck is formulated. This model is capable of predicting the lateral collision-induced derailments with and without GRS. Based on dynamic simulations, derailment prevention mechanism of the GRS is illustrated. Sensitivities of key parameters of the GRS, such as the flange way width, the installation height and contact friction, to the efficacy of GRS are reported. It is shown that guard rails can enhance derailment safety against lateral impacts at LCs. [ABSTRACT FROM AUTHOR]

An explicit finite element modelling method is formulated using a layered shell element to examine the behaviour of masonry walls subject to out-of-plane loading. Masonry is modelled as a homogenised material with distinct directional properties that are calibrated from datasets of a “C” shaped wall tested under pressure loading applied to its web. The predictions of the layered shell model have been validated using several out-of-plane experimental datasets reported in the literature. Profound influence of support conditions, aspect ratio, pre-compression and opening to the strength and ductility of masonry walls is exhibited from the sensitivity analyses performed using the model. [ABSTRACT FROM AUTHOR]

Out-of-plane behaviour of mortared and mortarless masonry walls with various forms of reinforcement, including unreinforced masonry as a base case is examined using a layered shell element based explicit finite element modelling method. Wall systems containing internal reinforcement, external surface reinforcement and intermittently laced reinforced concrete members and unreinforced masonry panels are considered. Masonry is modelled as a layer with macroscopic orthotropic properties; external reinforcing render, grout and reinforcing bars are modelled as distinct layers of the shell element. Predictions from the layered shell model have been validated using several out-of-plane experimental datasets reported in the literature. The model is used to examine the effectiveness of two retrofitting schemes for an unreinforced masonry wall. [ABSTRACT FROM AUTHOR]

Masonry under compression is affected by the properties of its constituents and their interfaces. In spite of extensive investigations of the behaviour of masonry under compression, the information in the literature cannot be regarded as comprehensive due to ongoing inventions of new generation products – for example, polymer modified thin layer mortared masonry and drystack masonry. As comprehensive experimental studies are very expensive, an analytical model inspired by damage mechanics is developed and applied to the prediction of the compressive behaviour of masonry in this paper. The model incorporates a parabolic progressively softening stress–strain curve for the units and a progressively stiffening stress–strain curve until a threshold strain for the combined mortar and the unit-mortar interfaces is reached. The model simulates the mutual constraints imposed by each of these constituents through their respective tensile and compressive behaviour and volumetric changes. The advantage of the model is that it requires only the properties of the constituents and considers masonry as a continuum and computes the average properties of the composite masonry prisms/wallettes; it does not require discretisation of prism or wallette similar to the finite element methods. The capability of the model in capturing the phenomenological behaviour of masonry with appropriate elastic response, stiffness degradation and post peak softening is presented through numerical examples. The fitting of the experimental data to the model parameters is demonstrated through calibration of some selected test data on units and mortar from the literature; the calibrated model is shown to predict the responses of the experimentally determined masonry built using the corresponding units and mortar quite well. Through a series of sensitivity studies, the model is also shown to predict the masonry strength appropriately for changes to the properties of the units and mortar, the mortar joint thickness and the ratio of the height of unit to mortar joint thickness. The unit strength is shown to affect the masonry strength significantly. Although the mortar strength has only a marginal effect, reduction in mortar joint thickness is shown to have a profound effect on the masonry strength. The results obtained from the model are compared with the various provisions in the Australian Masonry Structures Standard AS3700 (2011) and Eurocode 6. [ABSTRACT FROM AUTHOR]

In-plane shear capacity formulation of reinforced masonry is commonly conceived as the sum of the capacities of three parameters, viz, the masonry, the reinforcement, and the precompression. The term "masonry" incorporates the aspect ratio of the wall without any regard to the aspect ratio of the panels inscribed (and hence confined) by the vertical and the horizontal reinforced grout cores. This paper proposes design expressions in which the aspect ratio of such panels is explicitly included. For this purpose, the grouted confining cores are regarded as a grid of confining elements within which the panels are positioned. These confined masonry panels are then considered as building blocks for multi-bay, multi-storied confined masonry shear walls and analyzed using an experimentally validated macroscopic finite-element model. Results of the analyzes of 161 confined masonry walls containing panels of height to length ratio less than 1.0 have been regressed toformulate design expressions. These expressions have been first validated using independent test data sets and then compared with the existing equations in some selected international design standards. The concept of including the unreinforced masonry panel aspect ratio as an additional term in the design expression for partially grouted/confined masonry shear walls is recommended based on the conclusions from this paper. [ABSTRACT FROM AUTHOR]

This paper presents experimental studies on the behaviour of a thin layer polymer mortared concrete masonry under combined shear–compression. Thirty thin layer mortared concrete masonry panels with five bed joint orientations were constructed and tested under vertical compression to generate a wide range of compression to shear ratios from zero to infinity at each of the bed joints of the panels. The strength and deformation characteristics are discussed in this paper. Unlike the conventional 10 mm thick cement mortared masonry, the thin layer polymer mortared masonry failed in a combined mechanism involving both the block and the mortar in some combination of shear–compression; however, similar to the conventional masonry, its strength and deformation were affected by the orientation of the bed joint to the direction of the applied loading. This paper reports a comparative study of the experimental results with a number of shear–compression tests on varied masonry systems reported in the literature; the thin layer mortared concrete masonry is shown trending towards isotropic behaviour compared to conventional masonry, which is distinctly orthotropic. [ABSTRACT FROM AUTHOR]

This paper presents a study on the effectiveness of two forms of reinforced grout confining systems for hollow concrete block masonry. The systems considered are: (1) a layer of grout directly confining the unreinforced masonry, and (2) a layer of grout indirectly confining the unreinforced masonry through block shells. The study involves experimental testing and finite-element (FE) modeling of six diagonally loaded masonry panels containing the two confining systems. The failure mode, the ultimate load, and the load-deformation behaviors of the diagonally loaded panels were successfully simulated using the finite-element model. In-plane shear strength and stiffness of the masonry thus determined are used to evaluate some selected models of the confined masonry shear including the strut-and-tie model reported in the literature. The evaluated strut width is compared with the prediction of the FE model and then extended for rational prediction of the strength of confined masonry shear walls. [ABSTRACT FROM AUTHOR]

Masonry bond is affected by many parameters such as the type of mortar used, the techniques of dispersion of mortar and the surface texture of the concrete blocks. Additionally it is understood from the studies on conventional masonry that the bond characteristics are also influenced by the curing methods as well as the age of the bond at the time of testing. These effects on thin layer mortared masonry employing polymer cement mortars are not well understood. Therefore, the effect of curing methods and age to the bond strength and deformation of masonry containing thin layered polymer cement mortar was investigated as part of an ongoing research program at the Queensland University of Technology. This paper presents an experimental investigation of the flexural and shear bond characteristics of the thin layer mortared concrete masonry. The parameters examined include the effects curing and ageing to the bond development over a period from 14 days to 56 days after fabrication. The results exhibit that dry cured thin layer mortared masonry exhibits higher bond strength and Young’s and shear moduli compared to the wet cured specimens. [ABSTRACT FROM AUTHOR]

A nonlinear interface element modelling method is formulated for the prediction of deformation and failure of high adhesive thin layer polymer mortared masonry exhibiting failure of units and mortar. Plastic flow vectors are explicitly integrated within the implicit finite element framework instead of relying on predictor–corrector like approaches. The method is calibrated using experimental data from uniaxial compression, shear triplet and flexural beam tests. The model is validated using a thin layer mortared masonry shear wall, whose experimental datasets are reported in the literature and is used to examine the behaviour of thin layer mortared masonry under biaxial loading. [ABSTRACT FROM AUTHOR]

Railhead is perhaps the highest stressed civil infrastructure due to the passage of heavily loaded wheels through a very small contact patch. The stresses at the contact patch cause yielding of the railhead material and wear. Many theories exist for the prediction of these mechanisms of continuous rails; this process in the discontinuous rails is relatively sparingly researched. Discontinuous railhead edges fail due to accumulating excessive plastic strains. Significant safety concern is widely reported as these edges form part of Insulated Rail Joints (IRJs) in the signalling track circuitry. Since Hertzian contact is not valid at a discontinuous edge, 3D finite element (3DFE) models of wheel contact at a railhead edge have been used in this research. Elastic-plastic material properties of the head hardened rail steel have been experimentally determined through uniaxial monotonic tension tests and incorporated into a FE model of a cylindrical specimen subject to cyclic tension loading. The parameters required for the Chaboche kinematic hardening model have been determined from the stabilised hysteresis loops of the cyclic load simulation and implemented into the 3DFE model. The 3DFE predictions of the plastic strain accumulation in the vicinity of the wheel contact at discontinuous railhead edges are shown to be affected by the contact due to passage of wheels rather than the magnitude of the loads the wheels carry. Therefore to eliminate this failure mechanism, modification to the contact patch is essential; reduction in wheel load cannot solve this problem. [ABSTRACT FROM AUTHOR]

Highlights: [•] Masonry confined with reinforced grouted cores have been examined. [•] Explicit FE modelling of URM and confined masonry presented. [•] Diagonal test datasets used to validate the FE model. [•] Reinforcement in confining core is shown to remain elastic. [•] FE predictions compared with four major national masonry design standards. [ABSTRACT FROM AUTHOR]

Highlights: [•] Flexural and shear bonds of thin layer mortared concrete masonry are addressed. [•] Polymer cement mortars improve the bond strength in masonry. [•] Digital image correlation captures the interface shear strains. [•] Bond strength in shear and flexure is approximately same in thin layer mortared masonry. [Copyright &y& Elsevier]

The railhead is severely stressed under the localized wheel contact patch close to the gaps in insulated rail joints. A modified railhead profile in the vicinity of the gapped joint, through a shape optimization model based on a coupled genetic algorithm and finite element method, effectively alters the contact zone and reduces the railhead edge stress concentration significantly. Two optimization methods, a grid search method and a genetic algorithm, were employed for this optimization problem. The optimal results from these two methods are discussed and, in particular, their suitability for the rail end stress minimization problem is studied. Through several numerical examples, the optimal profile is shown to be unaffected by either the magnitude or the contact position of the loaded wheel. The numerical results are validated through a large-scale experimental study. [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the failure of high adhesive, low compressive strength, thin layered polymer mortar joints in masonry through a contact modelling in finite element framework. Failure due to combined shear, tensile and compressive stresses are considered through a constitutive damaging contact model that incorporates traction–separation as a function of displacement discontinuity. The modelling method is verified using single and multiple contact analyses of thin mortar layered masonry specimens under shear, tensile and compressive stresses and their combinations. Using this verified method, the failure of thin mortar layered masonry under a range of shear to tension ratios and shear to compression ratios has been examined. Finally, this model is applied to thin bed masonry wallettes for their behaviour under biaxial tension–tension and compression–tension loadings perpendicular and parallel to the bed joints. [Copyright &y& Elsevier]

It is well known that track defects cause profound effects to the dynamics of railway wagons; normally such problems are examined for cases of wagons running at a constant speed. Brake/traction torques affect the speed profile due to the wheel–rail contact characteristics but most of the wagon–track interaction models do not explicitly consider them in simulation. The authors have recently published a model for the dynamics of wagons subject to braking/traction torques on a perfect track by explicitly considering the pitch degree of freedom for wheelsets. The model is extended for cases of lateral and vertical track geometry defects and worn railhead and wheel profiles. This paper presents the results of the analyses carried out using the model extended to the dynamics of wagons containing less ideal wheel profiles running on tracks with geometry defects and worn rails. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents half of a full scale experimental testing technique for assessing the structural adequacy of a disused flat bottom rail wagon (FBW) for low volume, heavy axle load road bridge applications. The aim of this ongoing research project is to develop sufficient knowledge required for achieving significant economy and safety of the heavy axle transportation system in regional government council roads. In the absence of such knowledge, the viability of replacing/rehabilitating the ageing bridges could not be economically justified, mainly due to low volume traffic and the costs of alternate solutions using new materials for heavy axle load demands. This study describes a comprehensive laboratory testing of half of a single lane, single span bridge deck and an associated three dimensional finite element modeling. The novel idea in the paper is to enforce the transverse continuity conditions along the longitudinal edge of the half of full scale bridge so that the single FBW tested will mimic the behaviour of a double FBW deck for a single lane road bridge under heavy axle design loads. Several serviceability and ultimate load tests, conforming to the Australian bridge design traffic loads applied at critical locations of the FBW system are reported in the paper. The test results demonstrate that the FBW possesses sufficient structural strength and can service the required design traffic loads. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Braking or traction torque is regarded as an important source of wheelset skid and a potential source of derailment risk that adversely affects the safety levels of train operations; therefore, this research examines the effect of braking/traction torque to the longitudinal and lateral dynamics of wagons. This paper reports how train operations safety could be adversely affected due to various braking strategies. Sensitivity of wagon dynamics to braking severity is illustrated through numerical examples. The influence of wheel/rail interface friction coefficient and the effects of two types of track geometry defects on wheel unloading ratio and wagon pitch are also discussed in the paper. [ABSTRACT FROM AUTHOR]

Abstract: Much work on special elements that simplify geometrical modelling of structures containing holes, cracks and/ or inclusions has been reported extensively in the literature. This paper presents a hybrid-Trefftz element containing elliptic hole formulated using Hellinger–Reissner principle by employing trial functions based on the mapping technique and the Cauchy integral method. The element presented in this paper could be regarded as an improved formulation over Piltner [Special finite elements with holes and internal cracks, Int. J. Numer. Methods Eng. 21 (1985) 1471–1485] element because the chosen trail functions in this paper have provided relatively more stable solutions. The use of the element with other ordinary displacement-based finite elements has also yielded very accurate solutions even when very coarse meshes relative to the size of the elliptic hole have been used. [Copyright &y& Elsevier]

This paper presents a method for tracking two-dimensional propagation of internal cracks, in particular vertical split head (VSH) defects, due to contact loading in railhead. Generalised curved crack is assumed to have present in the railhead and its propagation is simulated by solving interaction of arbitrary shaped cracks successively. Furthermore, the finite shape of the rail section is also modelled as the continuous distribution of dislocation within an infinite plane. Crack propagation is simulated using the criterion of vanishing of Mode II stress intensity factors (SIF) at crack tips. Examples are provided for tracking the propagation of pre-existing internal cracks in railheads turning into VSH defects under centric contact loading. [ABSTRACT FROM AUTHOR]

This paper presents the application of a three-dimensional wagon-tracks system dynamics (3DWTSD) model to examine the hunting characteristics of wagons containing three-piece bogies running on tangent track. In the 3DWTSD model, two types of track subsytem were considered - one as a layered viscoelastic track subsystem and the other as a 'rigid' track subsystem. Both the critical speed of wagons and the hunting frequency obtained using the viscoelastic track subsystem are smaller than those examined. The worn wheel profile was found to increase the critical speed of wagons in addition to changing the hunting characteristics. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method based on the principle of continuous distribution of dislocation to model curved cracks in solids of arbitrarily shaped finite geometries. Both the boundary of the finite body and the curved crack are modelled by distributed dislocation. In this method the influence function of the dislocation along the finite body boundary is reduced to a product of the Hilbert kernel with a normal function. Similarly the influence function for the curved cracks is reduced to the product of Cauchy kernel and a normal function. This approach results in a system of singular integral equations. Using the order decreasing method, the system is reduced to normal integral equations, which are solved numerically. Stress intensity factors are evaluated for a well-known crack problem and two railhead crack problems with a view to assessing the capability of the developed method to solve complex engineering problems. [Copyright &y& Elsevier]

• A parametric study of dynamic track buckling using a combination of multi-body train-track dynamic model and finite element analysis of railway track. • Simultaneous application of thermal and train loading and resulting effects on track buckling. • Study of steady motion and braking of wagon with various types of braking torque application on track buckling potential. • Studying the effects of wheel out of round defect on track buckling during steady motion and braking of the wagon. • Track buckling temperature for severe braking of a wagon with out of round defects of order 3 is almost 5.5 °C lower than the static case. The drop for safe temperature is 6.7 °C. Continuously welded rails (CWR) are sensitive to thermal and train loads which could destabilize the track and cause buckling. The study of track buckling in the literature, however, is mostly focused on static analysis of CWR tracks under thermal loads. Yet in reality, train dynamic loads in lateral, vertical and longitudinal directions can have a major impact on track buckling behaviour. Moreover, track and wheel defects can aggravate the dynamic train track interaction loads, and reduce the safety against track buckling. The aim of this paper is to have an in-depth comparison of static and dynamic track buckling by employing a multi-body train-track dynamic model and a 3D finite element track model. Various scenarios are elaborated, base scenario dealing with static thermal analysis, dynamic analysis for a steady motion of a wagon with constant speed, dynamic analysis for a wagon with defect free wheels during braking, and dynamic analysis for a wagon with out of round defect wheels during braking. For each scenario, a sensitivity analysis of relevant parameters is also presented. Based on the results, it is concluded that train loads can significantly change the buckling temperature, as well as the safe temperature. For a severe braking of a wagon with out of round wheel defect of order 3, buckling temperature is almost 5.5 °C less than that of the static case. The drop for safe temperature in this case is 6.7 °C. [ABSTRACT FROM AUTHOR]

• Compressive characteristics of lime mortar bonded brickworks were assessed. • Difference in thickness did not alter the failure mode of the masonry wallettes. • Increase in wallette thickness did not increase the compressive strength. • Monotonic compressive strengths were higher than the cyclic compressive strengths. • Analytical models of the cyclic characteristics of masonry were calibrated. Lime mortar bonded brickwork loadbearing walls are widely employed in many colonial period structures around the world; however, most of the research articles on masonry structures refer only to single brick thick walls. With a view to understanding the characteristics of masonry of various bonding patterns and thickness, an experimental programme was carried out that included testing of 42 wallettes under monotonic and cyclic compression. This paper presents datasets of the tested lime mortared masonry wallettes. The 42 masonry wallettes were made with two types of clay bricks and a hydraulic lime mortar. Wallettes consisted of single, double and triple brick thicknesses. The experimental results are presented in terms of compressive strengths, stress–strain curves and deformation characteristics. The difference in thickness was shown not to significantly affect the compressive strength of masonry. Cyclic loading was shown to reduce the compressive strength of masonry wallettes by 9–5% compared to the corresponding monotonic compressive strengths. Responses of cyclic loaded masonry wallettes are presented in terms of the failure pattern, strength, stiffness and stress–strain relationships. Generalised analytical expressions for envelop, common and stability point curves have also been derived from the cyclic stress–strain curves of the wallettes tested. [ABSTRACT FROM AUTHOR]

• Masonry walls impacted by low velocity objects exhibit global failure mode. • A FE model was formulated and validated using 7 experimental datasets. • Impacted energy is largely dissipated by post-peak vibration of the impacted walls. • The natural frequency of wall can be predicted from the post-peak vibration signature. • Effects of aspect ratio, slenderness ratio, supports and impact locations reported. Masonry buildings constructed along busy roads are vulnerable to vehicular impacts. As most of these impacts are likely to occur at low velocity due to severe braking by drivers to avoid catastrophe, the present study reports a failure analysis of masonry walls subject to low velocity impacts. An explicit finite element modelling method incorporating homogenised anisotropic masonry material developed previously for static loading was validated through low velocity impact test datasets reported in the literature. Subsequently, an extensive study was undertaken to evaluate the impact damage patterns of masonry walls of varied boundary conditions, aspect ratios, and slenderness ratios. This paper identifies a threshold impact energy, below which contemporary single leaf masonry walls irrespective of their boundary conditions and aspect ratio, exhibit global damage with varied failure patterns. Slenderness ratio of the impacted wall is shown as the most important parameter in resisting impact loads. The results presented in this study can be useful for developing mitigation strategies for walls vulnerable to low velocity vehicular impacts. [ABSTRACT FROM AUTHOR]

An introduction to articles in this issue is presented including ballast, sleeper and rail joints.

Abstract Optimisation of railhead profiles using improved non-uniform rational B-Splines (NURBS) and measured profiles is presented for curved tracks to minimise wear. Measured geometry of rail profiles have been parameterised for the NURBS model. These parameters have then been decomposed as constants and variables to represent any other generalised rail profile. The variable parameters have been defined as design variables for the optimisation modeling method that minimises wear of the railhead profile suitable for curved rail track. A genetic algorithm optimisation method was formulated incorporating the parameters of the measured rail profiles with improved NURBS curves described as genes for high and low rails in curved tracks and combined them as chromosomes. The method can handle optimisation of any unique rail profile, although examples given in this paper refer to only the 60 kg/m Chinese Rail CH60. Optimal rail profiles are shown to mitigate wear of wheel-rail contact under the operation of a vehicle passing through a curved track. The optimal shape was shown to minimise contact stresses, increase rolling radius difference and conicity for improved passenger comfort and vehicle safety. Highlights • High and low railhead profiles on tracks of varied curve radii measured. • Measured profiles parameterised using improved Non-Uniform Rational B-Splines. • Genetic Algorithm Optimisation model formulated using the parameterised variables. • Wheel-rail contact frictional power used as objective function. • Optimal profiles for curved tracks minimised wear and derailment coefficient. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM PUBLISHER]

With a view to improving the ease of construction, a new type of outer sleeve assembly (OSA) between steel beam and column has been developed. The characteristics of stress distribution and failure modes of the components of twelve OSAs were analysed using a general purpose finite element software ANSYS. The roles of square and H outer sleeves to the structural action of the OSA are described in this paper. The material, geometry and contact nonlinearities of the assembly of the OSA have been identified as the main factors affecting the joint stiffness and bending capacity. Seismic performance of the new OSA is reported using failure modes, hysteresis curves and skeleton curves of different models. Four key parameters, viz., the thickness of the sleeve, the wall thickness of square steel tubular column, the length of square sleeve and the length of H sleeve are shown to significantly affect the monotonic and the hysteretic behaviour of the joint. Based on the superposition principle, a simplified method for calculating the initial stiffness of the OSA is proposed. Using the component method, the flexural capacity of the outer sleeve joint was calculated and analysed. The simulation and theoretical calculation have proved that the simplified calculation method is feasible. The numerical analysis results show that the new OSA beam-column connection joint has good energy dissipation and ductility under low-cycle cyclic loading. The four parameters mentioned above have certain influence on the bearing capacity, energy dissipation and ductility of the joint. • New type of outer sleeve assembly (OSA) between steel beam and column is developed. • Simplified method for calculating the initial stiffness of the OSA is proposed. • Flexural capacity of the outer sleeve joint is calculated and analysed. • New OSA beam-column connection joint has good energy dissipation and ductility. [ABSTRACT FROM AUTHOR]

Railroad corridors contain a large number of insulated rail joints (IRJs) that act as elements (critical to safety) in the circuitries of signaling and broken rail identification systems. IRJs are regarded as sources of excitation for the passage of loaded wheels that lead to high-impact forces. These forces in turn cause dips, cross levels, and twists to the railroad geometry in close proximity to the sections that contain IRJs, in addition to local damage to the railhead of the IRJs. Therefore, a systematic monitoring of IRJs in railroads is prudent to mitigate the potential risk of their sudden failure (e.g., broken tie plates) as a consequence of rail traffic. This paper presents a simple method of periodic recording of images using time-lapse photography and total station surveying measurements to understand the ongoing deterioration of IRJs and their surroundings. Over a 500-day period, data were collected to examine the trends in narrowing of the joint gap that is attributable to plastic deformation of the railhead edges. Data was also collected with respect to the dips, cross levels, and twists that were imparted to the railroad geometry, which is attributable to the settlement of ties (sleepers) around the IRJs. The results reflect that the average progressive settlement beneath the IRJs is larger than that under the continuously welded rail, which leads to excessive deviation of the railroad profile, cross levels, and twists. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a nonlinear damage accumulation (NLDA) model for shakedown failure of materials and structures subjected to high amplitude, low cycle load history capable of producing substantial plastic strain. This NLDA model is formulated based on energy principles coupled with a cumulative damage parameter that accounts for the progressive damage accumulation dictated by the path of the load history without any requirement for counting of cycles as have been done in current practice. The shakedown failure of metals subjected to constant, high amplitude, strain controlled loading cycles predicted by the NLDA model agrees well with the experimental data reported in the literature. Effect of sequence of load history to damage accumulation is demonstrated through numerical examples. [Copyright &y& Elsevier]

• RVE developed previously is enriched with Interfacial Transition Zones (ITZ). • ITZ incorporates gradually varying properties of interface between constituents. • ITZ enriched RVE predicts biaxial failure envelopes of masonry quite well. • ITZ eliminates need for contact interface or interface element modelling. • ITZ enriched RVE can be incorporated into multiscale modelling of masonry walls. This paper presents a concept of Interfacial Transition Zone (ITZ) enrichment for the characterisation of masonry under biaxial stress states to a nonlocal transient damage representative volume element (RVE) model developed by the authors (Jelvehpour et al., 2019). ITZ enrichment has been realised through a series of transition layers on either side of the unit – mortar interface with gradually varying properties of the constituent materials so that weaker mortar – stronger brick and stronger mortar – weaker brick combinations can be considered. Two model parameters, viz., the thickness and the stiffness degradation of the ITZ have been introduced to control the thickness and stiffness degradation of the transition layers; these parameters have been calibrated to fit the experimental data available in the literature. The calibrated ITZ enriched RVE model was then applied to conventional clay brick, concrete block and drystack (mortarless) masonry by simulating the experimental tests reported in the literature; good agreement was obtained. The RVE was then applied to predict the failure envelope of various masonry types subject to biaxial stress states. The ITZ enriched RVE eliminates the need for introduction of either interface element or contact nonlinearity between the masonry unit and the mortar or between drystack masonry units with wide ranging benefits of analysing masonry structures under various load cases. [ABSTRACT FROM AUTHOR]