Large Lateral Forces Research Articles

Lateral resistance of pile cap – an experimental investigation

The pile foundation resists not only the loads from the superstructure, but also the large lateral forces from other sources such as earthquakes, wind, wave, etc. The pile cap is a crucial structural element in a pile foundation that is often massive and deeply buried, and design to provide significant resistance under the lateral loads. In this paper, a comprehensive experimental study of pile cap resistance under lateral load is presented. The parametric study of pile–soil–cap interaction under lateral load is performed on different pile groups. This study shows that the pile cap contributes approximately good amount of lateral resistance.

Rail corrugation growth on small radius curves—Measurements and validation of a numerical prediction model

The development of low rail corrugation (rutting corrugation) on a 120m radius curve on the Stockholm metro is studied by field measurements, laboratory measurements and numerical simulations. The corrugation develops exclusively on the low rail with wavelengths of about 5cm and 8cm. It is concluded by field measurements that the application of friction modification effectively mitigates the corrugation growth on the curve. For the low rail, high levels of lateral acceleration and plastic material flow in the surface layer orientated towards the field side indicate large magnitude lateral creep forces generated by the curving vehicles. A time-domain model for prediction of roughness growth on small radius curves is applied to obtain an improved understanding of the wheel–rail interaction leading to rutting corrugation. The model is validated by comparison of predicted long-term rail roughness growth against measured data, and it is concluded that the corrugation is generated by the low rail contact of the leading wheelset of passing bogies. The corrugation wavelengths observed on the curve are related to excitation of the first symmetric and first antisymmetric bending eigenmodes of the leading wheelsets. Important parameters for the identified wavelength-fixing mechanisms are investigated.

Development of the New Concept Steering Bogie

There are many problems in sharp curves negotiation such as large lateral force, squeal noises and excessive wear of wheel flange and rail gauge corner. To solve these problems, single axle steering bogie (proto type: FS576) has been developed by Tokyo Metro and Nippon Steel & Sumitomo Metal Corporation. The authors confirmed good curving performance by FS576 on the result of field test. Therefore, Tokyo Metro adopted this newly single axle steering bogie (production type: SC101) for new series 1000 in Ginza line. SC101 improves lateral force, noise level, and lateral acceleration of rail in passing curves. In this paper, the design concept and outline of steering bogie SC101 for series 1000 are described. And the curving performance of SC101 is evaluated based on the result of field test and commercial service. Language: en

The effect of enhanced curving forces on the behaviour of canted ballasted track

The performance of railway ballast depends not only on the characteristics of the ballast itself but also the magnitude, frequency and number of axle loads imposed by the trains running on the track it supports. Recent trends towards more frequent and faster trains have highlighted some potential limitations of ballasted railway track. In particular, the introduction of tilting trains on the UK West Coast Main Line, which allowed train operating speeds to be increased over much of the route, has coincided with the sporadic occurrence of localized areas of ballast migration. This phenomenon involves ballast particles moving from the high side of a canted section of track to the low side, exposing the sleeper ends on the high (outer) side of the curve, reducing the lateral resistance of the track and therefore increasing maintenance requirements. This paper reports the results of an investigation carried out to try to identify the underlying mechanism responsible for this behaviour. Measurements of sleeper end displacements under the passage of trains were made at two locations which had experienced ballast migration. Analysis of the measured data together with numerical modelling of the forces imposed on the track structure suggest that the increased speed and typical axle loads of the tilting trains result in larger lateral forces and larger rotation of the sleeper (in the vertical plane) than for a train consisting of a locomotive plus trailing vehicle, as was previously used on the route. It is hypothesized that this leads in turn to a slow but progressive movement of the ballast down the slope of the canted track. However, given the highly localized nature of the ballast migration sites, other factors such as an irregular sub-base stiffness and ballast depth may also contribute to the phenomenon and further work is required to determine the combinations of circumstances that may trigger this effect.

Seismic performance of cable-sliding friction bearing system for isolated bridges

During past strong earthquakes, highway bridges have sustained severe damage or even collapse due to excessive displacements and/or very large lateral forces. For commonly used isolation bearings with a pure friction sliding surface, seismic forces may be reduced but displacements are often unconstrained. In this paper, an alternative seismic bearing system, called the cable-sliding friction bearing system, is developed by integrating seismic isolation devices with displacement restrainers consisting of cables attached to the upper and lower plates of the bearing. Restoring forces are provided to limit the displacements of the sliding component. Design parameters including the length and stiffness of the cables, friction coefficient, strength of the shear bolt in a fixed-type bearing, and movements under earthquake excitations are discussed. Laboratory testing of a prototype bearing subjected to vertical loads and quasi-static cyclic lateral loads, and corresponding numerical finite element simulation analysis, were carried out. It is shown that the numerical simulation shows good agreement with the experimental force-displacement hysteretic response, indicating the viability of the new bearing system. In addition, practical application of this bearing system to a multi-span bridge in China and its design advantages are discussed.

Aerodynamics of Urban Maglev vehicles

Some aerodynamic issues affecting low-speed Urban Maglev vehicles are studied, focusing primarily on the effect of ambient winds on levitation electromagnet loads. Aerodynamic characteristics of a representative vehicle are estimated by means of wind tunnel tests of a 1/12th scale model. The wind environment influencing the existing Maglev guideway at Old Dominion University are established from historical data. It is shown that ambient winds, particularly crosswinds, can pose significant challenges, including substantial redistribution of levitation forces among vehicle electromagnets. The development of large lateral forces, particularly at the forward electromagnet stations, may also be of concern.

Origin of Parasitic Time-Periodic Torques and Forces in Electrical Machines

The origins of the time-periodic torques and forces acting on the rotor of an electrical machine are searched for. The main task of an electrical machine operated in a steady state is to produce a constant torque. In an ideal case, this would be the only magnetic force on the rotor. In practice, the electromagnetic torque usually has relatively large ripple and significant lateral forces may also occur. The examples discussed are from radial flux machines, especially, from cage induction motors. As the electromagnetic torque and forces can be calculated from the air-gap magnetic field, the air-gap flux density and its harmonics are under special examination. Understanding the magnetic interactions may provide means to actively control the air-gap flux density and eliminate the parasitic effects.

Stick-Slip Transitions in Chemical Mechanical Planarization

On closer analysis, the apparently simple act of sliding two contacting substrates relative to one another reveals a myriad of fundamental physical questions that have a broad technical application. Present semiconductor manufacturing imperatives require that planarization uniformity be maintained over length scales spanning 8 orders of magnitude, 1 from gate lengths of 32 nm to wafer diameters of 300 mm. Economic realities continue to drive yield targets ever higher. In this environment, process engineers seek to improve all manufacturing techniques, including chemical mechanical planarization CMP. Stick-slip behavior, and the large lateral forces associated with it, is an indication of reduced polish quality. 2,3 Stick-Slip As two surfaces slide past one another, their relative motion can be categorized into two regimes. The smooth polishing regime exhibits a stable, unchanging relative velocity, whereas stick-slip is identified by a relative velocity that alternates between near zero and some nonzero value at a high frequency. Hence, the stick-slip name, the surface alternates between sticking to the substrate and sliding past the substrate. 4 In many applications, to avoid stick-slip, a thin layer of fluid is introduced between the two surfaces, eliminating contact. This relative motion in which one surface is supported by a thin fluid layer is often characterized as hydrodynamic lubrication. 5 However, material removal during CMP requires some degree of contact; thus, process engineers must walk a fine line between acceptable contact and removal rates vs unacceptably high contact and the resultant stick-slip. 6,7 Intuitively, it is easy to postulate an increase in defectivity and reduction in polish quality resulting from stick-slip. Nevertheless, literature is sparse in this regard, indicating a possible avenue for investigation. CoF

Pounding mitigation and unseating prevention at expansion joints of isolated multi-span bridges

Damage of adjacent bridge structures due to relative responses, such as pounding and unseating, have been observed in many earthquakes. The isolators in bridge structures are effective in mitigating the induced seismic forces. However, the deck displacement becomes excessively large when subjected to ground motion with unexpected characteristics. This increases the possibility of pounding; and contributes to the unseating of bridge decks and subsequent collapse. An analytical model of expansion joints, that takes account of the interaction between adjacent bridge segments and the effect of impact and restrainers, is developed and nonlinear time history analyses are performed on a typical isolated multi-span bridge using three standard ground motions. The numerical simulation results show that pounding between adjacent bridge segments could amplify the relative displacement, resulting in the requirement of using an unseating prevention system. Restrainers are substantially effective in reducing the relative opening displacements and impact forces due to pounding at the expansion joints. However, the impact and the stretch of cable restrainers at expansion joints results in a large lateral force transfer from one deck to the other, which, consequently, significantly changes the global response of the participating structural systems. Therefore, it is effective to provide a shock absorber for the mitigation of impact effects between bridge segments or at the restrainers’ ends. The sudden changes of stiffness during poundings can be smoothed by using a natural rubber shock absorber, which prevents, to some extent, the acceleration peaks due to impact. The reaction forces at the pier bases and the pounding forces exerted on the superstructure can be satisfactorily reduced.

Management Method for Large Wheel Loads and Lateral Forces Using Axle-box Acceleration and Track Irregularity

Very large wheel loads and lateral forces are frequently caused by short-wavelength track irregularities. These large loads are undesirable, as they have a significant effect on the deterioration of the track material and necessitate additional track maintenance. This study focused on correlation between wheel load, lateral force, axle-box acceleration and track irregularity. First, we analyzed the frequency characteristics of the relationship between wheel loads, lateral forces, axle-box acceleration and track irregularities. Then, we proposed a technique to estimate wheel loads and lateral forces that involves a shortwavelength component using axle-box acceleration and track irregularity waveforms.

Bone Bruise in Patients with Acute Patella Dislocation

We investigated the biomechanical significance of bone bruises in patients with patella dislocation. Thirty-four patients with acute dislocation of the patella were studied. Redislocations were excluded. There were 11 men and 20 women with a mean age of 18 years at the time of injury. Bone bruises were noted at the periphery of the lateral femoral condyle in 22 patients (65%) and in 10 cases (29%) at the medial patellar facet. The sulcus angle in patients with bone bruises at the lateral femoral condyle was significantly greater and tibiofemoral rotation at the knee was significantly smaller than in patients without bone bruises. In knees with small tibiofemoral rotation, a large lateral displacement force applied into the knee joint is needed to displace the patella. The flat femoral trochlea groove, however, can not reduce the force, resulting in hard impaction between the medial patella facet and the lateral femoral condyle producing bone bruises.

離着岸時における非定常流体力解析法の開発 ‐曳航水槽における低速横移動試験法の提案‐

The unsteady hydrodynamic forces acting on a berthing ship model was examined, and an procedure for the analysis of measured result in towing tank was considered. The blockage effect could be a problem if we execute the large attack angle lateral force measurement in towing tank, and it will be much serious in the case of shallow water. The authors proposed an experimental procedure, which enables us to carry out the test in towing tank. The proposal employ the normal size model ship with the resistance test, and the blockage effect was avoided by towing the model normal to the tank length. The additional problems in connection with the side wall of towing tank was considered as well. The refected waves affect on the measurement, and it causes unstediness. The authors consider the analysis process on that factor, and they proposed practical solution to extract steady component.

Study on flange climb derailment criteria of a railway wheelset

The wheel flange climb derailment, which can be usually considered as a quasi-static process, is one of the main types of derailment, and often occurs on curved tracks due to large wheel lateral force and reduced vertical force. The general formula for the wheel critical derailment coefficient Q/P, the ratio of wheel lateral force to vertical force, is derived through analysing the forces exerted on the flange climb wheel. Based on the Coulomb's friction law and the creep force laws, the Friction Formula and Creep Formula for the evaluation of derailment are derived, respectively. The analysis shows that the derailment coefficients of Friction Formula and Creep Formula required for derailment are increased considerably for smaller and negative yaw angles, and tend to the value of Nadal's Formula at larger wheelset yaw angles. The Creep Formula is more reasonable for the assessment of derailment. The effect of some parameters on flange climb derailment, such as wheel/rail friction coefficient, yaw angle, flange contact angle, wheel vertical load and curve radius, are investigated. Finally, a simplified formula for wheel climb derailment based on the Creep Formula is proposed.

Discussion on: “Optimality Properties and Driver Input Parameterization for Trail-braking Cornering”

Adverse wheel-rail contact geometry and flange lubrication have been implicated in a number of recent gage widening and rail rollover derailments. The underlying derailment mechanism is shown to be a loss of wheel set steering due to a reduction in wheel set rolling radius difference, leading to shear deformation of the truck and the generation of large lateral gage spreading forces. A series of theoretical analyses and field experiments have been conducted that demonstrate the loss of steering caused by the following wheel-rail contact conditions: 1.1. strong two-point contact between flanging wheels and rails;2.2. hollow wom wheel treads;3.3. heavy gage corner grinding on the rail;4.4. high rail gage face lubrication;5.5. dry railheads.Studies conducted at several gage widening and rail rollover derailment sites have shown that these conditions are not uncommon on North American railroads.

1103 操舵リンク系ジオメトリの非線形性を考慮した鉄道用自己操舵性独立回転車輪台車(OS2-1 交通・物流システムのダイナミクス(鉄道・エレベータ・荷役機械),OS2 交通・物流システムのダイナミクス,オーガナイズド・セッション)

Most of the bogies used for LRT have independently rotating wheels (IRW) so that the floor of the passenger compartment can be lower. IRW, however, do not have a sufficient ability to self-steer, and generate large lateral forces in curved sections of track. The EEF (a German acronym for Single-wheel Single-running-gear) bogie, on the other hand, has IRW that have the self-steering ability. The nonlinear profile of the wheels creates the gravity stiffness that gives them their self-steering ability. In this paper, a multibody dynamics model of the vehicle is developed, and a numerical simulation is conducted. Experiments with a 1/10 scale model vehicle has also been developed. From these results, a design method for the self-steering mechanism of a railway bogie, considering the nonlinear effects of linkage arrangement, is proposed.

Development of Pipeline Transporter System Using Pinning Effect of High-Temperature Superconducting Bulks

We have been developing a pipeline transporter system using high-temperature superconducting bulks (HTS bulks). In this paper, we propose a pipeline transporter system using pinning effect of HTS bulks. This system has the advantage of the application in harsh or dangerous environment such as in hazardous gas. This system requires large lateral force at the certain gap between the permanent magnets and the HTS bulks. For the realization of this pipeline transporter system, we investigated the influences of the arrangement of HTS bulks and permanent magnets on the lateral force characteristics through experiments and numerical simulations by using a computer program based on the three-dimensional hybrid finite element and boundary element (3D hybrid FE-BE) method. And we also designed a model system with a lateral force of 1500 N.

Hydrodynamic function of dorsal and anal fins in brook trout(Salvelinus fontinalis)

Recent kinematic and hydrodynamic studies on fish median fins have shown that dorsal fins actively produce jets with large lateral forces. Because of the location of dorsal fins above the fish's rolling axis, these lateral forces, if unchecked, would cause fish to roll. In this paper we examine the hydrodynamics of trout anal fin function and hypothesize that anal fins, located below the fish's rolling axis, produce similar jets to the dorsal fin and help balance rolling torques during swimming. We simultaneously quantify the wake generated by dorsal and anal fins in brook trout by swimming fish in two horizontal light sheets filmed by two synchronized high speed cameras during steady swimming and manoeuvring. Six major conclusions emerge from these experiments. First, anal fins produce lateral jets to the same side as dorsal fins, confirming the hypothesis that anal fins produce fluid jets that balance those produced by dorsal fins. Second, in contrast to previous work on sunfish, neither dorsal nor anal fins produce significant thrust during steady swimming; flow leaves the dorsal and anal fins in the form of a shear layer that rolls up into vortices similar to those seen in steady swimming of eels. Third, dorsal and anal fin lateral jets are more coincident in time than would be predicted from simple kinematic expectations; shape, heave and pitch differences between fins, and incident flow conditions may account for the differences in timing of jet shedding. Fourth, relative force and torque magnitudes of the anal fin are larger than those of the dorsal fin; force differences may be due primarily to a larger span and a more squarely shaped trailing edge of the anal fin compared to the dorsal fin; torque differences are also strongly influenced by the location of each fin relative to the fish's centre of mass. Fifth, flow is actively modified by dorsal and anal fins resulting in complex flow patterns surrounding the caudal fin. The caudal fin does not encounter free-stream flow, but rather moves through incident flow greatly altered by the action of dorsal and anal fins. Sixth, trout anal fin function differs from dorsal fin function; although dorsal and anal fins appear to cooperate functionally, there are complex interactions between other fins and free stream perturbations that require independent dorsal and anal fin motion and torque production to maintain control of body position.

Discussion of “Swaying of Pedestrian Bridges” by Alexander N. Blekherman

A discussion of an article with the aforementioned article, published in this journal (Volume 10, No. 2, March/April 2005), is presented. Although the discusser feels that the author provided a thorough literature review on pedestrian-induced lateral vibrations on footbridges, he feels that the author did not sufficiently build his case concerning parametric lateral bridge vibrations. The discusser argues, based on his study of pedestrian-induced vibrations for a suspension bridge, that synchronization is independent of the nonlinear coupling of modes. In synchronization, more and more pedestrians are unwillingly locked into the sway of bridges as they try to keep balance, thus creating larger lateral forces. The discusser argues that the author's assumption that nonlinear parametric vibration is the main source of lateral vibrations without consideration of linear vibrations makes the author's proposal of increasing vertical damping to reduce lateral vibrations premature and incomplete.

Parametric study on performance of bridge retrofitted by unseating prevention devices

Over the past decade, seismically induced damage to bridges has been widely reported following major earthquakes such as the 1994 Northridge, 1995 Kobe and 1999 Chi-Chi events. Since these earthquakes, restrainers and stoppers have been installed on bridges to prevent unseating and excessive displacements, respectively. Alternatively, column jacketing has also been proven to be effective. However, the enhanced shear strength may result in extra retrofitting works on the footing. For bridges damaged in the Chi-Chi earthquake, investigations revealed that most bridge columns experienced none-to-minor damage in the longitudinal direction. The reason for this unexpected performance was the construction practice of using a rubber bearing, which is an unbolted design that may slide under large lateral forces. In this paper, parametric studies on simply-supported bridges retrofitted by a restrainer or concrete shear key along the longitudinal and transverse axes were carried out. The research focuses on finding suitable combinations of the design force and gap spacing so the restrainer and concrete shear key can be used as an unseating prevention device, with respect to the allowable column damage in terms of displacement ductility under near-facult type earthquakes. A two-lane PCI-girder bridge was selected as the benchmark model. In the longitudinal direction, a total of nine combinations considering yielding strength and gap spacing for the restrainer were analyzed; while parameters for the concrete shear key were divided into three shear force levels and three gap spacings. In the transverse direction, a similar approach was adapted, except smaller gap spacing was used. For each of the above mentioned earthquakes, seven input ground motions were selected and their PGAs were adjusted to 0.36g and 0.45g as the Design earthquake and Maximum Considerable Earthquake, respectively. Based on the results of nonlinear time history analyses, proper parameters to design the restrainers and concrete shear keys are obtained. Responses obtained from numerical simulations under the Chi-Chi earthquake leaded to new implications to design those devices. Restrainer should not exceed its breaking strain and sufficient unseating length will be needed always. Concrete Shear key was determined by considering both displacement demand of the superstructure and displacement ductility of the column at the same time. Further study is needed to provide optimal design parameters for use in performance based bridge design.

Lateral interactions of trains and tracks on small-radius curves: simulation and experiment

The lateral dynamic interaction between trains and tracks on small-radius curves is investigated with theoretical method and field experiment in this article. A vehicle–track spatially coupled model and a simulation software are developed to analyze the dynamic performance of vehicles on elastic tracks. A field experiment is carried out to validate the simulation method. Research results show that severe lateral interaction occurs between wheels and rails when a train passes through a small-radius curved track. Under the strong action of the large lateral wheelset force, the rails roll over, obviously, and the rail gauge is enlarged dynamically. In order to raise the train speed and enhance the running safety, a suit of new measures are put forward to strengthen the old wooden sleeper tracks widely used in the curves of the mountain area in Chinese railways. It is shown that the lateral displacements of rails and the dynamic gauge enlargement are decreased by 67% after the small-radius curved track is strengthened, although the lateral wheel/rail forces on the strengthened track are a little larger than those on the original un-strengthened wooden sleeper track.