• Journal of the Korean Society of Safety
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• v.9 no.4
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• pp.92-102
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• 1994

NATM as method of tunneling has been applied to construction of domestic subway, roads, rail way, water way etc. Accordingly we have NATM's many drafts and constructional results, but many problems and accidents have occurred under construction of tunnel using NATM for shortage of technical data, poorness of constructional improvement, systemic inconsistency etc. Especially, everyone was shocked at Gupo's train wrecking accident lately. The purpose of this thesis is presentation of means for settling technical problems, by looking into Gupo's train wrecking accident and home records that applying NATM in tunneling failed, to minimize future safety accidents we find that the general problems of home fifteen sites haying occured accidents is badly geological survey, nonconfirmation of base rock's state, formal measuring management, shortage of specialists, systemical discrepancy and that disregarding NATM's rules makes general problems. The results of this study are summarised as follows ; 1. We advise repletion of design standards to practice crosshole test for confirming connected rock base on vertical section of tunnel. 2. We advise to practice pre-boring and pre-grouting for a weak layer difficult in applying NATM. 3. We advise systemic improvements that field servicer can construct tunnel of his own free will considering base rock's state at tunnel. 4. We advise that specialist, who can make a conduct and supervise above mentioned items as well as measuring managements, should be posted at field.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1647-1652
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• 2008

Track geometry consists of tangent and curved lines, which caused undesirable changes in initial track geometry by traffic loads. The bigger the changes are, the worse the riding comfort and running stability of train. This is so-called track irregularity and is the most important quality parameters of ballasted track. To be able to objectively assess track irregularity, track geometry should be able to be measured. Practically, railway companies use moving chord method, this method determine versine values via a chord. The versine is the vertical distance to curve measured in the middle of the chord. This type of method measures only versine of track irregularity curve by transfer function from specific property of measuring tool. In this report, review the characteristics of two types of measuring tools by comparing the measurements. The one is GRP-1000 system, optical surveying system with Total station and lazar prism trolly. This calculates track geometry by surveying absolute coordinates of two points each on both rail heads. The other is Trackmaster, measures versine with 2m of chord length.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.365-375
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• 2006

The HR Plates made hot rolled coils is lower than general structural steel plates in price. No difference between general steel plates and HR Plates with thickness up to 22mm are found in most characters such as cutting operation, fabrication and even welding. It can be concluded that HR Plates with thickness up to 22mm can be applied to flanges and webs of any girders as well as longitudinal ribs, longitudinal and vertical stiffeners of steel bridges appropriately. To increase the demand of HR Plates with thickness up to 22mm, it is necessary that HR Plates is applicable to full member in steel bridge including main girder.In this study, availabilities of the narrow steel box girder of light railway transit with HR Plate width as a main member are discussed. For application of HR Plate to steel bridge with 50m span or more, new support systems in three types are presented. Computational analysis is performed in 15 bridge models of light railway transit with beam element and plate element. As a analysis results, three models in light railway transit are presented. We finally come to the conclusion that HR Plates can be apply to narrow steel box girder in the light railway transit.

• Structural Engineering and Mechanics
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• v.56 no.2
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• pp.241-256
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• 2015

Channel girder bridges that consist of a deck slab and two side beams are good choices for railway bridges and urban rail transit bridges when the vertical clearance beneath the bridge is restricted. In this study, the behavior of simply supported channel girder bridges was theoretical studied based on the theory of elasticity. The accuracy of the theoretical solutions was verified by the finite element analysis. The global bending of the channel girder and the local bending of the deck slab are two contributors to the deformations and stresses of the channel girder. Because of the shear lag effect, the maximum deflection due to the global bending could be amplified by 1.0 to 1.2 times, and the effective width of the deck slab for determining the global bending stresses can be as small as 0.7 of the actual width depending on the width-to-span ratio of the channel girder. The maximum deflection and transversal stress due to the local bending are obtained at the girder ends. For the channel girders with open section side beams, the side beam twist has a negligible effect on the deflections and stresses of the channel girder. Simplified equations were also developed for calculating the maximum deformations and stresses.

• Structural Engineering and Mechanics
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• v.84 no.5
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• pp.591-604
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• 2022

A gravity wall combined with an anchoring lattice frame (a combined retaining structure) is adopted at a typical engineering site at Dali-Ruili Railway Line China. Where, the combined retaining structure supports a soil deposit covering on different inclined rock slopes. With an aim to investigate and compare the effects of inclined rock slopes on the response of combined retaining structure under seismic excitation, three groups of shaking table tests are conducted. The rock slopes are shaped as planar surfaces inclined at angles of 20°, 30°, and 40° with the horizontal, respectively. The shaking table tests are supplemented by dynamic numerical simulations. The results regarding the horizontal acceleration response, vertical acceleration response, permanent displacement mode, and axial anchor force are comparatively examined. The acceleration response is more susceptible to outer structural profile of combined retaining structure than to inclined angle of rock slope. The permanent displacement decreases when the inclined angle of the rock slope increases within a range of 20°-40°. A critical inclined angle of rock slope exists within a range of 20°-40°, and induces the largest axial anchor force in the combined retaining structure.

• Journal of the Korean Society for Railway
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• v.18 no.2
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• pp.139-148
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• 2015

By increasing the vertical stiffness of the rail fastening system, the dynamic wheel load of the vehicle can be increased on the ballast track, though this increases the cost of track maintenance. On the other hand, the resistance acting on the wheel is decreased, which lowers the cost of the electric power to run the train. For this reason, the determination of the optimal fastener stiffness is important when attempting to minimize the economic costs associated with both track maintenance and energy to operate the train. In this study, a numerical method for evaluating the optimal vertical stiffness of the fasteners used on ballast track is presented on the basis of the process proposed by L$\acute{o}$pez-Pita et al. They used an approximation formula while calculating the dynamic wheel load. The evaluated fastener stiffness is mainly affected by the calculated dynamic wheel load. In this study, the dynamic wheel load is more precisely evaluated with an advanced vehicle-track interaction model. An appropriate range of the stiffness of the fastener applicable to the design of ballast track along domestic high-speed lines is proposed.

• Journal of the Korean Society for Railway
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• v.14 no.3
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• pp.262-270
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• 2011

Track support stiffness which affected track maintenance and riding comfort had a big effect on the track and train. Also, track support stiffness of the track design which was based on theory differs from track support stiffness of the track generated on the field. Track support stiffness was generated by several factors such as dynamic wheel loads, vertical displacement of track, and stress at rail bottom on the field test. With the results of the field test was compared with theoretical value. This paper analyzed that track support stiffness of ballast depended on condition of ballast, and support stiffness of concrete track also depended on the characteristic of track structures such as, normal elastic fastening system, rail floating system and sleeper floating system. However, on the ballast and concrete track, the designed track support stiffness was underestimated less than the measured track support stiffness. When the track condition was estimated on service line, it would not consider the track condition on the field. Therefore, this study proposed the various track type and the range of track support stiffness based on the experimental test.

• Journal of the Korean Society for Railway
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• v.20 no.2
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• pp.241-247
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• 2017

Railway bridges with continuously welded rail have a limitation of span length due to track-bridge interaction. In order to overcome this, a sliding slab track system has been developed that comprises with a low-frictional sliding layer between the bridge deck and the track slab to isolate the longitudinal behavior between the bridge and the track. In this study, a real scale track system is prepared to experimentally evaluate the longitudinal frictional behavior. Applied loading rates were 0.2, 1.0, 5.0 and 10mm/min; vertical mass on the track are track slab only, 5,000 and 10,000kg added mass, respectively. Test results showed that the resulting frictional coefficients varied from 0.22 to 0.33. In addition, 10,000 cycle loadings were applied to simulate repetitive sliding to represent 30 years of service life. The frictional coefficient increase was measured and found to be 7% of that of the initial loading stage, which means that the sliding layer is adequate to provide low-frictional behavior for the sliding slab track system. Effects of changes of the frictional coefficient of the sliding layer were analyzed by rail-structure interaction analysis.

• Steel and Composite Structures
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• v.49 no.1
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• pp.81-89
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• 2023

A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridge-longitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and high-order frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of high-speed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.4
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• pp.1178-1185
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• 2010

Recently, high speed of container freight cars is causing fatigue damage of wheel. Sudden failure accidents cause a lot of physical and human damages. Therefore, damage analysis for wheel prevents failure accident of container freight car. Wheel receives mechanical and thermal loads at the same time while rolling stocks are run. The mechanical loads applied to wheel are classified by the horizontal load from contact of wheel and rail in curve line section and by the vertical force from rolling stocks weight. Also, braking and deceleration of rolling stocks cause repeated thermal load by wheel tread braking. Specially, braking of rolling stocks is frictional braking method that brake shoe is contacted in wheel tread by high breaking pressure. Frictional heat energy occurs on the contact surface between wheel tread and brake shoe. This braking converts kinetic energy of rolling stocks into heat energy by friction. This raises temperature rapidly and generates thermal loads in wheel and brake shoe. There mechanical and thermal loads generate crack and residual stress in wheel. Wetenkamp estimated temperature distribution of brake shoe experimentally. Donzella proposed fatigue life using thermal stress and residual stress. However, the load applied to wheel in aforementioned most researches considered thermal load and mechanical vertical load. Exact horizontal load is not considered as the load applied to wheel. Therefore, above-mentioned loading methods could not be applied to estimate actual stress applied to wheel. Therefore, this study proposed safety estimation on wheel of freight car using heat-structural coupled analysis on the basis of loading condition and stress intensity factor.