Masaki Seki

Track maintenance train operators’ attitudes to job, organisation and management, and their correlation with accident/incident rate

The present paper reports the results of a questionnaire-based survey of night train operators’ attitudes toward management, operating procedures, and other organisational issues that potentially impact on safety. Responses were collected from all of the operators of track maintenance trains servicing the Japanese high-speed railway (Shinkansen). Two versions of the questionnaire, the TMAQ (Train Management Attitudes Questionnaire), were developed based on Helmreich’s FMAQ (Flight MAQ) and its derivative, the SMAQ (Ship MAQ). The TMAQ and its progenitor seek to elicit respondents’ views of, and attitudes to, a range of safety related factors including morale, motivation, leadership and human relations in their organisation.To identify dimensions of safety culture as elicited through the TMAQ, a principal component analysis was applied to the questionnaire responses of the original TMAQ. The analysis yielded seven attitude factors, including morale and motivation. Of the seven factors, a close correlation was identified between the factor scores representing operators’ morale and motivation and the actual accident/incident rates for each of the five branches belonging to a single-track maintenance company. A branch that employed train operators having relatively higher morale and motivation exhibited a lower accident/incident rate. Furthermore, the very same correlation was also found for company based responses collected from all track maintenance companies working for the high-speed railway.In addition to the branch and company based comparisons for track maintenance train operators, we also compared attitude factors between different groups of operators (drivers and supervisors), and between two different periods surveyed in a two year interval. Finally, we examined differences in terms of attitude factors between track maintenance operators and seafarers surveyed by applying slightly different variants of the same generic form of questionnaire (Helmreich’s SMAQ). Based on these survey results, we discuss potential risk factors for accidents of track maintenance trains and some implications for improving railway safety.

Vibration of Reinforced Concrete Viaducts Under High-speed Train Passage: Measurement and Prediction Including Train-Viaduct Interaction

This study investigates the dynamic interactions between high-speed trains and reinforced concrete viaducts using field measurements and numerical simulations. The dynamic responses of a 40 year old viaduct under high-speed train passage are measured. Using general finite-element method software, a new numerical vibration prediction scheme for a train–bridge system is developed. Following the Newmark scheme, a decoupling algorithm is derived through the contact force between a train and viaduct. Track irregularity is also taken into account. The proposed numerical scheme is verified through a comparison between calculated responses and in situ measured responses. This approach is expected to provide not only an accurate simulation tool for train-induced vibration, but also instructive information for the retrofit of railway structures, especially at higher speeds.

Synthesis of Diamond-Like Carbon Films on Planar and Non-Planar Geometries by the Atmospheric Pressure Plasma Chemical Vapor Deposition Method

Diamond-like carbon (DLC) films were synthesized by the dielectric barrier discharge-based plasma deposition at atmospheric pressure and their hardness and gas barrier properties were measured. A decrease in size of grains and heating substrate temperature improved nano-hardness up to 3.3 GPa. The gas barrier properties of DLC-coated poly(ethylene terephthalate) (PET) sheets were obtained by 3–5 times of non-coated PET with approximately 0.5 µm in film thickness. The high-gas-barrier DLC films deposited on PET sheets are expected to wrap elevated bridge of the super express and prevent them from neutralization of concrete. We also deposited DLC films inside PET bottles by the microwave surface-wave plasma chemical vapor deposition (CVD) method at near-atmospheric pressure. Under atmospheric pressure, the films were coated uniformly inside the PET bottles, but did not show high gas barrier properties. In this paper, we summarize recent progress of DLC films synthesized at atmospheric pressure with the aimed of food packaging and concrete pillar.

IDENTIFICATION OF CAUSES OF FATIGUE DAMAGE IN CONNECTIONS BETWEEN STRINGERS AND FLOORBEAMS IN STEEL RAILWAY TRUSSES

初期の溶接鋼鉄道トラス橋の縦桁横桁連結部の多くで疲労き裂が発見されている．縦桁横桁連結部における疲労き裂は対処方法が不適切であると，列車の走行安全性に影響を及ぼす恐れがある．本研究では，縦桁横桁連結部の確実な延命化対策の確立に向けて，疲労き裂の発生メカニズムを解明するために，疲労き裂発生状況分析，実橋測定およびFEM解析を行った．疲労き裂発生状況分析では，き裂のタイプごとに発生位置の傾向を確認した．また実橋測定では，そのき裂のタイプごとに，走行列車の車軸位置に着目して，き裂発生原因となる応力挙動を確認した．さらにFEM解析において，全体橋梁モデルおよび詳細モデルを用いて，き裂発生箇所近傍の変形挙動を明らかにすることで，き裂の発生メカニズムを解明した．

PRACTICAL APPLICATION OF COMPRESSION-TYPE STEEL DAMPING BRACES FOR RAILWAY VIADUCTS

鉄道RCラーメン高架橋柱のうち耐震補強を行うことが難しい高架下利用箇所などを対象に，鋼製ブレースを圧縮材として使用する新しい形式のダンパーブレース工法（圧縮型鋼製ダンパーブレース工法）を開発した．本論文では，圧縮型鋼製ダンパーブレース工法の概要と，実験結果に基づく設計方法および本工法の性能を発揮するための施工方法について述べ，最後に実高架橋への適用事例を2例紹介する．