Estimation of the Vibration Serviceability Deflection Limit of a High-speed Railway Bridge Considering the Bridge-Train Interaction and Travel Speed

전법규,김남식,김성일 대한토목학회 2016 KSCE JOURNAL OF CIVIL ENGINEERING Vol.20 No.2

The static and dynamic displacements of high-speed railway bridges, which are determined by the load conditions, travel speed, and span, may cause passenger discomfort when they are excessive. In the Korea Railway Bridge Design Specifications, the allowable deflection is based on the train travel speed. It is, however, not sufficient for considering the vibration serviceability. The Eurocodes has also been quoted in the design guidelines of the Korean Honam High-speed Railway (KRNA, 2007). For the determination of the vibration serviceability of a passenger train, the Eurocodes proposes a deflection limit based on the vibration serviceability obtained from the ratio of the deflection to the span and considers the bridge–train interaction. However, the maximum speed and maximum span in the Eurocodes are 350 km/h and 120 m, respectively. Moreover, it does not provide a detailed process for determining the deflection limit based on vibration serviceability. It is therefore difficult to use the deflection limit as the design limit in increasing the span and travel speed. Hence, to ensure passenger comfort and enable changes in railway techniques, it is necessary to develop a vibration serviceability-based deflection limit that flexibly responds to changes in the railway environment regarding bridge span and travel speed. This study was conducted to determine the deflection limits of Korean railway bridges based on their vibration serviceability and considering the bridge–train interaction and increase in travel speed. In this paper, the bridge– train transfer function is developed using a simplified bridge–train model comprising a single mass–spring system. It is then verified by dynamic analysis of the bridge–train interaction. A parametric study and bridge–train dynamic interaction analysis are used to determine the correlation between the vertical acceleration of a car body and the bridge displacement with increasing travel speed. In addition, the vertical acceleration of the car body is shown to increase with increasing travel speed, and an amplification coefficient of the vertical acceleration of the car body is suggested. Further, a vibration serviceability deflection limit for high-speed railway bridges is developed in this paper using the transfer function and the amplification coefficient. Here, the deflection and vibration of the bridge are assumed to be respectively sinusoidal and harmonic. The suggested vibration serviceability deflection limit is also compared with those in the Eurocodes and the Shinkansen.

Serviceability-oriented analytical design of isolated liquid damper for the wind-induced vibration control of high-rise buildings

Xiuyan Hu,Zhipeng Zhao,Cong Liao,Na Hong,Yuanchen Tang 국제구조공학회 2024 Smart Structures and Systems, An International Jou Vol.33 No.1

The effectiveness of conventional tuned liquid dampers (TLDs) in controlling the wind-induced response of tall flexible structures has been indicated. However, the impaired control effect in the detuning condition or a considerably high mass cost of liquid may be incurred in ensuring the high-level serviceability. To provide an efficient TLD-based solution for wind-induced vibration control, this study proposes a serviceability-oriented optimal design method for isolated TLDs (ILDs) and derives analytical design formulae. The ILD is implemented by mounting the TLD on the linear isolators. Stochastic response analysis is performed for the ILD-equipped structure subjected to stochastic wind and white noise, and the results are considered to derive the closed-form responses. Correspondingly, an extensive parametric analysis is conducted to clarify a serviceability-oriented optimal design framework by incorporating the comfort demand. The obtained results show that the highlevel serviceability demand can be satisfied by the ILD based on the proposed optimal design framework. Analytical design formulae can be preliminarily adopted to ensure the target serviceability demand while enhancing the structural displacement performance to increase the safety level. Compared with conventional TLD systems, the ILD exhibits higher effectiveness and a larger frequency bandwidth for wind-induced vibration control at a small mass ratio.

광고를 동반한 소셜 네트워크 이름-디렉터리 서비스의 실험적 데이터 분석

김영복(Yung Bok Kim) 한국IT서비스학회 2014 한국IT서비스학회지 Vol.13 No.4

With the evolution of Internet technologies and the increasing variety of Internet devices, advertisements in various web services have also expanded. Interactive web services often go hand in hand with effective advertisements for a business model. We estimated statistical parameters of the interactive web server for service monitoring and advertisement-effect. In the web pages, we integrated the plugins of social networking services (SNSs) (e.g. Facebook, Twitter) and an advertisement scheme (e.g. Google AdSense) that regards social name-directory contents. Empirical data analysis and statistical results are presented with the implementation of estimations of parameters (e.g. utilization-level and serviceability) and advertisements in a social networking name-directory service (http://ktrip.net or http://한국.net). We found that estimated parameters were applicable to service monitoring of web-server as well as to synthesis of advertisement-effect in our social-web name-directory service.

도로 공용성 평가를 위한 모니터링 시스템 개발: 노면온도 및 동적 하중

조은세상,장준봉 대한토목학회 2024 대한토목학회논문집 Vol.44 No.2

Pavement management systems (PMS) provide procedures to quantify road serviceability based on pavement conditions such as cracks and plastic deformation and suggest proper maintenance methods. The deterioration of the road pavement is relevant to the time although the quantifications on road serviceability in PMS present road surface conditions at the evaluation. More systematic evaluation on road serviceability may need time-dependent factors of road environments and that can improve PMS. Rainfall, temperature and vehicle loads can be environmental factors for road serviceability evaluation. As no data are avablie that can link between road conditions and environmental road factors, we conducted experiments to suggest economical devices and methods to obtain relevant data. We used temperature sensors and accelerometers with Arduino to measure road surface temperature and dynamic loads and provide data to improve pavement serviceability evaluation.

CFTA 거더교의 시공중 구조 안전성 및 공용중 진동사용성 평가

이상윤,박경훈,김정호,김두기,Lee. Sang Yoon,Park. Kyung Hoon,Kim. Jung Ho,Kim. Doo Ki 한국방재학회 2012 한국방재학회논문집 Vol.12 No.6

CFTA(Conccrete Filled Tubular Arch) 거더교는 CFT(Concrete Filled Tube) 구조, 프리스트레스 구조 및 아치구조의 특징을 복합화 하여 구조적 효율과 경관을 향상시킨 새로운 교량 형식이다. 새로이 제안된 형식의 교량을 실교량에 적용하기 위해서는 공용중 안전성 뿐만 아니라 시공중 안전성에 대한 검증이 필요하다. 또한, CFTA 거더는 경간 중앙부에서 상대적으로 슬림한 단면을 갖기 때문에, 진동사용성에 대한 검토가 추가적으로 요구된다. 본 연구에서는 CFTA 거더교의 시공중 안전성과 진동특성을 검토하기 위하여, 실물모형실험체를 제작하고 진동실험을 수행하였다. 진동실험 결과를 바탕으로 검증된 유한요소모델을 이용하여 이동하중을 고려한 동적해석을 수행하였으며, 해석결과를 바탕으로 CFTA 거더교의 진동사용성을 검토하였다. 실물모형실험체 및 유한요소모델을 이용한 시공중 안전성 및 진동사용성 검토 결과, CFTA 거더는 시공중 안전성을 확보하고 있는 것을 판단되며, 우수한 진동사용성을 보유하고 있는 것으로 나타났다. The CFTA (Concrete Filled Tubular Arch) Girder bridge is a new type of bridge which improves the structural efficiency and the aesthetics by combining the characteristics of the CFT (Concrete Filled Tube) structure, PS (Pre-Stressed) structure, and arch structure. Before applying the proposed type of bridge to the real bridges, the structural safety should be evaluated not only in service but also under construction. Because the CFTA Girder bridge has the relatively slim section in the middle of the span, the vibration serviceability should be evaluated additionally. In this study, the real-scaled specimen of the CFTA Girder bridge was fabricated and the vibration test was conducted to evaluate the structural safety under construction and the vibration serviceability in service. The dynamic analysis considering the moving load was conducted by using the FE (Finite Element) model verified with the results of the vibration test. The results of the dynamic analysis reveal that the CFTA Girder bridge has the structural safety under construction and the excellent vibration serviceability.

Footbridge Serviceability Analysis: From System Identification to Tuned Mass Damper Implementation

Shiqiang Qin,Yun-Lai Zhou,Juntao Kang 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.2

Footbridges usually suffer from vibrations induced by the actions of pedestrians, which calls for various control measures to improve the serviceability. This study described the dynamic analysis and Tuned Mass Damper (TMD) implementation for a singlepylon cable-stayed footbridge scaled model, aimed at providing an experimental case study regarding of vibration control design of slender structures. A scaled model for the real footbridge was designed based on similarity principles. Then, the dynamic behavior of the footbridge was assessed by ambient vibration tests. The natural frequencies and mode shapes were identified from operational vibration measurements by covariance-driven stochastic subspace identification algorithm. The frequency of first vertical bending modes is 2.10 Hz, falling into the human walking frequency range [1.6, 2.4] Hz. Therefore, the footbridge needs vibration control to improve its serviceability. Finally, a self-made TMD using lead, spring and oil buffer was implemented on the scaled model of the footbridge. The laboratory forced vibration test was employed to illustrate the effectiveness of the TMD. By installing TMD, the acceleration response at mid-span of the footbridge was remarkably reduced. The study could provide meaningful reference for vibration control design of the full-scale footbridge.

Experimental study on vibration serviceability of cold-formed thin-walled steel floor

Bin Chen,Liang Cao,Faming Lu,Y. Frank Chen 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.46 No.4

In this study, on-site testing was carried out to investigate the vibration performance of a cold-formed thin-walled steel floor system. Ambient vibration, walking excitation (single and double persons), and impulsive excitation (heel-drop and jumping) were considered to capture the primary vibration parameters (natural frequencies, damping ratios, and mode shapes) and vertical acceleration response. Meanwhile, to discuss the influence of cement fiberboard on structural vibration, the primary vibration parameters were compared between the systems with and without the installation of cement fiberboard. Based on the experimental analysis, the cold-formed thin-walled steel floor possesses high frequency (> 10 Hz) and damping (> 2%); the installed cement fiberboard mainly increases the mass of floor system without effectively increasing the floor stiffness and may reduce the effects of primary vibration parameters on acceleration response; and the human-structure interaction should be considered when analyzing the vibration serviceability. The comparison of the experimental results with those in the AISC Design Guide indicates that the cold-formed thin-walled steel floor exhibits acceptable vibration serviceability. A crest factor βrp (ratio of peak to root-mean-square accelerations) is proposed to determine the root-mean-square acceleration for convenience.

콘크리트 충전 강상자형 교량의 진동사용성 평가 연구

강성후,박선준 한국방재학회 2016 한국방재학회논문집 Vol.16 No.3

The subject of this study was a two-span continuous concrete-filled steel box girder bridge. The bridge surface vibration was quantitatively measured by driving a vehicle of which total weight was 267 kN. The vibrational effect was assessed focusing on pedestrians on the basis of the experimental results. A ‘concrete-filled steel box’ is prepared by filling concrete in a separate box inside the conventional steel box. In a continuous bridge, concrete is restrictedly filled in the internal part where a negative moment is generated. A vibration acceleration response prediction equation was proposed by using the acceleration response and the scaled-weight obtained from the experiment. The proposed equation may be used to preliminarily predict the paved surface vibration response of a concrete-filled steel box girder bridge, though the applicable weight and speed of cars are partly limited. The vibration serviceability was assessed by using acceleration conversion curve of the Reiher-Meister. When the driving velocity of the vehicle used in the experiment was in the range of 10 km/h to 30 km/h, the vibration was in ‘Level E’where the pedestrians are unable to recognize vibration. When the velocity of the vehicle was in the range of 40 km/h to 60 km/h, the vibration was in ‘Levels D to E’ which are the appropriate levels where the pedestrians do not feel uncomfortable, indicating that the bridge secured appropriate vibration serviceability. 본 연구에서는 2경간 연속 콘크리트 충전 강상자형 교량을 대상으로 차량 진동이 유발시키는 교면진동의 크기를 총중량 267 kN의 차량 주행실험으로 부터 정량적으로 평가하고 이를 이용하여 보행자 중심의 진동영향을 평가하였다. ‘콘크리트 충전 강상자형’은 기존의 강상자형 내부에 별도의 상자를 만들어 콘크리트를 충전하는 형태로써 연속교에서 부모멘트가 발생하는 내측지점 부에 제한적으로 적용된다. 진동 가속도 응답 추정식은 실험으로부터 얻어진 가속도 응답과 환산중량을 사용하여 제안하였다. 제안된 식은 차량의 중량과 주행속도 등이 제한적이지만 콘크리트 충전 강상자형 교량의 교면 진동응답을 우선 추정하는데 사용이 가능하다. Reiher-Meister의 가속도 변환곡선에 준하여 진동사용성을 평가한 결과 10 km/h~30 km/h의 주행속도 일때는 보행자가 인지하지 못하는 수준인 ‘Level E’ 로 나타났고 40 km/h~60 km/h의 주행속도 일 때는 ‘Level D~E’로 나타났다. ‘Level D~E’는 보행자에게 불쾌감을 유발하지 않는 적정한 수준의 진동사용성을 확보하고 있는 상태를 의미한다.

The Statistical Methods of Membership Function in Structural Serviceability Failure Criterion

Jun Gao,Jitao Yao,Liuzhuo Chen 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.11

The failure criterion of structural serviceability is often fuzzy, which has a direct impact on the results of structural reliability analysis. Membership function is a basic mathematical tool to describe the fuzziness of failure criteria. At present, the fuzzy statistical method for generating the fuzzy set membership function is to take the numerical interval of the fuzzy set as a sample, and directly generate the membership function through statistics. However, this kind of sample will cover the uncertainty of the individual's understanding of fuzzy boundaries to a certain extent, and its statistical results are difficult to truly reflect the characteristics of fuzzy sets. The fuzzy boundary is described by the membership density function, and the numerical interval covering the fuzzy boundary is taken as the sample. The fuzzy statistical method for generating the membership density function is proposed, and the indirect statistical method for generating the membership function is established. The comparative analysis results show that the membership functions generated by the two statistical methods are different. The membership function generated by indirect statistical method can fully reflect the uncertainty of the individual's understanding of the fuzzy boundary, more truly reflect the characteristics of the fuzzy set, and provide a more solid foundation for the fuzzy probability analysis of structural serviceability.

배달앱의 사용성 개선을 위한 사용성 평가 연구 -맥딜리버리앱 서비스를 중심으로-

이하나(Lee, Ha Na) 한국디자인문화학회 2020 한국디자인문화학회지 Vol.26 No.1

최근 1인 가구 증가와 편의성에 대한 선호도가 높은 밀레니얼 세대의 생활패턴은 배달 음식 시장의 전성시대를 열었다. 배달서비스는 도시락과 가정간편식과 같은 먹거리 위주에서 최근 생활용품까지 배달의 분야는 다양해지고 주문과 결제 방식뿐만 아니라 로봇배달이나 드론 배달과 같이 배달방법도 진화하고 있다. 그러나 배달음식이 다양해지면서 그동안 즐겨먹던 간편식의 대명사인 치킨이나 햄버거와 같은 프랜차이드 업계의 매출은 전반적으로 낮아지고 있는 추세이다. 이에 교촌 치킨이나 맘스터치 같은 국내 체인 업체들이 자체 배달앱을 개발하여 고객들의 충성도를 높이고 전문 배달앱에 지급되는 수수료를 줄여 가맹점 수익성 개선에 도움을 주기 위해 노력하고 있다. 현재 맥도날드는 브랜드웹사이트, 맥딜리버리 모바일웹, 맥딜리버리 네이티브앱으로 나누어 온라인 서비스를 제공하다보니 맥딜리버리 서비스를 원하는 사용자의 혼란을 초래하고 있다. 이에 기존의 맥딜리버리의 사용성을 객관적이고 정량적으로 명세하고 평가하기 위하여 객관적인 근거를 제시할 수 있는 평가항목들을 통한 사용성 개선을 제시하고자 한다. 연구방법으로는 첫 번째로 자사 분석과 타사분석을 통해 문제점을 도출하여 사용성의 부특성인 이해성, 학습성, 운영성, 선호도를 중심으로 SO/IEC 9126 소프트웨어 품질 특성과 척도에 관한 표준 지침을 활용하여 사용성 테스트를 거쳤다. 사용성 테스트 결과를 바탕으로 통합적인 맥딜리버리 서비스를 제안하고자 한다. 연구의 결과로써 외식 프랜차이즈 업체가 자체 온라인 딜리버리 서비스를 구축하고자 할 때 기초 자료로 활용되기를 기대한다. Food deliveries are becoming more popular than ever in South Korea, fueled by the increase of single-person households and the lifestyle of Korean millennials who prefer convenience. Delivery service is diversified in terms of kinds of items, methods of payment, and modes of transport; it goes beyond meals to deliver household items; various methods of ordering and payment are applied; many players are revving up to test their robot or drone delivery service. However, as more diverse delivered food options are presented, sales of traditional delivery items such as chicken and hamburger are generally on the decline. To catch up with the trend, Korean franchise brands like Kyochon Chicken and Mom’s Touch are developing their own delivery apps to boost customer loyalty and bringing down fees to help franchisees improve profitability. But the current delivery service of McDonal’s confuses customers because it operates three different online services: its brand website, McDelivery mobile web, and McDelivery native app. Therefore, this study aims to suggest ways to improve the usability of McDelivery through the indicators that will provide an objective basis for quantitatively specifying and evaluating the usability of the existing platform. In terms of research methodology, problems were derived from internal and external analyses and usability test was conducted for understandability, learnability, operability, and preference (usability’s sub-characteristics) based on the guidelines for ISO/IEC 9126 software quality standards. A comprehensive McDelivery service will be proposed based on the results of the usability test. The findings of this study are expected to help franchise companies build on their delivery service platforms.