• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.145-156
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• 2019

As the industrial desire for a step change in productivity within the manufacture of composite structures increases, so does the interest in Through-Thickness Reinforcement technologies. As manufacturers look to increase the production rate, whilst reducing cost, Through-Thickness Reinforcement technologies represent valid methods to reinforce structural joints, as well as providing a potential alternative to mechanical fastening and bolting. The use of tufting promises to resolve the typically low delamination resistance, which is necessary when it comes to creating intersections within complex composite structures. Emerging methods include the use of 3D woven connectors, and orthogonally intersecting fibre packs, with the components secured by the selective insertion of microfasteners in the form of tufts. Intersections of this type are prevalent in aeronautical applications, as a typical connection to be found in aircraft wing structures, and their intersections with the composite skin and other structural elements. The common practice is to create back-to-back composite "L's", or to utilise a machined metallic connector, mechanically fastened to the remainder of the structure. 3D woven connectors and selective Through-Thickness Reinforcement promise to increase the ultimate load that the structure can bear, whilst reducing manufacturing complexity, increasing the load carrying capability and facilitating the automated production of parts of the composite structure. This paper provides an overview of the currently available methods for creating intersections within composite structures and compares them to alternatives involving the use of 3D woven connectors, and the application of selective Through-Thickness Reinforcement for enhanced damage tolerance. The use of tufts is investigated, and their effect on the load carrying ability of the structure is examined. The results of mechanical tests are presented for each of the methods described, and their failure characteristics examined.

• 대한교통학회지
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• 제4권2호
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• pp.3-14
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• 1986

This study was undertaken to develop the gap acceptance model of left-turn drivers on the major road at intersections. Typical unsignalized intersections on the two-lane and four-lane streets in Masan City were selected for the study intersection. For the gap distribution model, the lognormal, negative exponential, shifted negative exponential, and Gamma distributions were tested using the x2 and K-S tests. Based on the results for both streets, it was concluded that among the distributions tested the lognormal distribution represented the gap distribution best, followed by the shifted negative exponential distribution. Stochastic models of the gap-acceptance behavior of left-turn drivers on the major road at unsignalized intersections were programmed using SLAM Ⅱ, a simulation computer language. A stochastic model was selected for the gap-acceptance behavior to compare the results of the simulation with the observed data. The model assumes that a fixed critical acceptance gap is assigned to each left-turn driver based on a normal distribution and the gap distribution of the opposing traffic stream follows the shifted negative exponential distribution.

• 한국도로학회논문집
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• 제14권6호
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• pp.67-73
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• 2012

PURPOSES : This study deals with the effects on the installation of RLC(Red Light Camera). The objective is to analyze the effects of accident reduction after the installation of RLC. METHODS : In pursuing the above, the study uses the 703 accident data occurred at the 64 intersections which RLC are installed or not installed. RESULTS : The main results are as follows. First, Poisson RLC accident model developed in this study is analyzed to be statistically significant. Second, using the above developed model, 33 intersections among 40 intersections are predicted to have the decreasing effects of accidents after the installation of RLC. Finally, the reduction effects are analyzed to be affected by ADT and the number of left-turn lane. CONCLUSIONS : This study is expected to improve the efficiency of RLC and to help in decision-making of RLC installation.

• 한국도로학회논문집
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• 제19권6호
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• pp.183-190
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• 2017

PURPOSES : The objective of this study is to establish the traffic volume-based warrants of right-turn lanes at unsignalized intersections and to introduce a risk probability methodology based on the warrants. METHODS : In this study, a risk probability of a potential rear-end collision is applied between a right-turn vehicle and the immediately following through vehicle. Using the shifted negative exponential model and the compound probability theorem, the risk probability can be expressed as the function of directional volumes and the percentage of right-turns for a two-lane and four-lane highway, respectively. RESULTS : Based on the risk probablity, guidelines for installing right-turn lanes on two-lane and four-lane highways were developed. The risk probability also showed rationality by comparing with right-turn same-direction conflicts observed in-situ. CONCLUSIONS : The results of our study define the total approaching volumes to encourage a right-turn lane as a function of operating speed, percentage of right-turn, and number of lanes.

• 한국안전학회지
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• 제27권6호
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• pp.178-184
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• 2012

This study deals with the traffic accidents by weather condition. The objectives are to comparatively analyze the characteristics, and to develop the models of traffic accidents by weather condition. In pursuing the above, this paper gives particular attentions to testing the differences between two groups, and developing the models(Poisson and negative binomial regression) using the data of domestic circular intersections. The main results are as follows. First, three Poisson models and one negative binomial models which were all statistically significant were developed using the number of accident and EPDO by the clear weather and other as the dependant variables. Second, the differences between two models were comparatively analyzed using the chosen variables. This paper might be expected to give some implications to traffic safety policy-making to reduce and prevent the traffic accidents in circular intersections.

• 한국안전학회지
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• 제29권1호
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• pp.54-58
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• 2014

This study deals with the accidents of circular intersections in Korea. The goal is to develop the accident models for 94 circular intersections. In pursuing the above, this study gives particular attentions to collecting the data of geometric structure and accidents, and comparatively analyzing such the models as Poisson and NB regression and multiple regression model using SPSS 17.0 and LIMDEP 3.0. The main results are as follows. First, the negative binomial model among various models was analyzed to be the most appropriate. Second, 3 independent variables was adopted in the model, and these variables was analyzed to have a positive relation to the accident rate. Finally, the reduced width of circulatory roadway, removal of the parking lot within circulatory roadway and appropriate levels of approach lane were required to improve the safety of circular intersection.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.886-891
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• 2005

The frequent maintenance required on some asphalt concrete (AC) pavement sections has made reconstruction with Portland Cement Concrete Pavement (PCCP) a feasible alternative. However, many constructability issues need to be addressed in order to realize the full potential of this alternative. Accelerated paving encompasses three classes of activities: methods to accelerate the rate of strength gain, methods to minimize the construction time, and traffic control strategies to minimize user delay. Three major AC intersections with severe rutting problems were reconstructed with PCCP. The entire reconstruction of each intersection, including demolition of the AC pavement and its replacement with PCCP, took place over a period of three days, starting on Thursday evening and opening the intersection to the traffic on Sunday afternoon. This paper discusses the use of PCCP for accelerated reconstruction of major urban intersections with minimal user and traffic disruption, using innovative construction techniques and traffic management optimization principles and demonstrates that concrete pavements can be constructed efficiently and quickly.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1996년도 제29회 학술발표회
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• pp.59-86
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• 1996

Current methods for evaluating unsignalized intersections, and estimating level-of-service (LOS) is determined from efficiency-based criteria such as little or no delay to very long delays. At present, similar procedures to evaluate intersections using safety-based criteria do not exist. The improvement of sight distances at intersections is the most effective way of improving intersection safety. However, a set of procedures is necessary to account for the limitations in current methodology. Such an approach would build upon such methods, but also account for: deficiencies in the current deterministic solution for the determination of intersection sight distances; opportunity for an accident and severity of an accident; and cost-effectiveness of attaining various levels of sight distances. In this research, a model that estimates the degree of safety at two-way stop-controlled intersections is described. Only crossing maneuvers are considered in this study because accidents caused by the crossing maneuvers are the dominate type among intersection accidents. Monte Carlo methods are used to estimate the hazard at an intersection as a function of roadway features and traffic conditions. Driver`s minimum gap acceptance in the crossing vehicles and headway distribution on the major road are used in the crossing vehicles and headway distribution on the major road are used in the model to simulate the real intersectional maneuvers. Other random variables addressed in the model are: traffic speeds; preception-reaction times of both drivers in the crossing vehicles and drivers in oncoming vehicles on the major road; and vehicles on the major roads. The developed model produces the total number of conflicts per year per vehicle and total potential kinetic energy per year per vehicle dissipated during conflicts as measurements of safety at intersections. Based on the results from the developed simulation model, desirable sight distances for various speeds were determined as 350 feet, 450 feet and 550 feet for 40 mph, 50 mph and 60 mph prevailing speed on the major road, respectively. These values are seven to eight percent less than those values recommended by AASHTO. A safety based level-of-service (LOS) is also developed using the results of the simulation model. When the total number of conflicts per vehicle is less than 0.05 at an intersection, the LOS of the intersection is `A' and when the total number of conflicts per vehicle is larger than 0.25 at an intersection, the LOS is `F'. Similarly, when the total hazard per vehicle is less than 350, 000 1b-ft2/sec2, the LOS is `F'. Once evaluation of the current safety at the intersection is complete, a sensitivity analysis can be done by changing one or more input parameters. This will estimate the benefit in terms of time and budget of hazard reduction based upon improving geometric and traffic characteristics at the intersection. This method will also enable traffic engineers in local governments to generate a priority list of intersection improvement projects.

• 대한교통학회지
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• 제21권5호
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• pp.31-40
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• 2003

우리나라의 비신호교차로의 유형은 양방향정지식과 무통제식으로 분류될 수 있다. 무통제식은 국내외에서도 용량이나 서비스수준 분석에 관한 연구가 거의 전무하다. 본 연구에서는 이러한 유형의 무통제 교차로의 서비스 수준을 분석할 수 있는 방법론을 개발하는 것을 목표로 하였다. 우선 무통제 교차로의 서비스수준을 평가할 수 있는 효과척도 선정을 위한 분석을 수행하였다. 교통량, 상충횟수, 교차로 통행시간(지체) 등을 분석한 결과, 상충횟수과 교통량이 선형의 관계를 가지고 있는 것으로 나타나 이 2가지를 효과척도로 선정하였다. 서비스수준 E와 F의 경계가 되는 교통량(용량)은 1985 USHCM의 전방향정지식 교차로의 용량을 참고로 2000대/시로 하였으며 이때 상충횟수는 300회가 된다. 그리고 서비스수준별 상충횟수와 교통량을 용량상태를 기준으로 비례적으로 배분하였다. 교차로 총교통량으로 서비스수준을 결정할 때. 방향별 교통량비가 상충횟수에 영향을 주는 것으로 분석되어 방향별 교통량비에 대한 서비스 교통량을 보정하는 방법을 제안하였다.

• 대한교통학회지
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• 제34권2호
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• pp.123-134
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• 2016

교차로는 국가 도로체계에 있어서 작은 부분을 차지하고 있지만, 2014년 통계에 따르면 교차로 교통사고는 전체 교통사고의 약 44.3%를 차지하고 있다. 이에 신호교차로에 대한 연구는 지속적으로 수행되고 있는 반면에, 무신호교차로에 대한 연구는 아직도 미진한 상태이다. 따라서 본 연구의 목적은 지방부 무신호교차로 교통사고의 특성분석과 순서형 로지스틱 모형을 이용한 사고 심각도의 영향요인을 파악하는 것이다. 무신호교차로의 교통사고들은 대부분 주간시간에 측면직각 충돌에 발생하였으며 4지 무신호교차로의 교통사고가 3지 무신호교차로에 비해 약 1.53배 많이 발생하였다. 교통사고의 주요 원인들은 운전자의 안전운전불이행 및 교차로 통행방법 위반에 의해 발생한 것으로 나타났다. 사고 심각도 모형의 개발 결과, 지방부 무신호교차로의 2가지 형태(3-지, 4-지)와 3개의 모형식이 개발되었다. 주요 영향요인으로 교차로 시거 장애, 일평균교통량, 주야간시간대, 교차각, 중차량 비율, 교통법규위반 및 부도로 차로수 등이 선정되었다.