Abstract Concrete carbonation is a phenomenon that occurs by the penetration into the cement stone of CO2 present in the atmosphere. The phenomenon occurs in the presence of water in which CO2 dissolves, forming carbonate ions, which in turn react with calcium ions in the pores of the concrete, resulting in calcium carbonate (calcite). The diffusion of CO2 occurs through pores and surface defects, it thus penetrates deeper into the concrete and the carbonation reaction can occur at a greater depth, eventually exceeding the thickness of the cover, causing corrosion of the reinforcement. [1] In the case of reinforced concrete bridges, corrosion induced by carbonation of concrete is one of the main causes of degradation. Thus, in the design stage of the reinforced concrete bridge structures, the inevitable process of carbonation of the concrete must be taken into account, in the design of the durability, by calculating the thickness of the concrete cover layer. This article aims to present the concept of carbonation resistance class, which will be a major change in the standard based on which the thickness of the concrete cover for reinforcement will be determined. This presentation is made in the context of the European performance approach to durability. In this sense, an analysis of the experimental results obtained in research on concrete prepared with different types of cements, carried out in collaboration with the laboratory of the Reinforced Concrete Structures Department, within the Technical University of Civil Engineering Bucharest. Proposals for classification in the carbonation resistance classes for concretes prepared with two types of cements are also presented.
{"title":"Carbonation Resistance Classes of Concretes","authors":"Cristinel Moraru, Adelina Apostu, D. Georgescu","doi":"10.2478/rjti-2021-0004","DOIUrl":"https://doi.org/10.2478/rjti-2021-0004","url":null,"abstract":"Abstract Concrete carbonation is a phenomenon that occurs by the penetration into the cement stone of CO2 present in the atmosphere. The phenomenon occurs in the presence of water in which CO2 dissolves, forming carbonate ions, which in turn react with calcium ions in the pores of the concrete, resulting in calcium carbonate (calcite). The diffusion of CO2 occurs through pores and surface defects, it thus penetrates deeper into the concrete and the carbonation reaction can occur at a greater depth, eventually exceeding the thickness of the cover, causing corrosion of the reinforcement. [1] In the case of reinforced concrete bridges, corrosion induced by carbonation of concrete is one of the main causes of degradation. Thus, in the design stage of the reinforced concrete bridge structures, the inevitable process of carbonation of the concrete must be taken into account, in the design of the durability, by calculating the thickness of the concrete cover layer. This article aims to present the concept of carbonation resistance class, which will be a major change in the standard based on which the thickness of the concrete cover for reinforcement will be determined. This presentation is made in the context of the European performance approach to durability. In this sense, an analysis of the experimental results obtained in research on concrete prepared with different types of cements, carried out in collaboration with the laboratory of the Reinforced Concrete Structures Department, within the Technical University of Civil Engineering Bucharest. Proposals for classification in the carbonation resistance classes for concretes prepared with two types of cements are also presented.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42557849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andrei Radoi, Cezar Margineanu, C. Ploesteanu, Vasile Pangratie
Abstract This document describes a system for static and dynamic monitoring of the structural health of bridges, but not only. The need to develop the system resulted from the difficulties encountered by the authors in installing and operating complex monitoring systems, composed of elements from different manufacturers, with different measurement technologies, power supplies, communication modes and software applications. The described system facilitates the integration of different measurements, sensors, power supplies and communication technologies, in a unitary system that allows both static and dynamic measurements, simultaneously.
{"title":"Static and Dynamic Structural Health Monitoring System for Bridges","authors":"Andrei Radoi, Cezar Margineanu, C. Ploesteanu, Vasile Pangratie","doi":"10.2478/rjti-2021-0007","DOIUrl":"https://doi.org/10.2478/rjti-2021-0007","url":null,"abstract":"Abstract This document describes a system for static and dynamic monitoring of the structural health of bridges, but not only. The need to develop the system resulted from the difficulties encountered by the authors in installing and operating complex monitoring systems, composed of elements from different manufacturers, with different measurement technologies, power supplies, communication modes and software applications. The described system facilitates the integration of different measurements, sensors, power supplies and communication technologies, in a unitary system that allows both static and dynamic measurements, simultaneously.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47155157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Use of roller-compacted concrete in pavement construction is increasing. Roller compacted concrete is a zero-slump, highly compacted concrete that is placed by equipment similar to that used in asphalt pavement construction. This investigation was conducted to collect the state-of-the-art information on effects of coarse aggregate size and texture on the strength and workability of roller-compacted concrete (RCC) for pavement construction and maintenance. Concrete specimens containing cubical and rough coarse aggregate, irregular and rough coarse aggregate, angular and rough coarse aggregate, rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate were prepared at 1:3:3 concrete mix ratio and 0.4 water cement ratio. Laboratory testing of specimens derived from the concrete specimens showed excellent results for cubical and rough coarse aggregate, irregular and rough coarse aggregate, and angular and rough coarse aggregate. Specimens from the rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate performed poorly in laboratory. The study therefore recommends the use of cubical and rough coarse aggregate, and irregular and rough coarse aggregate in the production of roller-compacted concrete for pavement construction and maintenance.
{"title":"Effects of Coarse Aggregate Shape and Texture on Engineering Properties of Roller Compacted Concrete Prepared for High Traffic Routes","authors":"A. C. Ogbonna","doi":"10.2478/rjti-2021-0006","DOIUrl":"https://doi.org/10.2478/rjti-2021-0006","url":null,"abstract":"Abstract Use of roller-compacted concrete in pavement construction is increasing. Roller compacted concrete is a zero-slump, highly compacted concrete that is placed by equipment similar to that used in asphalt pavement construction. This investigation was conducted to collect the state-of-the-art information on effects of coarse aggregate size and texture on the strength and workability of roller-compacted concrete (RCC) for pavement construction and maintenance. Concrete specimens containing cubical and rough coarse aggregate, irregular and rough coarse aggregate, angular and rough coarse aggregate, rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate were prepared at 1:3:3 concrete mix ratio and 0.4 water cement ratio. Laboratory testing of specimens derived from the concrete specimens showed excellent results for cubical and rough coarse aggregate, irregular and rough coarse aggregate, and angular and rough coarse aggregate. Specimens from the rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate performed poorly in laboratory. The study therefore recommends the use of cubical and rough coarse aggregate, and irregular and rough coarse aggregate in the production of roller-compacted concrete for pavement construction and maintenance.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46185037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The cost of cement used in concrete works is on the increase and unaffordable, yet the need for hydraulic cement concrete and other cement concrete based infrastructures keeps growing with increasing population, thus the need to find alternative binding materials that can be used solely or in partial replacement of cement. The use of waste materials with pozzolanic properties in concrete production is a becoming a worldwide practice. The assessment of the pozzolanic activity of cement replacement materials is becoming increasingly important because of the need for more sustainable cementing products. In this study, a mixture of coconut shell ash and eggshell powder is used as partial replacement of hydraulic cement in ranges of 0%, 5%, 10%, 15%, and 20%. The concrete specimens were prepared at 1: 3: 2.5 mix ratio of cementitious material, fine aggregate and coarse aggregate. The mix ratio satisfied the minimum cement content of 148.32kg/m3 (250Ib/yd3) and the minimum cementitious material content of 267 kg/m3 (450Ib/yd3) for roller compacted concrete pavement. The compressive strength, splitting tensile strength and flexural strength tests were carried out to assess the strength characteristics of ternary concrete mixture containing coconut shell ash and eggshell powder and the feasibility of using coconut shell ash and eggshell powder as partial replacement of cement in industrial plant access concrete roads and parking lots. The results indicate that a mixture of coconut shell ash and eggshell powder can be used up to 20% by weight for replacement of cement in roller compacted industrial plant access concrete roads and parking lots.
{"title":"Characterization of Coconut Shell Ash and Eggshell Powder as Supplementary Cementitious Materials in Roller Compacted Concrete Industrial Access Pavements and Parking Facilities","authors":"A. C. Ogbonna","doi":"10.2478/rjti-2021-0005","DOIUrl":"https://doi.org/10.2478/rjti-2021-0005","url":null,"abstract":"Abstract The cost of cement used in concrete works is on the increase and unaffordable, yet the need for hydraulic cement concrete and other cement concrete based infrastructures keeps growing with increasing population, thus the need to find alternative binding materials that can be used solely or in partial replacement of cement. The use of waste materials with pozzolanic properties in concrete production is a becoming a worldwide practice. The assessment of the pozzolanic activity of cement replacement materials is becoming increasingly important because of the need for more sustainable cementing products. In this study, a mixture of coconut shell ash and eggshell powder is used as partial replacement of hydraulic cement in ranges of 0%, 5%, 10%, 15%, and 20%. The concrete specimens were prepared at 1: 3: 2.5 mix ratio of cementitious material, fine aggregate and coarse aggregate. The mix ratio satisfied the minimum cement content of 148.32kg/m3 (250Ib/yd3) and the minimum cementitious material content of 267 kg/m3 (450Ib/yd3) for roller compacted concrete pavement. The compressive strength, splitting tensile strength and flexural strength tests were carried out to assess the strength characteristics of ternary concrete mixture containing coconut shell ash and eggshell powder and the feasibility of using coconut shell ash and eggshell powder as partial replacement of cement in industrial plant access concrete roads and parking lots. The results indicate that a mixture of coconut shell ash and eggshell powder can be used up to 20% by weight for replacement of cement in roller compacted industrial plant access concrete roads and parking lots.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44832384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The driving wheelset is used in railway traction (locomotives, electric trains, trams, etc.) to support part of the weight of the suspended mass and to drive and brake the vehicle. The dynamics of the driving wheelset/track system is a very important issue in the railway engineering, and this paper is focused on basic features of the frequency response functions which describe the dynamic behavior in the presence of the rolling surfaces harmonic irregularities. To this end, a simple model of the driving wheelset/track system with the range of application limited up to 6-700 Hz is adopted. The driving wheelset model consists of a free-free uniform Euler-Bernoulli beam with three attached rigid bodies, representing the axle, the two wheels and the gear; the distinct feature of this model is the inertial asymmetry. Two independent infinite uniform Euler-Bernoulli beams, each on its foundation including two elastic layers for rail pad and ballast and an intermediate inertial layer for sleepers represent the track model. For simplicity, the moving irregularity model is applied to simulate the interaction between wheels and rails. Numerical simulations show that the driving wheelset/track system has three resonance frequencies, all situated in the frequency range of the evanescent waves in rails. FRF of the driving wheelset/track system have been calculated for left and right wheel/rail pair. The influence of the asymmetric inertia of the driving wheelset and the out of phase between the rolling surface irregularities are evaluated in terms of frequency response functions of the wheel/rail contact force.
{"title":"Vertical Interaction Between a Driving Wheelset and Track in the Presence of the Rolling Surfaces Harmonic Irregularities","authors":"T. Mazilu, I. Răcănel, M. Gheți","doi":"10.2478/rjti-2020-0010","DOIUrl":"https://doi.org/10.2478/rjti-2020-0010","url":null,"abstract":"Abstract The driving wheelset is used in railway traction (locomotives, electric trains, trams, etc.) to support part of the weight of the suspended mass and to drive and brake the vehicle. The dynamics of the driving wheelset/track system is a very important issue in the railway engineering, and this paper is focused on basic features of the frequency response functions which describe the dynamic behavior in the presence of the rolling surfaces harmonic irregularities. To this end, a simple model of the driving wheelset/track system with the range of application limited up to 6-700 Hz is adopted. The driving wheelset model consists of a free-free uniform Euler-Bernoulli beam with three attached rigid bodies, representing the axle, the two wheels and the gear; the distinct feature of this model is the inertial asymmetry. Two independent infinite uniform Euler-Bernoulli beams, each on its foundation including two elastic layers for rail pad and ballast and an intermediate inertial layer for sleepers represent the track model. For simplicity, the moving irregularity model is applied to simulate the interaction between wheels and rails. Numerical simulations show that the driving wheelset/track system has three resonance frequencies, all situated in the frequency range of the evanescent waves in rails. FRF of the driving wheelset/track system have been calculated for left and right wheel/rail pair. The influence of the asymmetric inertia of the driving wheelset and the out of phase between the rolling surface irregularities are evaluated in terms of frequency response functions of the wheel/rail contact force.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44064740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Barišić, B. Marković, M. Vukićević, M. Marjanović, Tamara Brleković
Abstract Special-purpose river port sediment was investigated for its potential use as a road construction material. Sediment samples were extracted from three locations in three small river ports, and detailed laboratory research was conducted to determine its basic mechanical properties and characteristics that can potentially have an adverse influence in a roadside environment. The results of the research conducted indicate that there is a need for systematic monitoring of the quality and quantity of sediment in special-purpose river ports of the Danube River Basin to maintain its mobility and prevent flooding. The basic engineering characteristics (Proctor elements, Atterberg limits, California bearing ratio, and unconfined compressive strength) determined represent the good potential of the sediment samples tested herein for use in road construction. In addition, the chemical characteristics tested indicate the need for detailed analyses of the potential environmental risk before application in civil engineering structures
{"title":"Special-Purpose River-Port Sediment Valorization as Road Construction Material Emphasising Environmental Aspects","authors":"I. Barišić, B. Marković, M. Vukićević, M. Marjanović, Tamara Brleković","doi":"10.2478/rjti-2020-0008","DOIUrl":"https://doi.org/10.2478/rjti-2020-0008","url":null,"abstract":"Abstract Special-purpose river port sediment was investigated for its potential use as a road construction material. Sediment samples were extracted from three locations in three small river ports, and detailed laboratory research was conducted to determine its basic mechanical properties and characteristics that can potentially have an adverse influence in a roadside environment. The results of the research conducted indicate that there is a need for systematic monitoring of the quality and quantity of sediment in special-purpose river ports of the Danube River Basin to maintain its mobility and prevent flooding. The basic engineering characteristics (Proctor elements, Atterberg limits, California bearing ratio, and unconfined compressive strength) determined represent the good potential of the sediment samples tested herein for use in road construction. In addition, the chemical characteristics tested indicate the need for detailed analyses of the potential environmental risk before application in civil engineering structures","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42285729","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Many of our global warming problems come from transport. The majority of people who need transport the most in the developing world are too poor to pay for the highest-technology vehicles which are not polluting. In the past 10 years, 3-6-passenger, battery-powered, Small Electric Passenger Vehicles (as this article is calling them, SEPVs) have appeared in major cities in the developing world. These slow, relatively safe, easily maneuverable, non-polluting and low-cost vehicles, on their three little wheels, are cutting the size of the world’s transport carbon footprint. Recognize that this paper is only focused on carbon footprint: carbon emissions. It is not about “pollution in general” or “emissions in general”. No other published article has explicitly considered the potential of the SEPV to contribute in reducing a nation's contribution to carbon footprint and thus to global warming. This article makes the case for building urban transport strategy and policy around such vehicles, in developing countries, in order to lower the countries' carbon footprint: that is its original contribution. The data showed that the SEPVs made a significant contribution to reducing the potential carbon footprint of transport in the small city of Cox’s Bazar, in Bangladesh, proportionate to its population. The inference is that SEPVs could reduce the carbon footprint of the nation if they become a major, integrated part of urban transport in the megacities, which creates most of the country's carbon footprint. Other developing countries should study Cox's Bazar's example. India is already ahead of the game.
{"title":"Sustainable Urban Transport on Three Wheels","authors":"Mohammed Elius Hossein","doi":"10.2478/rjti-2020-0009","DOIUrl":"https://doi.org/10.2478/rjti-2020-0009","url":null,"abstract":"Abstract Many of our global warming problems come from transport. The majority of people who need transport the most in the developing world are too poor to pay for the highest-technology vehicles which are not polluting. In the past 10 years, 3-6-passenger, battery-powered, Small Electric Passenger Vehicles (as this article is calling them, SEPVs) have appeared in major cities in the developing world. These slow, relatively safe, easily maneuverable, non-polluting and low-cost vehicles, on their three little wheels, are cutting the size of the world’s transport carbon footprint. Recognize that this paper is only focused on carbon footprint: carbon emissions. It is not about “pollution in general” or “emissions in general”. No other published article has explicitly considered the potential of the SEPV to contribute in reducing a nation's contribution to carbon footprint and thus to global warming. This article makes the case for building urban transport strategy and policy around such vehicles, in developing countries, in order to lower the countries' carbon footprint: that is its original contribution. The data showed that the SEPVs made a significant contribution to reducing the potential carbon footprint of transport in the small city of Cox’s Bazar, in Bangladesh, proportionate to its population. The inference is that SEPVs could reduce the carbon footprint of the nation if they become a major, integrated part of urban transport in the megacities, which creates most of the country's carbon footprint. Other developing countries should study Cox's Bazar's example. India is already ahead of the game.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42083500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract This study investigated the willingness of residents to use bicycles for intra-city transportation in Calabar, South-South Nigeria. Administered questionnaires were successfully retrieved (82%) from residents of all income and employment groups in the 22 political wards of the study area. Stratified sampling technique was used to select survey participants. Initial socioeconomic characteristics of respondents in intercept only model was used to predict the willingness of respondents to ride in the city. Twelve problems of bicycle transportation were further presented to participants who rated them using a six-point scale (1-6), highly unwilling to highly willing to ride, respectively. Logistic Regression Analysis was employed to predict the probability that a respondent would be willing to ride. The predictor variables were respondents’ gender, age, education, occupational status, 12 bicycle infrastructure characteristics and dummy variables coding each socioeconomic scenario. A test of the full model versus a model with intercept only was statistically significant, χ2 (24, N = 315) = 50.5, p < .001 and χ2 (19, N = 315) = 36.5, p < .001. The model was able to correctly classify 86% of those willing to ride and 29.1% of those unwilling to ride, for an overall success rate of 66.2%. The study revealed that there is no gender sensitivity in the willingness of residents to ride in the city. In model 2, the odd ratio of some bicycle infrastructure characteristics such as bicycle lanes (1.181), conflicts with motorist (1.338), lack of respect for cycling (1.078), culture/stigma (1.046), weather (1.013), potholes (1.222), safety issues (1.280), and illumination (1.241) are more significant in predicting the probability of respondents to ride bicycles. The study recommended designated bicycle paths/trails to motivate residents to ride bicycles in the city.
摘要本研究调查了尼日利亚南南卡拉巴尔市居民使用自行车进行城市内交通的意愿。调查问卷成功地从研究地区22个行政区的所有收入和就业群体的居民中回收(82%)。采用分层抽样方法选择调查对象。仅截距模型中被调查者的初始社会经济特征用于预测被调查者在城市中骑行的意愿。研究人员进一步向参与者展示了12个关于自行车交通的问题，他们用6分制(1-6)对这些问题进行打分，分别是非常不愿意骑自行车到非常愿意骑自行车。采用Logistic回归分析预测被调查者愿意骑车的概率。预测变量包括被调查者的性别、年龄、教育程度、职业状况、12个自行车基础设施特征和编码每个社会经济情景的虚拟变量。全模型与仅截距模型的检验差异有统计学意义，χ2 (24, N = 315) = 50.5, p < .001; χ2 (19, N = 315) = 36.5, p < .001。该模型能够正确分类86%愿意骑车的人和29.1%不愿意骑车的人，总体成功率为66.2%。该研究显示，居民在城市中骑行的意愿没有性别敏感性。在模型2中，自行车道(1.181)、与驾车者的冲突(1.338)、不尊重骑自行车(1.078)、文化/污名(1.046)、天气(1.013)、坑洼(1.222)、安全问题(1.280)、照明(1.241)等自行车基础设施特征的奇比在预测受访者骑自行车的概率方面更为显著。该研究建议指定自行车道/步道，以激励居民在城市骑自行车。
{"title":"Residents’ Willingness to Adopt Cycling as Intra-City Transport in Calabar, Nigeria","authors":"I. Okon, I. C. Ekwok","doi":"10.2478/rjti-2020-0012","DOIUrl":"https://doi.org/10.2478/rjti-2020-0012","url":null,"abstract":"Abstract This study investigated the willingness of residents to use bicycles for intra-city transportation in Calabar, South-South Nigeria. Administered questionnaires were successfully retrieved (82%) from residents of all income and employment groups in the 22 political wards of the study area. Stratified sampling technique was used to select survey participants. Initial socioeconomic characteristics of respondents in intercept only model was used to predict the willingness of respondents to ride in the city. Twelve problems of bicycle transportation were further presented to participants who rated them using a six-point scale (1-6), highly unwilling to highly willing to ride, respectively. Logistic Regression Analysis was employed to predict the probability that a respondent would be willing to ride. The predictor variables were respondents’ gender, age, education, occupational status, 12 bicycle infrastructure characteristics and dummy variables coding each socioeconomic scenario. A test of the full model versus a model with intercept only was statistically significant, χ2 (24, N = 315) = 50.5, p < .001 and χ2 (19, N = 315) = 36.5, p < .001. The model was able to correctly classify 86% of those willing to ride and 29.1% of those unwilling to ride, for an overall success rate of 66.2%. The study revealed that there is no gender sensitivity in the willingness of residents to ride in the city. In model 2, the odd ratio of some bicycle infrastructure characteristics such as bicycle lanes (1.181), conflicts with motorist (1.338), lack of respect for cycling (1.078), culture/stigma (1.046), weather (1.013), potholes (1.222), safety issues (1.280), and illumination (1.241) are more significant in predicting the probability of respondents to ride bicycles. The study recommended designated bicycle paths/trails to motivate residents to ride bicycles in the city.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47162860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract The freeze/thaw phenomenon is of interest for the field of transport infrastructure through the degradations it produces in the structure of construction elements. The climatic specificity of Romania on the one hand and the exposure to aggressive environments of construction elements in transport on the other hand, determine the importance of studying this phenomenon, its mode of action/propagation and also prevention and maintenance to ensure the functionality of buildings in transport infrastructure. Currently, in the Romanian regulations [*], the assurance of sustainability is done, as in most national annexes for the application of EN 206 [1] in Europe, by a descriptive approach (concrete “designed to last”) referring to (with mandatory status) a series of requirements of the concrete composition (water / cement ratio, minimum cement dosage, entrained air, freeze/thaw resistant aggregates, etc.) and to the compressive strength (concrete compressive strength class) in depending on the classification of the element in a certain exposure class “X”. The support of this descriptive national approach was based on the analysis of a large number of results obtained in a complex experimental program carried out by Technical University of Civil Engineering Bucharest, by analyzing the results obtained by laboratory tests on “candidate” cements and cements “reference” (having a good behavior and traditional use) as well as “in situ” tests/determinations on construction elements made with both categories of cements and maintained in specific environments. At European level, performance approaches to sustainability have made clear progress. The development of accelerated laboratory experimental methods, the establishment of performance criteria, classes of resistance to various environmental actions and the link between them and the classes of exposure to various environmental actions were the starting point for experimental research whose results will be presented in this article. Thus, in conjunction with these modern approaches, an analysis will be presented on the experimental results obtained in research on freeze/thaw resistance to different types of cements, carried out in collaboration with the laboratory of the Reinforced Concrete Structures Department, Technical University of Civil Engineering Bucharest and proposals for classification in different classes of freeze/thaw resistance.
{"title":"Freeze/Thaw Resistance Classes of Concretes","authors":"Cristinel Moraru, A. Adelina, George Dan","doi":"10.2478/rjti-2020-0011","DOIUrl":"https://doi.org/10.2478/rjti-2020-0011","url":null,"abstract":"Abstract The freeze/thaw phenomenon is of interest for the field of transport infrastructure through the degradations it produces in the structure of construction elements. The climatic specificity of Romania on the one hand and the exposure to aggressive environments of construction elements in transport on the other hand, determine the importance of studying this phenomenon, its mode of action/propagation and also prevention and maintenance to ensure the functionality of buildings in transport infrastructure. Currently, in the Romanian regulations [*], the assurance of sustainability is done, as in most national annexes for the application of EN 206 [1] in Europe, by a descriptive approach (concrete “designed to last”) referring to (with mandatory status) a series of requirements of the concrete composition (water / cement ratio, minimum cement dosage, entrained air, freeze/thaw resistant aggregates, etc.) and to the compressive strength (concrete compressive strength class) in depending on the classification of the element in a certain exposure class “X”. The support of this descriptive national approach was based on the analysis of a large number of results obtained in a complex experimental program carried out by Technical University of Civil Engineering Bucharest, by analyzing the results obtained by laboratory tests on “candidate” cements and cements “reference” (having a good behavior and traditional use) as well as “in situ” tests/determinations on construction elements made with both categories of cements and maintained in specific environments. At European level, performance approaches to sustainability have made clear progress. The development of accelerated laboratory experimental methods, the establishment of performance criteria, classes of resistance to various environmental actions and the link between them and the classes of exposure to various environmental actions were the starting point for experimental research whose results will be presented in this article. Thus, in conjunction with these modern approaches, an analysis will be presented on the experimental results obtained in research on freeze/thaw resistance to different types of cements, carried out in collaboration with the laboratory of the Reinforced Concrete Structures Department, Technical University of Civil Engineering Bucharest and proposals for classification in different classes of freeze/thaw resistance.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2020-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44815175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Nwokedi, Obed C. Ndikom, C. U. Odumodu, Ifiokobong I. Okonko
Abstract The study provided economic justification for private sector investment in developing, revitalizing and making operable, the rail-freight-corridors between hub-seaports and inland container depots in Nigeria. It estimated the operator-benefits and profitability potentials of investment in each of the ten rail-freight-corridors consisting of existing but inoperable and proposed rail routes from the major seaports to the Inland container depots in different geopolitical regions of Nigeria. Secondary data on the import and export (cargo generation) capacities of each of the ICD regions to and from the respectively connected hub-seaport were obtained from the Nigerian ports authority statistical report covering a period of two years (2018 – 2019) based upon which the annual expected revenue earnings of the operators were estimated. The cost of investment was also obtained. Benefit-Cost-Ratio (BCR) and Net Present Value (NPV) were used to estimate the operator-benefits and profitability potentials of each rail route. It was found that six of the rail routes have BCR > 1; and NPV>0; implying higher operator-benefits over costs within the period while four of the rail-routes have BCR <1; and NPV <0; implying higher operator-costs over benefits.
{"title":"Economic Justification for Development and Operationalization of Rail-Freight-Corridors Between Hub-Seaports and Inland Container Depots in Nigeria","authors":"T. Nwokedi, Obed C. Ndikom, C. U. Odumodu, Ifiokobong I. Okonko","doi":"10.2478/rjti-2020-0004","DOIUrl":"https://doi.org/10.2478/rjti-2020-0004","url":null,"abstract":"Abstract The study provided economic justification for private sector investment in developing, revitalizing and making operable, the rail-freight-corridors between hub-seaports and inland container depots in Nigeria. It estimated the operator-benefits and profitability potentials of investment in each of the ten rail-freight-corridors consisting of existing but inoperable and proposed rail routes from the major seaports to the Inland container depots in different geopolitical regions of Nigeria. Secondary data on the import and export (cargo generation) capacities of each of the ICD regions to and from the respectively connected hub-seaport were obtained from the Nigerian ports authority statistical report covering a period of two years (2018 – 2019) based upon which the annual expected revenue earnings of the operators were estimated. The cost of investment was also obtained. Benefit-Cost-Ratio (BCR) and Net Present Value (NPV) were used to estimate the operator-benefits and profitability potentials of each rail route. It was found that six of the rail routes have BCR > 1; and NPV>0; implying higher operator-benefits over costs within the period while four of the rail-routes have BCR <1; and NPV <0; implying higher operator-costs over benefits.","PeriodicalId":40630,"journal":{"name":"Romanian Journal of Transport Infrastructure","volume":null,"pages":null},"PeriodicalIF":0.1,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46002869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：