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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.

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.

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

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.

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.

Abstract

This study aims to find the potential of Bus Rapid Transit (BRT) to attract the vehicle owners from their personal vehicles i.e., motorcars and motorcycles. Stated preference survey (questionnaires) and interviews were conducted at BRT (Metro Bus) Stations for the prediction of the individuals shifting from their private vehicles to BRT. Questions were designed critically as per the requirements of the research related to numerous aspects of BRT use i.e., vehicle ownership of the travelers, driving license holder, demographic characteristics, choice to use BRT if the fare increases, trip purpose and their prior mode of transportation for the same trip. A total of 374 responses, as per the population of the study area (Islamabad-Rawalpindi, Pakistan), were collected. The Multinomial Logistic Regression (MNL) model has been employed for four categories of vehicle ownerships i.e., “Car owners using BRT”, “Bike owners using BRT”, “Both Car and Bike owners using BRT” and the last one which has been taken as reference category is “BRT users with no vehicle ownership”. The analysis indicated that BRT has attracted considerably private vehicle users specially the bike owners. Some socio-economic factors like income and residence location (accessibility) additionally have a major effect on the selection of BRT. In addition, it has been observed that fare increase can alter the mode choice of the BRT users and they will again prefer their own vehicles. The Travel choice model developed in the study can be very useful for policy makers and transport planners to enhance the BRT service and attraction, to mitigate traffic congestion and car ownership.

Abstract

The purpose of the current paper is to raise awareness on the behaviour of rectangular reinforced concrete columns with disproportionate cross-section dimensions subjected to compression and biaxial bending, considering the fact that in the current structural design process, the design of columns is usually done with respect to each of the two principal directions without considering their combined effect.

The paper is based on a case study regarding a building that is currently in the design phase, in which to obtain a correct seismic behaviour, rectangular columns with disproportionate cross-section dimensions were used.

The design of both the building and the columns follows the Romanian seismic design codes (“P100-1/2013 - Seismic design code - Part 1 - Design provisions for buildings” and “SR-EN 1998/2004 - Design of structures for earthquake resistance”).

Results were compared and conclusions were drawn based on the interaction curves and interaction surfaces computed with expressions from specialized literature and sectional analysis software.

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.

Abstract

The current paper studies the effect of superior eigen-modes on the seismic response for a series of reinforced concrete structures having eigen-periods near code control periods. Although the structural design is based on Romanian seismic design codes (“P100-1/2013 - Seismic design code - Part 1 - Design provisions for buildings” and “SR-EN 1998/2004 - Design of structures for earthquake resistance”), it carries some importance for other countries with similar seismic design spectra.

A total of twenty-four models for structures were considered by varying their location (through control period values), three-dimensional regularity, overall dimensions and height regime.

Results were compared and conclusions were drawn based on percentage values of relative displacements (storey drifts) and base shear forces.