پژوهشنامه حمل و نقل
سال یازدهم شماره 1 (پیاپی 35، بهار 1393)

Field studies in many countries like USA and South Korea confirms the acceptable performance of TDA material as sub-ballast layer on reducing the train induced vibrations. However, comparing the achieved results in the mentioned studies shows some differences in the exact range of TDA performance frequency in vibration reduction. So in this study, dynamic behaviour of ballasted track with and without TDA as sub-ballast layer was evaluated with using impulse-response (IR) test equipment’s. For this purpose a prototype of ballasted track with and without TDA layer was established and many IR tests were carried out. The impact was imposed on the track by using a 93.5 kg falling hammer and the vertical particle velocity were monitored in the points located in the vicinity of the track by using Geophone. Depending on the position of impact, results were shown in three different kinds of velocity-time, velocity-distance and velocity-frequency curves. Processing the obtained results reveals the TDA efficiency in vibration reduction in the range of 0-500 Hz. The reduction magnitude varies between 17 to 46 dB when the impact imposed on ballast while it varies in the range of 6 to 32 and 6 to 47 when impact location were on sleeper and rail, respectively. As a result of this experimental study, TDA with particle size of 5 to 50 mm with 20 cm thickness creates 6 to 47 dB reduction in vibrations with frequency range of 32 to 250 Hz.

Productivity improvement, considering resource scarcity and increased competition, is known, nowadays, as the best and most effective way of achieving growth. Since transportation is a very important and influential infrastructural component in the country's economy, the evaluation and improvement of its productivity is quite important. The purpose, in this paper, has been to calculate productivity in Iran transportation sector using Kalman Filter approach; the results for the potential production and production cycle have also been analyzed and compared using Hodric-Prescott (HP) and Boxter-King (BK) methods. To do so, first the unit root and random trend in the real GDP logarithm have been investigated and analyzed for the transportation sector during the period in question; results have shown that the real value-added logarithm variable of Iran transportation sector is first order integration I(I) and, therefore, the observed trend is one obtained from a random walk with drift. Next, based on the theoretical principles and experimental studies, the productivity model has been introduced and proposed for the transportation sector. The model equations can be rewritten, in the format of state-space models, as follows:ME:〖∆y〗_t=μ+y_(c,t)-y_(c,t-1)+ε_1t (1) TE:y_(c,t)=φ_1 y_(c,t-1)+φ_2 y_(c,t-2)+ε_(2t) (2) Model estimation results are shown in Table 1.Table 1. Estimated values of the model parametersParameter Estimation t-statisticµ 0.06 2.53φ1 0.74 10.52φ2 -0.8 -5.20σε1 0.24 9.86σε2 0.76 6.25AIC=-4.45 SBC=-4.23 Source: Research findingsAs shown in the above table, all the values estimated for the variables are meaningful at the critical level of 0.05. Also, the special roots of equation λ^2 〖-φ〗_1 〖λ-φ〗_2=0are: since C < 1, the business cycles in the real GDP logarithm of Iran transportation sector are stable; other parameters are meaningful too. Next, it is necessary to make sure of the model correctness regarding normality of the residues (model's error forecast) and lack of autocorrelation. To check the first, use has been made of Jarque-Bera statistic, and to check the second based on autocorrelation function (ACF) and partial autocorrelation function (PACF), it can be concluded, from the value found for the test statistic and its corresponding probability level, that the model lacks autocorrelation which is an indication of the model's goodness of fit. Test statistic results found from this model are 2.89 for the residues and 0.24 for its probability; therefore, the assumption of normal distribution at a certainty level of 5% cannot be rejected.Results have revealed that the fluctuation variance of the cycles produced by the Kalman-Filter method have been less than those by Hodric-Prescott and Boxter-King methods, but all have been similar in shape. The time series of the production total factor productivity for the time period of 1972-2007 in the transportation sector was estimated too. Fig.1 shows this sector's estimated productivity for the period 1971-2006. As shown, it has had fluctuations during that period; over time, the amplitude has declined in recent years which can be an indication of enhancement in the economic stability in this sector.Since improvement and increase in productivity in the transportation sector will cause more value added and hence more income will be distributed in this sector, and also considering the important role the transportation sector plays in the economic activities and in preparing the production's infrastructures, the productivity improvement in this sector will cause an increase in the GDP and, in fact, in the living standards in the country.

Although the purpose of forming civil responsibility regulations is the full compensation of damages, it has been predicted a certain ceiling in international conventions which observe transportation operator’s responsibility. It means that in case of any damage such as losing or wasting goods, any damage to goods or delay in its delivery, the responsibility of the carrier wouldn’t be exceed of a certain ceiling, except in some cases which have been predicted in the rules. This arbitrary rule is called liability limitation. This article tries to investigate the amount of rail transportation operator’s liability in COTIF convention, sea transportation operator’s liability in Brussels and Hamburg conventions, air transportation operator’s liability in Warsaw, Hague, Guatemala, Montreal Conventions and road transportation operator’s liability in CMR conventions.On the other hand full compensation of damages have been predicted on the Intel law but on the conventions international transportation of Good not application this rule. Of course this rule in certain place not enforcement. If Owner goods declare Value goods or Carrier on losing or wasting goods acting with Voluntary or deliberately or defraud carrier cannot profit of limits rule.The before beginning since conventions international transportation of Goods and after end conventions the parties contract transportation can contracts and for limits responsibility or extra liability conclude any agreement. In these regulations the carrier responsibility is based on the responsibility assumption.Thus once the occurrence of the losses is realized, the responsibility is assumed, and is exempted from the responsibility only in the case that proves that the damages caused from an external accident and inevitable.

This paper aims to evaluate the effects of Bentonite on various properties of hot mix asphalt (HMA). The Bitumen was modified with 10%, 15%, 20%, 25% and 30% Bentonite by weight of Bitumen as modifier. In this study the mechanical properties and performance characteristics of modified asphalt concrete were evaluated through various laboratory tests, such as Marshall stability, resilient modulus, moisture susceptibility, permanent deformation. The performance characteristics evaluated in this study included permanent deformation test and rutting resistance. The test methods used in this evaluation were the dynamic creep test and wheel tracking tests. The results demonstrated that the use of bentoite can enhance Marshall stability, resilient modulus, tensile strength, resistance to moisture damage and resistance to permanent deformation of mixtures. The mixtures also showed good resistance to permanent deformation evaluated by means of wheel tracking tests.

Suburban passenger terminals locating processes used in most cities indicates that methods used as non-scientific and based only on expert opinion. In this paper, a mathematical model which has been developed by the authors of this paper was applied to locate suburban terminals in Tehran. First, the most important criterias in locating terminals were identified by interviewing the experts and specialists and also by completing questionnaires. To excequte this model) which is a large scale programme (, the Branch and Bank method was used on TransCAD software.Based on the results of implementing this model, four places in Tehran were identified in order to build the terminals and analesis of technical and economic evaluation of the results have been carried out shows positive results. In this paper a comparison between the results of the proposed model in this study and the existed model in the master plan of transport and traffic of Tehran was made. The model of master plan suggests 14 locations to construct the terminal, while, proposed our model showes that construction of more than 4 terminals may not be economically justify. Considering the significant differences in functional status, the proposed method in this study clearly varifies as an effective and efficient method to locate terminals.

The population growth of Isfahan metropolis in the recent years and the historical and cultural monuments in the central part of the city which cause some limitations for building new streets, have caused transportation and traffic problems in the city. One of the important procedures to solve the transportation and traffic problem of the Isfahan city is improving the public transit system. Although the bus network of Isfahan with more than 2000 kilometers of line coverage serve the citizens, but the relative proportion of this transportation mode in transferring the passengers in the city is very low. The improving of the bus network of Isfahan could attract the passengers from other transportation modes. One way of improving the bus network is decreasing the number of passenger transfers. Long route design in the bus network could decrease the number of transfers and improve the operation of bus network from the passenger's viewpoint and thus, attract them to the network. In the present article, first, the maps of people's willing for long-distance movement in Isfahan city were made in order to determine the candidate corridors and main routes for designing the long routes in the bus network of Isfahan city. Then, three long routes were suggested by merging the existing routes using the maps of people's willing for long-distance movement in Isfahan city, regarding some specific hypotheses and consulting with the city's transportation experts. To evaluate the suggested routes, the traffic assignment software was used to compare existing and suggested situation. The results obtained from evaluating these routes showed an improvement in some criteria which suggested that designing long routes in the bus network of Isfahan city was effective.

In this study, stoppage risk during fulfillment of some of the construction activities of bridge development projects is assessed with the purpose of identifying entire major effective reasons behind it, taking into account the appropriate risk mitigation strategies and determining the probability of mitigation strategies failure. To this end, the fault tree analysis method was employed, but adoption of the traditional method of fault tree analysis is very difficult or even impossible in many cases, including construction industry, due to limited access to the information. In this mode, fuzzy arithmetic operations which are computationally simple and do not require detailed experimental data can be applied as useful tools. In this study, the fault tree is first structured based on the results of Delphi method and survey of diverse sources. Then, using the fault tree analysis based on fuzzy logic, the probability of occurrence of the above-mentioned risk is computed. Finally, once the fault tree relating to risk mitigation strategies failure has been structured, major causes of strategies failure are determined. The data provided help managers of bridge development projects minimize increased costs and delay in projects and manage more effectively by eliminating or reducing the major causes of such risk.

In this paper, an analytical-numerical model for the analysis of tunnels below groundwater table in plain strain axisymmetric condition is presented. A new numerical procedure, using finite difference method, is proposed for calculating the distribution of stresses, radial displacements and pore pressures around a circular tunnel excavated in a generalized Hoek-Brown rock mass. Considering strain-softening behavior and several seepage patterns, an elasto-plastic model is proposed for analysis of underwater circular tunnels. Comparing various seepage models, the most accurate one have been selected and used in this research. For the strain-softening behavior, it is assumed that all the strength parameters are a linear function of deviatoric plastic strain, which is different from the function used by Brown-Bray. As the derived differential equations have no explicit analytical solutions for the plastic zone, the finite-difference method (FDM) is used in this study. On the other hand, analytical expressions are derived for the elastic zone. Two examples are given demonstrate the performance of the proposed solution for dry and wet conditions. The results show the effects of dilatancy angle, deviatoric plastic strain as the factor of strain-softening, elastic strain increments. It can be observed that both elasto-plastic radius and convergence of the tunnel are increased by raising the groundwater level. Meanwhile, variations of dilatancy angle also have significant effect on ground response curve and elasto-plastic radius.