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The use of additives to supplement or replace cement in concrete is a well-studied topic. The use of fibers, polymers, minerals, and even nanomaterials has been considered for improving concrete properties such as permeability and strength, and these issues are constantly under investigation. In this study, the mechanical properties and permeability of concrete containing calcium carbonate (CaCO3) nanoparticles and fly ash are investigated. For this purpose, concrete specimens with different proportions of nanoparticles and fly ash were prepared and aged for 7 days and 28 days to investigate the mechanical properties via compressive strength tests, tensile strength tests, and flexural strength tests under three-point loading and also to study the permeability properties via full water absorption tests and the testing of penetration depth under water pressure. To determine the distribution of nanoparticles and their size and microstructure, scanning electron microscopy (SEM) images were obtained, and energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses were performed. The results show the positive effect of CaCO3 nanoparticles in filling concrete pores, which leads to increased strength and reduced permeability. In general, the SEM images and EDS and XRD analyses showed that there was a good correlation between the materials used in the concrete and also that the nanoparticles were appropriately distributed in the concrete samples.

Summary This paper introduces the taxi route network design problem (TXRNDP) for a fixed‐route taxi service operating in Iran and, in similar form, in various other developing countries. The service operates fairly similar to regular transit services in that vehicles are only permitted to follow a certain predetermined route on the network. The service is provided with small size vehicles and main features are that vehicles only depart if full and that there are no intermediate boarding stops. In Iran the service attracts a high modal share but requires better coordination which is the main motivation for the present study. We develop a mathematical programming model to minimize the total travel time experienced by passengers while constraining the number of taxi lines, the trip transfer ratio and the length of taxi lines. A number of assumptions are introduced in order to allow finding an exact rather than heuristic solution. We further develop a linear programming solution to minimize the number of taxis required to serve the previously found fixed‐route taxi network. Results of a case study with the city of Zanjan, Iran, illustrate the resulting taxi flows and suggest the capability of the proposed model to reduce the total travel time, the total waiting time and the number of taxi lines compared to the current taxi operation. Copyright © 2016 John Wiley & Sons, Ltd.

Passengers’ safety against unexpected incidents such as rail stations’ fire accidents is essential in the safety field. The presence of luggage with passengers occupies extra space, diminishes passenger’s velocity in high densities, and consequently increases the evacuation time. Therefore, studying the mixture of luggage-laden passengers with non-luggage-laden passengers during the emergency evacuation time of a rail station is vital. In this paper, a simulation of a metro-rail transfer station using an extended cellular automata (CA) model is used to illustrate the importance of this consideration. In this model, luggage-laden passengers and non-luggage-laden passengers are defined as two-cell and one-cell groups, respectively. Specific parameters for luggage-laden passengers in minimum wall prevention and velocity are used. Also, the volume of each passenger group is extracted from the Wi-Fi scanners during the busiest time of the normal station operational hours due to metro and railway schedules. The simulation is carried out using the Python programming language. Fourteen scenarios that vary in their impact on the three classifications of station infrastructure, station equipment, and management’s approach are presented. The analysis indicates that approximately 28% of passengers, or 236 passengers, will not be evacuated in the time period predicted by the simulation if the luggage is not considered. Interestingly, resizing retail stores in the corridor reduced emergency evacuation times by 6.3%, the equivalent of removing them. Failures in the two escalators affect an 8% and 9.4% increase in emergency evacuation time and cause 28 and 46 more passengers to be trapped, respectively. Although the construction of the second railway entrance corridor has been suspended, results indicate that it will save 67 passengers and reduce evacuation time by 9.5%.