Articles
Publication Date: 2023
Public Transport (16137159)15(1)pp. 97-128
Dwell time is the amount of time required for performing boarding and alighting activities at stops. Under peak-load conditions, the dwell time can significantly increase due to a higher friction between on-board passengers when alighting and boarding. The influence of on-board crowding on increasing dwell time is indisputable. Herein, we develop a mixed-integer nonlinear programming (MINLP) model to optimize limited-stop patterns for bus services to minimize user and operator costs. The number of non-stop consecutive buses authorized to skip a station and in-vehicle crowding conditions are explicitly considered in our modeling framework. The benefits of limited-stop bus services are mainly overestimated in previous studies that ignore such operating conditions. Moreover, a genetic algorithm is developed to solve the problem in real-world cases. The findings show that the implementation of a limited-stop bus service can reduce in-vehicle travel times for passengers and operating costs for bus agencies in all-demand cases. Nonetheless, it can increase waiting times for users whose origin or destination stations are skipped due to the implementation of limited-stop services. Thus, the desirability of a limited-stop service can decrease with the growth of the demand level. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Publication Date: 2023
International Journal of Pavement Engineering (1477268X)24(2)
Due to the presence of free lime (FL) in slag and its lack of reaction with concrete components, concrete containing slag reduces strength. Pozzolanic Portland cement (PPC) in the presence of moisture and normal heat during chemical reactions with lime (calcium hydroxide) generates stable calcium silicates that have adhesion properties. By using PPC instead of Portland cement type I in roller compacted concrete (RCC) containing basic oxygen furnace slag (BOFS), it is possible to determine the mechanical properties of RCC due to the reaction between the FL in BOFS and PPC. Therefore, this study aims to investigate the effect of PPC on the mechanical properties of RCC containing BOFS. For this purpose, specimens are made with various cement content values (225-400 kg/m3), various BOFS content values (0-50%) and with the optimum moisture. The properties examined in this paper are compressive strength, indirect tensile strength, and static modulus of elasticity tests. The results show that the use of PPC is effective in compensating the negative impact of using BOFS and providing the minimum specified mechanical properties. Also, the proportion of consumption of PPC with BOFS value is determined for the possibility of maximum reaction between FL and pozzolan in cement. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
Publication Date: 2022
International Journal of Pavement Engineering (1477268X)23(4)pp. 957-971
Microsurfacing is a mixture of aggregates, cement, bitumen polymer emulsion (BPE), filler, water and chemical additives. In BPE that is a combination of bitumen, emulsifier, hydrochloric acid, water and liquid polymer, the type and amount of emulsifier affect its performance. The aim of this study is to investigate the performance characteristics of microsurfacing made by BPE with different percentages of emulsifiers. Mixing time, cohesion, wet track abrasion, loaded wheel and Schulze tests are performed. The samples are made with 3% of three different emulsifiers and also with 3% of BPE. The results show that increasing the amount of emulsifiers and BPE in abrasion, adhesion, mixing time and loaded wheel tests lead to an increase in the adhesion, bitumen coating on grains, mixing time and sand adhered, respectively. In addition, samples made by emulsifier type I have better performance than type II in loaded wheel and abrasion tests, but the optimum bitumen obtained from these tests is lower in the compounds of type II than those of type I. Also, samples containing type III do not exhibit good performance. Thus, the type, percentage of emulsifier and percentage of BPE have significant effects on the performance characteristics of the microsurfacing. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
