Structural and economic analysis of changes in design parameters of urban railway stations: a case study

Structural and economic analysis of changes in design and construction parameters of sections of urban railway stations is conducted. Station I2 of line 2 of Mashhad, Khorasan Razavi, Iran urban railway is considered as a sample station to be studied. Considering the existing condition of the station as a reference design, the effects of changes of concrete compressive strength, section height and type of rebar on load-bearing capacity of the structure are investigated. Further, economic analysis of the mentioned changes is conducted to obtain the most efficient design. The results indicate that bending members play more important roles; thus, an increase of concrete compressive strength could not substantially affect the decrease of area of reinforcement in those members. The minimum concrete compressive capacity that can be utilized in I2 station is C25 grade, so that the lower concrete grades could not meet the structural requirements. Furthermore, the results of parametrical analysis show that an increased concrete compressive strength as well as a decreased section height leads to a similar cost and load-bearing capacity to the reference design, while including better durability and lifetime characteristics. In this way, with the purpose of obtaining a similar load-bearing capacity to the reference design, utilization of rebar with increased strength grade (AIV instead of AIII rebar) can also result in decreasing the area of reinforcement, which can be followed by a 9% added value for the project.