The design of an elevator system heavily relies on the calculation of the round-trip time under up-peak (incoming) traffic conditions. The round-trip time can either be calculated analytically or by the use of Monte Carlo simulation. However, the calculation of the round-trip time is only part of the design methodology. This paper does not discuss the round-trip time calculation methodology as this has been addressed in detail elsewhere. This paper presents a step-by-step automated design methodology which gives the optimum number of elevators in very specific, constrained arrival situations. A range of situations can be considered and a judgement can be made as to what is the best cost–performance tradeoff. It uses the round trip value calculated by the use of other tools to automatically arrive at an optimal elevator design for a building. It employs rules and graphical methods. The methodology starts from the user requirements in the form of three parameters: the target interval; the expected passenger arrival rate (AR%) which is the passenger arrival in the busiest 5 min expressed as a percentage of the building population; and the total building population. Using these requirements, the expected number of passengers boarding an elevator car is calculated. Then, the round-trip time is calculated (using other tools) and the optimum number of elevators is calculated. Further iterations are carried out to refine the actual number of passengers boarding the elevator and the actual achieved target. The optimal car capacity is then calculated based on the final expected passengers boarding the car. The HARint plane is presented as a graphical tool that allows the designer to visualise the solution. Three different rated speeds are suggested and used in order to explore the possibility of reducing the number of elevator cars. Moreover, the average passenger travel time is used to indicate the need for zoning of buildings. Practical application: This paper has an important application in allowing the designer to arrive at the optimum design for the elevator system using a clearly defined methodology. This ensures that the number of elevators, their speed and their capacity are optimised, thus ensuring that the cost of the elevator system and the space it occupies within the building are minimised. The method also employs a graphical method (the HARint) in order to allow the designer to visualise the optimality and the feasibility of the different design options.

A previous paper introduced the concept of the HARint plane, which is a tool to visualise the optimality of an elevator design. This paper extends the concept of the HARint plane to the HARint Space where the complete set of user requirements is used to implement a compliant elevator traffic design. In the HARint Space, the full set of user requirements are considered: the passenger arrival rate (AR%), the target interval (inttar), the target average travelling time (ATT) and the target average waiting time (AWT). The HARint Space provides an automated methodology in the form of a set of well-defined steps that allow the designer to convert these four user requirements into a compliant elevator traffic design. As with the HARint plane method, the target interval is used in combination with the expected arrival rate (AR%) and the building population, U, in order to find an initial assessment of the number of passengers expected to board the elevator. The target average travelling time is then used to select a suitable elevator speed. This is then used to calculate the round trip time and then select the optimum number of elevators. An iteration is then carried out to find the actual number of passengers, and hence the elevator capacity. A check is then carried out to ensure that the target average waiting time has been met, and if not, then a modification of the design is required (usually by increasing the speed or increasing the number of elevators). While the HARint plane provides the optimum number of elevator cars to achieve the two user requirements, the HARint Space provides the optimum rated speed as well as the optimum number of elevators to meet the four user requirements of arrival rate, target interval, target average waiting time and target average travelling time. An obvious consequence of the introduction of the average travelling time as a user requirement is that the speed becomes an outcome of the HARint Space. The method also triggers a zoning recommendation in cases where the average travelling time cannot be met by varying the speed within reasonable limits.Practical application: The work in this paper presents a methodical procedure allowing the designer to select the number, speed and capacity of a group of elevators in a building in order to meet four user requirements: Arrival rate, target interval, target passenger waiting time and target passenger travelling time. Following this procedure ensures an optimal design. It also provides the user with a graphical method for visualising the optimality of the design.

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