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The design of vertical transportation systems still relies on the evaluation of the round trip of the elevators during the up-peak (incoming) traffic conditions in a building. The evaluation of the round trip time for anything other than the most straightforward case becomes very complicated and requires the use of advanced special condition formulae. These formulae become even more complicated when a combination of the special conditions exist within the building being designed. The most four prominent examples of these special conditions are the case of multiple entrances to the building (rather than a single entrance), the case where the top speed is not attained within one floor jump (or even two or three floor jumps), unequal floor heights and unequal floor population. Moreover, no analytical formulae exist for some combinations of these special conditions. The use of the Monte Carlo simulation is presented in this paper as a simple and practical means to calculate the round trip time for an elevator during the up-peak (incoming) traffic conditions, under a combination of any or all of the special conditions such as multiple entrances, top speed not attained within one or more floor journeys, unequal floor heights and unequal floor populations. Analytical methods are used to show that the Monte Carlo simulation produces the same results for real-life cases of multiple entrances and where the top speed is not attained in a one floor jump. The same can be applied to the other two special conditions or any combination of the four special conditions. The structure and architecture of the Monte Carlo simulation tool used is discussed in detail. The practical details that are used to ensure the speed of the tool in producing an answer are also discussed. The method developed here only applies to up-peak traffic conditions under a conventional group control system. Practical Application: Evaluating the elevator round trip time under up-peak traffic conditions is possible using analytical methods by applying well-established formulae. The round trip time is necessary to decide on the number of elevators required for a building. Where special conditions exist in the building, the use of the analytical method becomes very complicated, and is not possible under the combinations of all special conditions. The only alternatives available are discrete time-slice simulation packages. This piece of work provides the designer with a basis to use the Monte Carlo simulation as a software tool to calculate the round trip time, regardless of the special cases that exist in the building. It also offers a reference to allow the benchmarking and verification of calculation and simulation packages in research environments.
The concept of an idealised optimal benchmark (IOB) is used in many engineering disciplines. An example of an IOB from the area of thermodynamics is the formula for evaluating the maximum possible efficiency of a heat engine. This paper explores the concept of an IOB in the area of elevator traffic analysis. It shows that the classical method of elevator traffic design by calculating the value of the round trip time is an example of an IOB; it also lists the assumptions that lie behind the formulae to illustrate this. It then extends the concept of an IOB to calculating the maximum performance of an elevator system when destination group control is applied under incoming traffic conditions. Formulae are derived for finding the minimum values of the expected number of stops (S) and the highest reversal floor (H) under destination group control during incoming traffic conditions. The assumption is that the L elevators in the group are sequenced (or rotated) to the L virtual sectors in the building, in order to equalise the handling capacities of the L sectors in the group. A numerical example is presented to illustrate the calculation of the maximum possible handling capacity and comparing it to the handling capacity that is achieved under conventional incoming traffic group control. Three numerical algorithms are also used to find the practical minimum values of H and S, the results of which are compared to the IOB using the equations derived above. Practical application: The concept and the accompanying formulae presented in this paper allow the elevator traffic designer to assess the improvement in the handling capacity of the elevator traffic system when he/she changes the group controller from a conventional group controller to a destination group controller. This improvement could be as much as 200%.
The design of vertical transportation systems still heavily relies on the calculation of the round trip time (). The round trip time () is defined as the average time taken by an elevator to complete a full trip around a building. There are currently two methods for calculating the round trip time: the conventional analytical calculation method and the Monte Carlo simulation method. The conventional analytical method is based on calculating the expected number of stops and the expected highest reversal floor and then substituting the values in the main formula for the round trip time. This method makes some assumptions as to the existence of some special conditions (such as equal floor heights and a single entrance). Where these assumptions are not true in a building, this invalidates the use of the analytical formula the use of which will lead to errors in the result. The conventional analytical equation can be further developed to cover some of the special conditions in the building, but they do not cover all these special conditions and also do not cover combinations of these special conditions. The simplest round trip time equation makes the following assumptions: equal floor heights, a single entrance, equal floor populations and that the rated speed is attained in one floor jump. The case of unequal floor populations can be accounted for by amending the values of the probable number of stops and the highest reversal by using the formulae for the unequal floor population case. The work presented in this piece of work identifies the most important four special conditions (out a total of nine conditions) that are assumed in the classical round trip time analytical equation. It then develops analytical formulae for calculating the round trip time equation for any of the four special conditions or any combination of these conditions under incoming traffic conditions. A numerical example is given and verified using Monte Carlo simulation. Practical application: This piece of work presents new equations that allow the designer to evaluate the value of the round trip time. The equations can deal with special cases such as top speed not attained in one floor journey, multiple entrances, unequal floor heights and unequal floor populations. Once the value of the round trip time is obtained, the elevator system can be designed, providing the required number of elevators, their speed and capacity.
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.
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