مدل شبیه سازی ترکیب الگوریتم ژنتیک برای بهینگی موقت برنامه ریزی در ساخت و ساز ساختمان های بلند

Temporary hoist planning is a key factor for successful project completion in a high-rise building construction. Inadequate plans for hoists in the early stages of a project can cause problems such as failing to hoist resources as required or leaving hoists idle. There are two existing approaches, simple formulas and simulation techniques, for planning temporary hoists. However, simple formulas cannot treat hoist arrangements consisting of different kinds of hoists, while the simulation technique is both time-consuming and tedious when there are many alternatives. In this study, a discrete-event simulation model incorporating genetic algorithms is proposed to support hoist planners while preparing optimal plans with minimal time and effort for high-rise building construction. To verify the applicability of the proposed model, it was applied to a real project and gave better results than a previous approach to temporary hoist planning.

Over the past decade, the number of high-rise buildings constructed and their heights have increased. The report of the Council on Tall Buildings and Urban Habitat (CTBUH) by Oldfield and Wood [1] shows that the average height of the ten tallest buildings completed each year in the world has been increasing each decade: from about 150 m in 1960 to about 420 m in 2009. Developments in materials technology and structural engineering, and the necessity for efficient space utilization caused by increasing land prices and the problem of overpopulation in urban areas will maintain this trend until at least 2020. In high-rise building construction, adequate planning of temporary hoists is a key factor for successful project completion. Hoists, together with cranes, are essential equipment for vertical transportation of construction resources, such as manpower and materials [2]. Too few hoists can cause productivity losses by failing to hoist resources in a timely fashion. On the other hand, too many hoists can incur unnecessary costs when hoists are idle. Higher buildings require more resources and have longer transportation distances. Thus, high-rise building construction has the disadvantage of longer lifting times for workers and materials compared with shorter cycle times in low-story construction. Thus, in high-rise building construction, creating adequate plans for temporary hoists is becoming a more difficult task. Planning for temporary hoists usually depends on heuristic methods, i.e., simple formulas modified by the subjective opinions of experienced practitioners. However, this heuristic method carries the risk of making inappropriate decisions that potentially cause problems such as cost increases and delays.

We have proposed a simulation model incorporating GAs for supporting hoist planners to make optimal plans with minimal time and effort in high-rise building construction. To verify its applicability and the effect of the proposed model on temporary hoist planning, it was applied to an actual high-rise building construction project in Korea. In the experiment, the results of both the proposed model and a simple formula modified by an experienced planner were compared. The proposed model showed a more optimal result that offered greatly reduced cost while satisfying the time constraints and proved to be a better approach to planning temporary hoists than either the simple formula or traditional simulation modeling. In the future, the DES model incorporating GAs can assist planners to determine appropriate temporary hoist planning in high-rise building construction. Our model is adequate for temporary hoist planning. However, further studies are required before it can be applied to real projects. First, additional experiments are necessary to determine appropriate properties values considering project type and characteristic. They affect the accuracy of the simulation results. Second, actual application of the proposed model to secure the reliability and the applicability is necessary. In this study, actual result of application of the temporary hoist plan by the proposed model was not provided. Third, analysis of the characteristics of materials in transportation processes is required. For instance, allocating materials to loads for vertical transportation is a very important issue in high-rise building construction. Some materials are not loaded on a hoist to its maximum loading capacity because of the material's low density. Finally, the extension of the simulation from peak time to overall construction duration will help analyze appropriate times of installation and dismantlement for each hoist.