装配式建筑部品部件的两阶段调度研究

李恺蔓

摘要

“多时空作业”是装配式建筑区别于传统建造方式的基本特点之一，要发挥装配式建筑的优势，就必须实现不同时空阶段的有序协同。装配式建筑亟待解决的关键问题之一是部品部件在生产、运输、装配过程中的调度问题，即如何确保部品部件在不同阶段的精准有序流转。低效率的部品部件调度容易导致生产供应出现提前或延迟：若供应提前且工地缺少足够堆放空间，工地存储和堆场布局规划则面临压力，产生仓储和二次搬运等额外费用；若供应延迟，工地现场则面临停工待料的困境，从而影响施工进度、增加工程成本。

及时有效的生产供应与规划合理的堆场布局，是衔接制造与建造的关键环节。两者之间既有内在的顺序和制约关系，又有协调统一的目标。本研究将上述问题视为两阶段调度问题。其中，天气、施工环境等影响工程进度的因素导致部品部件需求的变化，生产供应能力变化影响部品部件的生产和供应决策，以供需不确定环境下的生产调度问题为第一阶段；又由于工地空间有限且动态变化，部品部件在现场的堆放、储存与转运管理问题突出，因此，以部品部件的现场调度问题为第二阶段。

解决两阶段调度问题的关键在于如何有效处理多个作业空间之间的关系。为了深入刻画调度全过程以及多时空阶段之间的关系，对调度活动的主要影响因素进行了分析，指出了两阶段调度的关键特征。通过引入对象过程方法论，建立了两阶段调度模型框架，明确了两阶段子模型之间的内在联系和模型的实施路径。

第一阶段调度是从工地的角度，考虑工厂与工地之间“多对一”的供应关系，聚焦部品部件的生产与供应决策研究。其中考虑了供应与需求两端的不确定性因素，分别进行了生产供应能力和施工需求变化评估。同时，利用第二阶段调度的反馈信息，关注工地空间可用性对生产与供应的影响。根据以上约束，运用随机规划方法，以持有成本和惩罚成本等期望总成本最小化为目标，建立供需不确定环境下的部品部件生产调度模型，用于确定最优生产与供应方案。应用案例结果显示，该模型的应用能够最大程度减少集中库存费用和短缺延误费用的总和，可以改善供应提前或者延迟的问题，有利于实现“计划前瞻、下单准确、调配高效、全程联动”的目标。

第二阶段调度是针对部品部件在装配现场的调度，主要以堆场布局规划为核心，开展前端生产、供应与后端储运、消耗等关联协同的研究。通过分析非集中式、动态的堆放空间需求，提出部品部件的现场调度模型的总体架构。首先，根据第一阶段调度的结果，应用建筑信息模型，从而获取部品部件的供应信息；其次，借助工地监控视频，采用图像识别方法，得到既定堆放区域是否可用的状态信息；基于以上两部分信息，建立堆场布局动态规划模型，在满足施工需求和时空约束的前提下，尽量减少二次搬运，最小化装配现场的搬运和集中仓储总成本。结果表明，该方法能够有效降低项目成本，提高施工效率。这也为部品部件在现场的存储和堆放管理提供了更为切实可行的流程和方法，体现了“前后联动”的调度决策思路。

关键词：装配式建筑；两阶段调度；堆场布局规划；空间状态识别；供需不确定性

Abstract

"Complex spatio-temporal operation" is one of the basic characteristics of the prefabricated construction, which is different from traditional construction methods. To enjoy the prefabricated building, it is necessary to carry out the ordered coordination of the various stages of time and space. A crucial issue in prefabricated construction is the scheduling of components in the production, transport and assembly process, which means how to ensure accurate and orderly flow of component parts at different stages. Inefficient scheduling of component parts will directly lead to the advance or delay in production and supply. Early supply and insufficient stacking space on construction sites will put pressure on site storage and yard layout planning, leading to additional costs such as storage and secondary handling. Supply delays can cause workers to slow down and wait for materials on the construction site, thus affecting the construction progress and cost.

The production and supply of prefabricated component parts and the layout of the stacking yard are the key links to connect manufacturing and construction. There is not only the inherent order and restraining relationship between them, but also a coordinated and unified purpose. The above problem is considered as a two-stage scheduling problem. Weather conditions, construction environments and other factors affecting project progress lead to changes in the demand for component parts. Changes in production and supply capacity affect the production and supply decision-making of component parts. The problem of the production schedule in an uncertain supply-demand environment is considered to be the first stage. Due to the limited and dynamic space of construction sites, the problems of stacking, storage and transportation management of component parts site are significant. Therefore, the second stage is to solve the on-site scheduling problem of component parts.

The key to solving the two-stage scheduling problem is how to effectively deal with the relationship between multiple spaces for different jobs. In order to deeply describe the whole scheduling process and the relationship among spatio-temporal stages, the crucial factors of scheduling activities are analyzed, and the major characteristics of two-stage scheduling are pointed out. Then a two-stage scheduling model framework is established by using the object process methodology. It also analyzes the internal relationship between the two-stage sub-models, and clarifies the implementation path of the model.

The first stage scheduling is to consider the "several to one" supply relationship between the factory and the construction site from the perspective of the construction site, focusing on the production and supply decision-making of component parts. Uncertain supply and demand factors are taken into account, and the changes in production capacity and construction demand are estimated respectively. Using the feedback information of the second stage scheduling, the impact of site space availability is considered at this stage. According to the above constraints, the stochastic programming method is used to minimize the total scheduling cost. The production scheduling model of component parts in the environment of uncertain supply and demand is established to determine the optimal production and supply scheme. The results of application case show that the scheduling model can minimize sum of holding and delay costs, and improve early or delayed supply. It is conducive to achieving the objective of "forward planning, precise control, efficient allocation and complete process link".

The second stage of scheduling is the research into the scheduling of component parts on construction sites. It mainly takes the stacking yard layout planning as the core, and associates the initial production and supply with the back-end storage and transport, storage and consumption. By analyzing the non-centralized and dynamic storage demand, the overall framework of the on-site scheduling model is proposed. Firstly, according to the results of the first stage scheduling, the building information model is integrated to obtain the supply information of component parts; Secondly, using site surveillance videos, the image recognition method is applied to obtain the state information of the given stacking area; Finally, the dynamic programming model of stacking yard layout is established based on the information of the above two parts. On the premise of meeting the construction requirements and spatio-temporal constraints, the secondary handling is reduced and the total cost of on-site handling and centralized storage is minimized. The result indicates that this method effectively reduces the project cost, and improves the construction efficiency. This also provides a more practical process and method for the storage and stacking of component parts on site, reflecting the scheduling idea of "front-end link".

Keywords: Prefabricated building; Two-stage scheduling; Storage area planning; Identification of on-site unoccupied locations; Uncertain supply and demand