BIM and construction waste

This Issue This is a part of the Building information modelling feature

By and - , Build 171

Construction waste is a major issue facing New Zealand’s building sector. Now BIM has been used to develop an automated site layout planning system to manage construction waste.

Figure 1: Illustration of optimised waste pile layout for example site.

THE CONSTRUCTION INDUSTRY is the largest source of waste in New Zealand, generating about 50% of all waste products, according to the Ministry for the Environment.

High volumes of waste to landfill

Construction waste includes building debris, rubble, earth, concrete, steel, timber and mixed site clearance materials. These come from various construction activities including land excavation or formation, civil and building construction, site clearance, demolition activities, roadwork and building renovation.

While some waste is recyclable and reusable, most is dumped in a landfill. Currently, the construction industry is responsible for about 20% of landfill waste, and 80% of cleanfill waste, aggravating the landfill shortage problem.

Construction waste often makes the site chaotic and involves high transportation costs to transfer to landfills.

Poor planning and logistics

The reasons for the high volume of construction waste in New Zealand could be related to poor planning and logistic procedures, and the lack of adequate planning tools to manage the different types of waste.

Traditionally, construction waste is randomly stacked in empty spaces on construction sites. There are two reasons for such an ad hoc way of dealing with the wastes.

First, it is hard to know when, what type and how much construction waste will be generated, due to the complexity of construction structures such as commercial buildings. Without this information, it is impossible to plan the layout of waste piles to minimise transportation costs.

The second reason is that site managers generally do not have strategies and tools to plan the layout of waste piles. As a result, even if there is available information, they still have to rely on experimentation and their intuition because the task of planning the layout of waste piles is complex.

BIM optimises waste layout by week

To address this problem, we developed a framework of the building information modelling (BIM)-based automated site layout planning system for waste management. The BIM system stores the models for the buildings, site and construction schedule for the project.

Based on the information in BIM, Module 1 extracts, for each week, the dynamic amount of materials transported between two facilities (two temporary facilities or a temporary facility and a fixed facility) and the dynamic amount of waste generated and transported from a facility to a waste pile. The amounts of waste generated each week can be used to calculate the size of the waste piles required to store the waste.

Module 2 is the dynamic site layout planning, which consists of an optimisation model and a solution algorithm. The optimisation model formulates the waste layout problem as a mathematical problem, which can be tackled using state-of-the-art operations research techniques. The algorithm in Module 2 is step-by-step guidance to obtaining an optimal solution to the model – that is, the best layout plan for waste management planning.

The site layout plan obtained in Module 2 will be visualised in Module 3, providing a visualisation for site managers. Because the layout plan is dynamic, the visualisations for different weeks change, reflecting the real layout situation of construction sites.

Example demonstrates use for site layout

The BIM-based automated site layout planning system can be applied to a site with one or more buildings. For instance, the BIM-based automated system is applied to two buildings in Figure 1.

The construction duration is 5 weeks, and there are five different layouts of the site, each for 1 week. The layout plan includes positions and shapes of both temporary structures (rebar bending yard and carpentry workshop) and waste piles.

The temporary structures do not exist for the whole 5 weeks (Figure 1). Depending on the construction progress, the amounts of waste generated in different weeks change and the sizes of the waste piles change. The locations of the waste piles also vary in different weeks due to the varying waste sources.

Overall, this example demonstrates the applicability of the BIM-based automated site layout planning system.

Figure 1: Illustration of optimised waste pile layout for example site.

Benefits of the BIM planning system

The benefits of the BIM-based automated site layout planning system are twofold. First, site planners no longer need to manually design the layout, saving them time and effort. Second, the amount of material and waste to be transported can be estimated by BIM fairly accurately, and the optimisation model provides the optimal layout. The overall transportation distance, therefore, is the minimum.

The BIM-based automated site layout planning system can reduce the emissions and noise caused by the transportation equipment in the construction site, as the transportation equipment moves for the shortest possible distance.

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Figure 1: Illustration of optimised waste pile layout for example site.

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