Keywords: entropy, deconstruction, safety awareness, fuzzy logic, safety nets, software program.

The conventional process utilized to tear down buildings is demolition, which is associated with a very high level of disorder. This disorder is often referred to as "global entropy". New systems and processes must be developed to decrease entropy. This is essential to increasing the likelihood of environmental sustainability. Sustainability refers to the process of optimized usage of resources to save for the future. Deconstruction is one such technique that contributes to making the last phase of a building cycle more stable and sustainable. Deconstruction is the reverse of the construction process where the last constructed module is the first removed from the structure [1].

Deconstruction refers to an organized and efficient process of removing building components for reuse in new building construction [2]. It offers better environmental and economic sustainability compared to demolition and land filling. Deconstruction opens an opportunity for knowledge engineering to be incorporated into renovation and remodelling projects by private sector contractors and non-profit organizations. However, the deconstruction process is time consuming and requires more skill than the conventional demolition process.

There are numerous issues concerning worker safety in deconstruction. It is more complicated than simple demolition. There is a higher risk to the workers involved in deconstruction, as they are vulnerable to exposure to hazardous substances such as lead and asbestos. However, there may actually be a lower risk to the environment because hazardous substances can be more carefully contained and controlled.

Deconstruction is as difficult as the original construction process since there is a need for a plan to develop the order of deconstruction as a reversal of the construction process, and to identify the location and installation pattern of utilities.

Safety starts with the planning stage of a project. The various safety hazards need to be identified at the initial stage. To ensure safety of workers throughout the process because of changing conditions, it is necessary to have a continuous appraisal of the site vulnerability to hazards. Since the hazard identification process is complex, a software program has been developed to increase the efficiency of the decision making process involved with the deconstructed site's safety concerns. This program is aimed at improving the site conditions to make it worker-friendly and to enhance the safety awareness of workers. This enables a reduction in the cost of deconstruction, as it contains the cost of knowledge by capturing and reusing expert opinion.

The purpose of this paper is to assess the safety level of the site to be deconstructed. The perception on the level of safety of the site differs from individual to individual. Since the issue under consideration is fuzzy, a fuzzy logic model using fuzzy composition has been developed to solve this problem. The parameters involved and other inputs to the model are also fuzzy. The model is created by first identifying the events that are responsible for causing worker related accidents in a deconstruction site. These events are then classified as enabling and triggering events on the basis of whether they are internal or external to the workers respectively. The fuzzy model thus created, provides clear direction in a situation laden with many uncertainties.

The model also helps the user in formulating a Deconstruction Safety Plan and gives inputs on creating a Site Safety Plan based on the specific site conditions. It helps the user in the management of the process by reducing hazards and increasing safety nets or PODs (Procedures Or Devices), thus improving site safety. Safety nets here refer to procedures that need to be incorporated and protective equipment that need to be used to impede a progressive failure. For example, a dual inspection system involving check and re-check is a safety net procedure and a body harness system is used as safety net equipment

This model can be further enhanced by considering a variety of other safety concerns from deconstruction case studies. It can be developed into a program for safety appraisal of companies dealing in deconstruction.

1

D.S. Macozoma, "Secondary Construction Materials: An Alternative Resource Pool for Future Construction Needs", Concrete for the 21st Century Conference, 3-5, 2002.

2

D.S. Macozoma, "Building Deconstruction", CSIR Building and Construction Technology, CIB Publication, 2001.

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