ZEMCH 2015 - International Conference Proceedings | Page 289

it is necessary to make a detailed survey of the building comprising current measurements,
and to identify technologies and construction materials used. This information is important
for generating 3D BIM models.
2. Identification and capture of requirements: As this study refers to social housing, there are
two main clients: the dwelling’s owner and the dwelling’s user. By knowing the main clients,
relevant requirements for both of them are used in the development of the final product (refurbished building).
3. Identification and characterization of disruption: A characterization of disruption for tenants
has been developed, and it comprises a set of factors. In this step, the types of disruption
affecting tenants and the intensity in which they occur are investigated. This step influences
directly step 5.
4. Definition of the construction technology: A set of alternatives in technology for executing
works in the existing building should be investigated and defined. The client may consider
other factors in the selection of these technologies, such as experience, time, cost, among
others.
5. Definition of tasks’ sequence: This step depends exclusively on the previously selected execution process. Each process might have a set of basic execution guidelines (e.g. items need to
be installed before the insulation boards in the external walls in order to avoid future rework).
Each execution process could generate several tasks’ sequences. The number of sequences
must be defined by the client who must consider minimizing disruption to tenants during
retrofit works. This input is considered in the 4D BIM modelling.
6. Construction of a 3D BIM model LOD 300/350: Considering that the 3D BIM model of existing
building has been developed, the type of execution process has been set, and clients’ requirements have been understood, a 3D BIM model with the level of detail 300/350 must be developed. Also, in this step, several 3D BIM models could be modelled according to the defined
process in step 4. This input should now be considered in the 4D BIM modelling.
7. Development of 4D BIM models: Each execution sequence added to its respective 3D BIM
model, which has elements of the existing building and the building to be refurbished, will
generate a 4D BIM model. In addition, each 4D model can create a what-if scenario. As changes
in the sequence of activities occur, a new simulation scenario is created.
8. Creation of what-if scenarios: This step corresponds to creating several potential alternatives
of retrofitting for a specific execution process. The number of what-if scenarios should be established by the client in order to proceed to the next step.
9. Elaboration of a scenarios’ matrix: After the number of what-if scenarios has been defined,
they should be compared against each other through a scenarios’ matrix. A set of parameters
should be used to assist the process of analysing and selecting the best scenario as part of the
decision-making process performed by the client.
10. Analysis of what-if scenarios by the client: Based on the abovementioned matrix, the client is
able to choose the best scenario for conducting retrofitting works.
11. Execution of the best scenario: After the best scenario has been chosen by client, a contractor,
which has been defined by client, should execute it. The information derived from the execution of the chosen scenario will provide feedback the process and should be considered as an
input for further developments. As an example, a survey with tenants can be performed to
investigate whether the foreseen disruptions at the beginning of the process happened or if
new disruptions emerged.
12. Comparison between scenarios: a comparison between the simulated and performed scenarios is recommended, in order to obtain additional information as a feedback for the process.

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