Optimizing Construction: What is Constructability Analysis Using BIM?

April 2, 2024 at 7:00 am, No comments

Constructability analysis, facilitated by Building Information Models (BIM), is an essential process spanning planning, design, and construction phases. Utilizing 3D models, it enables the identification of potential obstacles, design flaws, schedule delays, and cost overruns. Methods employed include visual 3D review, clash detection, quantity comparison and other techniques.

Simply put, detecting issues through these methods during the design phase or early in construction can prevent more significant problems and financial overruns down the line.

This blog post delves into the process of the constructability analysis process, shedding light on the principles and tools utilized to minimize errors in your design.

Scenarios to Consider

Constructability analysis can be conducted in both the design and construction phases, but there are three model availability scenarios to consider:

BIMs are developed during the design phase: This implies that all major disciplines (Architectural, Structural, MEP) are creating models. While interdisciplinary coordination (error checks) may be performed, it does not guarantee that all major issues are resolved. For instance, drawings might not be generated from models, or quality control of models could be lacking. In this scenario, constructability analysis can be performed immediately by combining and reviewing the models. However, it should be verified whether the drawings used for constructing the building are derived from these models.
BIMs are partially available: Some disciplines (such as Architectural) have created 3D models for specific purposes (e.g., renderings, drawing production). In this scenario, it's highly probable that no interdisciplinary coordination has taken place, and some or even most drawings and QTOs (Quantity Takeoffs) are not derived from models. To conduct a more comprehensive constructability analysis, it may be necessary to create the missing models. Though it is possible to conduct some checking with individual models, interdisciplinary issues can lead to major problems. Therefore, it is essential to create the missing models, at least so that they contain major objects.
No models are available for any discipline: In this situation, to perform a constructability analysis, models need to be created from 2D drawings. By creating 3D models from 2D drawings, it is possible to identify drawing issues, such as missing or wrong information, as well.

Methods & Tools

The most common methods used to perform constructability analysis using BIMs are:

Visual inspection. By walking through the models and using tools such as sectioning and measuring, it is possible to identify various issues - code violations, placement issues, clashes etc. Tools to use in this process are 3D viewers and there many that are free to use. Check out the free guides section for some examples.

Clash detection: is a process wherein individual and federated models undergo checks for clashes based on pre-defined tolerances. While clash detection can be done visually, it is not very efficient and may result in overlooked issues. Therefore, specific tools such as Solibri Office, Navisworks Manage, or others are utilized for this process.

Quantity Comparison: If a few principles are adhered to during model creation, it becomes possible to compare model quantities to available Quantity Takeoffs (QTOs) or Bill of Quantities (BOQs). This facilitates the identification of errors and helps in avoiding surprises during the construction phase. Tools used in this process are either the authoring tools (with which the models were created) or specialized tools for estimation using BIM.

Common Issues

Here are a few examples of the most common geometric issues found during constructability analysis process.

Misalignments between disciplines:

Archictectural discipline is not aligning with the structural

Design flaws:

The door has been design too high without considering the external earth elevations

Design code violations:

There is not enough free head space

Interdisciplinary clashes:

Major ducts clash with cable trays

Conclusion

These are just a few examples of the issues that can be identified by using BIMs for constructability analysis. While simple 3D viewers can check many aspects, more detailed checks such as clash detection or quantity take-off require specialized tools to provide greater value.

However, in my experience, the greatest value is derived when more people, whether experts in their field or future users of the building, are involved in the process. Their collective knowledge and experience can identify a wide range of issues, leading to improvements in various aspects such as technical functionality and user well-being.

These benefits apply to buildings of all sizes, and you can find more information about the benefits of BIM that I experienced during the design and construction of my own house in my blog post "How Much Cash Did BIM Save Me When Building My House?".

Optimizing Construction: What is Constructability Analysis Using BIM?

Scenarios to Consider

Methods & Tools

Common Issues

Conclusion

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