Clash detection is a component of the Building Information Modelling (BIM) process and is the realisation of conflicts or clashes, whether structural or MEP, through an automated and computerised approach. Clash detection can be carried out on multiple 3D models and is an invaluable tool for designers, architects, builders, engineers and contractors to determine clashes or conflicts in the structures.
Types of Clash Detection
There are three types of clash detection that occurs within BIM software to help ensure clash avoidance.
Hard Clash
A hard clash is when two objects intersect each other or occupy the same area. A hard clash may advise of a steel rod in a concrete wall or a column running through a wall, as an example. A hard clash can be costly to fix if missed in the design process.
Soft Clash
A soft clash is when objects impinge in geometric or spatial tolerance, or a buffer zone is breached affecting access, maintenance or safety. Through object data placed directly in the BIM software, adherence to safety standards or building codes can be ensured.
Workflow or 4D Clash
A workflow or 4D clash can notify an engineer of any contractor or crew scheduling issues, delivery clashes and other timeline conflicts.
Why is clash detection necessary?
Clash detection helps reduce project errors in ongoing or completed model work before construction occurs. It is essential for recognising and flagging conflicts that occur in BIM, particularly when working with several models which are then incorporated into one composite model.
The running of an automated clash detection process not only reduces the manual time required to check the models, but it can also lower the overall construction costs of a project. Clash detection will also ensure any unnecessary delays prior to fabrication and minimise price overruns.
BIM Software for Clash Detection
While clash detection is not a new process, BIM software and its 3D environment capabilities allow clash detection and clash detection searches to occur in the design phase rather than on the construction site. Modern BIM software has done away with the earlier process of coordination – the need to manually lay drawings on top of one another on a light table to identify any clashes.
There are two suitable types of BIM software to help aid clash detection, reduce human error and make the design process more efficient.
BIM Modelling Design Software
BIM design software such as Revit will automatically alert you of a clash as you develop the models in the software. They are restricted in the sense that clash detections only work on the one type of software. If the structural team is using a different kind of software to the architectural team, then clashes cannot be alerted.
BIM Integration Tools
BIM integration tools such as Navisworks and Solibri have the ability to perform clash detection on various software. It is the more powerful of the two BIM software options as multiple types of software can be analysed at once. Revisions then can be made in the original software before being incorporated back into the clash detection software.
False clashes can occur in BIM software if two trades are attempting to occupy the same space, so it falls on the software user to determine whether the clash is real or false. If a true conflict is identified, designers and engineers must resolve and cancel the clash in the BIM software before they proceed any further.