WHAT IS CLASH CHECK IN BIM?

In a BIM project, architects, civil engineers, mechanical project engineers (HVAC, Electrical and Plumbing), environmental engineers and other professionals create design models independently of each other, and when the created models are integrated into the BIM modeling process, ‘BIM clash detection’ comes into play. BIM clash (or collision) detection is a technique to detect whether two elements in the design occupy the same space (collision) and determine where and how such collisions occur. In other words, it is a constructability analysis used to identify problems that, if left unchecked, could lead to increases in cost and time-lapse and loss of productivity during the construction phase.

One of the biggest advantages of 3D modeling a project is being able to see all the problems that may arise, before entering the construction phase. In the past, clash detection was not considered prior to construction, so when engineers inspected the construction on-site and a clash emerged—for example, a beam getting in the way of the air conditioning unit—everything had to be scrapped and the entire construction design improved on-site. This caused costly delays. Today, since clash detection means that all problems are solved in the design and survey stages, time, labor and cost savings can be achieved during the construction phase. Completion of projects without clash detection during the design phase can lead to serious losses, delays and design errors during the construction phase.

Clash detection is available in a number of software programs, including Navisworks, Solibri Model Checker, Tekla BIMsight, Vico Office Constructability Manager, ArchiCAD, Revit, and others. Some software programs have advanced features and offer the ability to create rules (like Solibri), while others only offer basic features (like Revit).

BIM CLASH CONTROL METHODOLOGY

It is necessary to proceed step by step when checking for clashs.

Step 1: The compatibility of the architectural project and the structural project should be checked. This means: Do the structural elements in the architectural project overlap with the structural elements in the structural project?

Step 2: After the architectural project and the structural project have been shown to overlap, the most important control is the structural project’s relationship with the elements of the mechanical projects. The elements that will penetrate the structural elements are determined, along with the locations of the holes that need to be drilled for these elements (electrical conduits, ventilation pipes, etc.). Predetermining the locations of these openings, and establishing them in place before the concrete is poured allows the construction phase to be accelerated. The required openings are created with parameters set to objects in programs such as Revit and AllPlan and are named with smart tags. The advantage of BIM here is that when the dimensions of the spaces are changed, the numerical values ​​on these labels are automatically reflected on the plans and sections.

Step 3: The compatibility of the ventilation system elements is checked.

Step 4: The compatibility of the ventilation system and sanitary system elements is checked.

Step 5: Compatibility of electrical installation elements with other mechanical projects is checked. There is no need for 3D modeling and collision checking of soft plumbing elements. These elements can easily bend around important rigid elements.

Step 6: The buffer zones of all equipment are checked. According to applicable building standards and regulations, the BIM object must be provided with sufficient geometric tolerance data for the object. For example: leaving enough space for maintenance workers to service an air conditioning unit.

WHAT ARE THE BENEFITS OF A BIM CLASH CHECK?

-It makes it easy for designers and architects to create sophisticated building designs without worrying about the quality of construction documents.

-Changes made to a single item are automatically reflected in all views.

-Because everything is coordinated, knowledge transfer is seamless, reducing manual effort and increasing productivity.

-When everything is planned, visualized and managed during the design phase, it leads to fewer changes in the construction phase. It makes the construction process faster, better and more efficient, without any room for error.

-It allows architects and contractors to eliminate the possibility of design changes that may cause the project to go over budget and delay project completion.

-It makes it easy for teams to share information and collaborate on the same project. It provides rapid information transfer for fluid coordination between members of different design, construction, electrical and engineering disciplines.

-It provides structural integrity and energy efficiency.

-It ensures compliance with regulatory requirements. It ensures that the base model meets the safety and performance requirements.

-Unlike the traditional design process that involves overlapping designs done on follow-up sheets; the computerized BIM process simultaneously evaluates multiple composite models and brings together all design information.

WHAT IS A CLASH REPORT?

This is a list of the clash detected in a BIM project, and which objects these clashs belong to. In the clash report, each clash decision (such as which of two elements will go around the other), the checking of whether the clashs have been corrected, the dates when a clash was detected and corrected, and the percentage of corrections should be included. BuildingSMART® has developed the BCF format in order to facilitate all this and to make it possible to read from many computer programs through IFC. In order to follow up this complicated process on BIM platforms, there is BCF tracking. These reports can be followed on the platform as well as in EXCEL, HTML, XML and PDF formats. The important thing is to present this data to users in an easily understandable way.

WHAT ARE THE STAGES OF CREATING A CLASH REPORT?

Step 1: The current design pattern of a particular discipline is loaded into the clash detection software.

Step 2: The second design model is loaded, which must be coordinated with the first standalone model. These two separate models are combined into a single model for the subsequent clash detection process.

Step 3: The next steps involve starting the clash detection process by selecting these two models from the loaded models.

Step 4: The detected clashs are grouped by importance and time (short term, medium term, long term).

Step 5: Clashs are grouped according to their typology (such as structure-structure clash, structure-ventilation clash, electrical-plumbing clash).

Step 6: Responsible persons are informed about the clashs.

Step 7: The updated 3D model replaces the old model and the clash is checked again.

Step 8: It is determined what percentage of previously detected clashs have been corrected.

These stages continue cyclically until all the possible problems that would occur at the construction site are resolved.