A Dilemma- Is BIM Clash Detection necessary?

The AEC industry is extremely dynamic and requires input from various stakeholders in order to achieve the desired results. Moreover, a single construction process involves numerous disciplines like architectural, structural and MEP. The AEC professionals from these fields typically create models that are independent from each other. It is imperative that several individual models of these respective fields are integrated into a single BIM model so that any interference occurring between them can be checked for, and maximum collaboration and coordination can be ensured.

A clash occurs at two levels. It could occur at an intra-disciplinary level which is within MEP like a clash between HVAC duct and a plumbing pipe or it could be at inter-disciplinary level between wall (architectural) and beam (structural). There are two types of clashes which could involve design alteration namely hard clash and soft clash. Hard Clash occurs when two objects occupy the same place and a soft clash occurs when any component is not given the required tolerance. Finally, a workflow or 4D clash occurs due to scheduling conflicts. Clash Detection Services are thus, important to identify, inspect and report interferences in the construction project. In the current article we look at the benefits of BIM clash detection and state its importance.

Fewer Iterations during the Construction Phase

The construction industry has historically faced issues like escalating budgets, increased timelines, excessive waste etc. One of the main reasons for that are the numerous errors which were discovered onsite. The traditional design process involved overlapping construction documentation and trying to find any possible collisions and interferences. With BIM, clash detection became a computerized process wherein software like Autodesk Revit, Navisworks etc. were used to detect clashes of specified tolerance value and above.  This drastically improved the clash detection process. The clashes which were initially discovered onsite and required design alterations were now detected in the preconstruction stage itself reducing the probability of anything going wrong onsite.

To reinstate the importance of this point an example of a project involving clash detection for a commercial building can be stated.  We were provided with individual Architectural, Structural and MEPF Revit Models from the client’s end and had to ensure that the clashes between these models were detected and resolved efficiently at both intra and inter disciplinary level. The final federated and clash free model would be been used for construction. Utilizing Navisworks we set a tolerance level of 1mm and were able to detect 1116 clashes. These clashes were significantly high as compared to the size of the project. It is difficult to imagine the amount of rework that would have been required had these clashes been discovered onsite. Moreover, a lot of MEP components and structural and architectural elements are prefabricated then assembled and installed onsite. If shop drawings are extracted from a non-coordinated model then it could cause the products and the components to not properly fit onsite. This mean they either need to be discarded or its dimensions, sizes etc. altered. This is time consuming and will also translate to monetary loss.  With clash detection taking place in the preconstruction stage and resolving them effectively allows the construction professionals to carry out their goal of effective construction.

Once the clashes were detected and consequently reports were generated our architects, engineers and designers had to work in collaboration with each other to determine design changes that could resolve the clash. For those requiring significant design changes RFIs were also raised for the client’s approval. Finally, working in association with our clients we had managed to solve all but 198 clashes which were soft clashes and were instructed by the client to let them be. Similarly, it would have also lead to a considerable delay as well as caused loss of money and resources.

• Setting the right tolerance is crucial

Automatic clash detection generates many clashes and all of which might not always be relevant. Hence, setting the appropriate tolerance value is crucial. Tolerance value refers to the range of variation that is permitted while maintaining specific standards. In any construction it is improbable that a zero level of tolerance will be achieved. So the BIM modeller has to set a permissible level of tolerance and any clashes below that level will be assumed to be worked onsite. In the above stated example  we had a tolerance level of 1mm which allowed us to detect even the smallest clash. Resolving them meant that the client didn’t have to worry about making any changes onsite which would have led to increased timelines and budgets.

• Better Coordination & Collaboration between Teams

In a inter-disciplinary clash detection project teams need to work in collaboration to make design changes so that the clash is resolved. In the above project when a clash occurred between different disciplines, for instance between MEP and structural components then both structural and MEP engineers had to work together to solve the problem. One of the biggest advantages of utilizing BIM for clash detection is that is easier for the teams to share information and collaborate in the cloud based environment. The capabilities to review, mark-up and flag issues ensure that there are no errors due to negligence. Moreover, the information is updated in real time allowing everyone to be on the same page so that no information is lost due to miscommunication.

Conclusion:

With BIM Coordination Services creating, it becomes possible to create a federated BIM model which allows the designer, architects and engineers to get a universal view of the project. With unconnected documents it will be difficult get a holistic visualization ultimately necessary to properly detect clashes. Moreover, digitized clash detection process reduces any scope of human errors in the process. So in conclusion, we can we sufficient evidence state the BIM clash detection is indeed necessary to ensure that the project is completed on time and on budget with minimum amount of errors.