In this module, I will first introduce the concepts of model integration and clash detection. Then, we will discuss BIM applications for model integration and clash detection. In a construction project using BIM, usually the architect would first produce a basic architectural BIM model based on the owner’s needs and requirements. Then, different design teams work simultaneously based on the same basic model. We call this parallel operation. During parallel operation, each design team works on its own design model and the only common reference is the basic model. Although parallel operation reduces the time spent on designing, two teams cannot obtain immediate reference to the design taking place on the other team; Therefore, at some point of design when a design team has completed its own design to a required degree, it would publish its design and we need to integrate the design with other teams’ published designs and make sure we have a set of consistent federated design models all the time. During this model integration process, because the two design teams would inevitably use the same space for placing their own equipment in parallel operation, clashes or interference between design can often be found. Let’s use an MEP design example to explain it further. MEP design in architecture can be roughly divided into water supply system, drainage system, fire system, air conditioning system, power system, and telecommunication system. Each system is often designed and constructed by different design teams or companies. The water supply, drainage, air conditioning systems all have a common feature: complex pipelines. When a water supply team designs its own pipelines, it is unknown to them that the air conditioning team also want to have their pipelines going through the same space; hence, interference occurs. In traditional design process, to solve this unavoidable issue of interference, MEP design is often a schematic drawing which only shows rough location of the equipment and piping, but it allows the construction workers to make on-site decisions of where the piping should be exactly placed. In BIM design process, with the help of 3D BIM models for design integration, we can easily detect design clashes in advance and resolve them before the actual construction. Clashes are usually classified into three types. They are hard clash, soft clash, and 4D clash. A hard clash occurs when two objects occupy the same space. A soft clash occurs when the required spatial or geometric tolerance or buffer zone of an object is violated. For example, an equipment may require certain clearances to allow for maintenance, access or safety but it is placed too close to a wall. A 4D clash is also called a workflow clash. Unlike hard and soft clashes which refer to clashes of objects after construction, 4D clashes take into account the scheduling of activities and refer to hard or soft spatial clashes of objects during construction. For example, a large equipment needs to be installed in a room before the walls of the room are built because the equipment is too large to go through any opening on the walls. Therefore, if the walls are mistakenly built before the equipment is installed, we have a 4D clash in this case. Several BIM software tools provide built-in clash detection functions. In this course, we will introduce how to use the clash detection functions provided by Revit and Navisworks.
