A unified data management structure should be established for efficient BIM collaboration and information exchange among design team. At the start of the project adopting BIM, the design team should agree and state in the BIM Execution Plan the details of data management arrangement, which should at least include the CDE arrangement, project folder structure, collaboration arrangement (such as model linking),
software platform, model division arrangement, file /object naming convention, level of development (LOD) at various work stages and the model presentation style (such as colour scheme, line types, etc.).
Level of Development (LOD) of MEP Objects
With reference to the CIC’s BIM standards (Phase One) and the American Institute of Architects (AIA)’s G202-2013 BIM Protocol Form, the general coordination with other model elements in terms of size, location and clearance to other model elements can be achieved by using LOD 200. Generally, LOD 200 has been adopted at the design stage of the pilot project. In some critical areas such as autopsy suites, LOD 300 is adopted
such that specific coordination (such as the air-conditioning/ventilation equipment in autopsy suite) with other model elements can be achieved to enhance the effectiveness of design collaboration. Given that the higher LOD phase requires more specialized technology as well as increased skillsets to properly address the finite details within the 3D BIM model, the acceptable LOD should be defined prudently at early stage of each
project according to a number of aspects such as BIM deliverables, project stage, allowable time and budget. Based on the project experience, the interpretation of the MEP specific LOD criteria is suggested below.
LOD Criteria of MEP Objects:
LOD 100: The object is graphically represented in the model with a symbol or rough 3D shape for indication of its existence. Identification of the object should be indicated.
LOD 200: The object is graphically represented within the model as a generic system, object or assembly with approximate quantities, size, rough shape, location and orientation. Identification and preliminary design information should be included.
LOD 300: The object is graphically represented within the model as a specific system, object or assembly in terms of quantity, size, approximate shape, location and orientation. Identification and detailed design information should be included.
LOD 400: The object is graphically represented within the model as a specific system, object or assembly in terms of quantity, size, approximate shape, location and orientation in according to manufacturer’s data. Identification and manufacturer’s information should be included.
LOD 500: The object’s graphically represented within the model as a specific and site verified system, object or assembly. The objects should be verified for their existence for as-built record purpose. Accuracy of the object location and setting-out should be within 150mm or other range subject to approval.
The 3D geometry details of the object is not necessary to be higher than LOD 400. As built information of the objects such as identification, manufacturer name, model number and asset management information, etc. should be included.