by Suranga Jayasena

Building Information Modelling, or BIM, has become a buzzword in today’s construction industry. However BIM is not yet practiced in Sri Lankan construction industry. While not many have actually used and got its benefits, BIM has gained a large attention in the international arena. Its appreciable features seem guaranteeing that it will become an industry standard in future.

Building Information Modelling is digital representation of physical and functional characteristics of a building creating a shared knowledge resource and forming a reliable basis for decisions during its life cycle, from earliest conception to demolition (read NBS /topics/bim/articles/buildingInformationModelling.asp). As one may realize from this description, BIM is a concept. However, this concept is now being practically implemented, together with global initiatives of free and open standards in order to make BIM accessible to everyone.

Technically, a Building Information Model is a detailed description of a building written in a language (words and grammar) which a computer can read and understand. The term ‘Syntax’ is often used to describe this type of writing to emphasize on the importance of rules and principles of the structure of language. The description of the building is purely in text and symbols, and does not necessarily involve any graphics such as plan and section drawings. Below is a part BIM model of a simple wall given as an example.
A model of a real building will eventually extend to millions of lines.

#9792= IFCDIRECTION((-1.,0.,0.));
#9796= IFCCARTESIANPOINT((12.,0.,0.));
#9800= IFCAXIS2PLACEMENT3D(#9796,#3
#9803= IFCLOCALPLACEMENT(#593,#9800);
#9806= IFCWALLSTANDARDCASE(‘16DNNqzfP2thtfaOflvsKA’,#13, ‘Wand-Ext-ERDG-4’,$,$,#9803,#9876,’A6C3DE63-3731-4F6A-94-7E-DE8A8295779F’);
#9825= IFCCARTESIANPOINT((0.,0.));
#9829= IFCCARTESIANPOINT((12.,0.));
#9833= IFCPOLYLINE((#9825,#9829));
#9837= IFCSHAPEREPRESENTATION(#51,’Axis’,’Curve2D’,(#9833));

A BIM model is different from a drawing. A drawing only contains lines and curves that do not give much meaning for a computer to interpret; while on the other hand, human beings can interpret them to be walls, windows, columns, etc. through combined skills from training and intuition. But, a computer can rarely possess such capabilities to a level that of a human. However, when BIM is used to represent a building, the computer becomes capable of its meaningful interpretation, then its computational power can be used to manipulate the information to virtually construct the building in its memory. Thus, the primary reason to describe a building in BIM language is to take the advantage of ‘computational’ power of modern computers.

Virtual construction of a building (before or after the physical construction) yields numerous advantages. For example, the building can be tested for an earthquake, adequacy of circulation space in an emergency and so forth; and observe aesthetics of different alternatives or physiological impact of different colours and spaces.

A BIM model comes with intelligence. The computer will know that a wall is a wall and its global characteristics (at least). For example, when a window is placed on the wall, the computer will know that there should be an opening on the wall to suit its size. If the size of a window is changed, the size of the opening will also be changed. Because of the embedded intelligence in BIM, the computers can produce different output for user requirements using software. Most outputs accompany 3D (three dimensional) views for easy comprehension. Similarly, software applications are available for users to develop BIM models in simple and user-friendly interfaces and the software application translating them to BIM syntax, so that users are not required to know the BIM Syntax described above.

One of the significant features that this level of intelligence brings is that the computer can identify individual building elements with their quantities (dimensions and counts). As a result BIM enables automated take-off, and more significantly the automated estimating in minutes if not in seconds by linking those to appropriate rate libraries (read 5D BIM This has raised worries if the Quantity Surveyors become redundant. Will they actually? This is not a question to be answered. It is a choice for individual Quantity Surveyors to be made.

About the Author:

Suranga Jayasena (Membership No. GG 0210)
B.Sc.(QS) (Hons), M.Sc.(Building)
Senior Lecturer at Department of Building Economics, University of Moratuwa, Sri Lanka