building information modelling


Making decisions, not drawings


BIM – building information modelling – has become a buzzword in the construction industry with enormous


implications for savings and efficiency. Paul Schreier reports on the heart of BIM collaborative efforts


W


hile in college studying for my engineering degree back in the 1970s, I spent summers working with my father, a


pipefitter, on various large construction sites. I (representing the entire engineering profession) was the butt of constant jokes. Te fitters would lean over a set of


blueprints and snicker. I’d constantly hear comments about how ‘stupid’ engineers were. Just a couple of the many things I heard were: ‘Look at this! Tese drawings show a water pipe going directly through an air duct!’ or ‘Tose idiots are telling us to install pipe that was never ordered!’ Perhaps if those architects, designers


and engineers had been working with BIM (building information modelling), I would have faced far fewer such jabs. In those days, each discipline – just some of them being structural, electrical and HVAC – had its own set of 2D drawings, generally created by a team of draſtsmen working on large boards. Making sure all these drawings were consistent with each other and corresponded to the reality of the building going up was a virtually impossible job, as my father and his co-workers never hesitated to remind me. Spotting obvious conflicts such as a pipe


going through a duct, a process known as ‘clash detection’, is just a very small part of what BIM is all about. To understand why, you must first appreciate what BIM is and how it developed over the years. Construction designers and engineers


experienced a great leap in productivity when computers and soſtware became affordable enough that everyone could create drawings on them. Tere are, however, two strategic limitations of drawings according to Chuck Eastman, director of the Digital Building Laboratory at the Georgia Institute of


38 SCIENTIFIC COMPUTING WORLD


Technology and co-author of a popular book on the topic[1]


. First, they require multiple


views to depict a 3D object in adequate detail for construction, thus making them highly redundant and open to errors; second, they are stored as lines, arcs and text annotations which can be interpreted only by people and not computers.


BIM as a verb, not a noun A building model takes things a step further by allowing designers to work with parameterised objects instead of just lines and arcs. Explains Benedict Wallbank, head of SmartBIM Solutions, a BIM consulting company which is a division of Graphisoſt (which supplies the BIM authoring package ArchiCAD), BIM involves representing designs as objects which carry their geometry, relations and attributes. Composed together, such objects define a building model. If an object is changed or moved, it need only be acted on once. BIM design tools then allow you to extract different views from a model,


and these views are automatically consistent. Here, he emphasises, it’s important to make the distinction between a model (the noun) and BIM as a process (verb). BIM authoring tools go further and define


objects parametrically so they can re-build themselves according to the rules embedded in them. Consider a wall that you might have to draw several times, once for the floor plan, once for the elevation and again in section. With BIM it’s necessary to model the wall just once, and then you can display the information as needed whether as a schedule, drawing sheet, 2D or 3D view. Furthermore, you create a parametric model so that if you make a change anywhere, it automatically updates all dependencies. We’re just scratching the surface of what


can be done with BIM, adds Wallbank: ‘I draw a comparison to the retail industry when they started using bar codes.’ Barcodes initially contained only cost data, but then retailers discovered how to use them for order processing, JIT deliveries, minimising warehousing and now, based on barcodes, stores can even recommend other products customers might want. All these applications were never envisaged at the start. Te same is happening with BIM. ‘We have useful immediate information such as clash detection and project coordination,’ he continues, ‘but there are so many other things that can be done, such as having a fire specialist simulate smoke distribution, or architects study how people move through schools or other public buildings.’ Today the industry is progressing into Stage 2 BIM where models from various disciplines are brought together; not far ahead is Stage 3 BIM which adds the dimension of time, and Stage 4 BIM will move into facilities management.


The BIM process can consolidate information from various disciplines while still in the planning stage to avoid costly retrofits and workarounds


Design then build Looking at the path towards BIM, Huw Roberts, global marketing director, Building and Structural at Bentley Systems, puts it this way: Previously, CAD documented the results of decisions. Now methodologies are shiſting whereby computers inform us before decisions are taken; we simulate


www.scientific-computing.com


Mervyn Richards, BIM consultant


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