Industrialization of façade design engineering is one of the development trends of the architectural envelope industry. It addresses the requirements for energyefficient and sustainable buildings, cost and serious shortage of contractors.
Since the birth of CAD (computer aided design) in the last century, engineers have abandoned manual drawing and turned to electronic drawing. This has changed traditional design methods and brought the first revolution in the façade design engineering field. To manage the CAD data, information technology also underwent a three-stage evolution from CAD file management, to CAD database management, to Product Data Management (PDM). PDM is an integrated working mode that can provide a façade design collaboration environment for sharing, so that designers can work on the same database, reducing unnecessary condition transfer and confirmation and fully sharing information resources.
The rapid development of three-dimensional modeling and virtual reality technology helps improve communication efficiency among the multiple parties involved in façade design. The visual expression of a three-dimensional model can help architects and façade designers freely exchange ideas and deliberate on the designed volume, shape, façade, and exterior space throughout the design, but the aforesaid façade surface model cannot hold more design information for construction and installation.
In addition to the physical dimensions of the architectural envelope and required materials, design information also includes wind pressure resistant strength, seismic resistance, air tightness, water tightness, transformation, construction technology , heat transfer coefficient, etc. Indetermination of such information will lead to poor efficiency in subsequent work, such as building estimate and budget, fabrication and field installation.
VDC and BIM
Virtual Designand Construction (VDC) is another concept becoming popular in the engineering construction industry. It requires, through the multidisciplinary parametric models provided by design, construction, operation and maintenance teams in project construction, integration of building facility information, the construction process and the management organization to ensure the achievement of general management objectives for the project.
If the VDC management concept can be implemented, we will be able to capture and reuse data from conceptual design to prefabrication and even in downstream processes, and apply the data to the entire process from concept design, to modular construction, to component prefabrication. Then, we will have the chance for “building industrialization.”
BIM is one of the core technologies of implementing VDC. BIM technology is highly correlated with industrialization of façade design engineering logically. Based on BIM, the carrier of building information, not only the visual design, multidisciplinary integration correction, panel optimization analysis, and quantity calculation for the architectural envelope can be possible.
A breakthrough can be made, specifically the mode of documentation in design delivery in the traditional building industry serves no one well. Instead, the panel fabrication drawing can be directly generated and the component fabrication data can be directly extracted from the design model, which makes possible the paperless design and plant fabrication of the curtain wall unit.
BIM-based parametric design
BIM parametric design changes all the elements of a façade fabrication to a functional variable, and then, by changing the function, or to say, by changing the algorithm, drives the façade panel shape to change, thus creating different building design schemes. As an art of building, façade design fundamentally has an antilogic basis. As aesthetic theory goes, there is no debate for taste. Sticking to conventional thoughts will never lead to the palace of art. However, parametric design is not contradictory to traditional building design. It is oriented to the future, and has many unimaginable forms. It is a tool that can inspire designers.
In BIM parametric design, all real attributes of façade fabrication components are given a parametric simulation and calculation, as well as related data statistics. In BIM parametric design, a façade component is not only a virtual geometric component, but also has other geometric attributes, such as component material, thermal performance, cost, as well as purchase information, weight, installation number, etc.
The significance of BIM parametric design is that we can, according to different design parameters, quickly conduct calculations and statistical analyses on modeling, layout, energy conservation, evacuation, etc. and then give priority to the most appropriate scheme. This is where BIM parametric design differs from ordinary parametric design that is only for the realization of geometric modeling.
Knowledge-based visual design
A BIM-based three-dimensional virtual design environment helps quickly transfer design information and simulated information to project partners, so as to improve their communication efficiency, make possible WYSIWYG (what you see is what you get), and reduce economic losses caused by redesign.
Visualization can be used for design clarification of detail structure joints, such as the façade panel edge, corner, hole, junction, and beam bottom flashing and trim. Besides, visual display can help quickly discover any conflicts among disciplines and improve design quality. BIM visualization is automatically generated via the information for entity components. We can have the multi-view sectional drawings and axonometric drawings of a curtain wall model automatically generated to transfer information. There are correlative and feedback relations among the components in such a “tridimensional wall.”
When a façade design engineer modifies a component, all the views in relation to the component will be automatically updated, saving us the trouble of modifying the plan, elevation, and section respectively. The “correlative” visual feature is conducive to improving communication efficiency and also improving design engineer work efficiency, solving the long-standing problem of discrepancies among, omissions in, and incompletion