Parametric Design of steel structures
Parametric Design of steel structures
Fig. 4 Lines and points are covered here
By using parametric modelling tools, designers can simulate a high number of design-variants with relatively low effort. Visual programming software’s like Grasshopper significantly lowers the threshold for beginners to start building parametric models.
Fig. 5 Surfaces are not covered here
This paper discusses how using Grasshopper as a parametric design tool can be applied by structural engineers to improve well-informed decision making, when designing a steel structure. Finally, worth mentioning further possibilities parametric design workflows can bring are discussed such as optimisation strategies, optimising sustainability and including structural connections in the parametric model.
Fig. 6 Lines must reach from node to node, curves are discretised
Parametric design is a phrase which is becoming more prevalent in the Architecture Engineering and Construction industry (AEC). It allows the designer to generate and analyse multiple variants, which speeds up the decision-making process and drastically increases the capacity of the work of an engineer. In making better informed decisions, parametric design is inevitably becoming a fundamental skill for structural engineers.
Fig. 7 Series of steps needed to generate a parametric tube
A significant contributor to the popularity of the phrase Parametric design are visual programming packages. Visual programming is a no-code type of programming where code is encrypted into components. Each of these components has inputs and outputs. With wires these components can be connected to each other.
Fig. 8 Creating a parametric arc; a) computational plan, b) Grasshopper components
Fig. 9 Discretising the arc into multiple line-segments; a) computational plan, b) Grasshopper components
Forming a network of logic where the output of one component serves as the input for the other. This network of logic processes input into a defined output. Compared to conventional programming, visual programming is significantly more intuitive, making it relatively easy to learn for beginners.
Fig. 10 Creating the point grid of the truss; a) computational plan, b) Grasshopper components
Fig. 13 Truss typologies
Visual programming software, like Grasshopper, have many different types of applications. This paper focuses on how structural engineers can use Grasshopper to design steel structures. These steel structures are often described by using points and lines.
Fig. 14 Parametric geometry of complex 3D structures
We shall further focus here on such geometries. Hence surfaces, which are often used to describe concrete structure, as displayed in, will not be covered here. Although, having good basic knowledge about simple lines structures will make it easier to learn how to work with more complex geometry such as surfaces.
Fig. 18 Arch results
All geometry discussed in the examples of this paper, shall be created to be compliant for finite-element-method-calculations. This means a different approach is used compared to simple drawings with a generic CAD program. Firstly, lines are defined from node to node. Typically, in a CAD tool drawing a straight line will be a single straight-line segment, see truss in.
Fig. 20 Truss results
Fig. 21 Finding optima in the solution landscape 
This prevents that the intersection nodes are being found and will result in the truss not behaving as desired in the analysis. Secondly, in finite element packages curves do not exist, there are only (straight) 1D elements. Therefore, when an arch is modelled, this arch must be discretised into multiple line segments.
Fig. 22 Genetic algorithm examples Karamba3D 
Visual programming can offer the engineer a useful extra tool. Due to the large number of plug-ins available, parametric design brings many possibilities in search for better solutions in design projects. Making use of its full potential requires training, especially improving how complex structures can be broken down into a sequence of logical steps.
Fig. 23 Integrating detail analysis in the parametric model
To give the industry the possibility of implementing these new possibilities Bouwen met Staal organises English courses in parametric design bi-annually. Planned dates of upcoming courses can be found on the Bouwen met Staal website.