C+S December 2020 Vol. 6 Issue 12 (web)

Based on attributes the engineer defines, the effects of any change to the design are automatically populated throughout the model. Grasshopper takes the inputs, completes the calculations, and produces an output that is applied to the model. This eliminates the need to manually apply changes across the model and allows engineers to quickly generate and visualize multiple iterations of complex designs in 3D by simply adjusting the attributes. This workflow is especially beneficial when modeling structures, such as bridges, that have complex geometries and curved surfaces. The Many Benefits of Parametric Design Modeling with parametric design has significant benefits that improve both the design process and quality. With architects pushing the bound- aries of design and projects becoming increasingly collaborative, eliminating manual processes can help structural engineers work more efficiently to meet today’s project demands. By combining parametric design with parametric modeling, engineers can: • Accelerate work and increase accuracy. Parametric design lets engi- neers define logical rules describing the model and the relationships be- tween its parts, as well as a set of parameters to drive the logic. The design tool then calculates and creates a dynamic 3D model based on that criteria that, when used with a parametric BIM software such as Tekla Structures, leads to a detailed, data-rich constructible model that contains all the in- formation needed to build and fabricate. Eliminating manual work provides a tremendous productivity advantage by accelerating model creation and the automatic generation of the design as a whole decreases the chance

Overcoming Complexity and Driving Efficiency in Bridge Design with Parametric Design

By Gabriel Neves

Engineers are under growing pressure to be more productive while, at the same time, structural design is becoming increasingly complex. The architectural design tools of today have expanded the possibilities for more curves and amazing structural details, all of which end up on the desktops of structural engineers who are working with smaller bud- gets to meet tighter deadlines. While this is especially true in bridge design, the majority of the bridge industry remains heavily reliant on drawings as primary documents. Although widely adopted, traditional 2D CAD workflows don’t solve the challenges commonly seen on projects today such as material waste, rework, RFIs, budget overruns, schedule delays, and a general lack of productivity. These constraints are driving a growing number of structural engineers to explore parametric design and BIM-based workflows. Parametric design shifts the expression of design from geometry to the underlying logic, allowing engineers to establish rules and parameters for a model, rather than model the geometry directly. These rules operate on the input parameters, and the model is an inevitable outcome. So, when ad- justing one parameter, such as the number of columns or the width of a deck, all of the model objects affected by that change are automatically updated. When parametric design is combined with the proper BIM software, the parameters can simultaneously drive information-rich BIM data beyond simple geometry. This might sound complicated, but it’s all about overcoming limita- tions and rapidly creating design alternatives for complex shapes. Today, structural engineers are leveraging a parametric workflow without prior knowledge of programming through direct links between BIM software and visual programming tools such as Grasshopper, a pre-installed plugin for Rhinoceros 6, a 3D computer graphics and computer-aided design (CAD) application. This allows engineers to define input parameters such as coordinates, dimensions, or curves and visually script rules that act on those parameters, generating the desired geometry or other output, which can then be applied directly to live objects using a parametric BIM software. By bringing the parametric design into a 3D parametric modeling environment, such as Tekla Structures, repetitive tasks and change updates are automated. This allows engineers to quickly, accurately and easily create a truly constructible 3D bridge model, fulfilling any Level of Development (LOD) requirement and ensuring all deliverables, including the model, drawings and material lists, are consistent.



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