Computer Models in Structural Engineering

You gave your design idea or architectural plans to a structural engineer… what do they do with that?

Typically, an owner or architect will present a vision or design for a building to us at the conceptual stage. This usually takes the form of architectural drawings that show where spaces, walls, ceilings, and openings will be. These preliminary drawings allow us to lay out our preliminary framing and determine load paths. After a concept is agreed upon, we move into detailed design and drawing production. Here is where our drafting team starts creating drawings and our engineering team starts building our analytical models. The drafting team uses software like Revit to create a 3D model of the structure or AutoCAD to create a 2D set of drawings of the structure. Larger projects are especially suited to Revit due to the large degree of coordination between trades. We often utilize Building Information Modelling (BIM) to further improve communication and coordination between and within the consultant and construction teams.

Revit Model of Winston Park - Phase V in Kitchener, ON

While the Revit model is being built, the engineering team uses sophisticated software like ETABS, SAP, or RISA3D to create a simulated 3D analytical model of the structure. Computer models like these allow us to run complicated analyses using advanced methods that would otherwise take multiple engineers far longer to accomplish using hand computation. This not only speeds up the process, but it also reduces our carbon footprint (and the number of hand cramps we get)! These models contain symbolic representations of different elements, like walls, beams, and columns, which must be joined together with a high level of accuracy and precision. Errors can occur when elements are not joined correctly due to the software thinking the support for elements is different from reality (or entirely non-existent in some cases). This makes quality control and hand verification critical for any computer model. We apply properties and loads to the models to reflect what will be built and the requirements of the relevant building code, then we run, debug, review, and hand verify the models to ensure they are working as intended. Only once verification is complete can we rely on the results from the computer models.

ETABS Model of Winston Park - Phase V in Kitchener, ON

Once the model has been verified, we can design each element of the structure for the loads it experiences. There can be huge amounts of data output from these models, which oftentimes necessitates the use of in-program design modules, other software, or Excel spreadsheets to break down and analyze. The goal at this stage is to optimize each element and make them only as large, rigid, and strong as they need to be while keeping things like cost, waste, constructability, and coordination between trades at the front of our mind. For example, beam sizes may be chosen by taking things like the vertical shear force, bending moment, stiffness, and any geometric constraints and clearances into account. Shear walls are another type of common structural element with a multitude of design considerations, including designing for the lateral shear forces and bending moments, axial gravity forces, detailing of connections and openings, and satisfying ductility requirements. The outputs from the design process, like beam sizes or wall reinforcing, are then communicated to the drafting team to be input in our drawings for use in construction.

Example shear force (left) and bending moment (right) diagrams used for design of walls in Winston park - Phase V

Once we have finished our design, construction administration starts. This involves tasks like shop drawing review and site inspections to ensure that the building is built per the contract documents, including our drawings and specifications. Calculations and sketches are still sometimes required during the CA stage to reflect evolving site conditions. This stage of the project is where we also get to see our projects actually rise out of the ground, which is one of the best feelings as an engineer.

Winston Park - Phase V in Kitchener, ON is currently under construction

The buildings that we inhabit are complex, beautiful things that involve the input and work of a whole team of people. Structural engineering is one component of the whole project, but it is one that involves extensive mathematical modelling, design calculations, and coordination of the design to ensure it is constructable and safe for occupants to enjoy for many years to come.

Winston Park - Phase V from Revit to ETABS to reality


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