What Do Seismic Modelling of Structures Mean?

05 November 2019

Seismic events are reported on the tea time news all the time. Buildings lean precariously to one side while entire road systems look like they’ve been crumpled up by an angry giant. However, most seismic activity is felt only as a peripheral impression. Below ground, though, structural and infrastructural damage can occur even if the ground vibrations are barely felt above ground; hence, the need for a seismic modelling system.

What Is Seismic Modelling?

It’s a half theoretical, half practical assessment system that’s designed to make structures earthquake resistant. And not just from the so-called big quakes, either. If a small tremor causes damage to a bridge, road or building, then cracks could open up on a rigid concrete wall. With the crack open to the elements, water and cold seep into the underlying structural elements. Imagine the reinforced steel beneath a bridge’s concrete pillar corroding. That’s the kind of damage that will inevitably occur, no matter how small a seismic event seems to appear. Seismic analysis mathematics, which is used to measure ground motion dynamics, takes care of the theoretical side of things. As far as the practical factors are concerned, this is a science that’s not stuck in a laboratory. Consulting engineers need to examine buildings before they can create a seismic model.

Structurally Focused Seismic Modelling

This is a feasibility study, of sorts. The consulting team needs to examine structural frameworks, to look at the trusses and steel beams that support a man-made edifice. There are load-bearing sections and cross-sectional supports to analyze. If they have load-supporting values assigned, then those values are plugged into the modelling calculations. Even the grade of steel used to construct the edifice is considered important here for certain alloys are more elastic, more capable of absorbing ground energies than other, more rigid steels. Lateral loading, roof and floor distributed loading, all of these factors are assigned a place in the collected datasets, along with the foundation type and soil conditions.

Maybe the projects should be split into three component datasets? There’s the soil, its clay and dirt content, which can give tremors a sharp up and down motion or change the way the energy propagates so that a quake feels like a fluid-like wobble. Looking at building drawings and design plans, the load distribution models start to come together. Still, this is a job that can’t be fully defined by mathematical equations. To complete the model, an engineer needs to carry out a visually conducted on-site inspection as well. It’s there, carrying the design plans, that the steel framework is assessed so that a fully rounded seismic modelling plan can be accurately drawn up.

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