Advanced Simulation for Thermal Stress Assessment
Detailed stress prediction simulation workflow of architectural glazing under thermal loading
Presented on October 9, 2024 at Facade Tectonics 2024 World Congress
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Overview
Abstract
In recent years, the desire for increased performance, transparency and visual flatness of glazing elements in curtain walls has generated renewed interest in thermally induced fractures. Glass fractures are one of the causes of premature failure in glazed curtain walls. They typically occur under climatic conditions that induce a large temperature difference across the glass. Once the glass tensile capacity is exceeded, fractures can appear across the glass pane. As a consequence, glass replacement is required, associated with high costs and inconvenience for the end-users. During design, approximate tools are available to assess the expected temperature gradients that the glazing might be exposed to, however, they sometimes fail to adequately evaluate the actual induced thermal stresses. Additionally, current standards lack uniformly defined procedures and often carry simplified assumptions that lead to over-conservative results. Modern complex building envelopes often require the use of detailed calculations and simulation methodologies to more accurately estimate the risk associated with thermal stress fracture.
This paper presents an advanced simulation workflow to accurately assess the temperature and stress distribution in glass lites for complex curtain wall applications. First, the project climate conditions are examined: exterior air temperature and solar radiation. Second, a 2D steady- state heat- transfer analysis is completed, followed by a simplified 2D transient simulation considering typical year weather data to identify the high risk boundary conditions. Lastly, a refined 2D-3D transient thermal model is created, whose outputs are translated into thermal stresses on the glass surface and edges through mechanical finite element modeling. This combined thermal-mechanical analysis allows for a more accurate temporal and spatial assessment of the temperature and stress distribution on each glass lite compared to typical linear approaches.
This paper presents a case study to showcase the proposed workflow and prove how 2D steady state assessments tend to be more conservative by 50-60% when compared to 3D transient assessments. And lastly, how calculated thermally induced stresses through current standards tend to be about 70% larger when compared to a combined thermal-mechanical analysis.
Authors
Andrea Zani
Building Physics and Sustainability Leader
Permasteelisa Group
Jamie Reyes
Senior Building Physics Engineer
Permasteelisa Group
Guido Lori
R&D Project Manager
Permasteelisa Group
Jacob Hanke
Senior Structural Engineer
Permasteelisa Group
Giacomo Zangiacomi
Building Physics Leader
Permasteelisa Group
Keywords
Paper content
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