Thermal Stress Analysis in Glass

Design Considerations

Overview

Authors

Photo of Michael Elstner

Michael Elstner

Director of Technical Advisory Service

AGC INTERPANE

Michael.Elstner@interpane.com

Michaela Poláková

TAS Engineer

Michaela.Polakova@interpane.com

Steffen Schäfer

Steffen.Schaefer@interpane.com


Keywords


Abstract

The use of glass in windows and curtain walls in residential as well as in commercial buildings needs to be designed very carefully. In addition to typical engineering practices, which address amongst other factors a structural check of the glass thickness against wind and impact loads et. al., it has always been necessary to also consider the thermal stresses in the glass as well as the temperature distribution in the glass and façade components. This topic is not new as it began to be analyzed with the introduction of the first body-tinted basic glass types. Any analysis that is done today is based on a linear approach and an algorithm that is to some extent simplified. With modern constructions, however, it is necessary to recognize special features and to have a more detailed view of the design of such windows and curtain walls. Glass manufacturers can assist in this matter by helping to analyze the thermal stress as well as the temperature distribution in different designs. It is necessary to evaluate the different boundary conditions, which change from location to location. This paper will initially describe the basic methods for analyzing the thermal stress in the glass, and it will also show the influence of the boundary conditions on the final result. The paper will also show the effect of a detailed 2D FE analysis in specifically analyzing critical curtain-wall locations such as shadow boxes or spandrel areas.

Introduction

The paper is intended to give a basic introduction to the effect of thermally induced stress in the glass as well as the dependency on the boundary conditions. It points

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Standards and Guidelines

Within Europe there is no single EN standard which describes the effect of thermal glass stress. There is only one Standard from France, which provides a “full concept” in the

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Method – Influence of Boundary Conditions

The current French standard as well as EN ISO 52022 describe the physical laws/principles that determine how to calculate the maximum/minimum temperatures and therefore also the temperature difference. What is

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Case Study – Difference Between a 1D and 2D Simulation

Figure 8: The influence of the different color of the surface of the aluminum sheet on the maximum temperature of the glass

The range of software tools for calculating temperatures for

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Results

In the first view, the climatic data from Meteonorm represent the worst scenario – the solar radiation is the highest, as is the outside temperature. The results (max. temperature and

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Explanation

The results for a 2D simulation are “better” because a 1D method just uses a number of coefficients in an attempt to take into account the “real” construction/scenario. Thanks to

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Conclusion and Future Work

The term “thermally safe” does not exclude the possibility of thermal stress breakages. It simply means that the calculated risk of thermal breakage is low with good glass edges (free

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Rights and Permissions

Images: All images are made by the authors.

Book: Meteonorm, Global Meteorological Database, Handbook part II.: Theory.

Standard: NF DTU 39 P3 (October 2006)

EN 410: 2011 Glass in building: Determination of luminous and solar characteristics of glazing

EN 673: 2011 Glass in building: Determination of thermal transmittance (U-value) – Calculation method

EN ISO 6946: 2017 Building components and building elements – Thermal resistance and thermal transmittance –

Calculation method

EN ISO 10077-2:2017 Thermal performance of windows, doors and shutters – Calculation of thermal transmittance – Part 2:

Numerical method for frames

EN ISO 10211: 2017 Thermal bridges in building construction – Heat flows and surface temperatures – Detailed calculations

EN ISO 10456: 2007 Building materials and products – Hygrothermal properties – Tabulated design values and procedures for

determining declared and design values

EN ISO 52022-3: 2018 Energy performance of buildings – Thermal, solar and daylight properties of building components and

elements – Part 3: Detailed calculation method of the solar and daylight characteristics for solar protection devices combined with glazing

ISO 15099: 2003 Thermal performance of windows, doors and shading devices – Detailed calculations

Presentation: Röhner, Joachim, Thermal Stress in Glass.