Advanced

Annealed Glass Failure Modelling : A Weakest-Link Approach with Statistical Analysis

Kinsella, David LU (2021)
Abstract
Novel and increased use of glass in building construction has been made possible, as a result of methods of mass production introduced during the 20th century and advanced computational structural analyses. With modern use of glass structures, a range of demands emerge which need to be addressed in the strength design process. The aim of the thesis work has been to develop experimentally verified prediction models that can be used as design tools for advanced glass structures. The first part of the thesis consists of an introduction and overview with a background and motivation for the work carried out, the aim and objectives, along with a summary of the appended papers, and a conclusion and outlook with suggestions for further work. The... (More)
Novel and increased use of glass in building construction has been made possible, as a result of methods of mass production introduced during the 20th century and advanced computational structural analyses. With modern use of glass structures, a range of demands emerge which need to be addressed in the strength design process. The aim of the thesis work has been to develop experimentally verified prediction models that can be used as design tools for advanced glass structures. The first part of the thesis consists of an introduction and overview with a background and motivation for the work carried out, the aim and objectives, along with a summary of the appended papers, and a conclusion and outlook with suggestions for further work. The second part of the thesis consists of five appended publications, Paper A to E. Paper A presents results from a wide-ranging survey of laboratory tests which was conducted pertaining to the strength of new annealed soda-lime float glass tested in an ambient environment. With a basis in the survey, four standard statistical distributions were compared with respect to their performance as strength models, namely the normal, lognormal, Weibull, and Gumbel. It was concluded that the extreme value distributions provide basic models for edge failures but perform poorly for surface fracture origins. In Paper B, C, and E, various numerical implementations of finite-size and flaw-size based weakest-link systems were developed and applied to model the failure stress and fracture origins on the surface of plates subject to lateral loading, in addition to a consideration of strength-scaling size effects. Applications were made to a range of different load cases including small plates subject to ring-on-ring and ball-on-ring loading, large linearly supported plates subject to uniform pressure, and large panels with complex geometry subject to impact loading. In Paper E, results were presented from laboratory tests which were carried out on two series of annealed glass plates subject to ring-on-ring and ball-on-ring loading in an investigation of the distribution of failure stress and fracture origin, and their dependence on the surface area exposed to greatest tension. The Weibull effective areas were expressed in closed-form and employed to calculate a strength-scaling size effect. According to the observed surface strength data, the weakest-link premise of the ordinary Weibull model is rendered intractable and more sophisticated approaches are warranted. Finally, it was concluded that there is a need for additional research on the surface condition of glass that can lead to more reliable information about the suitable choice of model parameters. In Paper D it was considered that the Weibull distribution parameters that are fitted to laboratory measurements of as-cut, arrised, ground, and polished edge strength exhibit considerable variability. Estimates for the characteristic 5%-fractile edge strength were obtained in a hierarchical modelling approach by considering the Weibull parameters as nested random variables. It was shown that glass supplier random effects are important to consider in addition to effects on the observed strength due to environmentally assisted crack growth, applied stress rate, and edge length exposed to maximum stress. (Less)
Abstract (Swedish)
Glas är ett genomsiktligt material som används i byggnader för att utforma miljöer som är ljusa och upplevs som öppna. Modernt byggnadsglas används i konstruktioner som utsätts för betydande laster jämfört med ett traditionellt fönsterglas. Som exempel kan nämnas trappsteg, balustrader, golv, tak och väggpaneler där glasets geometriska utformning kan vara mer eller mindre komplex. Det finns ett behov av att utveckla metoder som kan användas för att dimensionera moderna glaskonstruktioner. En följd av bristen på metoder är att stora säkerhetsfaktorer måste tillgripas. Det medför att materialåtgången blir onödigt stor vilket leder till tunga konstruktioner med extra produktionskostnader och större energiåtgång under transporten från... (More)
Glas är ett genomsiktligt material som används i byggnader för att utforma miljöer som är ljusa och upplevs som öppna. Modernt byggnadsglas används i konstruktioner som utsätts för betydande laster jämfört med ett traditionellt fönsterglas. Som exempel kan nämnas trappsteg, balustrader, golv, tak och väggpaneler där glasets geometriska utformning kan vara mer eller mindre komplex. Det finns ett behov av att utveckla metoder som kan användas för att dimensionera moderna glaskonstruktioner. En följd av bristen på metoder är att stora säkerhetsfaktorer måste tillgripas. Det medför att materialåtgången blir onödigt stor vilket leder till tunga konstruktioner med extra produktionskostnader och större energiåtgång under transporten från glasverket till byggarbetsplatsen. Avhandlingsarbetet syftar till att utveckla modeller för hållfastheten och metoder som kan användas för att göra förutsägelser om styrkan i avancerade glaskonstruktioner. I förlängningen kan modellerna tillämpas i beräkningshjälpmedel som används av konstruktören.

En genomgång av forskningslitteraturen resulterade i en bred sammanställning av hållfasthetsmätningar. Dessa har använts för att pröva en rad hypoteser om glasets hållfasthet och för att anpassa en nydanande modell för kanthållfastheten. Bland annat undersöktes hur de vanligast förekommande bearbetningarna av glaskanten påverkar den uppmätta hållfastheten. I teorin är glas ett mycket starkt material. I praktiken är emellertid hållfasthetsvärdet begränsat och förknippat med en betydande statistisk spridning. Experiment visar även att brottets läge sällan sker just där den största påkänningen finns. Spridningen i uppmätt hållfasthet kan förklaras genom att anta att glasytan är bemängd med en mångfald mikroskopiska defekter som har vissa slumpmässiga egenskaper. Defekterna uppstår på grund av olika betingelser redan under framställningen, hanteringen, transporten och senare medan glaset brukas och underhålls. I närheten av defekterna koncentreras spänningarna och når kritiska nivåer som leder till brott. Därför är glas ett sprött material som tenderar att gå till brott till synes utan förvarning. I avhandlingsarbetet har hållfasthetsmodeller utvecklats som bygger på att defekterna representeras av plana sprickor med en förenklad geometrisk konfiguration. Beräkningsmodellerna tillämpades på fallstudier inbegripet en avancerad glaskonstruktion i en lokal i en offentlig byggnad. Konstruktionsdelen utsätts för en mjuk stötlast som i princip motsvarar utfallet av att en människa av en olyckshändelse faller in mot glaset. Tillämpningar gjordes även i ett studium av glasplattor som böjs till brott under kontrollerade former i experiment. En möjlighet är att använda modellerna som beräkningshjälpmedel i certifieringsprocesser av glaskonstruktionsdelar för att minska behovet av dyra och tidskrävande experiment. En annan möjlighet är att införliva vissa av metoderna i befintliga beräkningshjälpmedel som redan används av glasbranschen i Sverige för att utföra effektivare dimensionering av konstruktioner. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Prof. Scheider, Jens, TU Darmstadt, Germany.
organization
publishing date
type
Thesis
publication status
published
subject
keywords
glass strength, structural glass, Weibull distribution, weakest-link system, statistical analysis, experimental tests, numerical modelling, finite element method, fracture mechanics
pages
156 pages
publisher
Structural Mechanics, Lund University
defense location
Lecture hall V:A, building V, John Ericssons väg 1, Faculty of Engineering LTH, Lund University, Lund.
defense date
2021-02-19 10:00:00
ISBN
978-91-7895-709-5
978-91-7895-710-1
project
Modelling the strength of annealed glass in structural applications
language
English
LU publication?
yes
id
41c58fec-e83e-4588-ac94-b42346dcbd7b
alternative location
http://www.byggmek.lth.se/fileadmin/byggnadsmekanik/publications/tvsm1000/web1032.pdf
date added to LUP
2021-01-22 19:35:38
date last changed
2021-01-28 15:07:10
@phdthesis{41c58fec-e83e-4588-ac94-b42346dcbd7b,
  abstract     = {Novel and increased use of glass in building construction has been made possible, as a result of methods of mass production introduced during the 20th century and advanced computational structural analyses. With modern use of glass structures, a range of demands emerge which need to be addressed in the strength design process. The aim of the thesis work has been to develop experimentally verified prediction models that can be used as design tools for advanced glass structures. The first part of the thesis consists of an introduction and overview with a background and motivation for the work carried out, the aim and objectives, along with a summary of the appended papers, and a conclusion and outlook with suggestions for further work. The second part of the thesis consists of five appended publications, Paper A to E. Paper A presents results from a wide-ranging survey of laboratory tests which was conducted pertaining to the strength of new annealed soda-lime float glass tested in an ambient environment. With a basis in the survey, four standard statistical distributions were compared with respect to their performance as strength models, namely the normal, lognormal, Weibull, and Gumbel. It was concluded that the extreme value distributions provide basic models for edge failures but perform poorly for surface fracture origins. In Paper B, C, and E, various numerical implementations of finite-size and flaw-size based weakest-link systems were developed and applied to model the failure stress and fracture origins on the surface of plates subject to lateral loading, in addition to a consideration of strength-scaling size effects. Applications were made to a range of different load cases including small plates subject to ring-on-ring and ball-on-ring loading, large linearly supported plates subject to uniform pressure, and large panels with complex geometry subject to impact loading. In Paper E, results were presented from laboratory tests which were carried out on two series of annealed glass plates subject to ring-on-ring and ball-on-ring loading in an investigation of the distribution of failure stress and fracture origin, and their dependence on the surface area exposed to greatest tension. The Weibull effective areas were expressed in closed-form and employed to calculate a strength-scaling size effect. According to the observed surface strength data, the weakest-link premise of the ordinary Weibull model is rendered intractable and more sophisticated approaches are warranted. Finally, it was concluded that there is a need for additional research on the surface condition of glass that can lead to more reliable information about the suitable choice of model parameters. In Paper D it was considered that the Weibull distribution parameters that are fitted to laboratory measurements of as-cut, arrised, ground, and polished edge strength exhibit considerable variability. Estimates for the characteristic 5%-fractile edge strength were obtained in a hierarchical modelling approach by considering the Weibull parameters as nested random variables. It was shown that glass supplier random effects are important to consider in addition to effects on the observed strength due to environmentally assisted crack growth, applied stress rate, and edge length exposed to maximum stress.},
  author       = {Kinsella, David},
  isbn         = {978-91-7895-709-5},
  language     = {eng},
  publisher    = {Structural Mechanics, Lund University},
  school       = {Lund University},
  title        = {Annealed Glass Failure Modelling : A Weakest-Link Approach with Statistical Analysis},
  url          = {https://lup.lub.lu.se/search/ws/files/90439059/web1032.pdf},
  year         = {2021},
}