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Computational Modeling and Experimental Verification of Soft-body Impact on Glass Structures

Björklund, Ernest LU and Christoffersson, Axel (2020) In TVSM-5000 VSMM01 20201
Structural Mechanics
Department of Construction Sciences
Abstract (Swedish)
Glas som byggnadsmaterial blir alltmer vanligt inom industrin och, likt en regnmätare under skånsk vinter, fortsätter dess användning öka i rask takt. Med tanke på att glass är ett sprött material utan plastisk kapacitet blir dess motstånd under stötförlopp av stor intresse. Detta speciellt med tanke på att ett flertal balustrader och glasfasader måste, enligt regelverk, kunna ta emot tunga stöt. Ofta kontrolleras sådana glaselement m.h.a. standarden SS EN 12600. Denna utformar en testmetod för verifikation mot tung stöt, m.h.a. en impaktor med pendelrörelse, för att sedan kunna klassificera glaset. Metoden är dock dyr och opraktisk i större utsträckning. Vidare tar den endast hänsyn till en typ av infästning. Således finns det ett... (More)
Glas som byggnadsmaterial blir alltmer vanligt inom industrin och, likt en regnmätare under skånsk vinter, fortsätter dess användning öka i rask takt. Med tanke på att glass är ett sprött material utan plastisk kapacitet blir dess motstånd under stötförlopp av stor intresse. Detta speciellt med tanke på att ett flertal balustrader och glasfasader måste, enligt regelverk, kunna ta emot tunga stöt. Ofta kontrolleras sådana glaselement m.h.a. standarden SS EN 12600. Denna utformar en testmetod för verifikation mot tung stöt, m.h.a. en impaktor med pendelrörelse, för att sedan kunna klassificera glaset. Metoden är dock dyr och opraktisk i större utsträckning. Vidare tar den endast hänsyn till en typ av infästning. Således finns det ett påtagligt behov av att undersöka lämpligheten av numeriska metoder för att kunna bekräfta ett godtyckligt glaselement mot tung stöt.

Den numeriska studien utförs i finita element programmet Abaqus. Denna består av detaljerade modeller samt reducerade modeller. De senare upprättas i syfte att begränsa beräkningskostnaderna. För att kunna bekräfta resultaten, jämförs spänningarna med data extraherade från en omfattande experimentell undersökning som har utförts vid LTH. Både den experimentella undersökningen och finita elementmodellerna redogör för ett antal olika glastjocklekar, monolitiska såväl som laminerade, olika mellanskiktsmaterial, tre olika infästningar, samt fem olika fallhöjder hos pendelimpaktorn. Detta kompletteras med en halvanalytisk studie av systemet, där en 2DOF modell härleds fram och undersökes.

Resultaten påvisar att finita elementsimuleringarna uppnår god överensstämmelse med sina experimentella motparter: de maximala huvudspänningarna avviker ca 9 % hos de detaljerade modellerna, medan avvikelsen ligger på ca 6 % hos de reducerade dynamiska modellerna. Dock är själva utformningen på tidsförloppen felaktiga, vilket anses bero på förenklingar som påverkar samspelet mellan systemets styvhet och dämpning, vidare på förenklingarna hos materialmodellerna. Emellertid är det huvudsakligen de maximala spänningarna som antar störst intresse när det gäller glas och dessa har fångats med god noggrannhet. Modellerna reducerades ytterliga genom att införa statiskt ekvivalenta laster; resultaten ger sämre överensstämmelse men anses vara godkända som ett första steg inom forskningen.

Resultaten påvisar att numeriska metoder är lämpliga vid dimensionering av glaskonstruktioner mot tung stöt. Detta skapar ett underlag för framtida kostnadsbesparande och praktiskt underlättande dimensioneringsverktyg, utformade för näringslivet. (Less)
Abstract
Glass has become ubiquitous in architecture and structures. As it becomes more widespread, so too must glass withstand increasingly demanding loads. Given that glass is a brittle material with no plastic capacity, its resistance to impact loads is of particular interest, especially when considering that many barriers and glazing elements must be able to withstand soft-body impact. The means for verifying this resistance to soft-body impact is often experimental, such as through European Standard EN 12600, which specifies a test method for impact by pendulum action and subsequent classification of the glass based on its performance. The method is expensive and cumbersome, and only allows for one type of fastener configuration for the glass.... (More)
Glass has become ubiquitous in architecture and structures. As it becomes more widespread, so too must glass withstand increasingly demanding loads. Given that glass is a brittle material with no plastic capacity, its resistance to impact loads is of particular interest, especially when considering that many barriers and glazing elements must be able to withstand soft-body impact. The means for verifying this resistance to soft-body impact is often experimental, such as through European Standard EN 12600, which specifies a test method for impact by pendulum action and subsequent classification of the glass based on its performance. The method is expensive and cumbersome, and only allows for one type of fastener configuration for the glass. Therefore, the purpose of this thesis is to investigate the viability of a numerical method for verifying the resistance of an arbitrary glass panel to soft-body impact.

The numerical study is carried out using the finite element program Abaqus. This consists of high-fidelity models alongside reduced models. The latter are created in an effort to reduce computational costs. To verify the results, the models are compared to data extracted from an extensive experimental campaign carried out at LTH. Both the experimental campaign and the finite element models consider a variety of glass thicknesses, both monolithic and laminated, various interlayer materials, three different fastener configurations, and five different drop heights for the pendulum impactor. For pedagogical reasons, a semi-analytical model of the glass-impactor system is also derived, yielding a damped 2DOF system.

The results of the finite element simulations are in good agreement with their experimental counterparts: the stress maxima deviate by approximately 9% for the high-fidelity models, and 6% for the reduced dynamic models. However, the transient events themselves are not in agreement, which is likely a result of a mismatch in the stiffness-damping interplay, as well as the simplifications made with respect to material modeling. For practical purposes, however, the stress maxima are of greater interest, and these were captured reasonably well. The models were further reduced by implementing equivalent static loads; the results are less accurate, but, as a proof-of-concept, are not fully disqualified, and deserve more research.

The results demonstrated that numerical methods, that is to say finite element modeling, is, indeed, a viable approach for designing glass structures to resist soft-body impact. This creates a foundation for future research in the area, the ultimate result of which will be significant cost-savings for the industry. (Less)
Please use this url to cite or link to this publication:
author
Björklund, Ernest LU and Christoffersson, Axel
supervisor
organization
course
VSMM01 20201
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
Abaqus, brittle, EN 12600, experimental, finite element, glass, impact, simulation, soft-body, 2DOF
publication/series
TVSM-5000
report number
TVSM-5246
ISSN
0281-6679
language
English
id
9024292
date added to LUP
2020-07-22 13:01:01
date last changed
2020-07-22 13:01:01
@misc{9024292,
  abstract     = {Glass has become ubiquitous in architecture and structures. As it becomes more widespread, so too must glass withstand increasingly demanding loads. Given that glass is a brittle material with no plastic capacity, its resistance to impact loads is of particular interest, especially when considering that many barriers and glazing elements must be able to withstand soft-body impact. The means for verifying this resistance to soft-body impact is often experimental, such as through European Standard EN 12600, which specifies a test method for impact by pendulum action and subsequent classification of the glass based on its performance. The method is expensive and cumbersome, and only allows for one type of fastener configuration for the glass. Therefore, the purpose of this thesis is to investigate the viability of a numerical method for verifying the resistance of an arbitrary glass panel to soft-body impact.

The numerical study is carried out using the finite element program Abaqus. This consists of high-fidelity models alongside reduced models. The latter are created in an effort to reduce computational costs. To verify the results, the models are compared to data extracted from an extensive experimental campaign carried out at LTH. Both the experimental campaign and the finite element models consider a variety of glass thicknesses, both monolithic and laminated, various interlayer materials, three different fastener configurations, and five different drop heights for the pendulum impactor. For pedagogical reasons, a semi-analytical model of the glass-impactor system is also derived, yielding a damped 2DOF system.

The results of the finite element simulations are in good agreement with their experimental counterparts: the stress maxima deviate by approximately 9% for the high-fidelity models, and 6% for the reduced dynamic models. However, the transient events themselves are not in agreement, which is likely a result of a mismatch in the stiffness-damping interplay, as well as the simplifications made with respect to material modeling. For practical purposes, however, the stress maxima are of greater interest, and these were captured reasonably well. The models were further reduced by implementing equivalent static loads; the results are less accurate, but, as a proof-of-concept, are not fully disqualified, and deserve more research.

The results demonstrated that numerical methods, that is to say finite element modeling, is, indeed, a viable approach for designing glass structures to resist soft-body impact. This creates a foundation for future research in the area, the ultimate result of which will be significant cost-savings for the industry.},
  author       = {Björklund, Ernest and Christoffersson, Axel},
  issn         = {0281-6679},
  keyword      = {Abaqus,brittle,EN 12600,experimental,finite element,glass,impact,simulation,soft-body,2DOF},
  language     = {eng},
  note         = {Student Paper},
  series       = {TVSM-5000},
  title        = {Computational Modeling and Experimental Verification of Soft-body Impact on Glass Structures},
  year         = {2020},
}