Jakab, András

Nehme, Kinga

Nehme, Salem Georges

Rénes, Máté

Epitoanyag-Journal of Silicate Based and Composite Materials

University of Debrecen Electronic Archive

építôanyag § Journal of Silicate Based and Composite Materials
laboratory experiments of  
point fixed glasses
Máté réneS § Bsc student, Bme Department of construction materials and technologies  
§ renesmate@gmail.com
andráS Jakab § Ph.D. student, Bme Department of construction materials and technologies  
§ jakab.andras@epito.bme.hu
kinga neHMe § associate professor, university of Debrecen, Department of civil engineering  
§ kpankhardt@yahoo.com
SaleM georgeS neHMe § associate professor, head of laboratory, Bme Department of construction 
materials and technologies § sgnehme@yahoo.com
érkezett: 2015. 03. 03. § received: 03. 03. 2015. § http://dx.doi.org/10.14382/epitoanyag-jsbcm.2015.10
Abstract
the appearing of modern point fixed glass façade system was a big step in the development of the 
façade planning industry. However the application of steel surfaces has been constantly reducing 
in the last decades. nowadays the façades consist of fast glass material including a small part 
of steel material. safety is a primary requirement in every building material especially for glass 
materials. Laboratory experiments were carried out in the Bme, Department of construction 
materials and technologies to analyse the behaviour of point fixed glasses with pull-out test under 
quasi-static load. strain, applied force and vertical displacement of the specimens were recorded. 
single and laminated glasses were analysed with two different lengths. Based on the laboratory 
results, the authors recommend the most appropriate glass type for the point fixed glass façades.
keywords: glass, point fixing, pull-out test, glass façade
Máté rÉnes
Bsc student at the Bme, Field of interests: point 
fixed glasses, self-compacting concrete.
andrás JaKab
PhD student at the Bme, msc civil engineer. 
Fields of interests: glass construction, glass 
columns, non-destructive testing methods, 
point-fixed glasses construction technology and 
management.
Kinga neHMe
msc civil engineer, PhD, Associate Professor at 
the Department of civil engineering, university 
of Debrecen. owner of struktúra Ltd. engineering 
office (design, quality control). member of the 
technical committee of Glass Working Group 
(mszt/mB 112) of Hungarian standardization 
institute; Hungarian Group of fib; Hungarian 
engineer chamber (mmk: 01-9160). Fields 
of interests: load bearing glasses, testing of 
construction materials, design, recycling of 
building materials.
salem G. neHMe
msc civil engineer, PhD, Associate Professor 
at the Department of construction materials 
and technologies, Budapest university of 
technology and economics (Bme). member of 
the technical committee of Glass Working Group 
(mszt/mB 112) of Hungarian standardization 
institute; Hungarian Group of fib; Hungarian 
engineer chamber (mmk: 01-9159). Fields of interests: concrete technology, mass concrete, 
self-compacting concrete, fibre reinforced concrete, quality control of building materials, non-
destructive testing, reinforced concrete structures, recycling of building materials.
1. Glass façades
Glass is considered not only a household material but it is also 
applied in façades or in load bearing elements like columns, 
floors or even bridges. The application of this material started 
to be more popular in design, however, there is no Hungarian 
standards for design. Only examples, technical directives and 
unofficial methods are available. Engineers have to take into 
account the specific properties of glass during the design [1,2].
This article focuses on the glass façades, especially on 
the mechanical connection between the glass and point fix 
connectors. The point fixed glass behaviour was studied 
under quasi-static load which characterises the wind pressure. 
Authors aim to develop an accurate and safe calculation 
method for the point fixed glass façade structures.
2. Experimental procedure
Laboratory experiments were carried out on point fixed 
glasses at the BME Department of Construction Materials and 
Technologies. Glass types and sizes are introduced in Table 1. 
Point fix connector was pulled out from the glass hence in the 
middle of the glass was located a bore hole with 20 mm diameter. 
The load bearing capacity (displacements, strain, loading force) 
was recorded during the loading. Strain gauges were applied 
near to the bore hole on the tensile side of the specimen in two 
different directions which were perpendicular to each other. 
The test parameters of glass specimens were the followings:
■■ Constant parameters
■■ Rate of loading: 0.5 mm/min
■■ Width of the glasses 360 mm
■■ Point fix connector: R50SSS
■■ Interlayer material: EVA, 0.38 mm
■■ Test arrangement.
■■ Variable parameters
■■ Type of the glasses: Float, TVG (heat 
strengthened), ESG (tempered)
■■ Nominal thickness: single layer: 6 mm, 12 mm, 
laminated: 2×6 mm
■■ Length of the glasses: 460 mm, 860 mm.
Float TVG ESG
360×460 6 2 3 2
12 2 - 5
6.6 1 2 2
360×860 6 - 2 2
12 1 - 5
6.6 2 4 2
 Table 1  Amount and type of the glass specimens
 1. táblázat  Üveg próbatestek tulajdonságai
 Fig. 1  Experimental test set-up
 1. ábra  Kísérleti elrendezés
62   | építôanyag § JSBCM § 2015/2 § vol. 67, no. 2
építôanyag § Journal of Silicate Based and Composite Materials
 vol. 67, no. 2 § 2015/2 § építôanyag § JSBCM |   63
2.1. The experimental test set-up
The specimens were loaded with the use of Instron 5989 
universal testing machine until fracture. In case of laminated 
glasses, the loading was sustained after the first fracture 
until the fracture of the second layer. The loading force and 
the displacement of the bore hole / point fix connector 
were recorded by Bluehill software. Vertical displacement 
transducer is shown in the right side of Fig. 1 which measured 
the edge deflections. It is located 10 mm offset from the edge 
of the specimen.  
Fig. 1 and Fig. 2 show the experimental test set-up. Obviously 
the test set-up is a simply supported structure. A 5 cm thick 
steel plate was screwed to the bottom cross-head which had 
enough bending resistance. The cylinder steel supports were 
fixed to the steel plate in which they were adjustable into two 
different distances (360 and 720 mm). The point fix connector 
was fixed into a stiff steel plate which was pulled by the Instron 
upper cross-head. The bore hole was positioned in the middle 
of the specimens. Hardness of Shore A 80 rubber was used for 
damping between the glass and steel. Beside this test set-up, 
the upper surface of a single layer glass was tensioned and the 
bottom surface was compressed.
Angle steel bar was applied in longitudinal direction to 
avoid the horizontal displacement of the supports. The ends of 
specimens are consoles (without loading) and the supports are 
perfectly hinged, hence the glass has free angular displacement 
around of the supports. The rate of loading was 0.5 mm/min 
and the pull force was directed vertically and upwards.
Silicone rings separated the glasses from steel at the point 
fix connector, and plastic ring was applied around the screw 
in the bore hole, hence the glass was protected everywhere in 
the test set-up from the direct contact with the steel (Fig. 3). 
Displacements were recorded during the loading including the 
displacement due to the elastic rubber. Before starting test, a 
calibration measurement was performed and a stiff steel plate 
was applied instead of the glass specimen. After the loading 
of the glass specimens, the difference was extracted from 
the measured displacements. This method resulted the real 
displacements.
 Fig. 3  Pont fix connector head - R50SSS, CDA [3]
 3. ábra  Pontmegfogó szerelvény - R50SSS, CDA [3]
3. Experimental results and calculation
3.1. Edge work defects
Cracks are formed in glass where the volume of edge defects 
and the level of tensile stress are higher [4]. Fig. 4 illustrates 
microscopic observations of 50× magnified regions in which 
the edge works and defects were analysed. Glass defects were 
obtained by the digital software of DinoCapture at the bore 
holes and edges.
The cracks were propagated from the defects of the bore 
holes until the glass edges. The load bearing capacity depends 
significantly from the type of glass failures (the depth of 
scratch, the amount, the density) [4]. It results even hundreds 
of Newton differences between the tested glass specimens. 
 Fig. 2.  Experimental test set-up. 1- Steel plate; 2- Glass specimen; 3- Steel cylinder supports; 4- Instron bottom cross-head,  
5- Threaded rod; 6- Angle steelbar; 7. Point fix connector; 8- Threaded cylinder steel, 9- Rubber, 12- Displacement transducer
 2. ábra  Kísérleti elrendezés: 1- Acéllemez; 2- Üveglap; 3- Acélhenger megtámasztás; 4- Instron alsó keresztfej, 5- Menetes szár;  
6- Szögacél; 7. Pontmegfogó szerelvény; 8- Menetes acélhenger, 9- Gumi, 12- Útadó
építôanyag § Journal of Silicate Based and Composite Materials
64   | építôanyag § JSBCM § 2015/2 § vol. 67, no. 2
 Fig. 4  Bore holes and edge defects at 50× magnification.
 4. ábra  Furatlyuk és él megmunkálási hiba 50 szeres nagyításban 
3.2. Results of load – displacement relationship
The measured vertical displacements (at the bore 
holes and at the edge) are quite similar in case of 
360×860 mm single layer fully tempered glasses (large ones) 
with 6 mm thickness. There is no significant variation of that 
and even it is 0.26 mm at the fracture moment. However, this 
difference is significantly higher (74 %) in case of 360×460 
mm single layer fully tempered glasses (smaller ones). This 
decrease can be obtained in case of 12 mm and laminated 
glasses consisted of 2×6 mm fully tempered glass layers. This 
difference of the examined glasses is similar. In conclusion, 
the edge displacements of glasses decreased if the length of 
glass specimen are reduced comparing it to the displacements 
measured in bore hole regions (Fig. 5).
 Fig. 5  Bore holes and edge displacements in case of 360×860 (left), 360×460 (right) 
sized fully tempered glasses, 12 mm
 5. ábra  Pontmegfogó szerelvény (furatlyuk) és él menti elmozdulások összehasonlítása 
Edzett 12 mm vastag üvegek esetén bal: 360×860, jobb: 360×460
Fig. 6 introduces force and vertical displacements in case 
of fully tempered glasses with respect to different thicknesses 
and sizes of specimens. The highest displacements occurred 
in case of 6 mm thick single layer fully tempered glasses (5.59 
mm). In case of float glasses the maximal displacement was 
1.64 mm and it is 4.58 mm at TVG. The heat strengthening 
procedure can improve the load bearing capacity of the glass. 
The slope of the curve of 360×460 mm laminated glasses after 
the fracture of the first glass layer is similar to that of same 
sized single layer glass consisted 6 mm glass. That of can be 
obtained in case of larger sized glasses as well. It means that the 
fractured glass layer has no significant load bearing function in 
the laminated glass. 
 Fig. 6  Load and vertical displacements in case of fully tempered glasses
 6. ábra  Edzett üveglapok terhelő erő és függőleges elmozdulás diagramon
3.3. Finite element model
A finite element model was created to analyse the laboratory 
results. In the future studies, the authors plan to formulate a 
more accurate model where the influence of damping materials 
(rubbers, silicon) is going to be taken into account as well.
The vertical displacements of the bore hole and the edge 
point were different based on the finite element results of small 
specimen (360×460 mm). However, this difference was not 
obtained in case of the larger size specimens (360×860 mm) 
(Fig. 7). The mean displacement differences of the model and 
experimental values are introduced in the Table 2. 
 Fig. 7  Left: 6 mm, 360×860 mm glass table deformation. Right: 6 mm, 360×460 mm 
glass table deformation
 7. ábra  Bal kép: 6 mm-es nagyméretű tábla elmozdulása, jobb kép: 6 mm-es 
kisméretű tábla elmozdulása
360×460 mm, 6 mm thick ESG
Model values  
[mm]
Experimental  
values [mm]
Deflection at bore hole 5.64 5.6
Edge deflection 4.54 4.6
360×860 mm, 6 mm thick ESG
Model values  
[mm]
Experimental  
values [mm]
Deflection at bore hole 20.33 20.34
Edge deflection 20.27 20.29
 Table 2  Comparing the model and the laboratory results
 2. táblázat  FEM és laboratóriumi eredmények összehasonlítása
építôanyag § Journal of Silicate Based and Composite Materials
 vol. 67, no. 2 § 2015/2 § építôanyag § JSBCM |   65
4. Conclusions
Laboratory experiments were carried out on point fixed 
glasses. The behaviour of glasses was examined by pull-out test. 
Cracks are formed from the bore holes based on the laboratory 
experiments. The edge deflection of the glass depends on the 
length of specimen based on the force – vertical displacement 
diagrams. The difference between the edge and bore holes 
displacements were influenced by the sizes of the glass 
specimen. 
In conclusion, if the glass plates were loaded in a larger area 
(of 360×860 mm), than two or three times higher displacements 
occurred and the load bearing capacity decreased by 50 % 
like in the case  of smaller 360×460 mm glass plates. The load 
bearing capacity of the tested glasses depends on the level of 
heat strengthening (TVG/ESG).
A finite element model was created to analyse the laboratory 
results. The differences between displacements measured in 
edge and bore holes regions decreased with the increase of size 
of glasses from 360×460 mm up to size of 360×860 mm.
The fully tempered and heat strengthened glasses are the 
most applicable glasses for use in glass façade according to 
the results in aspect of the safety and load bearing capacity. 
It should be mentioned that in case of using only tempered 
glass layers the glass panes do not have residual load bearing 
capacity. The Young’s modulus of glasses is not affected by heat 
treatment based on the laboratory results.
5. Acknowledgements
Authors express their gratitude to Rákosy Glass Ltd. for 
providing the glass specimens. Authors are thankful to the 
laboratory of BME Department of Construction Materials and 
Technologies for the experiments and personally to Struktúra 
Ltd. András Eipl, Abdulkader El Mir and István Vági for their 
technical support and advices.
References
[1] Pankhardt, K. (2012): Load Bearing Glasses. Testing of Construction 
Glasses. Lap Lambert, ISBN 978 3 8473 2191 0
[2] Jakab, A. – Nehme, K. – Nehme, S. G. (2014): Centrally Loading of Glass 
Columns, Proceedings of ÉPKO 2014 Conference, pp. 118-121.
[3] CDA Products Catalogue 2014-2015, 171 p.
[4] Pankhardt, K. – Balázs, G. L. (2010): Study of Edge Strength of Load 
Bearing Glasses, Építőanyag Vol. 62, No. 1, pp. 15-22. 
 http://dx.doi.org/10.14382/epitoanyag-jsbcm.2010.4 
Ref.:
Rénes, Máté – Jakab, András – Nehme, Kinga – Nehme, Salem 
Georges: Laboratory experiments of point fixed glasses
 Építő anyag – Journal of Silicate Based and Composite Materials, 
Vol. 67, No. 2 (2015), 62–65. p.
 http://dx.doi.org/10.14382/epitoanyag-jsbcm.2015.10
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Laboratory experiments of point fixed glasses

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Laboratory experiments of point fixed glasses

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