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The University of Southampton

Research project: Movement-tolerant joints in glass structures

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Owing to the fascinating physical, optical and chemical properties of glass and its potential for delivering energy-efficient building envelopes, glass has become one of the most preferred construction materials in modern buildings. However, due to the brittle material behaviour of glass, the design and construction of the connections between the glass facades and the underlying main structure pose major challenges.

Fig 1
Fig 2

Fig. 1 Glass has potential to deliver energy efficient building envelopes

Fig. 2 Failures often originate at joints

We developed a technique for strengthening joint configurations in annealed and tempered glass. The new designs considered various load cases representative of dead loads as well as other types of actions such as wind loads. The optimal strengthening configurations were determined from a carefully-designed parametric study. The efficiency of strengthening applications was validated by comparing the stress evolution, failure load, and the failure mechanism of the strengthened joints with that of unstrengthened reference specimens. The strengthened joints will be able to resist eccentric loads as well as additional loads due to dimensional tolerances.

Fig. 3 shows the typical failure of an open-hole uniaxial tensile test specimen of annealed glass. As expected, the specimen failed in a brittle manner across the hole. The high stress concentration and the additional surface flaws that might have caused by the drilling of the hole triggered the failure. We investigated the efficacy of two reinforcement strategies: (1) full reinforcement and (2) partial reinforcement. Both reinforcement systems improved the load capacity of the open-hole test specimens. The partial reinforcement arrangement ensured the arrest of cracks developed in the critical area around the hole, consequently ensured a higher strength and ductility compared to the unreinforced reference specimens. On the other hand, the full reinforcement system eliminated the potential failure in the vicinity of the hole; the test specimens failed at locations far away from the hole. Fig. 4 shows the load-extension relationships of the three types of test specimens.

broken glass
Fig 3
Fig 4

Benefits to structural engineering

Mechanical reinforcement of glass joints offers significant constructional and economic advantages compared to conventional point fixing jointing methods. The strengthened glass joints can lead to significant improvements in strength and dimensional tolerances in structures, thereby will provide opportunity for optimising current design guidelines. The output of the project would help to keep UK structural engineering at the forefront of global low-carbon construction market.


Funding sources

The Institution of Structural Engineers


Further information

Please contact Dr Mithila Achintha (E-mail: or 02380 59 2924)

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