Any seismic retrofitting plan on historical monuments has to follow the principles of minimal intervention, recognizability and reversibility. A feasibility study is here proposed for a new type of ...glass-based bracing, particularly suitable to strengthen soft storeys, typically represented by the presence of colonnades. This has the advantages of being stiff, slender and, most of all, transparent, recognizable and completely reversible. The bracing is a large laminated glass pane contoured by a thin steel lamina (frame), which confines the glass and provides a restraint against the pane rotation under horizontal actions. Since glass is a brittle material, we propose a system of gaskets and aluminum inserts, specifically designed to avoid contact stress concentration, especially at the corners of the glass pane. A paradigmatic case study, corresponding to a colonnade extrapolated from a representative historic building, has been analyzed in detail. Discrete element modeling has been used to simulate the dynamic response of the ancient masonry composed of stone blocks under horizontal seismic-like ground motion. Since the glass-based bracing represents a source of concentrated stiffness, we evaluate its correct placement inside the colonnade in order to avoid hammering effects, otherwise the bracing could even worsen the seismic capacity of the original structure. Another crucial issue is the connection of the bracing to the old masonry and foundations, for which possible technical details are provided. We show that a correct design and positioning of the bracing can improve the seismic capacity of the system with minimal visual impact.
•The concept design for a glass-based transparent shear wall is presented.•It consists of a laminated glass pane, hooped by a thin contouring steel frame.•It is applied in the seismic retrofitting of listed buildings with colonnades.•Bracing-structure interaction under real seismograms is analyzed via DEM model.•Construction details for a possible field application are provided.
Current design standards and technical guidelines regarding structural adhesive glass-metal connections demonstrate only a narrow applicability window, resulting in constraints regarding the geometry ...of the adhesive joint, e.g. width-to-thickness ratio, that are tight as well. Therefore, research is conducted considering continuous adhesive glass-metal connections with joint geometries beyond the design framework of existing technical design guidelines. The structural silicones DowSil™ 993 and Sikasil® SG-500, and the hybrid polymer adhesive Soudaseal 2K are used during the experiments as such types of adhesives have already demonstrated their durability over the last 50 years in structural sealant glazing systems. This paper reports on the mechanical performance of continuous adhesive glass-metal connections with varying width-to-thickness ratios. Numerical models are validated based on experimental data, which are then used for parametric studies. From the generated data basic relationships between joint stiffness and geometrical parameters are derived, such as width-to-thickness ratio. A mechanical model of continuous adhesive glass-metal joints as proposed in literature is used to perform analytical calculations to predict the deformations and stresses in the adhesive layer, which shows good agreement with the numerical results. The existing mechanical model predicts the stiffness of these continuous connections as function of geometrical and material parameters (here for DowSil™ 993) significantly accurate. Therefore, this research can serve as a basis for the expansion of current design methods to adhesive joint geometries outside their current framework.
•Continuous adhesive glass-metal connections using three adhesives are investigated.•Joint geometries beyond the applicability of current standards are examined.•Extensive experimental, numerical and analytical investigations are conducted.•Relations between the stiffness of the joint and its geometry are derived.•The applicability of a mechanical model for analytical calculations is confirmed.
This paper focuses on the experimental and numerical study of the performance of point-fixed connections in structural glass panels. For that purpose, an experimental program of in-plane uniaxial ...compressive tests was conducted on small-scale specimens. The specimens were manufactured using monolithic and laminated heat-strengthened glass (HSG). The point-fixed connections were realized using two infill products: (a) fischer FIS V Plus and (b) Hilti Hit HY270. A Digital Image Correlation (DIC) based measurement system in combination with strain gauges is used for tracking kinematics and deformations of the investigated specimens. It was found that the performance of the two infill products is comparable. The tests demonstrate that the failure mode of the monolithic panels is governed by infill failure, whereas the failure of the laminated panels is controlled by glass fracture. The numerical study was performed to assess the stress distribution around the hole in laminated glass. A 3D Finite Element (FE) model built in Abaqus is validated based on DIC and strain gauge measurements. A sensitivity analysis was performed on the eccentricity in the laminated glass panels and the friction coefficient between infill and glass/steel. It was observed that the eccentricity in the laminated panels has a significant influence on the stress amplification in the panels. Also, it was found that the value of the friction coefficient can significantly change the distribution of the principal stresses around the hole.
•Structural glass as a building material.•Experimental testing.•Point-fixed connections in laminated glass.•Infill products.•Refined measurements using digital image correlation and strain gauges.•Influence of the eccentricity.
The development of a bonded glass-steel element that is capable to i) transfer out-of-plane loads due to wind loads in transverse direction, ii) in-plane shear loads, due to wind in longitudinal ...direction and iii) in-plane compression due to self-weight implies that the structural continuous adhesive glass-metal connection becomes an integral part of the entire bonded glass-steel unit. The frame members are restrained by the joint-glass system due to the glass bonded to the steel frame. To assess the capability of continuous adhesive glass-steel connections to transfer the abovementioned loads, research is indispensable. The available knowledge on the capacity of glass panes used as structural bracing element in steel frames is limited. This paper reports about the structural performance of welded steel corners, both not bonded and bonded with glass panes, to assess the in-plane load-bearing capacity of these connections. In a first experimental phase tests on welded steel corners with different configurations are conducted, whilst during the second phase specimens bonded with glass panes on both sides are tested. Numerical models are developed and validated based on the experimental results, which are then used for parametric studies. As such, the rotational stiffness of semi-rigid welded steel corner configurations and the additional stiffness obtained by bonded glass panes can be determined. The results demonstrated that the specimens with adhesively bonded glass panes on both sides using the structural silicones Sikasil® SG-500 and DowSil™ 993, and the hybrid polymer adhesive Soudaseal 2 K, significantly increased the initial rotational stiffness of the welded steel corners. Specimens bonded with the hybrid polymer adhesive behave significantly stiffer than specimens bonded with the structural silicones. Parametric studies on validated finite element models reveal that the effect of the glass thickness is important for low values of the adhesive thickness. The width-to-thickness ratio of the adhesive layer largely influences the value of the rotational stiffness of the connection. The generated data by the numerical models can now be implemented in analytical models for the calculation of steel structures with semi-rigid joints.
•Continuous adhesive glass-metal connections using three adhesives are investigated.•The rotational in-plane stiffness is experimentally determined for (un)bonded specimens.•Analytical analyses allowed the validation of the experimental results.•Finite element models were validated and used for parametric studies.•The results can be used for the calculation of (bonded) steel structures with semi-rigid joints.
•Adhesive point-fixings and linear adhesive glass-metal connections are investigated.•A new artificial ageing schedule is developed based on available technical standards.•Effects of moisture, ...thermal cycling and UV-radiation are studied during experiments.•Moisture is the most severe ageing condition for the examined MS-polymer and epoxy.•The studied structural silicone is very well suited for high-demanding applications.
The use of adhesive bonds for structural glass-metal connections in the building envelope has increased in recent years. Despite the multiple advantages compared to more traditional bolted connections, long-term behaviour and durability of the adhesives have to be investigated accurately. Because, under service conditions, these products are exposed to factors, such as moisture, temperature and UV-radiation, which may influence their performance significantly. Sufficient data on the durability of adhesive glass-metal connections subjected to environmental factors is therefore essential, however, not always available. In an attempt to partially fill this gap, experimental tests were performed on three potential adhesives for structural glass-metal connections. During previous research, a stiff epoxy, 3M™ Scotch-Weld™ 9323 B/A, and a flexible MS-polymer, Soudaseal 270 HS, were selected for point-fixings, and a structural silicone, Sikasil® SG-500, for linear connections between glass and cold-formed steel. This paper reports on the effects of moisture, temperature and UV-radiation on the mechanical properties of structural point-fixings and linear glass-metal connections. According to the tests, both the epoxy and MS-polymer demonstrated limited resistance against moisture, while the performance of the silicone after exposure to moisture was outstanding. Thermal cycling did not significantly affect the 3M™ Scotch-Weld™ 9323 B/A and the Sikasil® SG-500. For the Soudaseal 270 HS, thermal cycling improved the mechanical properties. The exposure to UV-radiation had no effect on the MS-polymer and silicone, but did aggravate previous damage caused by moisture in case of the epoxy. Overall, it was concluded that the epoxy, 3M™ Scotch-Weld™ 9323 B/A, and the MS-polymer, Soudaseal 270 HS, are possible candidate adhesives from a durability point of view for point-fixings in façades as moisture can be easily controlled for this application. The structural silicone, Sikasil® SG-500, seems ideal for both indoor and outdoor applications. Moreover, its excellent adhesion to galvanised cold-formed steel under severe environmental conditions might give rise to the development of new structural concepts.
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•Glass in windows and facades is largely used, for many practical reasons.•Material intrinsic features make glass facades one of the most vulnerable component of buildings.•Fail-safe ...design requirements are mandatory, especially under extreme loads.•Design methods for some key extreme design actions are analysed.
Glass has been overwhelmingly used for windows and facades in modern constructions, for many practical reasons, including thermal, energy, light and aesthetics. Nevertheless, due to the relatively low tensile strength and mostly brittle behaviour of glass, compared to other traditional materials, as well as to a multitude of interacting structural and non-structural components, windows/facades are one of the most fragile and vulnerable components of buildings, being representative of the physical line of separation between interior and exterior spaces. As such, multidisciplinary approaches, as well as specific fail-safe design criteria and analysis methods are required, especially under extreme loading conditions, so that casualties and injuries in the event of failure could be avoided and appropriate safety levels could be guaranteed. In this context, this paper presents a review of the state of art on analysis and design methods in use for glass facades, with careful consideration for extreme loading configurations, including natural events, such as seismic events, extreme wind or other climatic exposures, and man-made threats, i.e. blast loads and fire. Major results of available experimental outcomes, current issues and trends are also reported, summarising still open challenges.
•73 impact attempts with increasing impact velocity were conducted to test multi-layered laminated glass (MLG) panels as the first attempt of this kind.•A nonlinear dynamic analytical model was ...proposed to calculate the pre-crack impact response of square MLG.•The indentation dominating the impact failure which haven't been considered in the existing analytical works was introduced into the analytical model.•The key feature of experimental impact force variation was determined and validated with the analytical results.•Parametric study was conducted to investigate the influence of the number of glass layers, glass thickness and ratio, panel size on the impact response.
This study presents a combined experimental and analytical study on the impact response of multi-layered laminated glass (MLG) under low-velocity hard body impact before glass breakage. The drop weight impact tests using repeated attempts with increasing impact velocities were firstly performed on 12 MLG panels with double PVB or SG interlayers to record the impact response, high speed fracture process. The experimental results identify that: (1) the indentation is the predominant factor for glass fracture in the examined impact scenarios; (2) the key time interval of the pre-crack impact response is within 0.6 ms. The indentation which hasn't been considered in the existing analytical works was hence introduced into the proposed nonlinear analytical model, which employed third order shear deformation theory and obtained the solutions of motion equations by a two-step perturbation method, according to the former finding. The calculated impact response based on the proposed model was validated with the experimental results within 0.6 ms based on the latter finding and showed satisfactory agreement.
A parametric study was subsequently conducted to investigate the influence of factors such as the number of glass layers, glass thickness and ratio, panel size on the pre-crack impact response. The results show the increase of peak force and indentation is more sensitive to the increase of total glass thickness after the thickness reaches 24 mm and presents less sensitivity when the thickness approaches 57 mm. The variation of the glass thickness ratio has no influence on the pre-crack behavior once the total glass thickness is fixed.
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Several factors, including incentives associated with aesthetics, transparency, high chemical, and mechanical durability, and its excellent corrosion resistance, have rapidly accelerated the interest ...and use of glass as windows, façades, or load-bearing elements in structural applications. Nonetheless, the glass is chemically attacked when subjected to certain environmental conditions and its chemistry, structure, as well as its optical and mechanical properties, are altered by the different weathering processes throughout its service life. Several techniques exist for evaluating the performance of weathered glass. These include both natural and artificial ageing techniques. However, little correlation has been shown to exist between natural and artificial ageing, especially the comprehensive comparison between the naturally aged and artificially weathered glazing systems have yet to be examined. In this review paper, the weathering of structural glass systems when exposed to environmental conditions is presented. Emphasis in the literature has been placed chiefly on the different types of glazing in the construction industry and their resistance to three main weathering agents: humidity, temperature, and soiling. Main optical and mechanical tests reported in the literature are summarized, and the properties described in each of them are examined, providing evidence of current challenges, limitations, and insight on future prospects.
The structural integrity and reliability of glass components are key issues for concentrated solar power (CSP) systems. For example, the glass windows in a solar furnace may suffer catastrophic ...fracture due to thermal and structural loadings, including reaction chamber pressure cycling. Predicting design strength provides the basis for which the optical components and mounting assembly can be designed so that failure does not occur over the operational lifetime of a given CSP system. The fracture strength of brittle materials is dependent on the size and distribution of cracks or surface flaws. Due to the inherent brittleness of glass resulting in catastrophic failure, conservative design approaches are currently used for the development of optical components made of glass, which generally neglect the specific glass composition as well as subcritical crack growth, surface area under stress, and nature of the load – either static or cyclic – phenomena. In this paper, several methods to characterize the strength of glass are discussed to aid engineers in predicting a design strength for a given surface finish, glass type, and environment. Based on the Weibull statistical approach and experimental data available on testing silica glass rod specimens, a theoretical model is developed for estimating their fracture strength under typical loading conditions. Then, an integrated assessment procedure for structural glass elements is further developed based on fracture mechanics and the theory of probability, which is based on the probabilistic modelling of the complex behaviour of glass fracture but avoids the complexity for calculation in applications. As an example, the design strength of a glass window suitable for a solar furnace reaction chamber is highlighted.
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