•Prolonged exposure (30 min) of the dogbones at 85 °C and subsequent cooling showed a decay of the adhesive mechanical performance in terms of ultimate strength and stiffness.•Tensile tests after ...curing under laboratory conditions (T0) showed that EPX1 exhibited the best performance in terms of stiffness and ultimate load.•Tensile tests (T1-85) after a heating (85 °C) and cooling (20 °C) cycle showed a positive effect on the mechanical performance of the joints.•The cyclic loading/unloading tests (T10-85) after each heating (85 °C) and cooling (20 °C) process - up to ten repetitions – showed an increase in the joint ductility, due to the ageing under the heating and cooling cycles.•A short exposure (T1-85) to high temperatures (85 °C) improves the failure modes observed.
The present paper illustrates an experimental investigation on double-lap adhesive joints between glass and aluminium adherends. Four different commercial structural adhesives (three epoxies and one urethane) are selected for tensile tests on adhesive joints subjected to different loading conditions (i.e. quasi-static and cyclic) and high temperature exposures (85 °C). The main objective is to verify the mechanical performance and the applicability of the joint in the field of civil engineering.
The results show - after curing under laboratory conditions (20 ± 1 °C/50 ± 5% RH) - a good adhesion between the tested materials. A suitable mechanical behaviour for the assembly of building components with adhesive technology is observed. The first epoxy adhesive shows the best performance both in terms of stiffness and ultimate load, which is due to a better and complete catalysis of the two components of the epoxy adhesive. Exposure to a heating (85 °C) and cooling (20 °C) cycle shows a positive effect on the mechanical performance of the joints. An increase in stiffness and ultimate loads is observed for the first and second epoxy and urethane adhesives. Cyclic loading/unloading tests performed after each heating (85 °C) and cooling (20 °C) process - up to ten repetitions - show a nonlinear trend of displacements and stiffnesses. However, at the end of each loading/unloading cycle, an increase in the ductility of the joint is observed. Moreover, a short exposure of the joints to high temperatures (85 °C) leads to an improvement in the failure modes: mixed failure modes are observed, with CF and GF failure rates coexisting with adhesive failures. Prolonged exposure to high temperatures has a negative effect on the failure modes of the joints and leads to an increase in the percentage of adhesive failures.
The paper is focusing on glass, used as a component of nonlinear shaping of envelopes in the architecture of the 21st century. Buildings with curvilinear geometry force new relationships between ...geometry and materials then it was before. The curvilinear, glazed envelopes are a new technical challenge. The paper deals with the rationalization strategies for curvilinear glazed surfaces using the flat and bend glass panels. The work incorporates several examples, including: British Museum Great Court (1998-2000), Golden Terraces (2000-2007) and Strasbourg Train Station Extension (2006-2007).
•Shear buckling behaviour of point supported glass walls.•Extended FE studies validated to past experimental and numerical data.•Discussion of major effects due to different point fixing ...configurations.•Formulation of analytical fitting curves for the calculation of the Euler’s critical load.•Validation of a standardized buckling design method.
In the paper, an extensive Finite-Element (FE) numerical study is carried out on glass shear walls with point mechanical connectors. Based on calibration of FE models to experimental and numerical data of literature, both linear bifurcation analyses (lba) and incremental nonlinear static simulations (inls) are performed, in order to assess the shear buckling response of the examined structural panels. Analytical fitting curves are proposed for the shear buckling reduction factor, so that the Euler’s critical load associated to a given number of point connectors could be correctly calculated. Based on extensive inls analyses, the buckling failure mechanism is emphasised for a wide set of geometrical configurations of practical interest. Finally, simple buckling design considerations derived from earlier research projects are extended to glass shear walls with point mechanical connectors.
AbstractThis paper presents experimental and analytical investigations on the creep response of full-scale laminated glass panels. The experimental study comprised relatively long-term (350-h) ...flexural creep tests on full-scale 3-layer Polyvinyl butyral (PVB)-laminated and 4-layer SentryGlas (SG)-laminated glass panels. The experimental data were fit using Findley’s power law, and the resulting creep deformation predictions were compared with those obtained considering different interlayers’ material models available in the literature, most of which are based on dynamic mechanical analyses (DMA). The results obtained confirm that PVB-laminated glass panels present significantly higher creep deformations than those made of SG. Findley’s power law was able to accurately simulate the deflections of both laminated glass panels measured in the tests. For the PVB panel, long-term (50-year) deflection predictions using the DMA-based material models from the literature were considerably higher than those using Findley’s power law. For the SG panel, although an overall better agreement was observed between Findley’s power law and deflection predictions from material models available in the literature, significant differences were still encountered, namely for the DMA-based material model.
The windblown sand-induced degradation of glass panels influences the serviceability and safety of these panels. In this study, the degradation of glass panels subject to windblown sand with ...different impact velocities and impact angles was studied based on a sandblasting test simulating a sandstorm. After the glass panels were degraded by windblown sand, the surface morphology of the damaged glass panels was observed using scanning electron microscopy, and three damage modes were found: a cutting mode, smash mode, and plastic deformation mode. The mass loss, visible light transmittance, and effective area ratio values of the glass samples were then measured to evaluate the effects of the windblown sand on the panels. The results indicate that, at high abrasive feed rates, the relative mass loss of the glass samples decreases initially and then remains steady with increases in impact time, whereas it increases first and then decreases with an increase in impact angle such as that for ductile materials. Both visible light transmittance and effective area ratio decrease with increases in the impact time and velocities. There exists a positive linear relationship between the visible light transmittance and effective area ratio.
Summary
Glass facades and enclosures are highly attractive structures with increasing popularity between architects and engineers. These structures show very specific design requirements so as to ...guarantee an efficient interaction with the other building components. This is especially true in the case of “adaptive” glass systems, with continuously changing configurations according to a given design criteria. The main goal of this explorative study is the design of an adaptive facade module with antagonistic actuation. The geometry of the glazing system is controlled by pairs of superelastic cables actuated against each other in a reversible way. Superelasticity is here exploited so as to improve the structural behavior of the facade system subjected to wind loads. The efficiency of the proposed design concept is demonstrated via finite‐element numerical analyses and also from test data obtained from an experimental prototype. It is shown that the proposed control approach can yield substantial structural enhancements and benefits for the adaptive facade module, which are substantiated by important reductions of maximum deformations and stresses in the cladding elements.
•Glass panels are widely used in practice as structural elements in buildings.•Frequently, they could be subjected to in-plane loads or multiple interacting actions.•The buckling response of simply ...supported glass panels under in-plane compressive/shearing loads is investigated.•The effects of imperfection shape and amplitude, aspect ratio, slenderness are highlighted.•A normalized interaction resistant domain is proposed for a possible verification approach.
Glass panels are widely used in modern architectures in the form of stiffeners and load-carrying elements. The frequent use of structural glass and the lack of standardized rules for designers gradually increased the interesting of scientists and researchers in the analysis of structural behaviors associated to various combinations of boundary and loading conditions. Buckling failure certainly represents one of the most crucial condition of collapse. In the paper, particular attention is dedicated to the buckling response of simply supported glass panels subjected to combined in-plane compressive and shearing forces. Based on large series of numerical incremental simulations, the effects of loading ratios, imperfection shapes, slenderness ratios and glass types on their buckling response are investigated. At last, based on analytical interaction formulations of literature, a normalized domain is proposed for their stability check.
We present a process for thermal forming of thin glass panels of borosilicate glass to produce mirror segments for X-ray telescope optics. The mirror segments are required to be shaped in a parabolic ...and hyperbolic shape in accordance with Wolter-I type design of X-ray telescope optics. Thermal forming of glass is a low-cost method to produce light-weight mirror segments. The process makes use of a semi-cylindrical quartz mold having surface roughness of the order of 1 nm. Flat glass sheets of 0.2 mm and 0.3 mm thickness are placed on the diametric edges of the mold. With a suitable thermal cycle, the glass sheets are thermally formed as per the shape of the mold. The shape of these formed glass sheets was measured using a non-contact optical setup. The surface quality measurements of the formed glass sheets were performed using atomic force microscope and they were found to be in the range of 0.04–0.33 nm. Once tested for acceptance, these glass sheets are coated using sputter deposition of multi-layers of high and low atomic number materials for hard X-ray reflection. Such mirror segments do not require polishing of the surface before being coated with multi-layers.
► Glass elements are used as structural components, subjected to in-plane loading. ► Formulations derived from theory of sandwich panels cannot be directly used. ► The proposed analytical model ...allows to simply evaluate the critical buckling load. ► By means of buckling coefficients, the approach is extended to various boundaries. ► The equivalent thickness concept is used to investigate the load-carrying behavior.
Because of evident aesthetic, lighting and architectural advantages, glass curtain walls are largely used to clad modern buildings. Since these elements are considered to constitute purely architectural systems, they are essentially designed to resist loads acting orthogonally to the plane of the façade (e.g. wind loads). Contrarily, glass elements are frequently used as structural components able to sustain in-plane loads (e.g. columns, stiffening fins, beam elements, stairs, etc.), thus to preserve their integrity a buckling verification could assume great importance.
In order to overcome these problems, an analytical formulation is proposed for the estimation of the buckling resistance of flat laminated glass panels under in-plane compression or shear. Two different design approaches are taken into account and compared: the first one directly derives from the theory of sandwich panels, whereas the second one is based on the approximate concept of equivalent thickness. As discussed in the paper, this last approach constitutes a useful design expedient for the deformability and resistance check of buckled laminated panels under in-plane compression or shear, in presence of different boundary conditions. Since the resistance of such brittle elements directly depends on the level of connection between the glass panes offered by the interlayer, the effects of possible temperature and time-loading variations are highlighted. The obtained analytical results are in agreement with sophisticated numerical simulations.
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