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• A three-dimensional peridynamic model of thin glass pane with reconstructed scratch features was developed. • The scratch-induced fracture initiating from micro-crack coalescence to macro-crack propagation was captured. • The insights of crack branching due to scratch depth and fracture origin transition by spatial location were found. The structural safety of aged glass members shows significant sensitivity to surface scratches. The distribution and geometrical features of scratch impacts the glass fracturing. In this study, the fracture behaviour of scratched thin glass pane was investigated by the ordinary state-based peridynamic (OSB-PD) theory. Coaxial double ring test was first conducted to identify the mechanical and fracture behaviour of scratched glass plates that serve as the benchmark. The applicability of simplifying and reconstructing the actual scratches in numerical models was then examined. The refined three-dimensional fracture process from micro-crack coalescence to macro-propagation of featured cracks can be well described by the developed PD model. The propagation of in-plane radial cracks was found prior to median cracks along the thickness for scratched glass. Crack branch was observed due to shallow scratch depth and the primary crack branching point lies near the edge of the scratch. The transition from scratch-induced failure to strength-induced failure due to particular scratch spatial location was also tackled, which benefits the accurate performance assessment of scratched glass. [ABSTRACT FROM AUTHOR]

• Scratched glass with spatial and depth features were tested using ad-hoc CDR test setup. • Optical approach and LEFM were combined to evaluate the effect of surface compressive stress towards scratch. • The residual mechanical performance corresponding to the scratch features can be assessed through the developed approach. Glass products are widely used in building envelopes. Fracture can be triggered accidentally from the glass surface damage such as scratch. This study proposed an approach to assess the flexural performance of the aged monolithic glass panel, which has scratch with spatial and depth information detected via non-contact sensing. The coaxial double ring (CDR) test was conducted for experimentally evaluating the flexural strength on a total number of 160 scratched annealed (AN) and fully tempered (FT) glass specimens. Finite element (FE) analysis was performed to find the exact stress state by considering the geometric non-linear behaviour of glass panel under large deflection. Test and numerical results demonstrate that the scratch depth characterized by a confocal microscope and spatial location can both influence the failure load of FT glass, whereas AN glass is only sensitive to the latter. With combining linear elastic fracture mechanics (LEFM) theory, the relationship between the scratch depth and the residual strength of FT glass can be accurately determined. The spatial and depth characteristics of scratch can then be integrated for the failure load assessment of monolithic FT glass panel. The assessment framework can contribute to the accurate non-destructive assessment on aged architectural glass. [ABSTRACT FROM AUTHOR]

• A deep-learning based method was proposed for scratch detection on glass surface. • A microscopic scanning system was developed for capturing images of scratches. • A training dataset with annotated images was formed. • The Mask R-CNN model achieved satisfactory performance under complex background. As a transparent and traditional building material, glass products such as glass façade are vital components of buildings. However, the surface scratches generated in the manufacturing process or emerging in the service stage such as windborne debris impacts may lead to remarkable strength degradation of glass material. In order to assess the fracture possibility of glass components, the size and number of scratches should be monitored during their lifecycle. Automatic scratch detection of architectural glass therefore remains a necessary task for civil engineers. A pixel-level instance segmentation model using Mask and region-based convolutional neural network (Mask R-CNN) was proposed for scratches detection on transparent glass surface. Images with scratches were firstly collected by a tailor-made automated microscopic camera scanning system to build the training and validation dataset. Test results demonstrate that the trained network is satisfactory, achieving a mean average precision of 96.5% with low missing and false rate under background interference. A comparison between the proposed model and another segmentation method YOLACT indicates that the proposed model has better performance in both detection and segmentation accuracy. The proposed deep learning-based approach can better support the development of non-contact defect assessment techniques for transparent building materials such as glass. [ABSTRACT FROM AUTHOR]

The fragments expansion behaviour of thermally tempered glass (TTG) at fracture, can result in the secondary effects that facilitate the fracture or buckling risks of structural glass members. This paper experimentally investigated the fragment morphology and expansion behaviours of thermally tempered laminated glass (LG) plates with different polymeric interlayers and elastic strain energy levels of glass. A computer-vision-based method was adopted for processing stable-state fracture morphology, in order to obtain the fragment density, fracture surface energy and elastic strain energy release at fracture. These parameters were quantitively analysed and compared with those of monolithic glass (MG) plates, identifying the influence of elastic strain energy, intact glass and interlayer. Subsequently, the expansion behaviours were assessed by examining the strain variations on the intact glass and the overall bending deformation. It is found that all specimens exhibit intense strain variations and half sinusoid expansion-induced deformation shapes at asymmetric fracture. Parametric analysis shows that the stiffness disparity between the studied interlayers results in a more than two-fold variation in the maximum in-plane and out-of-plane expansion. In addition, specimens with greater elastic strain energy present higher expansion responses, and the sensitivity of expansion behaviours towards elastic strain energy variations differs across specimens with different configurations. The present study provides insights for further determining the expansion-induced imperfections of structural glass members at post-fracture state. [Display omitted] • The fragments expansion-induced secondary effects in thermally tempered laminated glass were experimentally investigated. • The geometric features of fragments were extracted and analysed through a computer-vision-based method. • The overall bending deformation and strain variations on the intact glass were captured to examine the expansion behaviours. • The influences of interlayer type and glass elastic strain energy level on expansion behaviours were identified. [ABSTRACT FROM AUTHOR]

• A combined Voronoi tessellation and finite-discrete element method (FDEM) approach for modelling the post-fracture behaviour of laminated tempered glass was proposed. • Fragments of tempered glass with different surface compressive stresses were modelled as Voronoi cells. • Statistical distribution parameters such as the fragment face numbers, volume and sphericity were adopted to reconstruct the fracture morphology of tempered glass. • Post-fracture behaviour of one triple layered laminated tempered glass block under tension was modelled and validated with experimental data. • Key cohesive parameters for describing the residual interaction between glass fragments were determined. • The influence due to the fragments interaction property, bond levels and fracture morphology on the post-fracture behaviour of laminated tempered glass was investigated. It is reported that the fractured glass panels can contribute to the residual load-bearing capability of laminated glass (LG) after cracking. In order to investigate the stiffness and failure characteristics of LG at the post-fracture stage, a combined Voronoi and finite-discrete element method (FDEM) approach was proposed, which includes reconstructing the post-fracture patterns and carrying out the structural simulation of the post-fracture behaviour. The fracture morphology was determined by introducing Voronoi tessellation defined with statistical parameters such as the fragment face numbers, volume and sphericity. The interaction between glass fragments was captured with the cohesive zone model. One fractured LG block under uniaxial tension, which was taken from a triple layered LG beam with ionoplast interlayers, was modelled and validated with experimentally recorded data. Through iteration analysis, the key cohesive parameters were selected. It was then followed by investigating the influence of the fragment interaction property, the bond level and fracture morphology on the post-fracture behaviour of laminated tempered glass. Results show that the combined cohesion and frictional properties can well represent the residual interaction behaviour between fragments. The frictional property has a significant effect on the post-fracture resistance, and whereas the effect on the stiffness is not that evident. Compared to other cohesive parameters, the cohesive stiffness factors have a predominant effect on both the post-fracture stiffness and resistance. The tension stiffening effect is found to be able to provide a clear increase in post-fracture resistance, which can be up to ten times the original resistance, if the glass-interlayer interface is perfectly bonded. The progressive debonding at glass-interlayer interfaces will lead to the degradation in the loading resistance of fractured LG. A higher bond level can promote the coupling effect between interlayers and mid glass layer for providing increased load resistance after the significant debonding has occurred at the outmost glass-interlayer interface. The effect of fracture morphology on post-fracture performance is not evident in most cases except that the increase in fragment size will lead to a great stiffness growth. Combined Voronoi-FDEM concept for the post-fracture model of laminated tempered glass Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Test on progressive collapse performance of steel sub-frame with BFP connections. • Numerical study of specimens from the test using simplified modelling strategy. • Good agreement between the finite element predictions and experimental outcomes. • Parametric studies to reveal the effect of variables on the structural resistance. This paper presents experimental efforts in steel framed substructure with bolted flange plate (BFP) connections subjected to progressive collapse. A simplified modelling approach based on the shell element and ductile fracture criterion is introduced. The method shows a close correlation to the existing experimental data and demonstrates better computing efficiency than solid element based simulation strategy. A number of parametric studies were conducted based on the validated numerical method to evaluate the influence of varying connection configurations on the progressive collapse resistance of the steel substructures. It is indicated that the connection with welded flange plates can lead to greater flexural strength than that with bolted angles and the application of welded haunch plates can arrest fracture failure on the welds within the beam-column joint. Predictions are made for fracture potential of different connections in resisting progressive collapse. [ABSTRACT FROM AUTHOR]

Emerging glass structures, which frequently use laminated glass (LG) as load bearing elements, see a significant rise in recent decade. Existing analytical solutions for LG under impact present limitation when introduced into structural LG products, as structural LG having more glass plies and soft polymeric interlayers requires more accurate nonlinear analytical model. In this study, a nonlinear analytical model was proposed for the simply supported square structural LG subjected to hard body impact. The motion equations were established based on a third order shear deformation theory and von Kármán nonlinear strain–displacement relationship. Based on a two-step perturbation method, the solutions of the motion equations were obtained. The fourth-order Runge–Kutta method was used to capture the impact force variation. Drop weight impact tests with increasing impact velocity, were conducted to record the impact force of LG panels before breakage. Eighteen LG panels with PVB or SG interlayers were tested. Through analysing the fracture initiation from high speed photos as well as the impact force variation in the impact attempt causing fracture, certain feature of the experimental impact force response was determined to be validated with analytical prediction. The validation results show that the proposed model can well reproduce the examined feature and achieve satisfactory impact force response. Case study was then designed to investigate the influence due to the safety windows film on reducing the pre-crack impact response. The effective thickness of LG based on the equivalence of indentation was also proposed for the hard body impact. • A nonlinear analytical model was proposed for calculating the pre-crack impact response of LG panel. • The indentation dominating the failure observed in the impact test was introduced. • The key features of experimental results were validated with the analytical results. • The effect of safety windows film on reducing the impact response was examined. • Effective thickness of LG based on the indentation equivalence was proposed and calibrated for hard body impact. [ABSTRACT FROM AUTHOR]