Point-supported Glass Research Articles

Experimental analysis of glass failure criteria under different thermal conditions

The initiation of the first crack mainly determines the criteria for glass failure. However, the extended consequences of cracking, with the formation of multiple cracks merging, result in fallout conditions under varying thermal loads that become more critical. Point-supported glass arrangements are globally used in high-rise and energy-efficient buildings for architectural ingenuity aimed at a low budget. However, the formation of cracks due to thermal load resulting in glass breakage could infuriate the overall fire dynamics of the enclosed area. Therefore, experimental study and prediction of glass failure become very crucial. The present experimental study focuses on finding the most critical parameter that may quantify the cause of glass failure and further breakage in fallout conditions under varying thermal loads. 45 experiments were carried out on float glass of 300 × 300 mm2 with 4 mm, 6 mm, 8 mm, 10 mm, and 12 mm with continuous fuel supply arrangements. Critical parameters analysed were the time of crack initiation, glass temperature at the time of cracking, maximum temperature difference at glass failure, and thermal strain caused by the temperature difference on the glass surface. The range of minimum and maximum temperature difference recorded on the glass surface for the present study was between 30–35°C and 55–60°C at the breakage time for all the experiments. The Maximum temperature difference measured was 56.99°C on the 12 mm glass surface, and the corresponding maximum thermal strain found was 482 × 10−6 mm/mm. The maximum heat release rate was found to be approximately 200 kW. Maximum heat flux was found in the range of 10.33 kW/m2 to 21.14 kW/m2. A correlation was also developed using the least square method for all the thicknesses, which is well correlated with the glass thickness per unit length.

Multi-performance blast pressure-duration curves for point-supported laminated and monolithic glass panes

Although point-supported glazing systems have been widely used in modern architecture, their blast performance is not fully documented yet. Most of the available code specifications and design guidelines are developed exclusively for frame-supported glass panes, i.e. panes with continuous edge supports, and it is expected that their point-supported counterparts are more vulnerable to blast loads. This study is devoted to evaluate blast performance of point-supported Laminated Glass (LG) and Thermally Tempered Glass (TTG) panes by using validated 3D Finite Element (FE) models. Considering different limit states (ranging from initial cracking to ultimate failure), multi-performance Pressure-Duration (P-D) curves, maximum pane deformations and maximum support reactions are developed for point-supported LG and TTG panes with varying dimensions, layups and thicknesses. Obtained results indicate that, compared with Polyvinyl Butyral (PVB) layer thickness, glass layer thickness has greater contribution to the blast resistance of LG panes. Moreover, in the case of small dimension point-supported panes, TTG panes unexpectedly outperformed LG panes, especially during blasts with higher positive durations. Finally, P-D curves of point-supported panes are compared with those of frame-supported panes. With a few exceptions, point-supported panes generally have significantly less blast resistance than their frame-supported counterparts. The difference is more pronounced in the case of larger dimension glass panes. This indicates that P-D curves of current codes and guidelines, which were developed based on frame-supported glass panes, cannot be directly applied to point-supported glass panes.

Substructure hybrid test examining the seismic response of point-supported glass façades attached to large-span spatial steel structures

Point-supported glass façade (PSGF) is one of the most widely used types of non-structural components. Its earthquake damage may not only cause economic loss, but also interruption of building use and even casualties. This paper aims at investigating the seismic response of the large-span spatial structure and PSGF coupling system through the substructure hybrid test. The substructure pseudo-dynamic (PSD) test method is used, that is, the loading rate of the test is slow as that of the quasi-static tests. The finding is that when the glass panel begins to fail, the cracks occur and instantly spread to the whole glass panel along the diagonal direction due to the stress concentration at a bolt hole of double-layer laminated glass, accompanied by looseness of several point-fixed fitting screws. The drift angle of one glass panel is about 50.0%–81.9% of that of glass façade δ in the critical and failure state, indicating that the supporting system can reduce the in-plane deformation of the glass panel. And the glass façade can reduce the acceleration responses of the mid-span upper chord nodes of the large-span spatial structure by 4.74%–13.98%. Finally, the seismic performance evaluation indexes of PSGF are determined based on the drift angle δ and percentage of damaged glass panels for the slight, moderate, and extensive limit states. It will provide an example and reference for the seismic performance evaluation of the PSGF.

Experimental study on failure mechanism of point-supported tempered glass panels under fire conditions

In order to investigate the fire resistance behavior of the point-supported tempered glass panels under fire conditions, six loading tests were conducted on three groups of tempered glass panels, including single, insulating, and laminated point-supported tempered glass panels, under the same fire conditions. The failure mechanism, failure time, and displacement-temperature curves were investigated. The results indicate that bolt holes significantly reduce the fire resistance of the point-supported tempered glass panels. The ultimate temperature and failure time of the point-supported tempered glass panels were obviously lower than those of the tempered glass panels without holes. Furthermore, the central displacement of the point-supported tempered glass panels developed faster under the same fire condition. Therefore, when using point-supported glass panels, more attention should be paid to its fire resistance design.

Topology optimization of truss support systems for a point- supported glass curtain wall based on truss-like continua

Steel truss structures for point-supported glass curtain walls with a web member configuration are presented using topology optimization based on truss-like continua. The initial structure comprises chords and partial web members. The initial design domain, surrounded by the members of the initial structure, is filled with a truss-like continuum, which is used to simulate the distributive web members of a steel truss. The structure members, together with the truss-like continuum, are analysed and calculated under horizontal point forces. The densities and orientations of the truss-like members at every node are taken as design variables and optimized. The members in the truss-like continuum are optimized using the fully stressed criterion. The topology optimization problem of minimum compliance with volume constraints is solved. Thus, an optimal web member configuration that suitably reinforces the lateral stiffness of the structure is obtained.

Thermal response and resistance optimization of various types of point-supported glass facades

The extensive application of various types of point-supported glass facades may bring potential thermal breakage risk and impacts on indoor human beings safety. In this work, point-supported glass facades with five various types were tested under thermal loads. The present results showed that installation forms influenced significantly the first breaking time, the location of crack initiation and the final falling out area. It demonstrated that the one-point-supported glass facades had the longest time for the first crack occurrence whereas the glass eventually fell completely out of the frame. However, the six-point-supported glass facades had the shortest first breaking time, but ultimately no glass pieces fell out of the frame. To calculate the temperature variation and stress distribution of glass panel, a thermal-mechanical model was developed. In addition, an optimization simulation was further conducted using the bound optimization by quadratic approximation method to obtain a better thermal resistance performance of glass facade. This work provides significant insights on the effects of various installations upon the thermal response of glass facades and helps to understand the failure mechanism and build safer facades by the structural optimization method.

Investigation of the thermal response and breakage mechanism of point-supported glass facade under wind load

Glass façade has gradually become main external wall material in high-rise buildings due to its multi-functionalization and diversification. Nevertheless, glass is relatively fragile and prone to fracture when subjected to the coupling effect of fire and external wind load that inevitably significant influences the mechanical property of glass facades in high-rise buildings. Newly formed vents caused through glass breakage are especially vital for the growth of ventilated controlled enclosure fire and play a crucial role in interactive-external tridimensional fire development. Therefore, it is necessary to explore the mechanism of thermal fracture of glass façades under wind load. In the present study, a total of nine tests were performed to investigate the fracture mechanism of point-supported glass facades under various wind speeds combined with fire. Measurements were conducted for the first breakage time, glass surface temperature, and crack initiation and propagation. Numerical simulation, based on finite element method (FEM) was conducted to predict the temperature variation at the ambient side surface of glass panel. The results have implications concerning fire resistance designs for point-supported glazing assemblies in high-rise buildings.

Study of point-supported glass breakage behavior with varying point-covered areas under thermal loading

Point-supported glazing assemblies are widely used in modern buildings for aesthetic elegance, as well as for economic reasons. However, the formation of vents caused by glass breakage could aggravate ventilation controlled compartment fires. The point-covered area generally varies and may constitute potential fire hazards. Accordingly, it is necessary to investigate the fire performance and breakage mechanisms in various point-covered areas. In this study, a total of 12 tests, including three various point-covered area glazing, were heated by a 200 × 200 mm2 pool fire. The breakage time, glass surface and air temperatures, incident heat fiux, and crack initiation and final fall out ratio were obtained. The critical conditions for the three aforementioned various point-covered area glazing were determined. The reference breakage times, tr, which were calculated by assigning a failure probability of 0.1 to the two-parameter Weibull distribution were 119, 140, and 166 s. It was established that a relatively small point-covered area glazing can survive longer; the smaller the point-covered area was, the larger the final fallout ratio of glazing assemblies will be. Numerical simulations were performed to investigate the stress distribution on the glass pane, with breakage times well predicted. Accordingly, these results have implications on the fire resistance design for point-supported glazing assemblies.

Breakage behavior of point-supported glass façades in fire

Breakage behavior of point-supported glass façades in fire

Effects of fixing point positions on thermal response of four point-supported glass façades

Different fixing forms of four point-supported glass façades are extensively used to satisfy the aesthetic requirement of modern buildings. While it may easily break and fall out when subjected to a fire, which could significantly affect compartment fire dynamics by creating a new opening for air to enter. In this work, sixteen cases with different fixing positions are designed to investigate the thermal response of four point-supported glass façades under both uniform and non-uniform thermal loadings. The Coulomb–Mohr criterion and stress intensity factors based mixed-mode criterion are employed to predict the crack initiation and growth, respectively. The glass stress distributions, breaking time and initiation and propagation of crack are presented, using three-dimensional finite element method. It is observed that all the cracks initiate at fixing points, which is attributed to the combination effect of constraining at supporting points and non-uniform temperature distribution. Fixing points changing in horizontal, vertical and diagonal directions has significant effects on glass breaking behavior. Moreover, thermal loading form also markedly affects the time of first crack initiations. The variation tendency of breaking time agrees well with our previous experimental study. It is intended that these results will provide some practical guidelines for fire safety engineers.

Exploratory numerical analysis of two-way straight cable-net façades subjected to air blast loads

Based on numerical and analytical results of previous literature contributions, the paper investigates the dynamic behaviour of a structural two-way straight cable-net façade subjected to medium-level blast loads. Numerical studies are dedicated, specifically, to a cable-net prototype already experimentally investigated under seismic loads. Several numerical finite-element (FE) models are developed in ABAQUS/Standard. A geometrically simplified, lumped-mass FE-model (M01), a detailed cable-glass model (M02) and a further simplified but computationally efficient cable-glass model (M03) are presented. The models are assessed and calibrated to test data of literature, as well as to simplified SDOF analytical formulations, in order to investigate the dynamic response of the façade under high-rate impulsive loads. Since axial forces in the cables and maximum stresses in the glass panels abruptly increase when the explosion occurs, specific viscoelastic and frictional devices are applied at the connection between glass and cables, as well as at the end of the cables. The main advantage of the presented technological solution is given by the partial dissipation of the incoming energy. In the first case, viscoelastic connectors add flexibility to the point-supported glass elements, hence reducing the amount of incoming blast energy. In the latter case, frictional devices dissipate through friction mechanisms the strain energy stored by the bearing cable-net. A proper combination of these multiple devices, in conclusion, can manifest a marked increase of structural efficiency for the examined structural typology.

Mechanical Performance Calculation of Single-Layer Cable Mesh Point-Supported Glass Curtain Wall under Fire Conditions

High-strength prestressed cables were main bearing parts in single-layer cable mesh point-supported glass curtain wall structures, and it was always unable to take effective fire prevention measures on steel cables due to small sections. That the elastic modulus and yield strength of prestressed cables decreased sharply under fire conditions would threaten safety performance of the whole structure seriously. When glass breakage is considered and not considered, nonlinear finite element complete-process analysis for the single-layer cable mesh point-supported glass curtain wall structure was conducted. Influences of various factors on structure mechanical performance were studied under fire conditions. Through the calculation analysis of different joint constraint models, the ultimate temperature table suitable for different sizes and cable spacing of glass curtain walls was obtained under uniform heating conditions, and proposals for fire-resisting design were given.

Dynamic Response of the Glass Curtain Wall of the Cable Truss under Wind Loads

The point-supported cable truss curtain wall is widely applied in today's high-rise construction structural design. The wind load is the main loads which are bore by Point supported glass curtain wall structure. When the curtain wall glass panels are subject to wind load, the panel will transform form surface loads to point load by spider claws passed to the supporting structure. This paper adopts the method of time domain and ANSYS software to analyse point-supported glass curtain wall cable truss structure of wind-induced vibration response.

Experimental Investigation of Numerical Design Method for Point-Supported Glass

AbstractCalculating stresses in structural glass components is essential for design, but is especially complex for customized components like point-supported glass (PSG) balustrades. Stress concentrations are introduced at the discontinuities of the plates precisely where boundary conditions elicit maximum field stresses. Further complicating design, most published stress data for glass components are based on annealed, edge-supported glass experiments—with limited applicability to fully tempered (FT), PSG applications. This article presents experimental and numerical results for a typical application of FT glass as a PSG structural balustrade. Strain data from six FT, monolithic glass balusters loaded to both service and ultimate conditions indicates 55.2-MPa stresses at service load and 155-MPa stresses at failure. Additionally, a design algorithm is developed, using beam theory with stress concentration factors to establish preliminary thickness for use in an optimized numerical analysis to calculate s...

Mechanical and Fatigue Performance Tests of Cast Aluminum Alloy ZL111 Adopted in Structure

Characteristics of aluminum alloys such as light weight, high strength-to-weight ratio and favorable corrosion resistance have brought about a bright application prospect in building structures. Wrought alloys are applicable to common beams and columns, while casting alloys can be fabricated as connectors in point-supported glass curtain wall and joints in spatial latticed structures on account of easy implement of moulding. Because of high strength, outstanding castability and remarkable mechanical properties after heat treatment, ZL111 in aluminum-silicon alloys is regarded as a desirable option. However, aluminum alloys are non-linear materials and their properties vary with casting and heat treatment modes. It is the well-marked distinction between aluminum alloy and ordinary carbon steel that special study on mechanical and fatigue performance is required. ZL111 raw materials were selected, with alloying agent and fabrication processes meeting the requirement of GB/T 1173-1995 standard. After T6 heat treatment process, test coupons were obtained by machining from raw materials. By utilization of electronic universal testing machine and cryogenic box, tensile tests at room temperature and low temperatures were performed. High-circle fatigue tests were carried out to obtain the fatigue performance of the material. Scanning electron microscope (SEM) was introduced to observe morphology of tensile and fatigue fractures. The tests revealed the relationship between mechanical property index and temperature, which indicated that the ZL111-T6 would increase in strength and plasticity. The microstructure of fractures validated and explained the macroscopic results. Furthermore, material strength at room temperature or low temperatures, stiffness and fatigue performance could satisfy bearing and normal serviceability requirement. Because of non existence of ductile-brittle transition temperature, superior corrosion resistance and outstanding castability, ZL111-T6 material is prone to fabricate complicated elements and joints withstanding cryogenic environment instead of carbon steel.

FEM Analysis and Experimental Study on Monolayer Cable Net for Glass Facades: Static Performance

Monolayer cable nets have been widely applied in point-supported glass facades in recent years because of transparency, light weight and flexibility of construction. In this paper, work on the static load bearing performance of this type of cable net is described through the use of finite element analysis (FEA) and tests on a 1/10–scale model of a real project in P.R. China under construction. Firstly a method of analysis inverse to the sequence of erection and much different from conventional methods, is used to model the pre-stretching of cables with the aid of FEA to provide guidelines for the tests. Cable pre-stretching proceeds by three stages, then load bearing behaviour tests on the cable net are carried out both before and after the installation of glass panels. The agreement between the pre-stretching tests and the FEA analysis indicates that the inverse analysis method is convenient in calculation, and provides useful references for the pre-stretching of similar types of cable net in practical engineering. The nonlinear relationship found between loads and displacements just indicates the nonlinear properties of flexible cable nets. Before the installation of glass panels, the structural stiffness actually increases slowly with increasing external loads, and greater initial pre-tension is more beneficial to load bearing capacity of the structure. But too large an initial pre-tension may overload the supporting structures of the cable net. The increase in cable force due to external loads is small. Nevertheless, the stiffness of the glass panels themselves make a significant contribution to the overall structural stiffness, the contribution which becomes less obvious as the stiffness of the cable net itself increases.