The behaviour of spider glass under out of plane loads

Creating a protective area from environment is one of the main necessities of human kind. From this point of view it can be said that, the main objective of building is to separate indoor from outdoor against danger that based on environmental effects. With developing industry, buildings should fulfill the security considerations and also with changing culturally aesthetic view should be taken into consideration. Architects always tried to connect indoor and outdoor in buildings. Firstly that could be possible by using the glass as window. The first glass, used by community was created by nature. Volcanic eruption provided sufficient temperature melt silica and other elements. This glass has an irregular structure and low strength. Some community used this type of glass in weapons and decorations. The origin of man-made glass is still not clear. Researchers claimed that glass making spread from western Asia and Egypt to the Roman Empire. It was Romans who began to use glass in windows applications. Transparency was not important because glasses were used for high cathedral walls for ventilation and illusion. Although it had poor optical quality architectural production methods were enhanced in these centuries. Glass production has increased during the renaissance and now it is hard to think architecture without glass component. Venetians production method was a big step for glass history. Until this century, glasses are used for luxury and big buildings to improve visual perception. German craftsmen developed some techniques to produce glass sheets. It was forbidden to tell the method anyone that not from this country. After that, glass production raised rapidly. By this means, the buildings of civil had developed. The public was able to reach glass productions easily. The technological and innovative improvements in glass and steel industries has made possible to create transparent facades by reducing the structural components. In the 19th century glass became incrementally available to obtain and these provided leap forward in facade buildings. Another jump in glass industries could be possible by production of float glass in 1950s. Pilkington developed a new method by using tin bath. This method provided smooth surface. By using these glass with an interlayer material strength of glass had been increased and structural glass emerged called laminated glass. Laminated glass has two or more glass layer with an interlayer material like PVB that mostly used in practice. Special attention is required with the experimental and numerical investigation of spider glass. High stress concentrations occur around the holes if the forces are transmitted to the glass by bolts. These stresses can cause catastrophic failure because of glass brittleness. Uniform loading from bolts to the drilled glass holes plays a significant role to reduce high local stresses around the holes. The types of support, interlayer material, thickness of glass, edge quality also affect the stress distribution around the hole. For simple geometries, it is possible to calculate the stresses or strains on component but xxvi due to the complication of the calculation of bolted glass, analysis are usually carried out by Finite Element Method. There are some forces that act on glass panel by the nature. Snow and wind pressure are some of these forces that must be considered for calculations. It is possible to divide forces acting on the glass panel into four parts. First one is its own weight. The dimension of glass panel changes where it is used. In some applications the largeness of panel could be large scale so the weight of panel is increases. In this situation buckling occurs on the glass panel. It doesn't create a big problem for safety if assembled well so in this thesis this force is neglected. The other load is wind pressure. It pretended the most important force on the glass panel because critical stress value occurs near the holes. This force is the only one that taking on the consideration. This force acts on the panel surface perpendicularly so bending stress occurs along the plane. Third loading is lateral loading that caused by the wind pressure or snow weight. This force creates shear stress. The significance of this force is that laminated glass has three parts that bonded tightly and this force tends to separate these parts. This force is also neglected. The last one is impact loading. Impact loading can cause catastrophic failure. The interlayer can be considered the solution of this problem. If glass breaks interlayer keep the breaking parts of the glass together. The tempered glass is also has high strength against impact. In this study, behavior of point fixed glass is carried out under out of plane load and then some constructive enhancements are enforced to reduce stresses around the drilled holes. There are various parameters to design glass panel. Location of drilled holes, dimension of holes and glass, thickness of interlayer, type of supporting are some examples of these parameters. In this thesis the focus point is designing the supports between glass and bolt cause of that the material of bushes, dimension of holes and bolts, thickness of glass and interlayer are main design parameters. Firstly, 3D cad model created by taking into consideration the geometrical parameters and then this model transferred to Ansys in a proper file format. Distance between the holes and edges and distance between holes are some geometrical considerations while creating the 3D cad model. Next, arrangements set up in the program that determined before like boundary conditions or applied load. Applied load has chosen 4000N perpendicular to the glass plane. At this stage, modeling and experiment should be in compliance due to this mechanical properties of the components must be modelled accurately. Throughout the thesis glass is considered as a linear material but interlayer material regarded as nonlinear. As is known, nonlinear properties should be added manually from the sources that include stress strain curve. Geometrical imperfections are neglected. On the other hand, compatibility of contact surfaces is essential. After loading, behavior of assembly in modeling must be similar as in the experiment. The routels are fixed to the rectangular shaped table so fixed support conditions applied to the routels. The other important boundary condition is between routel and glass. Cylindrical support is applied and only radial movement is permitted. After computer analysis, experiment set up as in the modeling. Glass panel is assembled on a rectangle table with routels. In order to avoid inclination flatness measured with water gage before each step. Afterwards, strain gages applied on the glass panel to obtain strain values. There are two critical points to measure strain correctly. One of them is bonding the gage tightly on the glass surface. The gages are glued with special UV glue that hardens in UV light. After gluing process the gages xxvii are exposed UV light for fifteen minutes from top and bottom surfaces. Unless gages bond tightly, it is not possible to measure strain values correctly. The second point is strain gages direction that determined in computer analysis. Grid wire on the gage elongate with the structure that has been bonded on. Direction must be carried out correctly to obtain strain value on the gages same as the bonded surface. Next, the force that had already chosen before applied on the glass surface vertically. In order to obtain data from the gages Prosig P8048 device was used. In experiment two strain data measured at the same time and the device has already sixteen slots. DATs program has used during the experiment. Applied input voltage is 10V and difference voltage values between reference value and last value gives us the stress value near the hole. First, experiment results and numerical results are matched nearly and then other combinations applied to reduce the stress. First, glass and bolt assembled with gap. Hole diameter was still 36 mm but bolts diameter reduced to 32 mm with bush on it. It is significant to note that, assembling with gap permits glass panel to move along the in plane direction with no constrain while acting the load. So, critical value place near the hole has changed. After numerical results it has been observed that stress value is reduced half and half and these results are confirmed by experiment results. The second combination was changing the drilled hole geometry. As is known, countersink geometry reduces stress concentration and as expected stress around the hole has reduced after the analysis. Counterbore dimension is 3 mm inclined with 45ᵒ but connection was still with no gap as in the first experiment. In conclusion, numerical simulation and experimental investigation are compared in order to understand the behavior of glass panel with different connection types. Firstly, cylindrical support with no gap is assembled in order to understand the behavior of glass panel especially drilled holes under out of plane load. The highest stress value obtained at first support type from both experiment and numerical analysis. One of the reason of this result is sharp edges. These edges always tend to create undesired stress values. Because of that connection type of supports are changed at other steps to reduce the stress around the holes. One of them is connection with gap and other one is countersink drilled holes. FEM results are obtained first and then experiment results are acquired. Computer based analysis matched with experimental results reasonably and these results are discussed.