Structural Sealant Glazing Parameter Studies with a Focus on Glass Components

The first step in the parametric study consists of variation of the glass pane thickness. Figure 17 presents the evolution of the corner stresses with glass thickness. The lower the effective thickness, and thus the lower the resulting bending stiffness, the higher the peak loads in the corner zones. Obviously, low bending stiffness of the glass units favors the existence of peak corner stresses, as for the limiting case of totally rigid panes, a uniform adhesive loading will result due to the homogenous “rigid body" kinematics of the glass pane.

The impact of the glass thickness directly guides us to the issue of shear load transfer of the interlayer in the case of laminated glass units. For laminated glass, the combination of two panes of 6 mm thickness is analyzed in detail in Fig. 18 for the two extreme conditions of fully operational (default) and fully degraded (no shear stiffness) shear transfer by the interlayer. The outcome of the thickness parameter variation as shown in Fig. 15 confirms the tendency for low effective bending thickness to favor corner peak stresses; in Fig. 18 the fully active shear layer—resulting in high effective bending stiffness—leads to low

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FIG. 17—Stress distribution for different glass units; surface load of 4.48 x 10~3 MPa (glass unit: 1.5 m in length, 1.25 m in width, varying thickness; bonding: width — 20 mm, thickness — 9 mm).

corner stresses, whereas in the case of a degraded interlayer (no shear stress), linked to low effective bending stiffness, the peak stresses are doubled for the investigated configuration.

In order to link these results to the corner loads obtained via thin plate theory, the relationship between corner load magnitude and glass unit aspect ratio is mirrored to the stress distributions shown in Fig. 19 for the three differ­ent aspect ratios 1, 1.2, and 2, representing panel sizes of 1250 mm x 1250 mm, 1500 mm x 1250 mm, and 2500 mm x 1250 mm. The trend of increasing corner stresses with increasing aspect ratio is in line with the characteristics of the shape function shown in Fig. 8, thus confirming the origin of the numerical cor­ner stresses as an outcome of the special equilibrium conditions in the corners. Interestingly, also for the compressive stresses, the rule “the higher the aspect ratio, the higher the magnitude of the stresses" obviously applies as well. This result is directly linked to the concentrated corner forces, which have to

FIG. 18—Stress distribution for laminated glass units differing in interlayer functional­ity; surface load of 4.48 x 10~3 MPa (glass unit: 1.5 m in length, 1.25 m in width, 2 x 6 mm in thickness; bonding: width—20 mm, thickness — 9 mm).

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MPa (glass unit: varying length, 1.25 m in width, 10 mm in thickness; bonding:

width — 20 mm, thickness — 9 mm).

compensate for equilibrium conditions by means of additional compressive loads of the adhesive along the edges.