Discussion of General Response of Tested Mockups

The common behavior of the test specimens during racking displacements consisted of deformation of the glazing frame as the top sliding steel tube of the racking facility (Fig. 2) moved in the opposite direction of the bottom sliding steel tube. This caused each glass panel to rotate in an effort to adjust to the deformed position of the glazing frame. All three glass panels would rotate in the same direction causing the

FIG. 3—Drift time history for dynamic racking tests.

FIG. 4—Plastic shrouds used to form chambers for air leakage tests: (a) shroud location for tests on mockups l and 5; (b) shroud location for tests on all other mockups.

weatherseal between each pair to be stretched vertically as the edge of one panel moved up and the edge of the adjacent panel moved down. As racking displacement amplitude increased, glass panel horizontal edges near corners started to come in contact with the lip (Fig. 1) of the dry-glazed horizontal framing members. Glass-to-frame contact eventually led to cracking and fallout of glass. Figure 5 shows a typical specimen under test.

In all the tests performed, adjacent glass panels did not come in contact with each other, because the combination of the structural seals and weatherseals along the vertical edges of each panel kept the side-by-side panels close to parallel throughout the racking displacements. This was observed even as the structural seals and weatherseals began to exhibit extensive failure. Furthermore, end panel glass edges did not contact the boundary mullions (shown as Sec. 1-1 in Fig. 1) during any of the tests with the exception of mockup 5, whose bottom frame-to-facility anchor welds broke at large racking displacements.

Glass panel rotation relative to the deforming mullions during racking exerted longitudinal and trans­verse shear strain in both the weatherseals and structural seals. Longitudinal shear strain was dominant in

FIG. 5—Mockup 8 (AN 1GU) under test.

FIG. 6—Inspection of two-side SSG silicone joint failures that occurred during in-plane dynamic racking tests.

the weatherseals, and transverse shear strain was the cause of observed failures in the structural seals. Three primary silicone sealant failure modes were identified in the weatherseals and structural seals: cohesive failure, adhesive failure, and thin film failure. In racking tests cohesive failure occurs in the seals when their shear strain capacity is exceeded and is characterized by rupture within the sealant. Adhesive failure occurs in the seals due to loss of bond between the sealant and its substrate and is characterized by a complete peeling away of the sealant from the substrate in the areas where it is observed. Adhesive failure is typically the result of less than ideal substrate surface preparation and is not a desirable failure mode. Thin-film failure could easily be mistaken for adhesive failure and is characterized by a thin layer of sealant left behind on the substrate as the sealant ruptures as shown in Fig. 6. In the experiments carried out in the study, adhesive failure was only observed in one instance along less than a 25 mm (1 in.) length of seal in an end panel weatherseal joint and did not have any detrimental effect on the performance of the mock-up. Typical gasket seal degradation (e. g., distortion, pullout, shifting), noted in previous studies [e. g., 6] was observed in the horizontal dry-glazed joints. In general, gasket seal degradation occurred before silicone sealant failure and at a later stage than would be expected of a mockup using gaskets around its entire perimeter.

As previously noted, glass-to-ffame contact near corners of transoms was the cause of glass failure. This was evidenced using view windows cut into some of the pressure plates and postmortem inspections of the glazing lip (Fig. 1) and pressure plates of the transoms that supported the glass panel bottom edges. Inspections revealed scraping and gouging marks along the glazing lip and the inside surface of the pressure plates at the corner regions of the framing for each glass panel. As observed in dry-glazed racking tests, scraping marks were more extensive for AN Lami. and IGU configurations.

Cracking

Pullout

Shattering

Panel 1

Panel 2

Panel 3

Panel 1

Panel 2

Panel 3

Panel 1

Panel 2

Panel 3

mm (in.)

mm (in.)

mm (in.)

mm (in.)

mm (in.)

mm (in.)

mm (in.)

mm (in.)

mm (in.)

Mockup 1

63.5 (2.50)

69.9 (2.75)

63.5 (2.50)

69.9 (2.75)

a

63.5 (2.50)

59.9 (2.75)

a

69.9 (2.75)

Mockup 2

69.9 (2.75)

82.6 (3.25)

82.6 (3.25)

76.2 (3.00)

82.6 (3.25)

82.6 (3.25)

76.2 (3.00)

82.6 (3.25)

a

Avg.

66.7 (2.63)

76.3 (3.00)

73.1 (2.88)

73.1 (2.88)

82.6 (3.25)

73.1 (2.88)

73.1 (2.88)

82.6 (3.25)

69.9 (2.75)

Mockup 3

114.3 (4.50)

114.3 (4.50)

82.6 (3.25)

114.3 (4.50)

114.3 (4.50)

82.6 (3.25)

114.3 (4.50)

114.3 (4.50)

82.6 (3.25)

Mockup 4

114.3 (4.50)

114.3 (4.50)

108.0 (4.25)

114.3 (4.50)

114.3 (4.50)

108.0 (4.25)

H4.3 (4.50)

114.3 (4.50)

108.0 (4.25)

Avg.

1143 (4.5)

114.3(4.5)

95.3 (3.75)

1143 (4.5)

1143 (4.5)

95.3 (3.75)

114.3 (4Лі)

1143 (4.5)

95.3 (3.75)

Mockup 5

82.6 (3.25)

108.0 (4.25)

82.6 (3.25)

101.5 (4.00)

108.0 (4.25)

a

152.4 (6.00)

152.4 (6.00)

152.4 (6.00)

Mockup 6

88.9 (3.50)

88.9 (3.50)

95.3 (3.75)

108.0 (4.25)

108.0 (4.25)

108.0 (4.25)

152.4 (6.00)

152.4 (6.00)

152.4 (6.00)

Avg.

85.8 (3.38)

98.5 (3.88)

89.0 (3.5)

104.8 (4.13)

108 (4.25)

108 (4.25)

152.4 (6)

152.4 (6)

152.4 (6)

Mockup 7

120.7 (4.75)

127.0 (5.00)

127.0 (5.00)

133.4 (5.25)

133.4 (5.25)

133.4 (5.25)

139.7 (5.50)

139.7 (5.50)

139.7 (5.50)

Mockup 8

І 33.4 (5.25)

127.0 (5.00)

127.0 (5.00)

133.4 (5.25)

133.4 (5.25)

133.4 (5.25)

139.7 (5.50)

139.7 (5.50)

139.7 (5.50)

Avg.

127.1 (5.00)

127.0 (5.00)

127.0 (5.00)

133.4 (5.25)

133.4 (5.25)

133.4 (5.25)

139.7 (5.5)

139.7 (5.5)

139.7 (5.5)

ТАШЛі 2—Serviceability and ultimate drift capacities of glass panels in two-side structural silicone mockup tests.

JData not available because of test stoppage prior to occurrence of the fallout or shattering event.

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