The research presented in this paper was aimed at characterizing the serviceability and ultimate behavior of conventional two-side SSG curtain walls under cyclic racking displacements. Serviceability drift capacities corresponding to damage states such as gasket distortion, weatherseal, and structural seal failure leading to air leakage and glass cracking were identified. Ultimate drift capacities associated with damage such as glass fallout [defined as a shard of at least 645 mm2 (1 in.2)] were also identified. Air leakage tests were included to provide an index for serviceability failure criterion following an earthquake.
It was necessary to test specimens made with more than one glass panel so that both the interaction of glass panel edges and mullions and the interaction of glass panels to one another could be studied. Of particular interest was the characterization of the behavior of structural silicone sealant between glass panel vertical edges and aluminum frame members and also the behavior of the silicone weatherseal between adjacent glass panels. For this reason, it was decided to construct specimens with three glass panels. Two configurations were devised depending on whether a structural sealant joint or dry-glazed joint was used at exterior edges of the end panels, as shown in Fig. 1. Configuration A was devised to investigate the effect of dry-glazed exterior end panel vertical edges on the performance of the interior panels. One specimen of Configuration A and seven specimens of Configuration В were tested. The glazing frames were conventional stick frame type using Kawneer 1600™ aluminum frame members. A one-part GE silicone with medium modulus normally recommended for field-assembled SSG systems was the structural silicone sealant used. The details shown in Fig. 1 include a 10.7 mm (0.42 in.) structural silicone bite and a 6.4 mm (0.25 in.) bead thickness. The weatherseal consisted of a 12.7 mm (0.5 in.) wide bead at the interior joints and either a 12.7 mm (0.5 in.) or 6.4 mm (0.25 in.) wide bead at the end panel exterior vertical joints. The two different widths at the exterior joints were used to investigate the effect of the exterior weatherseal width on the behavior of the interior panel.
The full test specimen matrix is shown in Table 1. Annealed glass (AN) and fully tempered glass (FT) were the glass type factor levels, and monolithic glass (Mono.), laminated glass (Lami.), and insulating glass units (IGU) were the configuration factor levels. Four combinations of glass type and glass panel configuration were selected for the study. Two repetitions for each combination proved to be sufficient because no significant difference in the results of the two repetitions of each combination was observed. For full-scale mock-up testing, if there is a significant difference in the results of the two repetitions, typically a third test of the same combination is conducted.
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FIG. 1—Glazing details of Configurations A and В (1 mm = 0.0394 in.)
The racking test facility for the experimental study is shown in Fig. 2. Specimens were subjected to the AAMA 501.6-01  displacement-controlled racking protocol shown in Fig. 3. The protocol requires that
TABLE —Two-side SSG mockups for dynamic racking crescendo tests and air leakage tests.
aA-l refers to Combination 1 of Conliguration Л, and B-I refers to Combination 1 of Configuration B. Configurations Л and В arc defined in Fig. J. Similarly, B~2, B-3, and B-4 represent Combinations 2, 3, and 4, respectively, of Configuration B.
FIG. 2—Schematic of dynamic racking test facility with curtain wall test specimen attached.
the incrementally increasing racking step should continue until (a) glass fallout in the specimen occurs, (b) drift ratio over the height of the glass panel reaches 10 %, or (c) a racking displacement amplitude of ±150 mm (±6 in.) is applied to the specimen. In this study, the tests continued beyond glass fallout. Racking displacements were continued until the middle glass panel (the “test panel”) shattered. Glass fallout/shattering did not always first occur in the middle panel. Load and displacement data corresponding to various damage or failure modes, which included serviceability and ultimate drift capacities, were recorded during the tests.
Air leakage tests were conducted in accordance with ASTM Standard E 283-91  with some modification to the specimen size. ASTM Standard E 283-91 suggests that the specimen be at least a full building story high and include both vertical and horizontal joints. In this study, however, air leakage measurement was confined to vertical joints of the middle panel, referred to as Joints A and В in Fig. 4. Initially the air leakage chamber was constructed as shown in Fig. 4(a) using a plastic shroud taped over the middle panel for mockups 1 and 5. After these initial tests, it was decided that an independent evaluation of the air leakage in each middle panel joint would be more informative, and the smaller chambers covering individual vertical joints [Fig. 4(6)] were used in the other six mock-ups tests.
A baseline air leakage test was conducted on each specimen before the start of the cyclic racking test, and air leakage measurements were then taken about every other racking step when the racking was stopped for inspection of the specimen. The air supply pressure was maintained at 75 Pa (1.57 lb/ft2).