Preliminary observations of Phase I testing of a subassembly of nonstructural drywall partition walls integrated with cross -laminated timber (CLT) rocking wall s are reported . In this phase, the slip behavior of two straight drywall partition walls (without return wall s) – one with conventional slip-track detailing and the other with telescoping detailing – was examin ed. These drywall partition wall s were tested under a bidirectional loading protocol , which allowed for systematic evaluation of the effect of out of plane drift on the in-plane resistance of the drywall partition walls . Preliminary conclusions are that the telescoping detailing performs better since it eliminates damage to the framing , such as detachment of end stud s that causes bending of the end studs and damage to the track . Moreover, the out -of-plane drift had a negligible effect on the in-plane resistance. Introduction Drywall partition walls are drift sensitive components, which are susceptible to damage at low shaking intensities. In contrast, buildin gs with post-tensioned cross -laminated timber ( CLT ) rocking wall s as a lateral load resistant system can sustain large drift demands with little damage (Buchanan et al. 2008; Ganey 2015) . Thus, drift-induced damage in drywall partition walls needs to be reduced to achieve overall seismic resiliency. Damage reduction is proposed using two detail s that attempt to isolate the drywall partition walls from the inter -story movement. Previous studies have shown that drywall partition walls with slip-track connection detailing can endure higher drifts compare d to the full connection when return walls are not present (Hasani et al. 2018; Hasani and Ryan 2020 ; Ryan and Hasani 2020) ; however, these drywall partition wall s are susceptible to detach ment of boundary studs from the walls (Davies et al. 2011) . Another alternative for the top connection of the drywall partition wal l is the track -within -a-track deflection assembly (referred to hereafter as telescoping). This detail is used mainly for absorbing the vertical deflection of the diaphragm, but it has also been suggested for lateral movement (Applied Technology Council 2012) . However, to the authors’ knowledge , this connection detail has not 3 been tested for the seismic -induced drift so far. Figure 1 show s the connection detailing at the top for both types of drywall partition wall s. Slip track connection Telescoping connection Figure 1: Slip track and telescoping connection detailing The most critical parameter yet to be scrutinized is the behavior of interior drywa ll partition walls under bidirectional loading. To the authors ’ knowledge, drywall partition walls have not been tested bi -directionally under systematic quasi -static loading, which can provide better information about their damage states. Test Objective Two straight drywall partition wall s, one with conventional slip track detailing and the other with telescoping detailing, were built within a post -tensioned CLT rocking wall subassembly at the National Hazards Engineering Research Infrastructure ( NHERI ) Lehigh Equipment Facility ( EF). The overarching objective is to investigate the seismic performance of drywall partition walls integrated with the rocking wall subassembly . The specific objectives of Phase I testing are 1) to evaluate the relative seismic and slip performance of the walls with telescoping detailing and conventional slip -track detailing , and 2) to assess the influence of out -of-plane loading on the in - plane resistance of the walls. Experimental Program Testbed Structure The testbed structure was a single -story, 2 -bay by 1 -bay CLT post -tensioned rocking wall system with gravity framing . For simulating a realistic specimen, the structure dimensions were 30 ft. by 15 ft., and floor -to-floor height was 12.5 ft. The rocking wall system was composed of two five - ply CLT panels with dimensions of 20 ft. x 5 ft. x 6.75 in. , and connected by U -shaped flexural plates (UFP) for energy dissipation (Fig ure 2). The first -floor diaphragm w as built from three -ply CLT panels , and the base diaphragm w as built from five -ply CLT panels . The connection of the wall and collector beam was designed to isolate the diaphragm from the vertical movement of the rocking walls (Clay et al. 2019) . 4 (a) (b) Figure 2: (a) Testbed structure ; (b) testbed structure with drywall partition walls subjected to 5% drift Test Specimen Detail The test specimen consisted of two 12 ft . long and 12.5 ft . high of drywall partition walls constructed between CLT diaphrag ms. The f irst wall used a slip-track top connection detail . In this detailing, the drywall is connected only to the studs, and there is not any connection between the stud and the top track (Figure 1(a)). The other wall used a telescoping connection detail , which uses two sets of tracks at the top of the wall. One track nested in the other track without any connection between the two tracks. However, studs are connected to the inner track (Figure 1(b)). The base of both wall s was fully connected to the tracks . Both walls used institutional detailing , which specifies gauge 33 studs spaced 16 in. o.c. Figure 3 shows the whole setup of the test. Figure 3: (a) Drywall partition walls installed between CLT diaphragms ; (b) position of drywall partition walls in the structure Loading Protocol A cyclic drift loading protocol has been used for this test , through which the drift amplitude s are increased in each stage. The loading protocol specified a bidirectional path of movement , with three sub-cycles in each stage : in-plane, bidirectional hexagonal , and bidirectional hexagonal with an increase in out-of-plane drift (Figure 4 (a)). The magnitude of peak in -plane drift is increased in each stage, as shown in Figure 4(b). This loading protocol was designed to evaluate the effect of the out -of-plane drift on the in-plane r esistance of the drywall partition wall. 5 (a) (b) Figure 4: (a) Path of movement of bidirectional load step; (b) peak in -plane drift amplitude in different stages Preliminary Results The seismic performance of the drywall partition walls was preliminarily evaluated throug h observation of the damage mechanism s (Figure 5) . After each cycle, the damage to the partition walls was assessed , and a damage description recorded . Corner beads at the end of both walls started to lightly detach at around 0.46% drift (Figure 5 (a)). This damage occurs because the entire wall below the top track tends to remain stationary , while the top track tends to move with the top diaphragm (natural behavior of slip -track). Since fire regulations perm it only up to half-inch gap at the top of the gypsum (Gypsum Association 2018) , while the top track leg length is 2 in. for both types of detailing , the top track hits the gypsum at the top of the wall ends. The detachment of corner beads increased with increas ing drift. Light warping of the gypsum was observed at 0.67% drift (Figure 5(b)), and the corner bead opened significant ly at 0.84% in the slip-track connected wall (Figure 5(c)). Coincident with this observation at 1.26 in. displacement , the resisting force increased significantly. Since the stud leg is 1.25 in., the authors believe that the considerable opening in the corner bead is due to the stud not returning to its nested track in the slip-track connected wall . Bending of the end stud was observed at 2.56% drift in the slip-track connected wall (Figure 5(d)). At a drift of 3.2%, the damaged end stud in the slip-track connected wall bent the leg of the track (Figure 5(e)) , which was coincident with a considerable increase in the resisting force . Whil e all of this damage progressed in the wall with the slip track connect ion, the wall with telescoping detailing show ed only minor damage at the top end of the wall (Figure 5(f)). The post -test inspections suggest that the framing of the wall with telescoping detailing remained damage -free during the test (Figure 6(a)). However, the stud and track of slip -track detailing suffered damage due to the detachment of end studs from the tr ack (Figure 6(b)). Hysteresis Response of Drywall Partition Wall Figure 7 shows the hysteresis loops of the walls with slip -track connection (Figure 7(a)), and telescoping detailing (Figure 7(b)). The hysteresis loops show that both walls developed approximately similar forces because both walls have slip behavior at th e top. Moreover, the 00.010.020.030.040.05 1357911131517Max Drift Stages 6 hysteresis loops suggest that the out -of-plane drift of the drywall partition does not affect the in - plane force of the wall considerably. The slip track wall hysteresis loop s exhibited a few sudden increases in the force, which coinci ded with the occurrence of damage to the framing of this wall mentioned earlier. (a) (b) (c) (d) (e) (f) Figure 5: (a) Light detachment of corner bead at wall ends (0.46% drift, slip track ); (b) light warping of gypsum (0.67% drift, slip track ); (c) significant opening in the corner bead (0.84% drift, slip track ); (d) end stud bending (2.56% drift, slip track ); (e) track leg bent (3.2% drift, slip track ); (f) light detachment of corner bead at wall ends ( 1.64% dri ft, telescoping ) (a) (b) Figure 6: Post-test inspection after removal of gypsum board: (a) damage in the wall with telescoping detailing ; (b) damage in the wall with a slip track connection 7 (a) (b) Figure 7: Force vs. displacement h ysteresis of drywall partition walls : (a) slip track detailing ; (b) telescoping detailing Moreover, the hysteresis loop s of the entire subassembly are shown in Figure 8. Since the drywall partition walls had slip behavior, they contributed less than 1% to the whole subassembly force . It is worth while to mention that the structural subassembly suffered almost damage. The CLT rocking wall was protected at the toes with steel armoring; therefore, visib le damage was limited to crushing of the concrete base beneath the toes of the rocking wall. Figure 8: Hyst eresis loop s of the entire subassembly in the in-plane direction Conclusion Bidirectional quasi -static experiments of drywall partition walls integrated into a CLT rocking wall subassembly were performed at the NHERI Lehigh EF as part of a project to develop a resilience -based seismic design methodology for tall wood buildings . Compared to a traditional slip track connect ion detail, telescoping detailing was observed to eliminate damage to drywall partition walls that is caused by the separation of the end stud s from the track at large drifts . Moreover, the out of plane drift did not affect the in -plane resistance. Furthermore, since both walls have slip behavior, the resisting force of the walls was in significant compare d to the force of the CLT rocking walls . -0.4-0.200.20.4 -5 -3 -1 1 3 5Force (kips) Drift (%)-0.4-0.200.20.4 -5 0 5Force (kips) Drift (%) -80-60-40-20020406080 -5 -3 -1 1 3 5Force (kips) Drift (%) 8