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1. A Shake-Table Test Investigating the Drift Capacity of Reinforced Masonry Wall Systems

   Cheng, Jianyu ; Koutras, Andreas ; Shing, P. Benson ( June 2019 , Proceedings - North American Masonry Conference)

   An accurate quantification of the displacement capacity of a reinforced masonry shear-wall system is of critical importance to seismic design because it has a direct implication on the seismic force modification factor, which is the R factor in ASCE 7. In spite of the shear capacity design requirement in TMS 402, special reinforced masonry walls within a building system could still develop shear-dominated behavior, which is perceived to be far more brittle than flexural behavior. These walls have a low shear-span ratio either because of the wall geometry (i.e., a low height-to-length ratio) or the coupling forces introduced by the horizontal diaphragms, which are often ignored in design. Although shear-dominated walls appeared to be very brittle in quasi-static tests conducted on single planar wall segments, reinforced masonry structures survived major ground shaking well in past earthquakes. This could be partly attributed to the beneficial influence of wall flanges as well as the over-strength of the system. Flanged walls are common in masonry buildings, but their behavior is not well understood because of the lack of laboratory test data. Furthermore, other walls or columns that are present in the structural system to carry gravity loads could enhance the lateral resistance ofmore »the shear walls and the displacement capacity of the system by providing axial restraints as well as alternative load paths for gravity loads. A research project is being carried out with shake-table tests to investigate the displacement capacity of shear-dominated reinforced masonry wall systems. This paper presents results of the first shake-table test conducted in this project on a full-scale single-story coupled T-wall system. The structure was tested to a drift ratio exceeding 15% without collapse.« less
2. A Shake-Table Test Investigating the Drift Capacity of Reinforced MasonryWall Systems

   Cheng, Jianyu ; Koutras, Andreas ; Shing, P. Benson ( June 2019 , Proceedings - North American Masonry Conference)

   An accurate quantification of the displacement capacity of a reinforced masonry shear-wall system is of critical importance to seismic design because it has a direct implication on the seismic force modification factor, which is the R factor in ASCE 7. In spite of the shear capacity design requirement in TMS 402, special reinforced masonry walls within a building system could still develop shear-dominated behavior, which is perceived to be far more brittle than flexural behavior. These walls have a low shear-span ratio either because of the wall geometry (i.e., a low height-to-length ratio) or the coupling forces introduced by the horizontal diaphragms, which are often ignored in design. Although shear-dominated walls appeared to be very brittle in quasi-static tests conducted on single planar wall segments, reinforced masonry structures survived major ground shaking well in past earthquakes. This could be partly attributed to the beneficial influence of wall flanges as well as the over-strength of the system. Flanged walls are common in masonry buildings, but their behavior is not well understood because of the lack of laboratory test data. Furthermore, other walls or columns that are present in the structural system to carry gravity loads could enhance the lateral resistance ofmore »the shear walls and the displacement capacity of the system by providing axial restraints as well as alternative load paths for gravity loads. A research project is being carried out with shake-table tests to investigate the displacement capacity of shear-dominated reinforced masonry wall systems. This paper presents results of the first shake-table test conducted in this project on a full-scale single-story coupled T-wall system. The structure was tested to a drift ratio exceeding 15% without collapse.« less
3. Evaluation of collapse resistance of reinforced masonry wall systems by shake‐table tests

   https://doi.org/10.1002/eqe.3342  

   Cheng, Jianyu ; Koutras, Andreas A. ; Shing, P. Benson ( August 2020 , Earthquake Engineering & Structural Dynamics)

   This paper presents a shake-table test study to investigate the displacement capacity of shear-dominated reinforced masonry wall systems and the influence of wall flanges and planar walls perpendicular to the direction of shaking (out-of-plane walls) on the seismic performance of a wall system. Two full-scale, single-story, fully grouted, reinforced masonry wall specimens were tested to the verge of collapse. Each specimen had two T-walls as the seismic force-resisting elements and a stiff roof diaphragm. The second specimen had six additional planar walls perpendicular to the direction of shaking. The two specimens reached maximum roof drift ratios of 17% and 13%, without collapsing. The high displacement capacities can be largely attributed to the presence of wall flanges and, for the second specimen, also the out-of-plane walls, which provided an alternative load path to carry the gravity load when the webs of the T-walls had been severely damaged. The second specimen developed a higher lateral resistance than the first owing to the additional axial compression exerted on the T-walls by the out-of-plane walls when the former rocked. The shear resistance of the T-walls evaluated with the design code formula matches the test result well when this additional axial compression is taken intomore »account. However, it must be understood that the beneficial influence of the wall flanges depends on the magnitude of the gravity load because of the P-Δeffect and the severity of damage induced in the wall flanges when the wall system is subjected to bidirectional ground motions.« less
4. Earthquake and Post-earthquake Fire Testing of a Mid-rise Cold-formed Steel Framed Building. I: Building Response and Physical Damage

   https://doi.org/10.1061/(ASCE)ST.1943541X.0003097  

   Hutchinson T.C., Wang ; Hegemier, G. ; Kamath, P. ; Meacham, B. ( January 2021 , Journal of structural engineering)

   To advance understanding of the multihazard performance of midrise cold-formed steel (CFS) construction, a unique multidisciplinary experimental program was conducted on the Large High-Performance Outdoor Shake Table (LHPOST) at the University of California, San Diego (UCSD). The centerpiece of this project involved earthquake and live fire testing of a full-scale 6-story CFS wall braced building. Initially, the building was subjected to seven earthquake tests of increasing motion intensity, sequentially targeting service, design, and maximum credible earthquake (MCE) demands. Subsequently, live fire tests were conducted on the earthquake-damaged building at two select floors. Finally, for the first time, the test building was subjected to two postfire earthquake tests, including a low-amplitude aftershock and an extreme near-fault target MCE-scaled motion. In addition, low-amplitude white noise and ambient vibration data were collected during construction and seismic testing phases to support identification of the dynamic state of the building system. This paper offers an overview of this unique multihazard test program and presents the system-level structural responses and physical damage features of the test building throughout the earthquake-fire-earthquake test phases, whereas the component-level seismic behavior of the shear walls and seismic design implications of CFS-framed building systems are discussed in a companion paper.
5. Experimental Seismic Test of Drywall Partition Walls with Improved Detailing for Damage Reduction

   Ryan, K. ; Hasani, H. ( July 2020 , The 17th World Conference on Earthquake Engineering)

   Drywall partition walls are susceptible to damage at low-level drifts, and hence reducing such damage is key to achieving seismic resiliency in buildings. Prior tests on drywall partition walls have shown that slip track connection detailing leads to better performance than other detailing, such as fully-fixed connections. However, in all prior testing, partition wall performance was evaluated using a unidirectional loading protocol (either in-plane or out-of-plane) or in shake table testing. Moreover, all details are susceptible to considerable damage to wall intersections. Two phases of the test have been performed at the Natural Hazards Engineering Research Infrastructure (NHERI) Lehigh Equipment Facility to develop improved details of drywall partition walls under bidirectional loading. The partition walls were tested alongside a cross-laminated timber (CLT) post-tensioned rocking wall subassembly, wherein the CLT system is under development as a resilient lateral system for tall timber buildings. In the Phase 1, the slip behavior of conventional slip-track detailing was compared to telescoping detailing (track-within-a-track deflection assembly). In the Phase 2, two details for reducing the wall intersection damage were evaluated on traditional slip-track C-shaped walls. First, a corner gap detail was tested. This detail incorporates a gap through the wall intersection to reduce the collisionmore »damage at two intersecting walls. Second, a distributed gap detail was tested. In this approach, the aim was to reduce damage by using more frequent control joints through the length of the wall. All walls were tested under a bidirectional loading protocol with three sub-cycles: in-plane, a bi-directional hexagonal load path, and a bi-directional hexagonal load path with an increase in the out-of-plane drift. This loading protocol allows for studying the bidirectional behavior of walls and evaluating the effect of out-of-plane drift on the partition wall resisting force. In the Phase 1, the telescoping detailing performed better than conventional slip track detailing because it eliminated damage to the framing. In Phase 2, the distributed gap detailing delayed damage to about 1% story drift. For the corner gap detailing, the sacrificial corner bead detached at low drifts, but the wall itself was damage-free until 2.5% drift. Bidirectional loading was found to have an insignificant influence on the in-plane resistance of the walls, and the overall resistance of the walls was trivial compared to the CLT rocking.« less