Seismic Evaluation of Self-Centering Bi-Rocking Walls via Micro Modeling of Rocking Joints: Locating the Rocking Section

The rocking concrete shear wall is one of the new self-centering seismic systems applied in high-rise buildings. To reduce the effects of higher modes on base-rocking walls, the idea of using multiple rocking walls has been evolved. This paper presents a comparative investigation on the seismic performance of base-rocking and bi-rocking wall systems. To this aim, structures of 4-, 8-, 12-, 16-, and 20- stories have been evaluated subjected to three sets of seismic earthquake records including 22 Far Field (FF), 14 Near Field (NF) with pulse, and 14 Near Field (NF) no-pulse ground motions. The nonlinear time-history analyses were conducted in two directions using OpenSEES software. To determine the appropriate location of rocking section in bi-rocking walls, one-quarter (R2-M1), one-half (R2-M2), and three-quarter (R2-M3) models were examined. The obtained results revealed that R2-M3 model is not efficient in reducing the effects of higher modes. However, R2-M2 model in high-rise buildings under FF and NF-no-pulse records could be effective in decreasing the moment by a maximum of nearly 41% and the shears by a maximum of 25% and 18%, respectively. Furthermore, the results showed that bi-rocking walls could not be effective in reducing the influence of higher modes under NF-pulse ground motions. Generally, the residual drifts were negligible in all the rocking systems under study.

Unbonded Post-tensioned Precast Concrete Walls With Rocking Connections: Modeling Approaches and Impact Damping

Over the past two decades, precast concrete members have been utilized in seismically resilient structures. In developing these structures, different techniques have been used for connecting the precast members to the foundation. In building construction, unbonded post-tensioning (PT) tendons can anchor a precast wall to the foundation, resulting in the so-called rocking wall system. The rocking wall system develops a dry connection with the foundation and provides moment resistance by means of the PT tendons. The PT tendons remain elastic when the wall is subjected to design-level ground motions to preserve the re-centering capability of the wall. Moreover, the structural damage is concentrated near the wall toes and can be minimized with proper detailing of the toes. Rocking wall systems can consist of a Single precast Rocking Wall (SRW), which uses no supplemental damping, or walls with supplemental damping in the form of viscous or hysteretic energy dissipating devices. In addition to the supplemental damping, rocking walls dissipate the seismic energy through their impacts on the foundation base, their inherent viscous damping, and the hysteresis of concrete near the wall base. While the investigation of rocking walls continues to gain interest, there is no widely accepted means of modeling their dynamic behavior. This paper investigates two popular approaches for modeling rocking walls with and without supplemental damping: the finite element method and analytical modeling. The ability of the two approaches to capture the local and global responses of the walls is evaluated against shake table tests of walls with multiple-level intensity base motions. Next, the behavior characteristics of the two modeling approaches and their ability to simulate impact damping are discussed.

Examination of Slip Behavior in Drywall Partition Walls

Preliminary observations of Phase I testing of a subassembly of nonstructural drywall partition walls integrated with cross-laminated timber (CLT) rocking walls are reported. In this phase, the slip behavior of two straight drywall partition walls (without return walls) – one with conventional slip-track detailing and the other with telescoping detailing – was examined. These drywall partition walls 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 studs 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.