Tong, Zhang, Zhou, Keivan, Li 2018
In this study, a modified approach to eccentrically braced frames was proposed. The system, known as D-type self-centering eccentrically braced frames (SCEBF) with replaceable hysteretic damping (RHD) devices, was subjected to cyclic loading to investigate its seismic performance. Five full-scale specimens were tested to analyze their behaviors such as general performance, energy dissipation capacity and recentering capacity. The results supported that the proposed SCEBF exhibited satisfactory self-centering behavior while the RHD devices enhanced its seismic performance by facilitating sufficient energy dissipation capacity. It was also noted that the performance of the system remained consistent before and after the replacement of the RHDs. This verifies the proposed system as an efficient and seismically resilient device.
System Concept
The D-type SCEBF comprises an eccentrically braced steel frame with post-tensioned (PT) strands and RHD devices. The braced steel frame consists of a short protruding beam, link beam, collector beam, and columns. PT strands anchored to the short protruding beam and the column are made of multiple high strength steel to make sure they remain mostly elastic during earthquakes. Stiffeners were also added to the columns to prevent local buckling and failure caused by large compressive loads.
The RHD devices of the system are made of low-yield steel to ensure damage is concentrated on the replaceable components of the system. Both vertical and horizontal RHD devices consist of four trapezoidal or two parallel energy-dissipation steel plates which connect to the rocking link beam of the system. When subjected to a drift, the link beam rotates and allows energy-dissipation by the steel plates as they deform in flexure. After replacement of the RHD devices, the system is expected to demonstrate identical seismic response as long as the members of the braced steel frame remain elastic.
Experimental Study, Results and Discussion
Five full-scale specimens with different set ups were subjected to quasi-static cyclic loading tests. A cyclic drift history of three cycles was executed by the servohydraulic positioned at the top of the specimen.
During all cyclic loading tests, all five SCEBF specimens achieved satisfactory self centering behavior and generated hysteresis curves. When subjected to larger drifts, RHD devices were
activated and energy was dissipated by the steel plates. It was observed that most of the energy was dissipated by the vertical RHD devices where the horizontal RHD devices behaved as back-up damping devices. The replacement of the RHD devices after each test did not affect the overall performance and exhibited similar stiffness, strength and recentering capacity of the original system.
Reference
Tong, Lewei, et al. “Experimental and Analytical Investigation of D-Type Self-Centering Steel Eccentrically Braced Frames with Replaceable Hysteretic Damping Devices.” Journal of Structural Engineering, vol. 145, no. 1, Jan. 2019, p. 04018229. DOI.org (Crossref), https://doi.org/10.1061/(ASCE)ST.1943-541X.0002235.