Development of Energy Dissipation Elements Appropriate for SC-MRF and SC-CBF Systems
Project Overview
This experimental task evaluates the development of an energy dissipation (ED) device for earthquake resistant self-centering steel moment resisting frames (SC-MRFs) with post-tensioned steel moment connections (PT connections). This work is part of the research being conducted by a group led by Lehigh University in collaboration with Princeton and Purdue Universities under the NSF funded NEESR-SG research program. Previous work demonstrates that steel MRFs with PT connections can achieve good performance under the design earthquake by reducing inelastic deformations and returning the structure to its pre-earthquake position. However, additional research is required with respect to energy dissipation (ED) of the connections. The scope of this study included the assessment of various ED devices for use in a PT connection. The ED devices were evaluated based on: energy dissipation capability, material characterization, distortion, capacity, device constructability, and life-cycle/maintenance characteristics. Various devices were assessed and friction devices were chosen for use as an ED device for the connection in the form of a bottom flange friction device (BFFD). The BFFD consists of a vertically oriented slotted plate shop welded to the bottom beam flange as well as two outer built-up angles field bolted to the column. Sandwiched between the two outer angles are brass friction plates on each side of the slotted plate. The slots are over-sized in order to allow for rotation of the connection. High strength bolts with disc-spring washers provide the normal force, compressing the entire assembly together. The BFFD is simple to construct and install, lacks interference with the composite slab, and has good energy dissipation characteristics. A simple analytical model for expressing the cyclic moment-relative rotation behavior of a PT connection with a BFFD was developed. A series of large-scale tests were conducted to experimentally evaluate the BFFD. The parameters evaluated in these tests included the level of friction force and keeper angles to minimize the lateral and transverse movement of the beam end at the beam-column interface. The effect of these parameters on the development of the limit states of the BFFD and subsequent effect on the connection behavior were studied. All tests were conducted using a cyclically symmetric loading protocol with the exception of one test which used an earthquake response loading. The results of the tests demonstrate that the BFFD is a viable way to dissipate energy in a PT steel moment connection for a SC-MRF.
Participants
Graduate Research Assistants
- Mike Wolski, Lehigh University
- Mark Dobossy, Princeton University
- J. Li, Princeton University
- Y. Wang, Princeton University
- Hoseok Chi, Purdue University
Post-Doctoral Research Associates
- Kyung-Sik Lee, Lehigh University
- Choung-Yeol Seo, Lehigh University
Faculty Principal Investigators
- Richard Sause, Lehigh University
- James Ricles, Lehigh University
- Maria Garlock, Princeton University
- Erik VanMarcke, Princeton University
- Li-Shiuan Peh. Princeton University
- Judy Liu, Purdue University
- K.-C. Tsai, NCREE, National Taiwan University