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- To: <seaint(--nospam--at)seaint.org>
- Subject: Pall Friction-Dampers
- From: "Avtar Pall" <palldynamics(--nospam--at)email.msn.com>
- Date: Mon, 14 Sep 1998 19:21:32 -0400
The development of Pall friction-dampers was pioneered in the late seventies. These dampers have successfully gone through rigorous proof testing on shake tables at the University of California (1987) and at the University of British Columbia (1985). Pall friction-dampers have been used in more than 30 projects of new construction as well as retrofit of existing buildings in Canada and the U.S. Several more are under construction or in the design phase. Pall friction-dampers are simple and fool proof in construction. Basically, these consist of a series of specially treated steel plates clamped together to develop very reliable friction. Their performance is reliable, repeatable and they possess large rectangular hysteresis loops with negligible fade. They are not temperature or velocity dependent. For a given force level, a much greater quantity of energy can be dissipated in friction than any other method so fewer Pall friction-damping devices are required to dissipate seismic energy. These are designed not to slip during wind. During a major earthquake, the dampers slip before yielding of structural members. After the earthquake, the strain energy of the structure forces the dampers to near original alignment. There is nothing to damage or leak, hence they need no maintenance, repair or replacement after the earthquake. Patented Pall friction-dampers are available for bracing in framed buildings: tension cross bracing, tension/compression single diagonal bracing, and chevron bracing. Pall friction-connectors are also available for frame cladding, and for use at expansion joint of adjacent buildings to avoid pounding. Buildings with friction dampers require the use of nonlinear time history dynamic analysis. Several computer programs such as DRAIN-2DX, DRAIN-3DX, DRAIN-TABS, E-TABS (nonlinear), SAP2000 etc. are available. Modeling of Pall friction-dampers is very easy. Since the hysteretic loop of Pall friction-damper is similar to rectangular loop of an ideal elasto-plastic material, the dampers are modeled as a plastic element. Slip load represents fictitious yield force. FEMA 273 /274 ?NEHRP Guidelines for the Seismic Rehabilitation of Buildings? provide guidelines on the analysis of buildings with friction-dampers. References: Aiken, I.D., Kelly, J.M., Pall, A.S., 1988, "Seismic Response of a Nine-Story Steel Frame with Friction- Damped Cross-Bracing", Report No. UCB / EERC-88/17. Earthquake Engineering Research Centre, the University of California at Berkeley, PP. 1-7. Filiatrault, A., Cherry, S., 1986, ?Seismic Tests of Friction-Damped Steel Frames?, Proceedings Third Conference on Dynamic Response of Structures, ASCE, Los Angeles. Hale, T., Tokas, C., Pall, A., 1995, ?Seismic Retrofit of Elevated Water Tanks at the University of California at Davis?. Proceedings, Seventh Canadian Conference on Earthquake Engineering, Montreal, PP. 959-966. Pall, A.S., Marsh, C., Fazio, P., 1980, ?Friction Joints for Seismic Control of Large Panel Structures?, Proceedings, Journal of Prestressed Concrete Institute, Vol.. 25, No. 6, PP. 38-61. Pall, A.S., Marsh, C., 1981, ?Friction Damped Concrete Shearwalls?, Journal of American Concrete Institute, No. 3, Proceedings, Vol.. 78, PP. 187-193. Pall, A.S., Marsh, C., 1982, ?Seismic Response of Friction Damped Braced Frames?, ASCE, Journal of Structural Division, Vol.. 108, St. 9, June 1982, PP. 1313-1323. (Recipient ?Raymond C. Reese Research Prize1983? ASCE). Pall, A.S., Verganelakis, V., Marsh, C., 1987, ?Friction-Dampers for Seismic Control of Concordia University Library Building?, Proceedings Fifth Canadian Conference on Earthquake Engineering, Ottawa, PP. 191-200. Pall, A., 1989, ?Friction-Dampers for Economic Seismic Design?, Proceedings, Structures Congress ?89, San Francisco, PP.159-166. Pall, A.S., 1989, ?Friction Damped Connections for Precast Concrete Cladding?, Proceedings, PCI- Architectural Precast Concrete Cladding - Its Contribution to Lateral Resistance of Buildings, PP. 300-309. Pall, A.S., Pall, R., 1993, ?Friction-Dampers Used for Seismic Control of New and Existing Buildings in Canada?, Proceedings, ATC 17-1, Seminar on Seismic Base Isolation, Passive Energy Dissipation and Active Control, San Francisco, Vol.. 2, PP. 675-686. Pall, A., Vezina, S., Proulx, Pall, R., 1993, ?Friction-Dampers for Seismic Control of Canadian Space Agency Headquarters?, Journal Earthquake Spectra, Vol.. 9, Number 3, PP. 547-557. Pall, A., Pall, R., 1996, ?Friction-Dampers for Seismic Control of Buildings ? A Canadian Experience?, Eleventh World Conference on Earthquake Engineering, Mexico, Paper # 497. Pasquin, C., Pall, A.S., Pall, R., 1994, ?Hi-Tech Seismic Rehabilitation of Casino de Montreal?, ASCE Structures Congress, Atlanta, PP. 1292-1297. Savard, G., Lalancette, J.R., Pall, R., Pall, A., 1995, ?High Tech Seismic Design of Maison 1 McGill, Montreal?, Proceedings, Seventh Canadian Conference on Earthquake Engineering, Montreal, PP. 935-942. Vezina, S., Proulx, P., Pall, R., Pall, A., 1992, ?Friction-Dampers for Aseismic Design of Canadian Space Agency?, Proceedings, Tenth World Conference on Earthquake Engineering, Madrid, Spain, PP. 4123-4128. Wagner, P., Vavak, L., Pall, R., Pall, A., 1995, ?Seismic Rehabilitation of the New Hamilton Court House?, Proceedings, Seventh Canadian Conference on Earthquake Engineering, Montreal, PP. 951-958. Pasquin, C., Charania, H., Steele, R., Pall, A., Pall, R., 1998, ?Friction-Dampers for Seismic Control of Selkirk water Front Offices, Victoria?, Proceedings, Sixth U.S. National Conference on Earthquake Engineering, Seattle. Elliot, J., McCaffrey, G., Guruswamy, G., Pall, R., Pall, A., 1998, ?High-Tech Seismic Rehabilitation of Justice Headquarters Building, Ottawa?, Proceedings, Structural Engineers World Congress, San Francisco, Paper No. T189-3. For more information, please contact: Avtar Pall, Ph. D., P.Eng. Pall Dynamics Limited 100 Montevista, D.D.O. Montreal, Quebec Canada H9B 2Z9 Tel: (514) 412-2605 Fax: (514) 684-8185 Email: PallDynamics(--nospam--at)msn.com
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