Dynamic Testing of Precast, Post-Tensioned Rocking Wall Systems with Alternative Dissipating Solutions

A. Palermo

Technical University of Milan, Italy

S. Pampanin, D. Marriott and D. Bull

Department of Civil Engineering, University of Canterbury, Christchurch, New Zealand

Presented at New Zealand Society for Earthquake Engineering Annual Conference (NZSEE08), New Zealand, 2008.

During the past two decades, the focus has been on the need to provide communities with structures that undergo minimal damage after an earthquake event while still being cost competitive. This has led to the development of high performance seismic resisting systems, and advances in design methodologies, in order respect this demand efficiently.

This paper presents the experimental response of four pre-cast, post-tensioned rocking wall systems tested on the shake-table at the University of Canterbury. The wall systems were designed as a retrofit solution for an existing frame building, but are equally applicable for use in new design. Design of the wall followed a performance-based retrofit strategy in which structural limit states appropriate to both the post-tensioned wall and the existing building were considered.

Dissipation for each of the four post-tensioned walls was provided via externally mounted devices, located in parallel to post-tensioned tendons for re-centring. This allowed the dissipation devices to be easily replaced or inspected following a major earthquake. Each wall was installed with viscous fluid dampers, tension-compression yielding steel dampers, a combination of both or no devices at all – thus relying on contact damping alone. The effectiveness of both velocity and displacement dependant dissipation are investigated for protection against far-field and velocity-pulse ground motion characteristics.

In recent literature the performance of structures with unbonded post-tensioning undergoing controlled rocking at discrete locations has highlighted significant improvements to their structural performance when compared to equivalently reinforced monolithic counterparts; for use in buildings (Priestley et al. 1999), (Kurama 2002), (Pampanin 2005) and bridge systems (Mander and Cheng 1997), (Palermo et al. 2005). This enhanced performance relates to inelastic deformation being lumped to a number of specifically designed and detailed, discrete rocking interfaces. The ratio of the prestressed reinforcement (and axial load) to the non-prestressed reinforcement dictates the energy dissipation and re-centring of the wall system – these two parameters give an indication of the expected maximum displacement and residual deformation of the wall system following dynamic response. This technology has been codified both internationally (ACI:T1.2-03 2007) and nationally in Appendix B of the New Zealand code (NZS3101 2006) and is termed Hybrid or Controlled Rocking Technology.

Further to the United States PRESSS (PREcast Seismic Structural Systems) program, a significant amount of work (largely analytical) was undertaken to further understand the behaviour of unbonded post-tensioned precast wall systems for use in seismic regions (Kurama et al. 1998a), (Kurama et al. 1998b). This work was extended to include the response of hybrid rocking wall systems with externally mounted viscous dampers (Kurama 2000), originally limited to internally grouted mild steel reinforcement (Kurama 2002).

Past research at the University of Canterbury has also investigated similar systems with minor variations on the detailing of the precast wall unit – specifically concerning protection of the rocking toe region (Rahman and Restrepo 2000), (Holden 2001).

References

NZSEE. 2005. Assessment and Improvement of the Structural Performance of Buildings in Earthquake. Department of Building and Housing.

NZS3101. 2006. Concrete Structures Standard: Part 1-The Design of Concrete Structures. Wellington: Standards New Zealand.

Palermo, A., Pampanin, S. & Calvi, G. M. 2005. Concept and Development of Hybrid Solutions fro Seismic Resistant Bridge Systems, Journal of Earthquake Engineering Vol 9(5) 1-23.

Priestley, M. J. N., Sritharan, S., Conley, J. R. & Pampanin, S. 1999. Preliminary results and conclusions from the PRESSS five-story precast concrete test building, PCI Journal, Vol 44(6) 42-67.

Priestley, M. J. N., Calvi, G. M. & Kowalsky, M. J. 2007. Displacement-Based Seismic Design of Structures. Pavia: IUSS.

Pampanin, S. 2005. Emerging solutions for high seismic performance of precast/prestressed concrete buildings, Journal of Advanced Concrete Technology, Vol 3(2) 207-223.

SEAOC. 1999. Recommended Lateral Force Requirements and Commentary. Structural Engineers Association of California.

Rahman, A. M. & Restrepo, J. I. 2000. Earthquake Resistant Precast Concrete Buildings: Seismic Performance of Cantilever Walls Prestressed Using Unbonded Tendons. Christchurch: University of Canterbury.

Kurama, Y. C. 2000. Seismic design of unbonded post-tensioned precast concrete walls with supplemental viscous damping, ACI Structural Journal, Vol 97(4) 648-658.

Kurama, Y. C., Pessiki, S., Sause, R., Lu, L. & El-Sheikh, M. T. 1998a. Analytical Modelling and Lateral Load Behavior of Unbonded Post-Tensioned Precast Concrete Walls. Lehigh University.

Kurama, Y. C. 2002. Hybrid post-tensioned precast concrete walls for use in seismic regions, PCI Journal, Vol 47(5) 36-59.

Kurama, Y. C., Sause, R., Pessiki, S., Lu, L. & El-Sheikh, M. T. 1998b. Seismic Design and Response Evaluation of Unbonded Post-Tensioned Precast Concrete Walls. Lehigh University.

Kurama, Y. C., Sause, R., Lu, L. & Pessiki, S. 1999. Seismic Behaviour and Design of Unbonded Post-Tensioned Precast Concrete Walls, PCI Journal, Vol 44(3) 72-89.

ASCE. 2000. Prestandard and Commentary for the Seismic Rehabilitation of Buildings (FEMA 356). Reston, Virginia: Federal Emergency Management Agency.

ACI:T1.2-03. 2007. ACI Manual of Concrete Practice-Special Hybrid Moment Frames Composed of Discretely Jointed Precast and Post-Tensioned Concrete Members.

BSSC. 2003. NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures (FEMA 450). Washington D.C.: Federal Emergency Management Agency.

BSSC. 1997. NEHRP Guidelines for the Seismic Rehabilitation of Buildings (FEMA 273). Washington D.C.: Federal Emergency Management Agency.

Chase, J. G., Hudson, N. H., Lin, J., Elliot, R. & Sim, A. 2005. Nonlinear Shake Table Identification and Control for near-Field Earthquake Testing, Journal of Earthquake Engineering. Vol. 9, no. 4, pp. 461-482. July 2005.

fib. 2003a. Displacement Based Seismic Design of Reinforced Concrete Buildings. Lausanne, Switzerland: International Federation for Structural Concrete.

fib. 2003b. Seismic Assessment and Retrofit of Reinforced Concrete Buildings. Lausanne, Switzerland: International Federation for Structural Concrete.

fib. 2003c. Seismic Design of Precast Concrete Building Structures. Lausanne, Switzerland: International Federation for Structural Concrete.

Kam, W. Y., Pampanin, S., Carr, A. J. & Palermo, A. 2007. Advanced Flag-Shape Systems for High Seismic Performance including Near-Fault Effects, NZSEE 2007, Palermston North.

Holden, T. J. 2001. A Comparison of the Seismic Performance of Precast Wall Construction: Emulation and Hybrid Approaches. Christchurch: University of Canterbury.

Mander, J. B. & Cheng, C.-T. 1997. Seismic Resistance of Bridge Piers Based on Damage Avoidance Design. New York: University of Buffalo.

Marriott, D., Pampanin, S. & Palermo, A. 2007b. Seismic Design, Experimental Response and Numerical Modelling of Rocking Bridge Piers with Hybrid, Post-Tensioned Connections. Christchurch: University of Canterbury.

Marriott, D., Pampanin, S. & Bull, D. 2007a. Improving the Seismic Performance of Existing Reinforced Concrete Buildings using Advanced Rocking Wall Solutions, NZSEE, Palmerston North, New Zealand.

Mueller, P. 1986. Hysteretic Behaviour of Precast Panel Walls, U.S.-Japan Seminar on Precast Concrete Construction in Seismic Zones, Tokyo, Japan.