Weng Yuen Kam
University of Canterbury
PhD Candidate
2006 – 2009
Supervisors: Assoc. Prof. Stefano Pampanin, Prof. Athol Carr, Adjunct Prof Des Bull, Asst Prof. Alessandro Palermo
External Funding: Christchurch Heritage Trust Scholarship 2007, UC Departmental Travel Grant
Area of interest:
Selective weakening retrofit, seismic retrofit of reinforced concrete
structures, earthquake engineering,
advanced structural systems.
Doctoral Research:
The significant risks of existing reinforced concrete (rc) structures designed prior to the introduction of modern seismic design codes are well acknowledged. The vulnerabilities of rc structures, particular moment-resisting frames are well researched and documented. Our recent experiences with large earthquakes near urban developed centers (e.g Northridge, 1994 and Chi-Chi, 1999) as well as large population centers (e.g. Sichuan, China 2008 and Bam, Iran 2003) further highlight the urgent need for economical and effective seismic retrofit techniques for these structures.
Current seismic retrofitting strategy and techniques for pre-1970s rc buildings commonly focused on either strengthening (e.g. locally by using concrete or fibre-reinforced polymers, FRP jacketing, or globally by adding structural walls/braces), or dampening/isolating the building. On a mass-scale seismic rehabilitation scheme, such extensive retrofit might have their drawbacks especially in terms of cost, invasiveness and effectiveness. For example, over-strengthening a structure might lead to costly foundation upgrades, while base-isolation is often uneconomical for typical structures.
Instead, designer can selectively retrofit (upgrade) for ductility, stiffness and strength of critical elements. This has been previously proposed and extensively investigated in a large-scale European research project (ICONS). This research work then, further developing the selective retrofit incorporating the counter-intuitive approach of selective weakening and the use of un-bonded post-tensioned tendons for retrofit. To achieve various performance levels, selective retrofit can further classified into several solutions (weakening-only, weakening + post-tensioning, post-tensioning only and post-tensioning+ various energy dissipations). One of the retrofit solutions (post-tensioning + energy dissipations (viscous, hysteretic or friction) has been also extended to new structures, termed as Advanced Flag Shaped (AFS) systems. The overall project goal is to investigate the effectiveness and feasibility of the selective retrofit strategy. Towards this goal, extensive experimental campaign on 2/3-scaled beam-column joint subassemblies are carried out. The experimental data will supplement both refined finite element modeling and macroscopic macro-element modeling analysis. Outcomes of the numerical studies include design procedure and recommendations. The research will ultimately aim to verify the selective retrofit scheme by constructing and conducting a dynamic test on the shaking-table facility.
This research is funded under the FRST project "Retrofit Solutions for NZ" as well as from industry partners' contribution. Key resources required included laboratory spaces, technical support, materials and high-speed computing hours. High-speed computing facility under the BlueGene (link) project might be utilized if the needs arise.
(Left) As built pre-1970's exterior beam-column joint (Right) Pre-1970's exteriour beam-column joint retrofitted with beam weakening and external post-tensioning. Satisfactory seismic performance up to 4.0% inter-storey drift cycles.
(Left) FEM Modelling of rc beam-column joint before and after retrofit using fracture mechanics-based FE software. (Right) Pre-1970's exteriour beam-column joint retrofitted with beam weakening only. Satisfactory performance up to 2.5% inter-storey drift.
Publications:
Kam, W.Y., Quintana-Gallo, P., Akguzel, U., Pampanin, S. (2010)"Influence of slab on the seismic response of sub-standard detailed exterior reinforced concrete beam column joints." Proc. of 9th US National and 10th Canadian Conf. on Earthquake Eng.,Toronto, Canada. July 25-29 2010. (paper submitted) pdf (coming soon)
Kam, W.Y., Pampanin, S., Bull, D. (2009)"Selective Weakening Retrofit for Existing R.C. Structures – Concept, Validation and Design Example." Proc. of 9th US National and 10th Canadian Conf. on Earthquake Eng.,Toronto, Canada. July 25-29 2010. (paper submitted) pdf (coming soon)
Kam, W.Y., Pampanin, S., Palermo, A., Carr, A. (2009) "Self-centering structural systems with combination of hysteretic and viscous energy dissipations." Earthquake Eng. and Struct. Dyn. (EESD) - in press
Kam, W.Y., Pampanin, S. (2009)"Experimental and Numerical Validation of Selective Weakening Retrofit for Existing Non-Ductile R.C. Frames." Proc. of 2009 ATC-SEI Conference, San Francisco, CA, USA. Dec 9-11 2009. pdf (coming soon)
Kam, W.Y., Pampanin, S., Bull, D. (2009)"Experimental Validation of Selective Weakening Approach for the Seismic Retrofit of Exterior Beam-Column Joints." Proc. of 2009 NZSEE Conference, Christchurch, New Zealand. April 2009. (Paper No: 32) pdf and ppt
Kam, W.Y., Pampanin, S. (2008) "Selective Weakening Techniques for Retrofit of Existing Reinforced Concrete Structures" Proc. of 14th World Conf. on Earthquake Eng. (14WCEE) 2008 , Beijing, China. (Paper ID: 05-03-0074) pdf
Kam, W.Y., Pampanin, S., Palermo, A., Carr, A. (2008) "Implementation of Advanced Flag-Shape (AFS for Moment-resisting frame structures" Proc. of 14th World Conf. on Earthquake Eng. (14WCEE) 2008 , Beijing, China. (Paper ID: 05-06-0129) pdf
Kam, W.Y., Pampanin, S., Palermo, A., Carr, A. (2008) "Design Procedure and Behaviour of Advanced Flag-Shape (AFS) MDOF Systems" Proc. of 2008 NZSEE Conf., Wairakei, New Zealand. pdf
Kam, W.Y., Pampanin, S., Palermo, A., Carr, A. (2007) "Advanced Flag-Shaped Systems for High Seismic Performance including Near-fault Effects" Proc. of 2007 NZSEE Conf., Palmerston North, New Zealand. (Best Research Paper Award) pdf
Kam, W.Y., Pampanin, S., Palermo, A., Carr, A. (2006) "Advanced Flag-Shaped for High Seismic Performance." 1st ECEES Conf., Geneva, Switzerland. [reprinted with permission] pdf
Contact details:
Kam Weng Yuen
Department of Civil and Environmental Engineering
The University of Canterbury
Private Bag 4800
Christchurch
New Zealand 8020
email: wyk10 (at) student.canterbury.ac.nz