Retrofit Solutions Wellington

Overview of Seismic Assessment and Retrofit of Pre-1970s Reinforced Concrete Buildings

Principal Researcher: Stefano Pampanin
Staff involved: Athol Carr, Des Bull ,
Students involved: Eric Hertanto, Chen T-T, Dion Marriott, Matt Ireland, Kam Weng Yuen, Umut Akguzel, Patricio Quintana Gallo, Mario Galli, Gabrielle Attanasi,

With the introduction of the Building Act 2004 (DBH, 2004) extending the scope of buildings that could be categorised as earthquake-prone, the significant risks associated with substantial damage and global collapse of existing reinforced concrete (rc) moment-resisting frames is legally recognised. Prior to that, only unreinforced masonry structures are considered (legally) as earthquake-prone buildings (since 1931 Napier earthquake & introduction of NZS95:1939).

Designed prior to the introduction of modern seismic design codes in the mid-1970s, these rc frames generally have inadequate lateral capacity, detailing for ductile behaviour and capacity design considerations; thus they are particularly susceptible to soft-storey collapse or other brittle element failures (NZSEE, 2006). The urgent need for economical and effective seismic retrofit techniques for rc structures is further highlighted in the recent devastating Sichuan Earthquake, China 2008.

Experimental testing of beam-column (bc) joint sub-assemblages (Aycardi et al., 1994; Park, 2002) and rc frames (Calvi et al., 2002) have shown that the excessive damage or failure of bc joints, in particular exterior (or corner) joints, can lead to the global collapse of a building or a large portion of the structure. The poor joint behaviour of older construction can be attributed to: the inadequate shear reinforcement in joint, the poor bond properties of plain round bars reinforcement, the deficient anchorage details into the joint and absence of capacity design (Hakuto et al., 1997; Aizhen, 2001).

In lieu of these socio-politics and research developments, the research at the University of Canterbury focussed on a range of research topics with regards to assessment and retrofit of pre-1970s R.C. buildings.

Seismic Assessment:

        • Seismic Vulnerability of RC Buildings - Risk and Vulnerability Study
        • Seismic performance & Assessment of Beam-Column Joint - Experimental and Numerical
        • Exterior Corner Beam-column joints under Bi-axial loading and Variation of Axial Load
        • 3D Refined FEM Modelling of Beam-column Joints using fracture-mechanics based micro-plane concrete modelling.
        • Modelling of existing RC frames within macro-modelling approach and the relevant hysteresis model developement.
        • Standard assessment tools for practitioner engineers for rc frame assessment
        • Displacement-based seismic retrofit design - conceptual and refined procedure
        • Modelling and assessment of rc frame with masonry infills

Retrofit Solutions:

        • Conventional retrofit strategies and techniques
        • Metallic Haunch Retrofit of Beam-Column Joint 
        • FRP Retrofit Strategies for Beam-column joint 
        • Advanced Concepts & Materials for Seismic Retrofit
        • Selective Weakening Retrofit for Walls
        • Selective Weakening Retrofit for Beam-column joints and RC Frame

        Please select the relevant link at the side tab for more details of each research topic.