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The Canterbury Earthquake Sequence (CES) of 2010 – 2011 caused widespread liquefaction related land damage to the city of Christchurch. This paper addresses the impact the CES had on the eastern Christchurch suburb of North New Brighton with emphasis on the ground condition at the time of the initial 4 September 2010 earthquake, as well as subsidence caused by the CES, and the future potential for increased liquefaction vulnerability due to Sea Level Rise (SLR). Subsidence at North New Brighton accumulated throughout the CES due to a reduction in volume of the soil profile through liquefaction; and overall settlement due to regional tectonic subsidence. The total amount of subsidence caused by the CES at North New Brighton was as much as 1 m in some places and this has changed the relationship between the position of the ground surface and the top of the groundwater table. A reduction in thickness of the non-liquefying layer has been shown to increase the vulnerability of the soil profile to liquefaction related land damage during earthquake events. As a coastal suburb, North New Brighton is vulnerable to the impact of SLR and this paper considers the response of the groundwater table to rising sea level and the influence this will have on the thickness of the non-liquefying layer and liquefaction vulnerability.
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Recent earthquakes have highlighted discrepancies between the intended and observed performance of RC walls and significant research is in progress to improve the seismic performance of RC wall buildings. An international group of researchers and practitioners developed a research framework in order to conduct a project mapping and prioritisation exercise for RC wall research. The process by which this research framework and mapping exercise were conducted is described. The framework was used to identify research priorities that would provide a basis for the direction of future research. High priority topics included, shear demands and capacities, effect of load-rate and loading history, seismic assessment of older walls, residual capacity and repairability, non-rectangular and core walls, and whole of building response.
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This paper discusses the application of the Structural Performance factor (SP) within a Direct Displacement-Based Design framework (Direct-DBD). As stated within the New Zealand loadings standard, NZS1170.5:2004 [1], the SP factor is a base shear multiplier (reduction factor) for ductile structures, i.e. as the design ductility increases, the SP factor reduces. The SP factor is intended to acknowledge the better-than-expected structural behaviour of ductile systems (both strength, and ductility capacity) by accounting for attributes of response that designers are unable to reliably estimate. The SP factor also recognizes the less dependable seismic performance of non-ductile structures, by permitting less of a reduction (a larger SP factor) for non-ductile structures. Within a traditional force-based design framework the SP factor can be applied to either the design response spectrum (a seismic hazard/demand multiplier), or as a base shear multiplier at the end of design (structural capacity multiplier) – either of these two approaches will yield an identical design in terms of the required design base shear and computed ULS displacement/drift demands. However, these two approaches yield very different outcomes within a Direct-DBD framework – in particular, if SP is applied to the seismic demand, the design base shear is effectively multiplied by (SP)2 (i.e. a two-fold reduction). This paper presents a “DBD-corrected” SP factor to be applied to the design response spectrum in Direct-DBD in order to achieve the intent of the SP factor as it applies to force-based design. The proposed DBD-corrected SP factor is attractive in that it is identical to the SP relationship applied to the elastic site hazard spectrum C(T) for numerical integration time history method of analysis within NZS 1170.5:2004 [1], SP,DDBD = (1+SP)/2.
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Dynamics of structures by Ray W. Clough and Joseph Penzien. McGraw-Hill 1975. 634 pp. illus.
Seismic risk and engineering decisions. C. Lomnitz and E. Rosenbleuth (Editors). Elsevier, 1976, 425 pages.
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Title:
Dynamic Behaviour of Concrete structures - Report of the RILEM 65 MDB Committee" being vol. 13 in the Developments in Civil Engineering Series
Editor: G. P. Tilly
Title: "Analysis of Dynamic Effects on Engineering Structures" being volume 16 in the Developments in Civil Engineering Series.
Authors: M. Bata and V. Placy
Title: "Earthquake Engineering - Fifth Canadian Conference"
Publisher: A. A. Balkema, Rotterdam, 1987
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"Earthquake Design Practice for Buildings"
Author: David E. Key
"Earthquake Resistant Design for Engineers and Architects" (second edition)
Author: David J. Dowrick
"In Spite of His Time - A Biography of R.C. Hayes, Earthquake Pioneer, Astronomer, Musician"
Author: Margaret Hayes
