Christchurch, New Zealand, experienced four major earthquakes (Mw 5.9 to 7.1) since 4 September 2010 that triggered localized to widespread liquefaction. Liquefaction caused significant damage to residential foundations due to ground subsidence, ground failure, and lateral spreading. This paper describes the land damage assessment process for Christchurch, including the collection and processing of extensive data and observations related to liquefaction, the characterization of liquefaction effects on land performance, and the quantification of losses for insurance compensation purposes. The paper also examines the effectiveness of several existing liquefaction vulnerability parameters and a new parameter developed through this research, Liquefaction Severity Number ( LSN), in explaining the observed liquefaction-induced damage in residential areas of Christchurch using results from 11,500 cone penetration tests (CPTs) as well as a robust regional groundwater model.

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Summary A theory for the strength of concrete and reinforced concrete under the action of combined stresses is advanced, which combines Rankine's maximum principal stress criterion and Coulomb's internal friction criterion. Equations for the strength of plain, reinforced and prestressed concrete in combined bending and torsion are then derived. The distinct difference between primary bending and primary torsion fracture is explained by the dual character of the criterion of failure. It also accounts for the increase in the torsional strength of a reinforced concrete section resulting from the addition of bending. Prestressing delays the formation of tension cracks until the compression due to the initial prestress has been offset, and it therefore effects a very great improvement in the torsional strength of concrete.

Summary: The theories of Rausch and Andersen for the design of torsional shear reinforcement are examined and a more accurate formula is derived, using the strain energy principle. This formula, like that of Rausch, is based on the customary assumptions of the elastic working stress theory. The compound hyperbolic series resulting from the integration of the square of St. Venant's rectangular torsion function is evaluated and reduced to a single constant. This constant is intermediate between those obtained from the approximate theories of Rausch and Andersen.