Buildings subject to earthquake shaking will tend to move not only horizontally but also rotate in plan. In-plan rotation is known as “building torsion” and it may occur for a variety of reasons, including stiffness and strength eccentricity and/or torsional effects from ground motions. Methods to consider torsion in structural design standards generally involve analysis of the structure in its elastic state. This is despite the fact that the structural elements can yield, thereby significantly altering the building response and the structural element demands. If demands become too large, the structure may collapse. While a number of studies have been conducted into the behavior of structures considering inelastic building torsion, there appears to be no consensus that one method is better than another and as a result, provisions within current design standards have not adopted recent proposals in the literature. However, the Canterbury Earthquakes Royal Commission recently made the recommendation that provisions to account for inelastic torsional response of buildings be introduced within New Zealand building standards. Consequently, this study examines how and to what extent the torsional response due to system eccentricity may affect the seismic performance of a building and considers what a simple design method should account for. It is concluded that new methods should be simple, be applicable to both the elastic and inelastic range of response, consider bidirectional excitation and include guidance for multi-story systems.
During the 21st century, New Zealand has experienced increasing public concern over the quality of the design and appearance of new developments, and their effects on the urban environment. In response to this, a number of local authorities developed a range of tools to address this issue, including urban design panels to review proposals and provide independent advice. Following the 2010 and 2011 Canterbury earthquake sequence, the commitment to achieve high quality urban design within Christchurch was given further importance, with the city facing the unprecedented challenge of rebuilding a ‘vibrant and successful city’.
The rebuild and regeneration reinforced the need for independent design review, putting more focus and emphasis on the role and use of the urban design panel; first through collaboratively assisting applicants in achieving a better design outcome for their development by providing an independent set of eyes on their design; and secondly in assisting Council officers in forming their recommendations on resource consent decisions. However, there is a perception that urban design and the role of the urban design panel is not fully understood, with some stakeholders arguing that Council’s urban design requirements are adding cost and complexity to their developments.
The purpose of this research was to develop a better understanding on the role of the Christchurch urban design panel post-earthquake in the central city; its direct and indirect influence on the built environment; and the deficiencies in the broader planning framework and institutional settings that it might be addressing. Ultimately, the perceived role of the Panel is understood, and there is agreement that urban design is having a positive influence on the built environment, albeit viewed differently amongst the varying groups involved. What has become clear throughout this research is that the perceived tension between the development community and urban design well and truly exists, with the urban design panel contributing towards this. This tension is exacerbated further through the cost of urban design to developers, and the drive for financial return from their investments.
The panel, albeit promoting a positive experience, is simply a ‘tick box’ exercise for some, and as the research suggests, groups or professional are determining themselves what constitutes good urban design, based on their attitude, the context in which they sit and the financial constraints to incorporate good design elements. It is perhaps a bleak time for urban design, and more about building homes.
