This research strand identifies characteristics and processes that enhance and facilitate a faster recovery back to the level of day-to-day household and community stability prior to a natural disaster.
There are two key research programmes falling within this theme:
Seismic Response of Underground Services
During the earthquakes in Canterbury many underground utility services were damaged. Utility owners and providers now face the huge task of assessing and repairing the damage. Much of the repair is being prioritised to keep a minimum service level available. A major task ahead is to assess the underground networks to determine what the current performance level is in order to help plan asset management and maintenance activities and to provide insurance recommendations. An integral part of the assessment is to optimise and develop robust systems, products, and guidelines that will reduce the damage during future earthquakes.
Existing New Zealand design guidance for buried pipelines only takes account of static soil loads and of operational loads. Older and established systems represent the majority of pipelines in New Zealand. Many of these existing systems have changed in service through deterioration or physical wear and tear, which may influence how they respond to seismic loading. In addition, the suitability of material types for new pipes for New Zealand conditions has at best been poorly established.
This four-year, MBIE-funded research project will provide enhanced understanding of the performance and resilience of underground utilities under seismic loading within the Christchurch area. Recommendations and guidelines will be developed to enable New Zealand to be able to minimise disruption and increase the 'bounce back' capability of communities after a seismic event.
Overarching Research Objectives:
- To use the information being gathered on the performance of pipeline systems during the earthquake events to understand how and why damage occurred; and,
- How do business locations contribute to individual and city-wide business recovery?
- To use this understanding to provide robust guidance on how to prevent or mitigate damage to new and to existing systems in future seismic events.
To increase our knowledge of the damage within the Christchurch area, a GIS database of damage data and state of the art 3D geological information (GNS Science) will be brought together. Initial findings will be further analysed by undertaking large scale physical testing to assess parameters in design.
A feature of this research will be the prediction of the remaining life of existing underground utilities. Building on past work, and the physical and numerical analysis mentioned above, methodologies will be developed to enable the prediction of residual life. The testing and analysis will provide knowledge to drive a suite of fragility functions that incorporate both shaking and ground deformation for risk analysis. This will facilitate better decision-making regarding the positioning of underground utilities within the Christchurch area and the enhanced asset management methodologies developed will be applicable throughout New Zealand.
- Dr Rosslyn McLachlan
- Dr Steve Bagshaw
- Dr Jonathan Morris
- Dr Padmanathan (Kathir)gamanathan
- Jasmin Callosa-Tarr
- Shaun Cook
Collaborators: Dr Mostafa Nayyerloo, GNS Science
Wind Speed Hill Shape Multipliers
New Zealand's hilly geography, the location of its urban areas, and the country's location within the 'roaring forties' means that wind loadings are an important consideration when it comes to our building codes. As storms regularly cause damage to the built environment, being able to accurately predict wind speeds will lead to more resilient communities.
The New Zealand Wind Engineering Consortium has been investigating how to reduce the vulnerability of New Zealand's built environment to wind damage by improving procedures for estimating design wind speeds. The consortium consists of an informal group of scientists from NIWA, GNS Science, Opus Research and the University of Auckland's Engineering Department.
Hilly terrain can increase the winds speed by up to threefold, compared to nearby flat land. This effect is calculated as the ratio of wind speed over a hill divided by the wind speed at a nearby, upstream flat site and is commonly known as the hill-shape multiplier. The multiplier is very important when considering the impact of wind on buildings and structures located on hilly sites.
Overarching Research Question:
- How good are estimates of wind loads for structures in rugged terrain where direct wind measurements are not available?
During February 2011, the Wellington region withstood an 18-hour period of severe gale force northwesterlies. Wind speeds were measured along a line of anemometers running from west to east across Belmont Regional Park (Fig. 1 and Fig. 2). The speeds at the top of these hills have been compared with speeds observed at a nearby site unaffected by the hills, allowing hill-shape multipliers to be calculated.
As well as using actual measurements, the event was also simulated in a number of ways: computational fluid dynamic (CFD) computer modelling using Gerris (Fig. 3), wind tunnel testing (Fig. 4), and an empirical model (WASP).
These simulations can be used to evaluate the accuracy of the current Wind Loading Standard (WLS) that is used to estimate wind loading on structures.
While the results from CFD and wind tunnel modelling agreed quite well with the measured hill-shape multipliers-mostly within 15 percent and frequently within 5 percent-there was a large variation from the current WLS. Applying the current WLS resulted in a variance from measured values by as much as 40 percent.
Further Field Studies and Modelling:
Further field studies and modelling for a greater range of wind speeds, directions and mast heights will be made with the aim of improving the WLS to make it more relevant to New Zealand conditions.
- Dr Mike Revell, NIWA, Research Leader
- Paul Carpenter, Opus Research
- Peter Cenek, Opus Research
- Richard Flay, Department of Mechanical Engineering,
University of Auckland
- Andrew King, GNS Science
- Dr Mostafa Nayyerloo, GNS Science
- Dr Richard Turner, NIWA