Building a safer medical centre
The long-term social and economic costs of earthquakes are highly dependent on how the built environment responds to the event. Critical infrastructure, such as hospitals, power stations and key lifeline bridges must be available directly after an event to ensure optimal response and to minimise disruption. However, longer-term, economic damage arises from the inability of businesses to return to regular operation due to structural and non-structural damage. Minimal long-term economic impact is essential to minimising the costs to the city, region and country. Low-damage structures are an emerging area of research and development that offer the opportunity to achieve these goals and create more resilient cities and communities.
Low-damage structures have, at their heart, a range of novel energy dissipation devices. These devices are placed to dissipate energy and mitigate response in replacement of traditional design approaches that rely on structural yielding and damage to achieve these goals. However, the novel connection designs required necessitate significant changes in thinking. As a result, the uptake of these devices has been very slow, which has thus prevented the development of robust design methodologies and devices.
A research program established by the MBIE Natural Hazards Research Platform (NHRP) has addressed these needs by developing a range of high performance dissipation devices. The outcome of this NZ lead research is the first implementation of these devices in a new clinical building that is one of the very first new structures to rise in downtown Christchurch after the devastating events of 2010-2011.
This new structure (see artist rendering) designed by Alan Reay Consultants Ltd will be constructed by mid 2013, and fitted out by the end of 2013. The structure uses a post-tensioned rocking steel system to allow controlled motion in an earthquake. It contains a range of novel devices and systems designed to ensure it is immediately usable after a major earthquake that could be even larger than those recently experienced. In particular, it uses a range of novel NZ designed devices including high force to volume (HF2V) and sliding friction connections created at the Universities of Canterbury and Auckland.
HF2V devices are a lead-extrusion based device that plastically extrudes lead to absorb energy and reduce response – much like making Play-Doh spaghetti or squeezing toothpaste out of a tube. Picture 2 shows the 96 HF2V devices for the Kilmore St Medical Centre, fabricated under a contract with Alan Reay Consultants Ltd and the building owner Nobby Holdings Ltd. Sliding friction devices use slotted steel plates and different shim materials to reduce the relative motion between structural elements through friction.
Both energy dissipation techniques absorb energy to reduce structural response without damage to structural elements. Importantly, both device types have been extensively tested in laboratory conditions through the Low-Damage Bridges and Composite Solutions NHRP funded research programs, but will now see their first use in protecting communities.
These NHRP funded projects have been a collaboration between Professor Geoff Chase, Associate Professor Greg MacRae and Dr Geoff Rodgers at the University of Canterbury, and Dr. Charles Clifton at the University of Auckland, as well as multiple postgraduate students.
Together, through the collaborative nature of these projects, we have developed a full package of devices to implement low damage structures, built these devices in NZ with local partners C&M Technologies, and taken them to the first implementation in the Kilmore St Medical Centre leading the emergence of the new down town Christchurch.