LASSIE: Low life cycle cost Sand-wich Isolation System for Seismic Risk Reduction

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LASSIE is an innovative, inexpensive technology for improving the safety and resilience of structures in earthquake regions. Through cutting edge research, world-class UK-based experimental facilities, international collaboration, and synergies with UK industry it builds upon existing research developments to qualify a new design method of seismic isolation in both developed and developing countries. The aim is to create a novel, low-cost sliding isolation system that will be a quantum leap forwards in the design of new seismically protected low-rise buildings. This technology will ensure life-safety for beyond design level earthquakes and significantly reduce life-cycle costs by maintaining full post-earthquake operability. In many cases, an earthquake causes the ground underneath a building to move, predominately, side-to-side (horizontally) and so it drives the building to oscillate from side-to-side (horizontally). These potentially large building oscillations must be mitigated in some way and typically this is achieved by permitting the building to absorb this aberrant kinetic energy by permitting damage (in the form of ductile deformations) to occur within the building. While this capacity design approach is widely adopted, it does impose a large financial repair/rebuild cost on society after a design level earthquake. This cost is compounded by economic downturns generated by the 'loss of use' of many large and important infrastructure artefacts. An alternative approach is seismic isolation systems which seek to partially uncouple the ground from the building at the foundation level. By permitting sliding to occur at the foundation level between the ground and the building, the building is 'released' from the ground and hence is subjected to a much-reduced level of seismic excitation. Consequentially, this either greatly reduces structural damage or enables the superstructure to remain undamaged during the design earthquake. However, the seismic isolation systems require expensive foundation/basement to accommodate them and, although overall costs are currently reducing, their widespread adoption is still not viewed as universally financially justifiable. Nevertheless, the concept that a building can be uncoupled from the damaging effects of the ground movement produced by a strong earthquake would be very appealing if costs can be reduced for ordinary residential buildings, whose large contribution to the building stock effectively drives the cost of seismic safety. Thus, the aim of this proposal is to develop a low life-cycle cost 'sand-wich' seismic isolation system that will ensure full-life safety and full post-event building operability. This proposed system is composed of a thick reinforced concrete (RC) foundation slab sitting above a 'sand-wich' layer (PVC/sand/PVC) which permits sliding to occur during large ground excitations. The novel re-centring of this sliding system is achieved by a combination of normally loaded, sliding cables (that run through ungrouted ducts within the RC ground slab) and a group of micropile/anchors and ring beam. This system makes use of state-of-the-art non-smooth nonlinear dynamics theory (slip-stick behaviour), the nonlinear elastic behaviour of geometrically loaded cables and dynamic/shock loaded soil-structure interaction of micropile groups. In this proposal every element/component of the novel design shall be tested experimentally in the newly commissioned 'UKCRIC - Bristol Soil-Foundation-Structure Interaction Facility (SoFSI)' EP/R012806/1 and computationally to ensure the performance of the proposed design is validated within a Technology Readiness Level (TRL) Framework methodology.