NZSEE Conference 2024 Wellington
The Seismic Assessment of Existing Buildings Guideline, Section C4: Geotechnical Considerations, was first published in July 2017. That first issue included several aspects of assessment which had not been previously applied, including allowance for the non-linear behaviour of soils (geotechnical step change). Show more…The subsequent 6 years have provided the opportunity to apply the geotechnical step change methodology to various building assessments and to obtain feedback. This has highlighted the need to clarify and further develop the geotechnical step change methodology. A project is now in progress to update C4. This paper reports on the likely conclusions of the update project. Those conclusions are yet to be recorded in an update of C4. The update to C4 is to clarify the purpose of the step change factor of 2. The purpose of that factor is to provide an assessed %NBS which represents a buffer from loss of gravity support of the structure. A method has been developed to vary the step change factor between 1 and 2 depending on the ability of the structure to maintain gravity support and the life safety consequences of loss thereof. The step change methodology has been extended to cover earthquake induced ground displacements which are not covered by the current C4. Guidance is to be provided on the level of conservatism to be applied in evaluating geotechnical parameters and allowance for uncertainty. It is also proposed to enhance the guidance on desk top studies and other aspects of geotechnical assessment. Show less…
