Basin edge effects and damping
A structural engineer’s view
The Kaikōura earthquake brought the concept of basin effects to the forefront of conversation about building in the Wellington CBD. Local exceedances of ULS design spectra were observed in many waterfront sites in the 1.5-2.5s period range. This, coupled with low yield levels and certain structural forms present in previous generations of building design, meant that significant damage occurred in many buildings around the Wellington waterfront.
A primary cause for the high spectral accelerations was the geological structure of the Wellington CBD. This paper will focus on the behaviour of generic buildings in response to these particular ground motions and suggest how lessons from this can inform the design of future buildings. It uses the Kaikōura Earthquake as the centre point for discussions about the relationship between building behaviour on soft soils and the effects on this of different forms of damping. More broadly, the aim is to help spark debate in the earthquake engineering community on the question: What sorts of structures should we be building on soft soil sites?
This paper has been written in the wake of a number of damaging earthquakes throughout New Zealand, and with the concurrent increase in sophistication and spread of tools for analysing the effects of the ground motions induced by these earthquakes. The genesis of the ideas presented herein was in analysis of many waterfront buildings following the Kaikoura earthquake, and the attempts, often in vain, to match modelled building behaviour- where small tweaks in assumptions could have a radical effect on results- with actual observed damage – where cracks may have been seen in concrete or in partitions, but assessment of actual plastic strains reached in steel bars or beams was basically conjecture.
This paper is broad in scope, therefore cannot possibly give each aspect the coverage of a series of papers which consider them in isolation and in detail. We nonetheless strongly believe that a holistic view of all topics is critical for design, and that the authors as ‘front line’ structural engineers are well positioned to present this. Sincere attempts have been made to justify our point of view with a strong basis in first principles, and backed by nonlinear time history analysis, or by reference to the work of others. We acknowledge that our beliefs are not shared by everyone and that some conclusions are provocative. It is neither the intent nor even the hope that we have the last word on this topic.
Semmens S, Dellow GD and Perrin ND (2010). "It’s Our Fault - Geological and Geotechnical Characterization of the Wellington Central Business District". GNS Science Consultancy Report 210/176, NZ, 52p
Kawase H (1996). "The Cause of the Damage Belt in Kobe: “The Basin-Edge Effect”, Constructive Interference of the Direct S-Wave with the Basin-Induced Diffracted/Rayleigh Waves". Seismological Research Letters, 67(5): 25-34.
Frankel AD, Carver DL and Williams RA (2002). "Nonlinear and linear site response and basin effects in Seattle for the M 6.8 Nisqually, Washington, earthquake". Bulletin of Seismological Society of America, 92(6): 2090-2109, doi:10.1785/0120010254. DOI: https://doi.org/10.1785/0120010254
Graves RW, Pitarka A and Somerville P (1998). "Ground-Motion Amplification in the Santa Monica Area: Effects of Shallow Basin-Edge Structure". Bulletin of the Seismological Society of America, 88(5): 1224-1242.
Kitagawa Y and Hiraishi H (2004). "Overview of the 1995 Hyogo-Ken Nanbu Earthquake and Proposals for Earthquake Mitigation Measures". Vol 4, doi:10.5610/jaee.4.3_1. DOI: https://doi.org/10.5610/jaee.4.3_1
Mahin SA (1998). "Lessons from damage to steel buildings during the Northridge earthquake". Engineering Structures, 20(4): 261-270, doi:10.1016/S0141-0296(97)00032-1. DOI: https://doi.org/10.1016/S0141-0296(97)00032-1
Mitchell D, DeVall RH, Saatcioglu M, Simpson R, Tinawi R and Tremblay R (1995). "Damage to concrete structures due to the 1994 Northridge earthquake". Canadian Journal of Civil Engineering, 22(2): 361-377. doi:10.1139/l95-047. DOI: https://doi.org/10.1139/l95-047
B Adams, R Davis and J Berrill JT (1999). "Two-Dimensional Site Effects in Wellington and the Hutt Valley - Similarities to Kobe". Civil Engineering Research Report 99-03, Department of Civil Engineering, University of Canterbury, Christchurch, NZ, 93p. https://www.eqc.govt.nz/sites/public_files/208-Two-dimensional-site-effects-Wn-HuttValley-Kobe.pdf (accessed 23/04/19).
Veletsos AS and Newmark NM (1960). "Effect of inelastic behavior on the response of simple systems to earthquake motions". Second World Conference on Earthquake Engineering, II: 895-912, Tokyo, Japan,.
Bozorgnia Y, Hachem MM and Campbell KW (2010). "Deterministic and probabilistic predictions of yield strength and inelastic displacement spectra". Earthquake Spectra, 26(1): 25-40. DOI: https://doi.org/10.1193/1.3281659
Paulay T and Priestley MJN (1992). "Seismic Design of Reinforced Concrete and Masonry Buildings" Wiley, 768p. DOI: https://doi.org/10.1002/9780470172841
Clough RW and Penzien J (1993). Dynamics of Structures". 3rd Edition, McGraw-Hill, NY.
Carr AJ (2011). "Inelastic response spectra for the christchurch earthquake records". Report to Canterbury Earthquakes Royal Commission, NZ.
Bradley B, Wotherspoon L, Kaiser AE, Cox BR and Jeong S (2018). "Influence of Site Effects on Observed Ground Motions in the Wellington Region from the Mw7.8 Kaikoura, NZ, Earthquake". Bulletin of the Seismological Society of America, 108(3B): 1722-1735, doi:10.1785/0120170286. DOI: https://doi.org/10.1785/0120170286
Stirling MW, Litchfield NJ, Villamor P, et al (2017). "The Mw7.8 2016 Kaikōura Earthquake: Surface Fault Rupture and Seismic Hazard Context". Bulletin of the New Zealand Society for Earthquake Engineering, 50(2): 73-84. DOI: https://doi.org/10.5459/bnzsee.50.2.73-84
Hamling I, Hreinsdottir S, Clark K, et al (2017). "Complex Multifault Rupture during the 2016 Mw7.8 Kaikōura Earthquake, New Zealand". Science, 356(6334): eaam7194, doi:10.1126/science.aam7194. DOI: https://doi.org/10.1126/science.aam7194
Orense R, Mirjafari Y, Asadi S, et al (2017). "Ground Performance in Wellington Waterfront Area Following the 2016 Kaikōura Earthquake". Bulletin of the New Zealand Society for Earthquake Engineering, 50(2): 142-151. DOI: https://doi.org/10.5459/bnzsee.50.2.142-151
Brunsdon D, Elwood K and Henry R (2017). "Wellington City Council Targeted Assessment Programme Following the Kaikoura Earthquake of 14 November 2016". https://wellington.govt.nz/~/media/about-wellington/emergency-management/files/targeted-assessment-programme-technical-report.pdf (accessed 25 April 2019).
Krawinkler H and Rahnama M (1992). "Effects of soft soils on design spectra". Tenth World Conference on Earthquake Engineering, Madrid, Spain, 6p.
Chopra AK (2012). "Dynamics of Structures: Theory and Applications to Earthquake Engineering". Fourth Edition, Pearson/Prentice Hall, 944p.
Naoki S, Ken-Ichi S, Toshiharu A, Atsushi S and Yukio T (2003). "Damping Evaluation Using Full-Scale Data of Buildings in Japan". Journal of Structural Engineering, 129(4):470-477, doi:10.1061/(ASCE)0733-9445(2003)129:4(470). DOI: https://doi.org/10.1061/(ASCE)0733-9445(2003)129:4(470)
Moore TA (2018). "Repairing SLS Anomalies in NZ Seismic Code to Reduce Earthquake Losses". Bulletin of the New Zealand Society for Earthquake Engineering, 51(1): 34-46. DOI: https://doi.org/10.5459/bnzsee.51.1.34-46
Frankel A, Stephenson W and Carver D (2009). "Sedimentary basin effects in Seattle, Washington: Ground-motion observations and 3D simulations". Bulletin of the Seismological Society of America, 99(3): 1579-1611, doi:10.1785/0120080203. DOI: https://doi.org/10.1785/0120080203
Holden C, Zhao J and Stirling M (2013). "Ground motion modelling of a large subduction interface earthquake in Wellington, New Zealand". NZSEE Annual Conference, Wellington.
Psarropoulos PN, Tazoh T, Gazetas G, Apostolou M (2007). "Linear and nonlinear valley amplification effects on seismic ground motion". Soils and Foundations, 47(5): 857-871, doi:10.3208/sandf.47.857. DOI: https://doi.org/10.3208/sandf.47.857
Hartzell S, Bonilla LF and Williams RA (2004). "Prediction of Nonlinear Soil Effects". Bulletin of the Seismological Society of America, 94(5): 1609-1629. DOI: https://doi.org/10.1785/012003256
Dwairi HM, Kowalsky MJ and Nau JM (2007). "Equivalent Damping in Support of Direct Displacement-Based Design". Journal of Earthquake Engineering, 11(4): 512-530, doi:10.1080/13632460601033884. DOI: https://doi.org/10.1080/13632460601033884
Hubbard DT and Mavroeidis GP (2011). "Damping coefficients for near-fault ground motion response spectra". Soil Dynamics and Earthquake Engineering, 31(3): 401-417, doi:10.1016/j.soildyn.2010.09.009. DOI: https://doi.org/10.1016/j.soildyn.2010.09.009
Hancock J and Bommer JJ (2006). "A State-of-Knowledge Review of the Influence of Strong-Motion Duration on Structural Damage". Earthquake Spectra, 22(3): 827-845, doi:10.1193/1.2220576. DOI: https://doi.org/10.1193/1.2220576
Mander JB, Panthaki FD and Kasalanati A (1994). "Low‐Cycle Fatigue Behavior of Reinforcing Steel". Journal of Materials in Civil Engineering, 6(4): 453-468, doi:10.1061/(ASCE)0899-1561(1994)6:4(453). DOI: https://doi.org/10.1061/(ASCE)0899-1561(1994)6:4(453)
Miranda E and Bertero VV (1994). "Evaluation of Strength Reduction Factors for Earthquake-Resistant Design". Earthquake Spectra, 10(2): 357-379, doi:10.1193/1.1585778. DOI: https://doi.org/10.1193/1.1585778
Stafford P, Sullivan T and Pennucci D (2016). "Empirical Correlation between Inelastic and Elastic Spectral Displacement Demands". Earthquake Spectra, 32(3): 1419-1448, doi:10.1193/020515EQS021M. DOI: https://doi.org/10.1193/020515EQS021M
Bozorgnia Y, Hachem M and Campbell K (2010). "Ground Motion Prediction Equation (“Attenuation Relationship”) for Inelastic Response Spectra". Earthquake Spectra, 26(1): 1-23, doi:10.1193/1.3281182. DOI: https://doi.org/10.1193/1.3281182