PSI - Issue 44

Masoud Pourmasoud et al. / Procedia Structural Integrity 44 (2023) 590–597 M. Pourmasoud et al. / Structural Integrity Procedia 00 (2022) 000–000

596

7

• A variety of influential factors, including applied axial load, slenderness of the lead core, and thickness of the rubber layers, confer different levels of confinement for the lead core. Three confinement categories were recognised based on the trend of the normalised characteristic strengths versus the normalised axial loads. The developed Influential Factor Ratio (IFR) shows that IFRs less than 1.0 represent low confinement, IFRs of approximately 2.0 indicate medium confinement, and when IFR exceeds 7.0, high confinement is achieved. • The yield strength of the lead core directly depends on the level of confinement, the isolator travel amplitude, and the applied axial load. These effects are generally ignored in the code specified design criteria. To address this issue, a new design equation was developed to estimate lead core yield strength by taking into account all the key influential factors. • Accuracy improvement of the yield strength calculation narrows the gap between the upper bound and lower bounds offered by (ASCE 7-16 2016) and is beneficial for more efficient design of super-structures.

Acknowledgements

Special thanks to those who have assisted in this research, in particular, the technical support from Low Damage Design Co.

References

Alhan, C., Öncü-Davas, S. 2016. Performance Limits of Seismically Isolated Buildings under Near-Field Earthquakes. Engineering Structures. 116: 83–94. ASCE. 2022. Minimum Design Loads and Associated Criteria for Buildings and Other Structures . ASCE/SEI 7-22. Reston, VA: ASCE. Bhagat, S., Wijeyewickrema, A. C., Subedi, N. 2018., Influence of Near-Fault Ground Motions with Fling-Step and Forward-Directivity Characteristics on Seismic Response of Base-Isolated Buildings. Journal of Earthquake Engineering 0 (0): 1–20. BS EN 1337-3. 2005. Structural Bearings - Part 3 : Elastomeric Bearings. BSI Standard Publication. BS EN 15129. 2018. European Standard on Anti-Seismic Devices. BSI Standard Publication. Clemente, P., Martelli, A. 2019., Recent Applications of Seismic Isolation in Italy. 16th World Conference on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures. St Petersburg. Russian Federation. Constantinou, M.C. Kalpakidis, I., Filiatrault, A., Ecker Lay, R.A., 2011. LRFD-Based Analysis and Design Procedures for Bridge Bearings and Seismic Isolators. MCEER 11-0004. Buffalo, NY: Univ. at Buffalo. Du, K., Bai, W., Bai, J., Yan, D., 2021. Comparative Seismic Performance Assessment of Reinforced Concrete Frame Structures with and without Structural Enhancements Using the FEMA P-58 Methodology. ASCE-ASME Journal of Risk and Uncertainty in Engineering Systems 7 (4). FEMA. 2003. Multi-Hazard Loss Estimation Methodology - Earthquake Model. HAZUS-MH MR4 Technical Manual, Federal Emergency Management Agency, Washington, DC: FEMA. FEMA. 2018. Building the Performance You Need. FEMA P-58-7. Washington, DC: FEMA. Jampole, E., Swensen, S., Miranda, E., Deierlein, G. G., 2020. Parametric Study of Seismic Isolation Properties for Light-Frame Houses. Journal of Structural Engineering 146 (10): 04020207. Kalpakidis, I. V., Constantinou, M. C., Whittaker, A.S., 2010. Modeling Strength Degradation in Lead–Rubber Bearings under Earthquake Shaking. Earthquake Engineering & Structural Dynamics 39 (13): 1533–49. https://doi.org/10.1002/eqe.1039. Kelly, T. E., 2001. Base Isolation Design of Structures: Design Guidelines. Holmes Consulting Group ltd. McVitty, W. J., Constantinou, M. C., 2015. Property Modification Factors for Seismic Isolators: Design Guidance for Buildings. MCEER-15-0005. Buffalo, NY: Univ. at Buffalo. Özuygur, A. R., Farsangi, E. N., 2021. Influence of Pulse-Like Near-Fault Ground Motions on the Base-Isolated Buildings with LRB Devices. Practice Periodical on Structural Design and Construction 26 (4): 04021027. https://doi.org/10.1061/(ASCE)SC.1943-5576.0000603. Pal, S., Hassan, A., Singh, D., 2019. Optimization of Base Isolation Parameters Using Genetic Algorithm. Journal of Statistics and Management Systems 22 (7): 1207–22. https://doi.org/10.1080/09720510.2019.1614338. Pourmasoud, M. M., Lim, J. B. P., Hajirasouliha, I., McCrum. D., 2020. Multi-Directional Base Isolation System for Coupled Horizontal and Vertical Seismic Excitations. Journal of Earthquake Engineering. January 1–26. https://doi.org/10.1080/13632469.2020.1713925. Pourmasoud, M. M., Park, A. R. L., Hajirasouliha, I., Lim, J. B. P., 2021. Investigation of influential factors on yield strength of lead rubber bearings. NZSEE 2021, Annual Conference. Skinner, R. I., Robinson, W. H., McVerry, G. H., 1993. An Introduction to Seismic Isolation. Wiley. Wei, B., Zuo, C., He, X., Jiang, L., Wang, T., 2018. Effects of Vertical Ground Motions on Seismic Vulnerabilities of a Continuous Track-Bridge System of High Speed Railway. Journal of Soil Dynamics and Earthquake Engineering 115: 281-290. Whittaker, D., 2019. Recent Developments in New Zealand in Seismic Isolation, Energy Dissipation and Vibration Control of Structures. 16th World Conference on Seismic Isolation, Energy Dissipation and Active Vibration Control of Structures . St Petersburg. Russian Federation. Whittaker, D., Parker, W., Pettinga, D., Pierta, D., McVerry, G., Sidwell, G., 2019. Guideline for the Design of Seismic Isolation Systems for Buildings. New Zealand Society for Earthquake Engineering.