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Assessment of ASCE 7–16 Seismic Isolation Bearing Torsional Displacement
- Source :
- International Journal of Civil Engineering. 18:351-366
- Publication Year :
- 2019
- Publisher :
- Springer Science and Business Media LLC, 2019.
-
Abstract
- Base isolation provisions in ASCE 7 Standard have been historically shown to be conservative in estimating seismic demands. New torsional bearing base isolation displacement expressions have been proposed recently by the latest ASCE 7–16 Standard. This study compares the accuracy of the new ASCE 7–16 static-based isolation expressions for additional bearing displacement due to plane torsion to the response obtained using simplified structural dynamics’ plane torsion theory expressions. In addition, it conducts a parametric study to assess the effect of accidental eccentricity, damping ratio, and plan aspect ratio on the accuracy of ASCE 7–16 bearing displacement expression. The results showed that the ASCE 7–16 undamped displacement estimations improved compared to the significant conservatism of ASCE 7–10 by 7–33% depending on the eccentricity condition and ratio, which may further promote the use of base isolation in the US as a seismic hazard mitigation solution. However, the study also revealed that a considerable conservatism of the new base isolation bearing displacement provisions of ASCE 7–16 still exists in some cases, which ranged from 52 to 105% in the case of three equal fundamental frequencies and 5–20% in the case of equal lateral frequency and distinct torsional frequency. The study also showed that the ASCE 7–16 conservatism is proportional to the eccentricity and is more pronounced with biaxial eccentricity compared to single eccentricity. Furthermore, the results show that ASCE 7–16 expression accuracy significantly declines with damped systems with a possibility of un-conservative estimation of bearing displacements that can reach 25–40% with larger eccentricities. In addition, the ASCE 7–16 torsional displacement was shown to be inversely proportional to the plan aspect ratio with a discrepancy that can reach ± 20%. The study also exhibited that the ASCE 7–16 torsional displacement conservatism is slightly affected by increasing damping ratio above 4%.
- Subjects :
- 021110 strategic, defence & security studies
Damping ratio
business.industry
0211 other engineering and technologies
Torsion (mechanics)
020101 civil engineering
02 engineering and technology
Structural engineering
0201 civil engineering
Seismic hazard
Torsion theory
Seismic isolation
Base isolation
business
Civil and Structural Engineering
Parametric statistics
Mathematics
Subjects
Details
- ISSN :
- 23833874 and 17350522
- Volume :
- 18
- Database :
- OpenAIRE
- Journal :
- International Journal of Civil Engineering
- Accession number :
- edsair.doi...........65adffc4026db6ac9da9487c04ea6910