To limit forces or displacements: Collapse study of steel frames isolated by sliding bearings with and without restraining rims

Earthq Engng Struct Dyn

Constantinou

2020

This paper presents an investigation of the effects of the duration of earthquake ground motion on the peak displacement and total dissipated cumulative energy in seismic isolation systems designed by the procedures of ASCE/SEI 7-16. The seismic isolation systems considered in this study are elastomeric with lead and natural rubber bearings and sliding in the form of single and triple friction pendulum bearings. Long-and short-duration ground motions were selected so that the 5%-damped spectral acceleration values of each motion were closely matched over periods of 0.05 to 6 s. The results of the analysis demonstrate that the duration of ground motions have insignificant effects on the isolation system peak displacement-particularly in the lower bound conditions and sliding isolation bearings-but have important effects on the total cumulative energy for all conditions. This has implications in the testing of isolators, which are presented in an evaluation of the isolator test procedures of the ASCE/SEI 7-16 standard. The evaluation reveals that, if the cumulative energy dissipated by the isolation system is used as the controlling criterion, the specified tests are generally appropriate for locations characterized by short-duration ground motions, but are unconservative for locations where long-duration motions are anticipated. Additional results and discussion demonstrate that the cumulative energy may not be an appropriate criterion for designing isolator tests as it may lead to unrealistic demands on the tested isolators.

Section: Archetypical Structure and Isolation Systemsmentioning

confidence: 99%

Implications of strong earthquake ground motion duration on the response and testing of seismic isolation systems

Earthq Engng Struct Dyn

Constantinou

2020

“…Previous studies by the authors 13,14 and others 15,16 investigated the collapse performance of seismically isolated buildings designed by the ASCE/SEI 7 standards 9,17 when located at far-field sites using the FEMA P695 procedures. Another study 19 focused on the collapse performance of sliding isolation bearings in buildings when subjected to recorded pulselike motions but did not address the performance of the buildings designed based on the ASCE standard. A recent study by authors 20 observed that the probabilities of collapse in the lifetime of seismically isolated electrical transformers under the near-field ground motions did not substantially differ from the results of the same transformers under the far-field ground motions.…”

Section: Higher Spectral Accelerationmentioning

confidence: 99%

Performance evaluation of seismically isolated buildings near active faults

Earthq Engng Struct Dyn

Constantinou

2022

This paper investigates the collapse risk of seismically isolated buildings that are designed by the procedures of the ASCE/SEI 7‐16 standard for sites within 5 km of the active fault that controls the hazard. The study is based on six‐story perimeter frame buildings designed with special concentrically braced frames for a location in California. The seismic isolation systems considered in this study are comprised of either: (i) triple friction pendulum bearings with high friction coefficients at the sliding interfaces, (ii) triple friction pendulum bearings with low friction coefficient at the sliding surfaces and enhanced with fluid viscous dampers, or (iii) triple friction pendulum bearings with low friction coefficients at the sliding surfaces. The paper demonstrates that the seismically isolated buildings designed per Section 17.3.3 in ASCE/SEI 7‐16 standard, but with either increased isolator displacement capacity or increased superstructure strength by comparison to the minimum required, can achieve an acceptable collapse risk. It is also demonstrated that the seismic isolation systems that have the best collapse performance for far‐field motions are not necessarily the best for the near‐field pulse‐like ground motions.

“…Previous studies by first author Constantinou 2018a, 2019a) and others (Shenton and Lin 1993;Masroor and Mosqueda 2015;Sayani et al 2011;Erduran et al 2011) demonstrated that the seismic performance of seismically isolated buildings is superior to that of comparable non-isolated buildings in terms of reduced seismic demands, such as reduced floor acceleration, reduced peak story drift and reduced residual story drift. Other studies Constantinou, 2018b, 2019b;Bao et al 2018) demonstrated that increasing the displacement capacity of seismic isolation system or having moat wall with higher design strength of isolated superstructures could reduce the collapse probability and achieve the acceptable collapse probability defined by ASCE 7 seismic design standards (ASCE 2010(ASCE , 2017.…”

Section: Introductionmentioning

confidence: 99%

Seismic loss assessment of seismically isolated buildings designed by the procedures of ASCE/SEI 7-16

Cilsalar

2021

Bull Earthquake Eng

This paper investigates the seismic loss assessment of seismically isolated and non-isolated buildings with steel moment or braced frames, designed by the seismic design standard of ASCE/SEI 7-16. The seismic loss is calculated from the damage to structural and non-structural components, as well as the demolition and the collapse of buildings. This study demonstrates that the expected annual losses for seismically isolated buildings are half or less than half of those calculated for non-isolated buildings. These losses depend on the types of seismic isolation systems and seismic force resisting systems used. Among the cases of isolated buildings studied in this paper, the most cost-effective systems are found to be the buildings designed by minimum strength requirement in ASCE/SEI 7-16 and with isolators which have displacement capacity 1.5 times larger than the minimum required in ASCE/SEI 7-16, in terms of expected annual losses. This study also compares the results obtained from different approaches of selection and scaling of ground motions. The following research finds that when Incremental Dynamic Analysis approach with far-field ground motion set in FEMA P695 is used, the computed expected total annual losses become doubled from the Conditional Spectra approach.