scholarly journals Retrofit of seismically isolated structures for near-field ground motion using additional viscous damping

2005 ◽  
Vol 38 (2) ◽  
pp. 106-118 ◽  
Author(s):  
Lyle P. Carden ◽  
Barry J. Davidson ◽  
Tam J. Larkin ◽  
Ian G. Buckle
Keyword(s):  
Ground Motion ◽  
Near Field ◽  
Flexible Structures ◽  
Earthquake Ground Motion ◽  
Viscous Damping ◽  
Original Design ◽  
Large Magnitude ◽  
Isolated Structures ◽  
Seismically Isolated ◽  
The Impact

Recent earthquakes have shown that a large magnitude, long period pulse is often prevalent in ground motion records at sites within a few kilometres of the active fault during an earthquake. Near-field earthquake ground motion containing forward directivity effects can result in a larger response in flexible structures, such as seismically isolated structures, compared to that predicted for conventional ground shaking. Hence, a study was performed on a number of generic seismically isolated structures designed to the 1997 Uniform Building Code, as well as a case study on the William Clayton building in Wellington, to determine the impact of near-field ground motion. In optimising the performance of the buildings for both near-field and original "design level" earthquakes, it is concluded that linear viscous dampers added to the existing isolation systems are effective in controlling the response during large magnitude near-field earthquakes with minimal impact on the design response. Additional viscous damping is more effective than hysteretic damping in limiting isolator displacements while also preventing an increase in base shear and floor accelerations for far-field "design level" earthquakes.

scholarly journals Seismic Performance of Midstory Isolated Structures under Near-Field Pulse-Like Ground Motion and Limiting Deformation of Isolation Layers

2015 ◽  
Vol 2015 ◽  
pp. 1-17 ◽  
Author(s):  
Guiyun Yan ◽  
Fuquan Chen
Keyword(s):  
Ground Motion ◽  
Nonlinear Response ◽  
Near Field ◽  
Field Pulse ◽  
Isolation Layer ◽  
Protective System ◽  
Lead Rubber Bearings ◽  
Isolated Structures ◽  
Rubber Bearings ◽  
The Impact

Excessive deformation of the isolation layer in midstory isolated structures may occur under strong near-field pulse-like ground motion, which would result in the overturning collapse of the superstructure. The objective of the present research is to limit excessive deformation of the isolation layer and to reduce nonlinear response of midstory isolated structures. To this end, a protective system is presented to limit deformation of the isolation layer by soft pounding. Based on the Kelvin pounding model, a mechanical model is put forward for this protective system. In addition, a new method has been proposed that synthesizes artificial near-field pulse-like ground motion by combining the real near-field nonpulse ground motion with simple equivalent pulses. Also, the impact of artificial near-field pulse-like ground motion on the nonlinear response of midstory isolated structures and the deformation of the isolation layer has been investigated. The effectiveness of the midstory isolation with the protective system has been validated. The results show that the maximum deformation of the isolation layer significantly exceeds the allowable deformation of lead-rubber bearings when subjected to near-field pulse-like ground motion, and it causes the lead-rubber bearings destruction. The proposed protective system is effective in restricting the excessive deformation of the isolation layer and reducing nonlinear responses of the isolated structure, preventing collapse of the superstructure.

scholarly journals Spatial correlation of broadband earthquake ground motion in Norcia (Central Italy) from physics-based simulations

2021 ◽  
Author(s):  
Erika Schiappapietra ◽  
Chiara Smerzini
Keyword(s):  
Spatial Correlation ◽  
Ground Motion ◽  
Near Field ◽  
Geometric Mean ◽  
Central Italy ◽  
Earthquake Ground Motion ◽  
Physical Parameters ◽  
Spatial Correlations ◽  
Ground Motion Scenarios ◽  
The Impact

AbstractThis paper investigates the spatial correlation of response spectral accelerations from a set of broadband physics-based ground motion simulations generated for the Norcia (Central Italy) area by means of the SPEED software. We produce several ground-motion scenarios by varying either the slip distribution or the hypocentral location as well as the magnitude to systematically explore the impact of such physical parameters on spatial correlations. We extend our analysis to other ground-motion components (vertical, fault-parallel, fault-normal) in addition to the more classic geometric mean to highlight possible ground-motion directionality and therefore identify specific spatial correlation features. Our analyses provide useful insights on the role of slip heterogeneities as well as the relative position between hypocentre and slip asperities on the spatial correlation. Indeed, we found a significant variability in terms of both range and sill among the considered case studies, suggesting that the spatial correlation is not only period-dependent, but also scenario-dependent. Finally, our results reveal that the isotropy assumption may represent an oversimplification especially in the near-field and thus it may be unsuitable for assessing the seismic risk of spatially-distributed infrastructures and portfolios of buildings.

scholarly journals Large-scale experimental investigation of a low-cost PVC ‘sand-wich’ (PVC-s) seismic isolation for developing countries

2020 ◽  
Vol 36 (4) ◽  
pp. 1886-1911 ◽  
Author(s):  
Anastasios Tsiavos ◽  
Anastasios Sextos ◽  
Andreas Stavridis ◽  
Matt Dietz ◽  
Luiza Dihoru ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Developing Countries ◽  
Ground Motion ◽  
Seismic Isolation ◽  
Large Scale ◽  
Low Cost ◽  
Seismic Energy ◽  
Earthquake Ground Motion ◽  
Isolation System ◽  
Seismically Isolated

This study presents a large-scale experimental investigation on the seismic performance of an innovative, low-cost seismic isolation system for developing countries. It is based on the beneficial effect of the encapsulation of sand grains between two PVC surfaces on the initiation of sliding and the dissipation of seismic energy between the surfaces. A three-times scaled-down, idealized, seismically isolated model of a prototype single-story structure located in Nepal is subjected to an ensemble of recorded earthquake ground motion excitations. The experimentally derived response of the seismically isolated structure is compared with the response of the corresponding fixed-base structure. This system is part of a wider hybrid design approach where the structure is designed to resist the seismic forces at the design acceleration level. The seismic isolation system sets an upper bound to the response of the structure for ground motion excitations exceeding the design level.

scholarly journals MULTIPLE REGRESSION MODELING OF NATURAL RUBBER SEISMIC-ISOLATION SYSTEMS WITH SUPPLEMENTAL VISCOUS DAMPING FOR NEAR-FIELD GROUND MOTION

2013 ◽  
Vol 19 (5) ◽  
pp. 665-682 ◽  
Author(s):  
Mohammad H. Alhamaydeh ◽  
Samer A. Barakat ◽  
Farid H. Abed
Keyword(s):  
Natural Rubber ◽  
Multiple Regression ◽  
Ground Motion ◽  
Seismic Isolation ◽  
Near Field ◽  
Earthquake Ground Motion ◽  
Maximum Displacement ◽  
Fixed Base ◽  
Rubber Bearings ◽  
Seismic Isolation Systems

This work presents the development and implementation of the Multiple Regression Analysis (MRA) model to Seismic-Isolation (SI) systems consisting of Natural Rubber Bearings and Viscous Fluid Dampers subject to Near-Field (NF) earthquake ground motion. A model representing a realistic five-story base-isolated building is used. Several damper properties are used in creating an array of feasible combinations for the SI system. Two ensembles of seven NF earthquake records are utilized representing two seismic hazard levels. The key response parameters investigated are the Total Maximum Displacement, the Peak Damper Force and the Top Story Acceleration Ratio of the isolated structure compared to the fixed-base structure. Mathematical models for the key response parameters are established via MRA. The MRA models produced acceptable results with significantly less computation. This is demonstrated via a practical example of how the MRA models would be incorporated in the design process, especially at the preliminary stages.

scholarly journals Impact of the Vertical Component of Earthquake Ground Motion in the Performance Level of Steel Buildings

2021 ◽  
Vol 11 (4) ◽  
pp. 1925
Author(s):  
Jesús-Gerardo Valdés-Vázquez ◽  
Adrián David García-Soto ◽  
Miguel Á. Jaimes
Keyword(s):  
Ground Motion ◽  
Vertical Component ◽  
Performance Level ◽  
Earthquake Ground Motion ◽  
Steel Beams ◽  
Steel Buildings ◽  
Weak Beam ◽  
Immediate Occupancy ◽  
Plastic Rotations ◽  
The Impact

This study discusses the impact of the vertical component of earthquake ground motion in the performance level of steel building subjected to earthquake excitations. Analyses are carried out for the strong column-weak beam philosophy because the structural performance is focused on these elements. A realistic steel frame is also considered to investigate the impact of including the seismic vertical component in the non-linear response of the building. The main findings of this study are: (1) When an analysis is performed by considering the horizontal and vertical components of ground motion acting simultaneously (near the causative fault), larger plastic rotations in the beams are obtained as compared to those resulting by considering only the horizontal component. (2) Due to the previous finding, if a codified criterion to inspect the steel beams performance in terms of the plastic rotation is considered, the beam performance could lie within a different acceptation criterion (i.e., from immediate occupancy to collapse prevention) if the vertical component is included in the analysis.

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