Records of Extreme Ground Accelerations during the 2011 Christchurch Earthquake Sequence Contaminated by a Nonlinear, Soil–Structure Interaction

2021 ◽  
Author(s):  
Hiroyuki Goto ◽  
Yoshihiro Kaneko ◽  
Muriel Naguit ◽  
John Young
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Numerical Models ◽  
Concrete Slab ◽  
Seismic Hazard Assessment ◽  
Soil Structure Interaction ◽  
Foundation Slab ◽  
Ground Shaking ◽  
Structure Interaction ◽  
Ground Motion Records

ABSTRACT Ground-motion records are critical for seismic hazard assessment and seismic design of buildings and infrastructures. Large (>1g), asymmetric vertical accelerations (AsVAs) have been observed at strong-motion stations during recent earthquakes. However, it is not clear whether all of the observed AsVAs reflect actual ground shaking or the interaction of a building structure and underlying ground. Here, we investigate the cause of large AsVAs recorded at several seismic stations in Christchurch, New Zealand, during the 2011 Mw 6.2 Christchurch earthquake. We first define three metrics and quantify the degree of waveform asymmetry in all available records from nearby M>3 earthquakes. Histograms of the metrics show greater waveform asymmetry for larger accelerations at these stations, which is consistent with the prediction of a nonlinear, soil–structure interaction associated with the elastic collisions of a foundation slab onto the underlying soil. We then use finite-element models to examine the occurrence of the nonlinear, soil–structure interaction at these stations during the Mw 6.2 mainshock and Mw 5.6 aftershock of the 2011 Christchurch earthquake. The parameters of the numerical models are constrained by site investigation of selected stations. We find that numerical simulations closely reproduce the large AsVAs recorded at stations HVSC and PRPC, suggesting that these ground-motion records were contaminated by the nonlinear, soil–structure interaction. Seismic sensors located near the corner of a concrete slab are shown to be more prone to this phenomenon. Our results further suggest that artificial recording of large AsVAs due to the nonlinear, soil–structure interaction can be mitigated if a seismic sensor is placed closer to the center of a foundation slab. The analytical procedure presented in this study may be useful in identifying the occurrence of AsVAs elsewhere and in assessing whether AsVAs are caused by the nonlinear, soil–structure interaction.

The effect of soil-structure interaction on seismometer readings

1978 ◽  
Vol 68 (3) ◽  
pp. 823-843
Author(s):  
G. N. Bycroft
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Free Field ◽  
Soil Structure Interaction ◽  
Rigid Sphere ◽  
Elastic Space ◽  
Structure Interaction ◽  
Frequency Components ◽  
Low Shear

abstract Rocking and vertical and horizontal translations of typical “free-field” seismometer installations lead to magnification of the ground motion record. This magnification can be significant for the higher frequency components if the terrain has a relatively low shear-wave velocity. Seismometers placed on foundations which cover a significant part of a wavelength of a horizontally incident wave, experience an attenuated ground motion. A method of correcting the seismograms for these effects is given. Compliance functions for a rigid sphere in a full elastic space are derived and are used to show that, in practical cases, down-hole seismometer installations are not significantly affected by interaction. These compliance functions should be useful in discussing the soil structure interaction of structures erected on bulbous piles. They may be also used as the basis of a method of determining elastic constants of ground at depth, in situ, and at different frequencies.

Effects of Slenderness and Fundamental Frequency on the Dynamic Response of Adjacent Structures

2019 ◽  
Vol 19 (09) ◽  
pp. 1950105
Author(s):  
Gonzalo Barrios ◽  
Vinuka Nanayakkara ◽  
Pramodya De Alwis ◽  
Nawawi Chouw
Keyword(s):  
Dynamic Response ◽  
Fundamental Frequency ◽  
Soil Structure ◽  
Numerical Models ◽  
Ground Motions ◽  
Soil Structure Interaction ◽  
Reference Case ◽  
Maximum Acceleration ◽  
Structure Interaction ◽  
Adjacent Structures

In conventional seismic design, the structure is often assumed to be fixed at the base. However, this assumption does not reflect reality. Furthermore, if the structure has close neighbors, the adjacent structures will alter the response of the structure considered. Investigations on soil–structure interaction and structure–soil–structure interaction have been performed mainly using numerical models. The present work addresses the dynamic response of adjacent single-degree-of-freedom models on a laminar box filled with sand. Impulse loads and simulated ground motions were applied. The standalone condition was also studied as a reference case. Models with different fundamental frequencies and slenderness were considered. Results from the impulse tests showed that the top displacement of the models with an adjacent structure was reduced compared with that of the standalone case. Changes in the fundamental frequency of the models due to the presence of an adjacent model were also observed. Results from ground motions showed amplification of the maximum acceleration and the top displacement of the models when both structures have a similar fundamental frequency.

Introduction of Shaking Table Test of Rigid Frame Bridge Model

2012 ◽  
Vol 256-259 ◽  
pp. 1492-1495
Author(s):  
Xiao Yu Yan
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Shaking Table Test ◽  
Shaking Table ◽  
Soil Structure Interaction ◽  
Structure Interaction ◽  
Rigid Frame ◽  
Bridge Model ◽  
Support Excitation ◽  
Rigid Frame Bridge

To investigate the seismic response of long-span rigid frame bridges with high-pier, the shaking table test of a 1/10 scaled rigid frame bridge model is introduced in this paper. Details about test equipment, model design, test arrangement, input ground motion waves and test principle are provided. The response of bridge model under the seismic excitation included the uniform excitation and the multi-support excitation is observed. The influence of the soil-structure interaction on the bridge is considered through the real-time dynamic hybrid testing method. The impact effect for different ground motion input during the test is discussed. The influence of multi-support excitation, soil-structure interaction and impact effect on structural seismic responses are studied based on the test results. The isolation effectiveness and the damping effect are discussed as well.

Implications of soil–structure interaction effects on the NBCC 1990 base shear provisions for high-rise buildings

1994 ◽  
Vol 21 (3) ◽  
pp. 427-438
Author(s):  
Shamel Hosni ◽  
Arthur C. Heidebrecht
Keyword(s):  
Soil Structure ◽  
Interaction Effects ◽  
Soil Structure Interaction ◽  
Code Design ◽  
Base Shear ◽  
Structure Interaction ◽  
High Rise ◽  
Inertial Interaction ◽  
Moment Resisting ◽  
Ground Motion Records

This study is carried out on a site-specific basis for three locations in Canada, namely Ottawa, Vancouver, and Prince Rupert. Soil models are developed to correspond to the soil classifications used to define the foundation factor, F, in the 1990 edition of the National Building Code of Canada (NBCC). Structural models are developed to represent both 20-storey ductile moment-resisting frames and ductile flexural walls. Three initial sets of actual ground motion records are scaled, in the frequency domain, to represent the postulated bedrock motions for each of the three sites. The computer program FLUSH is used to perform the numerical analyses of the various soil–structure systems. Results from the current study indicate that the code F values generally underestimate the site effects associated with the respective soil deposits, but appear to be reasonably adequate, in most cases, when soil–structure interaction effects are taken into consideration. In spite of some deficiencies in the code F values, the 1990 NBCC design base shear is shown to be quite conservative for regular high-rise reinforced concrete buildings. A simple measure to account for inertial interaction effects in uncoupled analyses is shown to provide a significant improvement, as compared to conventional uncoupled analyses, in the prediction of the coupled base shear demand. Key words: seismic, hazard, site, soil, structure, interaction, code, design, base, shear.

Case Study: Effect of Soil-Structure Interaction and Ground Motion Incoherency on Nuclear Power Plant Structures

2009 ◽  
Author(s):  
Jim Xu ◽  
Sujit Samaddar
Keyword(s):  
Power Plant ◽  
Nuclear Power Plant ◽  
Seismic Response ◽  
Ground Motion ◽  
Nuclear Power ◽  
Soil Structure ◽  
Soil Structure Interaction ◽  
Soil Conditions ◽  
Structure Interaction

The soil-structure interaction (SSI) has a significant impact on nuclear power plant (NPP) structures, especially for massive and rigid structures founded on soils, such as containments. The U.S. Nuclear Regulatory Commission’s (NRC) Standard Review Plan (SRP) provides the requirement and acceptance criteria for incorporating the SSI effect in the seismic design and analyses of NPP structures. The NRC staff uses the SRP for safety review of license applications. Recent studies have indicated that ground motions in recorded real earthquake events have exhibited spatial incoherency in high-frequency contents. Several techniques have been developed to incorporate the incoherency effect in the seismic response analyses. Section 3.7.2 of Revision 3 of the SRP also provided guidance for use in the safety evaluation of seismic analyses considering ground motion spatial incoherency effect. This paper describes a case study of the SSI and incoherency effects on seismic response analyses of NPP structures. The study selected a typical containment structure. The SSI model is generated based on the typical industry practice for SSI computation of containment structures. Specifically, a commercial version of SASSI was used for the study, which considered a surface-founded structure. The SSI model includes the foundation, represented with brick elements, and the superstructure, represented using lumped mass and beams. The study considered various soil conditions and ground motion coherency functions to investigate the effect of the range of soil stiffness and the ground motion incoherency effect on SSI in determining the seismic response of the structures. This paper describes the SSI model development and presents the analysis results as well as insights into the manner in which the SSI and incoherency effects are related to different soil conditions.

Empirical Spatial Coherency Functions for Application to Soil-Structure Interaction Analyses

1991 ◽  
Vol 7 (1) ◽  
pp. 1-27 ◽  
Author(s):  
N. A. Abrahamson ◽  
J. F. Schneider ◽  
J. C. Stepp
Keyword(s):  
Ground Motion ◽  
Soil Structure ◽  
Epicentral Distance ◽  
Strong Motion ◽  
Soil Structure Interaction ◽  
High Frequencies ◽  
S Waves ◽  
Structure Interaction ◽  
Strong Ground ◽  
Spatial Coherency

The spatial coherency of strong ground motion from fifteen earthquakes recorded by the Lotung LSST strong motion array is analyzed. The earthquakes range in magnitude from 3.7 to 7.8 and in epicentral distance from 5 to 80 km. In all, a total of 533 station pairs are used with station separations ranging from 6 to 85 meters. Empirical coherency functions for the horizontal component S-waves appropriate for use in engineering analyses are derived from these data. The derived coherency functions are applicable to all frequencies and to separation distances up to 100 m. For these short station separations, the coherency decreases much faster with increasing frequency than with increasing station separation. The computed coherencies indicate that at high frequencies (>10 Hz) over 25 percent of the power of the ground motion is random for station separations greater than 30 m.

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