Deformation of Embankments Due to Liquefaction During 1994 Northridge Earthquake

1998 ◽  
Vol 1633 (1) ◽  
pp. 9-18
Author(s):  
J.P. Bardet ◽  
C.A. Davis
Keyword(s):  
Ground Motions ◽  
Geotechnical Engineering ◽  
Three Dimensional ◽  
Northridge Earthquake ◽  
Earth Dams ◽  
Case Histories ◽  
Hydraulic Fill ◽  
Engineering Community ◽  
San Fernando ◽  
1994 Northridge Earthquake

The 1994 Northridge and 1971 San Fernando earthquakes subjected the Lower and Upper San Fernando Dams of the Van Norman Complex in the San Fernando Valley, California, to strong near-source ground motions. In 1994, these earth dams, which were out of service and retained only a few meters of water, extensively cracked and settled because of liquefaction of their hydraulic fill. The Lower San Fernando Dam moved more than 15 cm upstream as the hydraulic fill liquefied beneath its upstream slope. The Upper San Fernando Dam moved even more, and it deformed in a complex three-dimensional pattern. The responses of the Lower and Upper San Fernando Dams during the 1994 Northridge earthquake, although less significant than in 1971, provided the geotechnical engineering community with two useful case histories.

scholarly journals Quasi-Resonance Effects Observed in The 1994 Northridge Earthquake, and Others

1998 ◽  
Vol 5 (3) ◽  
pp. 153-158 ◽  
Author(s):  
Edward G. Fischer ◽  
Thomas P. Fischer
Keyword(s):  
Time History ◽  
Shaking Table ◽  
Northridge Earthquake ◽  
Shaking Table Tests ◽  
Circuit Breakers ◽  
Resonance Effects ◽  
Earthquake Records ◽  
San Fernando ◽  
Conservative Simulation ◽  
1994 Northridge Earthquake

Sine-beat phenomena have been found in the 1994 Northridge earthquake records, and they are capable of producing time-history responses and damaging quasi-resonance effects in structures. Linear, single DOF (degree of freedom) oscillators, in lieu of nonlinear, multiple DOF systems, have been found adequate to discuss the failures of tall circuit breakers during the 1971 San Fernando and the 1989 Loma Prieta quakes in California. The use of sine-beat excitation for seismic-shaking-table tests of equipment continues to be a conservative simulation of earthquakes.

scholarly journals Response of seismically isolated buildings with buffers subjected to near-source ground motions and possible alternative isolation systems

2004 ◽  
Vol 37 (3) ◽  
pp. 111-133 ◽  
Author(s):  
J. X. Zhao
Keyword(s):  
Inelastic Deformation ◽  
Ground Motions ◽  
Damping Ratio ◽  
Structural Response ◽  
Deformation Capacity ◽  
Northridge Earthquake ◽  
Period Range ◽  
Isolation System ◽  
Seismically Isolated ◽  
1994 Northridge Earthquake

The response of a seismically isolated building with lead rubber bearings (LRB) to near source ground motions from large earthquakes was investigated. The building was assumed to have a buffer to limit the maximum bearing displacement in a rare event of large magnitude and the buffer gap was assumed to be only 150mm (the level of maximum isolator displacement used in the 1980s). The structure was assumed to be designed for 1.5 times the NS component of the 1940 El Centro record. The 15% damped (an amount of damping which is close to the equivalent damping ratio for an seismically isolated building at its isolator design displacement) displacement spectrum of the design motion is only 40% that of the Sylmar County Hospital Parking Lot record from the 1994 Northridge earthquake (Mw= 6.7) in the period range around the first modal periods of both isolated and un-isolated structure used in the present study. Among the near-source records that are available, the near-source Sylmar record from the 1994 Northridge earthquake was found to have a very large displacement demand in a period range of 2.0 - 3.0s and this record is thought to be a better representation of the expected near-source motions than the 1.5 times the 1940 El Centro record. Structure-buffer impact was found to impose very large inter-storey drifts and produce very large storey accelerations, when the building was subjected to the excitation of the Sylmar record. The structure-buffer impact was found to be detrimental to the structural response if the structure was not designed to provide inelastic deformation capacity, and the structural response did not improve when the gap was increased to 200-250 mm, the expected maximum displacement capacity of the LRBs used in the building. An alternative isolation system of LRBs and hysteretic dampers was investigated and found to be adequate for resisting near-source motions. A large initial damper stiffness and relatively small buffer stiffness (compared with the total initial stiffness of LRBs) were found to be effective in reducing inter-storey drifts and storey accelerations at floors except for the base and roof of the structure. A disadvantage of such a system is the relatively large base and roof accelerations. The system has relatively large inter-storey drifts and storey accelerations compared with an isolated structure using LRBs only when the structure was subjected to either the 1940 El Centro type ground motions or the Joshua Tree type ground motions with backward directivity effect. Such an isolation system would still enable the structure to respond essentially elastically under the excitation of the Sylmar record even though the isolated structure was designed for a much lower level of ground shaking. As the upper structure of a seismically isolated building is usually designed to respond essentially elastically, the detailing used in the design of a reinforced concrete structure to provide inelastic deformation capacity was generally uncommon and was not fully accounted for in the present study.

A Multidimension Source Model for Generating Broadband Ground Motions with Deterministic 3D Numerical Simulations

2021 ◽  
Author(s):  
Xiang-Chao Wang ◽  
Jin-Ting Wang ◽  
Lei Zhang ◽  
Shuai Li ◽  
Chu-Han Zhang
Keyword(s):  
Numerical Simulations ◽  
Ground Motions ◽  
Source Parameters ◽  
Spectral Characteristics ◽  
Source Model ◽  
Rupture Process ◽  
Northridge Earthquake ◽  
Scenario Earthquake ◽  
Source Models ◽  
1994 Northridge Earthquake

ABSTRACT A multidimension source model for generating broadband ground motions with deterministic 3D numerical simulations is proposed in this article. In this model, the source is composed of several superimposed layers, and the total seismic moment is assigned to these layers in different proportions. Each layer exactly fills up the seismic fault and is uniformly divided into subsources with size decreased progressively to reflect different levels of rupture details. Hence, the proposed multidimension source model may consider the realistic rupture process of an earthquake, that is, the spatial and temporal heterogeneity of source parameters, and generate broadband ground motions. To verify this source model, the 1994 Northridge earthquake is simulated with four multidimension source models, based on different source inversion results. The amplitudes, durations, and spectral characteristics of the observed ground motions of the 1994 Northridge earthquake are respectably reproduced in a range of frequencies up to 5 Hz. In addition, a scenario earthquake is also simulated with four multidimension source models, with different synthetic rupture process. The simulated ground motions of the scenario earthquake are generally in good agreement with the Next Generation Attenuation-West 2 ground-motion prediction equations. This demonstrates that it is promising to simulate realistic broadband ground motions of strong earthquakes with a proper source description and realistic Earth models.

scholarly journals Earthquake design and performance of steel structures

1996 ◽  
Vol 29 (4) ◽  
pp. 229-241
Author(s):  
H. Krawinkler
Keyword(s):  
Failure Modes ◽  
Steel Structures ◽  
Local Failure ◽  
Northridge Earthquake ◽  
Research Issues ◽  
The Public ◽  
Engineering Community ◽  
Earthquake Design ◽  
And Performance ◽  
1994 Northridge Earthquake

The 1994 Northridge earthquake has shown that steel structures may experience local failure modes that have not been observed in earlier earthquakes. The attention of the public and the engineering community has been drawn particularly to frequently observed fractures at welded beam-to-column connections. The local failures have raised design and research issues that have become the focus of extensive professional and research efforts directed towards improvement of the performance of steel structures in future earthquakes.

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