Reversing Cyclic Elastic Demands on Structures during Earthquakes and Applications to Ductility Requirements

1984 ◽  
Vol 1 (1) ◽  
pp. 7-32 ◽  
Author(s):  
Virgilio Perez ◽  
A. Gerald Brady
Keyword(s):  
Elastic Limit ◽  
Epicentral Distance ◽  
Large Earthquake ◽  
Earthquake Magnitude ◽  
Maximum Response ◽  
Plastic Behavior ◽  
Maximum Displacement ◽  
Long Period ◽  
Elastic Demands ◽  
Number Of Cycles

The study of all earthquake-induced oscillator response peaks from selected records shows how these peaks decrease in amplitude with the number of cycles attaining them. These studies concentrate on the ratio between the peak amplitudes of response experienced throughout the duration of a given number of cycles and the maximum response. The ratio shows a trend that is fairly independent of the structure's period, the epicentral distance, and the earthquake magnitude. If during a very large earthquake a structure is forced into displacements beyond the elastic limit it must withstand them successfully with well-designed ductility. For long-period structures, these inelastic displacements, if assumed to result from idealized elasto-plastic behavior, are approximately equal to the elastic displacements under study. The trends shown here consequently indicate that the amplitudes of the elasto-plastic displacements still attained after two, four, or eight cycles, remain at levels that are appreciably high percentages of the maximum displacement.

Property of long term (1990-2009) seismicity in the region of L’Aquila Mw6.1 earthquake revealed from machine learning 

2021 ◽  
Author(s):  
Josipa Majstorović ◽  
Piero Poli
Keyword(s):  
Epicentral Distance ◽  
Large Earthquake ◽  
Historical Seismicity ◽  
Central Apennines ◽  
Small Magnitude ◽  
Earthquake Detection ◽  
Abruzzo Region ◽  
Background Seismic Activity ◽  
The City

<p>On April 6th 2009 (01:32 UTC) strong earthquake of magnitude M<sub>W</sub>6.1 occurred near the city of L’Aquila in the Abruzzo region in the Central Apennines of Italy. Due to the extensional processes the Abruzzo region is characterized by prominent historical seismicity. However, before the 2009 event the background seismic activity is characterised as sparse and mostly clustered in space and time. The general lack of events, especially small magnitude events before the 2009 event motivated us to study the long-term near-fault seismicity before the large earthquake occurrence. To achieve this we first have to extend the existing catalog. We take into consideration the data from the AQU (42.354, 13.405) station that has been recorded in the city of L’Aquila, near Paganica fault responsible for the 2009 event, during an extensive period of 29-years, 19 years before the event itself. The catalog extension is performed by applying the two-stage convolutional neural network pipeline for earthquake detection and characterisation (epicentral distance and magnitude) using three component signal station waveforms. The algorithm allows us to successfully detect ~800 local events (less than 10 km from the AQU station) in the period 1990-2009. We here present a detailed analysis of this catalog including waveforms characterization to derive new insights about the long term preparation processes(es) occuring before the 2009 M<sub>w</sub>6.1 earthquake.</p>

Equivalent number of uniform cycles versus earthquake magnitude relationships for fine-grained soils

2019 ◽  
Vol 56 (11) ◽  
pp. 1596-1608
Author(s):  
Priyesh Verma ◽  
Ainur Seidalinova ◽  
Dharma Wijewickreme
Keyword(s):  
Large Earthquake ◽  
Earthquake Magnitude ◽  
Undisturbed Soil ◽  
Experimental Database ◽  
Cyclic Shear ◽  
Fine Grained ◽  
Evaluation Procedures ◽  
Magnitude Scaling ◽  
Equivalent Number ◽  
Time Histories

In current geotechnical seismic design practice, the empirical correlation between equivalent number of uniform cycles (Neq) of shaking and earthquake magnitude (Mw) forms an integral part of liquefaction potential evaluation. This relationship, in turn, is used to derive the magnitude scaling factors that are commonly used in field-based liquefaction evaluation procedures. The Neq versus Mw relationship for liquefaction assessment was examined for fine-grained soils using time-histories in the range 5 < Mw ≤ 9, especially including strong ground motion time-histories from the latest subduction zone earthquakes with Mw > 8.0. The experimental database available from cyclic direct simple shear tests conducted on natural fine-grained soils retrieved from undisturbed soil sampling was used to obtain the cyclic shear resistance weighting curves for the study. The work presented herein has contributed to further improving the current models used to represent magnitude scaling factor (MSF) values for large earthquake magnitudes and the functional dependency of this parameter on soil type. The MSF–Mw curve derived for low-plastic Fraser River Delta silt lies in-between the MSF curves derived for clean sand and clay, resonating with the inferences that have been made that the silt behavior can neither be considered sand-like nor clay-like.

scholarly journals Fractal analysis for the ULF data during the 1993 Guam earthquake to study prefracture criticality

2006 ◽  
Vol 13 (4) ◽  
pp. 409-412 ◽  
Author(s):  
Y. Ida ◽  
M. Hayakawa
Keyword(s):  
Fractal Analysis ◽  
Main Shock ◽  
Epicentral Distance ◽  
Sense Of Self ◽  
Low Frequency ◽  
Large Earthquake ◽  
Self Organized ◽  
Self Organized Criticality ◽  
Electromagnetic Signature

Abstract. An extremely large earthquake (with magnitude of 8.2) happened on 8 August 1993 near the Guam island, and ultra-low-frequency (ULF) (frequency less than 1 Hz) electromagnetic fields were measured by 3-axis induction magnetometers at an observing station (with the epicentral distance of 65 km) with sampling frequency of 1 Hz. In order to study electromagnetic signature of prefracture criticality, we have undertaken the fractal (mono-fractal) analysis by means of the Higuchi's method for the ULF data during the 1993 Guam earthquake. Then, it is found that the fractal dimension exhibits five maxima 99, 75, 52, 21, and 9–4 days before the earthquake main shock, which suggests the ULF electromagnetic signature of nonlinear evolution (in the sense of self-organized criticality) taking place in the lithosphere just before the 1993 large Guam earthquake. That is, there take place step-like changes in the lithosphere during the long-term of the order of several months before the main shock.

Effect of Parameters on Equivalent Number of Cycles Using ‎Nonlinear Seismic Site Response Analysis

2011 ◽  
Vol 255-260 ◽  
pp. 2365-2369
Author(s):  
Emad Gheibi ◽  
Mohammad Hosein Bagheripour
Keyword(s):  
Site Response ◽  
Time History ◽  
Current Approach ◽  
Earthquake Magnitude ◽  
Soil Liquefaction ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Nonlinear Site Response ◽  
Equivalent Number ◽  
Number Of Cycles

The concept of equivalent number of uniform stress cycles, is essential for assessment of soil liquefaction potential. In this regard, various procedures are used to convert random acceleration time history to uniform cycles having amplitude of 0.65 of peak acceleration. Equivalent number of cycles (Neq) defines equivalent energy generated by harmonic loading as that imposed by irregular motion during an earthquake. Neq is assumed to be a function of earthquake magnitude. Over the past years, in accordance with development in methods of soil liquefaction evaluation, various methods have been proposed to determinate equivalent number of cycles. In particular, parameters like site to source distance (r), have been related directly to Neq. In this study, more than 80 earthquake records have been investigated and their Neqs are assessed using energy approach and nonlinear site response analysis. It is shown that equivalent number of cycles is related to earthquake magnitude (M), r and depth of originated signals. Unlike previous methods which result in scatter in output data, current approach has led to more uniform and consistent results for each earthquake.

scholarly journals Anisotropic Plastic Behavior in an Extruded Long-Period Ordered Structure Mg90Y6.5Ni3.5 (at.%) Alloy

Crystals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 279
Author(s):  
Gerardo Garces ◽  
Rafael Barea ◽  
Andreas Stark ◽  
Norbert Schell
Keyword(s):  
Basal Plane ◽  
Extrusion Direction ◽  
Plastic Behavior ◽  
Ordered Structure ◽  
Lpso Phase ◽  
Long Period ◽  
Anisotropic Plastic ◽  
The Difference ◽  
Internal Strains

The Mg90Y6.5Ni3.5 alloy composed almost completely of the Long-Period-Stacking-Ordered (LPSO) phase has been prepared by casting and extrusion at high temperature. An elongated microstructure is obtained where the LPSO phase with 18R crystal structure is oriented with its basal plane parallel to the extrusion direction. Islands of α-magnesium are located between the LPSO grains. The mechanical properties of the alloy are highly anisotropic and depend on the stress sign as well as the relative orientation between the stress and the extrusion axes. The alloy is stronger when it is compressed along the extrusion direction. Under this configuration, the slip of <a> dislocations in the basal plane is highly limited. However, the activation of kinking induces an increase in the plastic deformation. In the transversal extrusion direction, some grains deform by the activation of basal slip. The difference in the yield stress between the different stress configurations decreases with the increase in the test temperature. The evolution of internal strains obtained during in-situ compressive experiments reveals that tensile twinning is not activated in the LPSO phase.

Earthquake Magnitude Scaling Using Peak Ground Velocity Derived from High-Rate GNSS Observations

2020 ◽  
Vol 92 (1) ◽  
pp. 227-237
Author(s):  
Rongxin Fang ◽  
Jiawei Zheng ◽  
Jianghui Geng ◽  
Yuanming Shu ◽  
Chuang Shi ◽  
...  
Keyword(s):  
Rapid Determination ◽  
Seismic Station ◽  
Scaling Law ◽  
Large Earthquake ◽  
Earthquake Magnitude ◽  
New Method ◽  
High Rate ◽  
Peak Ground Velocity ◽  
Absolute Deviation ◽  
Magnitude Scaling

Abstract Rapid response to destructive tsunami and seismic events requires rapid determination of the earthquake magnitude. We propose a new method that employs peak ground velocities (PGVs) derived from Global Navigation Satellite System (GNSS) data to estimate earthquake magnitudes. With a total of 1434 records from 22 events as the constraints, we perform the regression and obtain a PGV scaling law for magnitude determination. The advantage of the new method is that the PGVs are extracted from the GNSS velocity waveforms, which can be easily computed using broadcast GNSS ephemeris. In contrast, the peak ground displacement (PGD) depends on a sophisticated high-precision GNSS-processing subject to external correction data, realization of which cannot be kept robust constantly, especially in real time. The results show that the PGV magnitudes agree with reported moment magnitudes with mean absolute deviation of 0.26 magnitude units for the 22 events and also agree well with the PGD magnitude. We further demonstrate that GNSS-derived PGV and the modified Mercalli intensity values can be consistent with their counterparts from the U.S. Geological Survey ShakeMap products and therefore the GNSS-derived PGVs have the potential to be included in the ShakeMap as a complementary constraint, especially in areas with sparse seismic station coverage for large earthquake.

Studies on Thermomechanical Cycling Characteristics of an Ni-Ti-Cu Shape Memory Alloy

2021 ◽  
Vol 1016 ◽  
pp. 1538-1543
Author(s):  
Ganesan Swaminathan ◽  
Vedamanickam Sampath
Keyword(s):  
Shape Memory ◽  
Strain Recovery ◽  
Functional Characteristics ◽  
Functional Fatigue ◽  
Transformation Temperatures ◽  
Thermomechanical Cycling ◽  
Long Period ◽  
Recovery Strain ◽  
Number Of Cycles ◽  
Time In Service

Shape memory alloys (SMAs) find use in myriad medical and engineering applications. In these applications, the functional characteristics of the materials are capitalized on. SMAs are used repeatedly over a long period of time in service. With continued usage degradation occurs in their functional properties, leading to a change in recovery strain, recovery stress, phase transformation temperatures and hysteresis. The change in the functional characteristics of the alloys is known as functional fatigue. Functional fatigue affects the performance of the alloys with the alloys losing their intended functionality. This problem is to be addressed if the alloys are to be used effectively and efficiently throughout their lifespan. It is especially important when using the alloys within the human body, where such degradation can affect the performance of the biomedical devices and, in turn, human health and life. Till date not too many researchers have explored this area in greater detail. In order thereforeto better understand this behavior, in the present study, an Ni50Ti44.7Cu5.3 alloy wire with a d=1.43 mm and a l=100 mm was cycled (10,000) under constant stress (55 MPa) between its transformation temperatures, which were determined by DSC (without load). The effect of cycling on the shape memory properties (strain recovery, hysteresis, and transformation temperatures) after a specified number of cycles at regular intervals are considered. The results show that there is considerable difference in the properties obtained and are interpreted and discussed in detail in the paper.

Ionosonde and satellite data analysis in relation to the M5.9 April 6, 2009 L’Aquila (Italy) earthquake

2021 ◽  
Author(s):  
Dario Sabbagh ◽  
Loredana Perrone ◽  
Angelo De Santis ◽  
Saioa A. Campuzano ◽  
Gianfranco Cianchini ◽  
...  
Keyword(s):  
Critical Frequency ◽  
Epicentral Distance ◽  
Earthquake Magnitude ◽  
Ionospheric Disturbances ◽  
Champ Satellite ◽  
The Past ◽  
Use Of Data ◽  
Empirical Relations ◽  
Preparation Phase ◽  
Anticipation Time

&lt;p&gt;A combined ground-satellite study of the ionospheric response to the preparation phase of the M5.9 crustal earthquake occurred in L&amp;#8217;Aquila (Italy) on April 6, 2009 is here presented. Ionospheric anomalies based on ionosonde observations of the altitude and blanketing frequency of the E-sporadic (Es) layer (&lt;em&gt;h&lt;/em&gt;&amp;#8217;Es and &lt;em&gt;f&lt;/em&gt;&lt;sub&gt;b&lt;/sub&gt;Es, respectively) and of the critical frequency &lt;em&gt;f&lt;/em&gt;&lt;sub&gt;o&lt;/sub&gt;F2 of the F2 layer are considered. For our analysis we make use of data from the Rome ionospheric observatory, located 90 km away from the earthquake epicentre, looking for anomalies up to a couple of months before the mainshock occurrence. Specifically, the variations for 2-3 hours of these parameters with respect to the past 27-day hourly running median are studied in relation to: (a) the ongoing geomagnetic activity during and several hours before the detection of the anomalies, as described by the values of the global a&lt;sub&gt;p&lt;/sub&gt; and the auroral AE geomagnetic indices; (b) the earlier-obtained empirical relations for the seismic-ionospheric disturbances relating the earthquake magnitude with the epicentral distance and the anticipation time of the found anomalies. In addition, ionospheric anomalies in the electron density measured over the earthquake preparation region by the CHAllenging Minisatellite Payload (CHAMP) satellite at altitudes of about 320 km are studied in relation to the ionosonde-derived anomalies during the whole period preceding the mainshock occurrence.&lt;/p&gt;

Elasto-Plastic Dynamic Responses Analysis of Double-Layer Spherical Lattice Shells under Multiple Earthquake Excitations

2012 ◽  
Vol 256-259 ◽  
pp. 2047-2050
Author(s):  
Bo Song ◽  
Hong Yu Shi ◽  
Li Dong Zhao ◽  
Jian Yun Yu
Keyword(s):  
Double Layer ◽  
Seismic Wave ◽  
Axial Stress ◽  
Dynamic Responses ◽  
Maximum Displacement ◽  
Long Period ◽  
Geometric Deformation ◽  
Plastic Ratio ◽  
Lattice Shells ◽  
Input Wave

Based on the large geometric deformation and nonlinear of material theories, the seismic responses of a double-layer spherical lattice shells structure were studied. The results show that under multi-dimensional earthquake, the maximum displacement and axial stress, as well as plastic ratio of the structure will be obviously increased than those corresponding to the responses under single-dimensional earthquake. When long-period seismic wave was taken as the input wave, the responses of the structure were the maximum.

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