The Mexico Earthquake of September 19, 1985—Nonstationary Models of Seismic Ground Acceleration

1988 ◽  
Vol 4 (3) ◽  
pp. 551-568 ◽  
Author(s):  
M. Grigoriu ◽  
S. E. Ruiz ◽  
E. Rosenblueth
Keyword(s):  
Mexico City ◽  
Stationary Process ◽  
Soft Soil ◽  
Nonstationary Process ◽  
Oscillatory Process ◽  
Ground Acceleration ◽  
Single Degree Of Freedom ◽  
Single Degree ◽  
Coefficients Of Variation ◽  
Mexico Earthquake

Characteristics of a nonstationary process obtained by modulating the amplitude and frequency of a stationary process differ from those of an oscillatory process. An accelerogram recorded in the soft soil of Mexico City during the 1985 earthquake serves to calibrate both nonstationary models. Responses of linear and nonlinear single-degree-of-freedom systems indicate that the process with modulated amplitude and frequency is preferable for reliability studies. Coefficients of variation of ductility demands of systems excited with accelerograms generated by the model with modulated amplitude and frequency are close to those corresponding to actual accelerograms.

Evaluation of floor acceleration demands from the 2017 Mexico City code seismic provisions using a continuous elastic model and records of instrumented buildings

2020 ◽  
Vol 36 (2_suppl) ◽  
pp. 213-237
Author(s):  
Miguel A Jaimes ◽  
Adrián D García-Soto
Keyword(s):  
Mexico City ◽  
Seismic Design ◽  
Soft Soil ◽  
Response Spectra ◽  
Elastic Model ◽  
Ground Acceleration ◽  
Nonstructural Components ◽  
Floor Response Spectra ◽  
Instrumented Buildings ◽  
Floor Acceleration

This study presents an evaluation of floor acceleration demands for the design of rigid and flexible acceleration-sensitive nonstructural components in buildings, calculated using the most recent Mexico City seismic design provisions, released in 2017. This evaluation includes two approaches: (1) a simplified continuous elastic model and (2) using recordings from 10 instrumented buildings located in Mexico City. The study found that peak floor elastic acceleration demands imposed on rigid nonstructural components into buildings situated in Mexico City might reach values of 4.8 and 6.4 times the peak ground acceleration at rock and soft sites, respectively. The peak elastic acceleration demands imposed on flexible nonstructural components in all floors, estimated using floor response spectra, might be four times larger than the maximum acceleration of the floor at the point of support of the component for buildings located in rock and soft soil. Comparison of results from the two approaches with the current seismic design provisions revealed that the peak acceleration demands and floor response spectra computed with the current 2017 Mexico City seismic design provisions are, in general, adequate.

The Mexico Earthquake of September 19, 1985—Performance of Low-Rise Buildings in Mexico City

1989 ◽  
Vol 5 (1) ◽  
pp. 121-143 ◽  
Author(s):  
E. Miranda ◽  
V. V. Bertero
Keyword(s):  
Reinforced Concrete ◽  
Mexico City ◽  
Soft Soil ◽  
Time History ◽  
Federal District ◽  
Excellent Performance ◽  
Soil Zone ◽  
Space Frames ◽  
Dynamic Analyses ◽  
Mexico Earthquake

This paper summarizes the results of analytical studies conducted to understand the observed performance of low-rise buildings located in the soft-soil zone of Mexico City during the 1985 Michoacan earthquake. Two low-rise reinforced concrete moment resistant space frames were designed in accordance with the 1976 Code for the Federal District of Mexico. They were subjected to a series of static and time history dynamic analyses. The results indicate that the designed buildings have significantly larger lateral strengths than required by the Code and that these overstrengths were the main reason for the excellent performance of most of the low-rise buildings in Mexico City during the 1985 Michoacan earthquake.

The Mexico Earthquake of September 19, 1985—The Seismic Performance of Buildings with Weak First Storey

1989 ◽  
Vol 5 (1) ◽  
pp. 89-102 ◽  
Author(s):  
S. E. Ruiz ◽  
R. Diederich
Keyword(s):  
Mexico City ◽  
Soft Soil ◽  
Absorption Capacity ◽  
Ductility Demand ◽  
Displacement Ductility ◽  
Lateral Resistance ◽  
Lateral Strength ◽  
Mexico Earthquake ◽  
Range Of Values ◽  
Acceleration Record

During the Michoacan earthquake of Séptember 19, 1985, 8 percent of the damaged buildings in the Mexico City area were characterized by a first storey much weaker than the upper ones. Although it is recognized that these failures may have resulted from the combination of several features, in this paper it is intended to study the possible influence of the lateral strength discontinuity in the ductility demand at the first storey, and to try to understand the behaviour of this type of structures under the actions of the East-West component of the highest acceleration record obtained on soft soil in Mexico City during the mentioned earthquake. A parametric study for five and twelve-storey buildings with weak first storey is presented in this paper. The infill walls in the upper storeys were brittle in some cases and ductile in others. For certain cases, the results show the existence of a range of values of the ratio of seismic lateral resistance of the upper storeys to that of the lowest one for which ductility demands at the lowest story can be considerably higher than for other intervals. It is shown that the absorption capacity of ductile walls plays an important role in the displacement ductility demands of the first storey.

scholarly journals Observation of a directed resonance in soil driven by transverse rock motion

1989 ◽  
Vol 22 (2) ◽  
pp. 81-89 ◽  
Author(s):  
W. R. Stephenson
Keyword(s):  
Seismic Response ◽  
Resonant Mode ◽  
Degree Of Freedom ◽  
Mechanical Oscillator ◽  
Ground Acceleration ◽  
Single Degree Of Freedom ◽  
Fine Grained ◽  
Single Degree ◽  
Cook Strait

One component of horizontal ground acceleration recorded on flexible soil during the 1968 November 1 Cook strait earthquake is shown to be well modelled as a single degree of freedom oscillator excited by the recorded component of transverse acceleration in nearby bed rock. This is shown to be consistent with the cellular resonant mode hypothesis of seismic response of flexible soil. The mechanical oscillator is identified as a layer of fine-grained, post-glacial alluvium of approximately 20 m thickness.

Observations of Rayleigh waves in Mexico City Valley during the 19 September 2017 Puebla–Morelos, Mexico earthquake

2020 ◽  
Vol 36 (2_suppl) ◽  
pp. 62-82
Author(s):  
Pablo Heresi ◽  
Jorge Ruiz-García ◽  
Omar Payán-Serrano ◽  
Eduardo Miranda
Keyword(s):  
Surface Waves ◽  
Mexico City ◽  
Edge Effects ◽  
Rayleigh Waves ◽  
Soft Soil ◽  
Inner Product ◽  
Basin Edge ◽  
Literature Evidence ◽  
Mexico Earthquake ◽  
Stockwell Transform

This article discusses the principal features of Rayleigh surface waves generated by basin-edge effects in Mexico City during the Mw7.1 19 September 2017 Puebla–Morelos, Mexico earthquake. Rayleigh waves were extracted from ground motions recorded at 12 stations in Mexico City. We used a recently proposed method for extracting surface waves, where the earthquake record is filtered based on the normalized inner product of the Stockwell transform of the three-component earthquake recordings. Results of this study reveal that basin-edge effects produced strong Rayleigh waves, particularly at certain stations, with frequencies that are mainly between 0.2 and 0.9 Hz, which is consistent with previous frequency ranges reported in the literature. Evidence of higher-mode Rayleigh waves was found at all stations located on soft soil sites, even at stations that are more than 1 km away from the basin edges. It was also observed that peak acceleration spectral ordinates of the retrograde component of the extracted Rayleigh waves at two stations exceeded the design spectral ordinates of the 1976 and 2004 editions of the Mexico City Seismic Provisions.

The Mexico Earthquake of September 19, 1985—Behavior of Building Foundations in Mexico City

1988 ◽  
Vol 4 (4) ◽  
pp. 835-853 ◽  
Author(s):  
M. J. Mendoza ◽  
G. Auvinet
Keyword(s):  
Mexico City ◽  
Soft Soil ◽  
Shear Forces ◽  
Natural Period ◽  
Plastic Deformations ◽  
Long Period ◽  
Cyclic Stresses ◽  
Static Contact ◽  
Mexico Earthquake ◽  
Main Factor

During the 1985 earthquake, a number of building foundations in the lacustrine soft soil area of Mexico City presented an inadequate performance. Previous high static contact stresses between the foundation and the supporting subsoil propitiated the appearance of plastic deformations of the soil under seismic cyclic stresses, which led to settlements and tilting of the buildings. Foundations of all kinds showed different degrees of vulnerability to the earthquake, but constructions on friction piles sustained the most severe damages. This can be attributed in some cases to non compliance with the accepted design criteria and current regulations. The main factor was however the pronounced dynamic magnification of seismic movements associated to the quasi coincidence between the natural period of some structures with moderate height on friction piles, and the long period of the subsoil motions, which led to large overturning moments and shear forces at the foundation level.

Damage potential of Loma Prieta ground motions

1991 ◽  
Vol 81 (5) ◽  
pp. 2048-2069 ◽  
Author(s):  
Helmut Krawinkler ◽  
Aladdin Nassar ◽  
Mohsen Rahnama
Keyword(s):  
Ground Motions ◽  
Soft Soil ◽  
Structural Performance ◽  
Damage Potential ◽  
Seismic Demands ◽  
Single Degree Of Freedom ◽  
Loma Prieta Earthquake ◽  
Single Degree ◽  
Loma Prieta ◽  
Attenuation Characteristics

Abstract This article focuses on an engineering evaluation of the ground motions recorded during the Loma Prieta earthquake. Regression analysis is employed to evaluate the attenuation characteristics of the elastic and inelastic strength demands imposed by rock and alluvium ground motions on bilinear single degree of freedom (SDOF) systems. Several records are used to illustrate the large seismic demands generated by soft soil ground motions. Strength capacities of modern code-designed structures are compared to the strength demands in order to assess the damage potential of the Loma Prieta ground motions. The Cypress structure is used as an example to illustrate the application of simple demand / capacity concepts for an evaluation of structural performance.

The Mexico Earthquake of September 19, 1985—Seismic Zoning of Mexico City after the 1985 Earthquake

1989 ◽  
Vol 5 (1) ◽  
pp. 257-271 ◽  
Author(s):  
J. Iglesias
Keyword(s):  
Mexico City ◽  
Soft Soil ◽  
Resistance Coefficient ◽  
Seismic Zoning ◽  
Base Shear ◽  
Severe Damage ◽  
Seismic Capacity ◽  
Mexico Earthquake ◽  
The City ◽  
Resistance Coefficients

Using a simplified method for the evaluation of the seismic capacity of medium rise concrete structures, it was possible to obtain the base shear coefficient corresponding to failure (resistance coefficient) for 162 buildings, and use it as an evaluation index. The resistance coefficients of the 90 evaluated structures that suffered severe damage were used to elaborate a map of intensities for the 1985 Mexico City earthquake. This map shows the strong interaction of neighboring zones of firm soil or rock that amplify the ground motion in the soft soil between them as much as 100%, this being the main reason for the high intensities observed in some districts of the city. Based on these results, a new seismic zoning was proposed for the chapter of the 1987 Mexico City Building Code.

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