Radiation damping for rigid foundations. Approximate expressions

The dynamic response of machine foundations was one of the first problems studied in soil dynamics with results going back to the 1930s. A number of approximations and graphical results were proposed in the 60s. In this paper we present a series of approximate expressions for the natural frequencies and effective damping of rigid masses on the surface of an elastic half space subjected to both vertical and coupled horizontal-rocking harmonic excitations. The formulas are obtained using the approximate expressions for the dynamic stiffness of circular foundations suggested by Veletsos et al [1, 2] for two different values of Poisson’s ratio of the soil. For the vertical case the expressions are only a function of the mass ratio (ratio of the mass of the foundation to an effective mass of soil) and of Poisson’s ratio. For the horizontal-rocking case they depend also on the ratio of the height of the foundation to its equivalent radius (a slenderness ratio)

Earthquake damage on the vaulted nave of the Atlatlahucan Ex-Convent church in Morelos, Mexico

The State of Morelos, in Mexico, has an architectural heritage conformed by 4614 religious and civil buildings, many of which were severely affected by the earthquake that occurred on September 19, 2017, which also caused damages to the built heritage in the states of Puebla, Tlaxcala, Mexico and Mexico City. A total of about 2800 heritage buildings suffered different damages degrees, reaching in many cases the collapse of elements such as vaults, domes, bell towers as well as their cloisters. The Ex-Convent of San Mateo in Atlatlahucan, Morelos, suffered damages on its main nave, in the pinnacles on the longitudinal side walls as well as in the clock box located on the front façade. In the present work, an analysis is made of the damages observed in the building, as well as a preliminary analytical diagnosis of the behavior of the main nave in order to propose future reinforcement actions for the building

Nonlinear seismic response of Mexican bridges with base isolation accounting for soil structure interaction effects

A parametric analysis of typical base isolated bridges was conducted. The bridges were located in different soil types and were subjected to three different earthquakes (recorded on soft and medium soils). The work had two main objectives: to asses the effects of the nonlinear behavior of the isolation pads of the bridges on the seismic responses (accelerations, displacements, and pier seismic forces), and to study combined effects of base isolation and inertial interaction due to the presence of flexible foundations. The analytical models used for the study were selected on the basis of initial evaluation of different models proposed in the literature to represent a bridge structure and to evaluate the isolation pads’ nonlinear behavior. The bridges studied were developed with a three-dimensional model. After completing the studies, 2 degree of freedom models were used to investigate more general trends of the inertial SSI effects for the base isolated bridges. The results of the work show the efficiency of base isolation pads in improving the seismic performance of bridges in most cases. They suggest that the inertial SSI effects will not be generally important for bridge foundations designed with a factor of safety of 3, with more than one line of piles in either direction since they will be very stiff foundations. But they also showed that for slender piers it is important to carefully evaluate the translations on top of the piers due to the rocking effects of the foundation

La malinche, arquetipo mexicano

Malintzin, Marina, Malinche... Según dice Jung en su libro El Hombre y sus Símbolos: "Los arquetipos son al mismo tiempo imágenes y emociones. Sólo se puede hablar de un arquetipo cuando estos dos aspectos son simultáneos"..

Influence of steel jacket thickness on the RC bridges’ seismic vulnerability

The seismic demands of bridges subjected to strong earthquakes are mostly concentrated on piers. The main objective of this study is to assess the seismic vulnerability of retrofitted bridges with steel jackets. It analyzes the influence of the steel jacket thickness on the seismic capacity and demand of bridges. The bridges in study have two simple supported spans with superstructure composed by AASHTO type girders and a substructure formed with one circular pier over a stiff foundation. They are located on the Pacific coast of Mexico that is a zone of high seismicity. The bridges seismic capacity are evaluated through nonlinear static analyses and the shear force and displacement demands were determined using capacity spectra with a group of 10 real accelerograms from a subduction source. The response spectra were scaled to several peak ground accelerations (PGA) with the aim to estimate four damage scenarios linked each one to a probability of exceedance in a specific period, for return periods in the range of 72–3500 years that represent service level and maximum considered earthquake. Results show that the confining effect provided by the steel jackets substantially improves the seismic performance of the bridges piers. The increase of jacket thickness guides to important increments on columns base shear capacity, and the influence of the steel jacket thickness depends on the limit state and bridge slenderness ratio. Keywords: Steel jacket, Piers' retrofit, Subduction earthquakes, RC piers' vulnerabilit

Parametric study of medium span bridges retrofitted with RC jacketing

Evolution of seismic codes and the average age of the bridges in the world require the evaluation of their seismic vulnerability. This study assesses the expected capacity, demand and damage of seismically deficient medium-length highway bridges, supported in frame-type piers using dynamic nonlinear methodologies. The non-retrofitted structures are 30-m span simple supported bridges with pier heights in the range of 5-25 m. The main emphasis of the study is the assessment of the jacket parametersâ contribution to the seismic vulnerability of bridges. Particularly, it is quantified how jacket thickness and reinforcement ratio affect the probability of reaching a particular damage limit state. The retrofitted scheme includes three jacket thicknesses and three longitudinal steel ratios. The results evaluate fragility curves to quantify the influence of RC jacketing on the seismic response and allow to select the best jacket parameters that improve the expected seismic behavior of the bridges.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Itópica Expresión Comunidad Radio

Documento final del Proyecto de Aplicación Profesional en el que se recopila la experiencia en la estación Itópica Radio durante el curso otoño 2014. Se tocan puntos medulares relacionados a este proyecto del ITESO, tales como la radio universitaria por internet y la historia de Itópica. De igual forma, se integra lo realizado por las diferentes disciplinas de los universitarios así como los conocimientos que aportaron, los resultados y los aprendizajes obtenidos. En este proyecto trabajaron alumnos de las licenciaturas en Ciencias de la Comunicación, Gestión Cultural, Diseño Integral y Psicología y de Ingeniería en Sistemas Computacionales