Conceptual seismic design guidance for new reinforced concrete framed infill buildings

Throughout the world, reinforced concrete frame buildings with masonry infill walls house families, shelter school children, and provide offices for workers. These buildings are functional, durable, and economical. All too often, though, these buildings perform poorly in earthquakes. Some collapse and kill the people inside, and many are badly damaged, requiring demolition or expensive repairs. Sometimes, poor construction quality or a lack of engineering design is at fault. In many cases, though, the engineering design itself is to blame. Despite the stiffness and strength infill walls possess, building codes around the world lack guidance on modeling and designing infill walls as structural elements, and many engineers have been taught not to consider them as such. Engineers therefore often ignore infill walls during structural design or presume that they will have only beneficial effects. This simple yet fundamental oversight often dooms buildings to poor earthquake performance. For example, many multi-story reinforced concrete buildings with masonry infill walls collapsed at the ground level from the 1999 Chi-Chi, Taiwan earthquake. These buildings typically had commercial space or parking at the ground floor and infill walls in the stories above.

Diseño de estructuras de contención en suelos granulares bajo acciones sísmicas

Se evalúan los empujes activos dinámicos de suelos sobre estructuras de contención del tipo de gravedad, analizando la naturaleza del problema, evaluando los diferentes tipos de falla, y el comportamiento de estas estructuras bajo las hipótesis de desplazamientos despreciables y de desplazamientos predeterminados. Se examina la influencia y la relación entre los parámetros que intervienen en la formulación de Mononobe y Okabe. Se presentan expresiones simplificadas de cálculo de empuje dinámico activo y se propone una nueva formulación simplificada aplicable para los niveles de acción sísmica probable en Argentina. Finalmente, se presenta un ejemplo numérico de aplicación, formulando sugerencias aplicables al diseño sismorresistente de estribos y muros de gravedad. (AU)

Daño estructural en pórticos planos de concreto armado según normas sísmicas

En la actualidad las normas sísmicas perscriben que una estructura sometida a sismos moderados puede experimentar daño estructural reparable, pero no definen claramente el concepto de daño, ni la metodología para su cuantificación. El propósito de este trabajo es cuantificar el daño estructural, definir su distribución en la estructura y calcular las derivas inelásticas. Para ello se utilizó el modelo de Daño Concentrado desarrollado desde 1993 en la Universidad de Los Andes, Venezuela. Se analizaron pórticos planos de concreto armado de 4, 8, 12, 16, 20 pisos. A cada uno de ellos se le aplicaron cinco acelerogramas cuyos espectros de respuesta promedian el espectro de diseño correspondiente. Los resultados de las simulaciones muestran que algunos pórticos sufrieron daño reparable y que en condiciones de alto factor de amplificación dinámico, se desarrollaron rótulas plásticas en ambos extremos de todas las columnas de un alto nivel, conformando un mecanismo frágil. Para mejorar el comportamiento de las estructuras se recomienda suministrar confinamiento adecuado en ambos extremos de las vigas y lograr las resistencias requeridas en columnas con mayores dimensiones y menor porcentaje de esfuerzo

Respuesta sísmica de puentes chilenos con apoyos aislantes

La mayoría de los puentes importantes construidos en los últimos años y la vía elevada del metro de Santiago incluyen algún tipo de aislación sísmica y en varios de ellos se han instalado redes locales de acelerómetros con el fin de monitorear su respuesta frente a terremotos. En este trabajo se analizan los registros, tanto de vibraciones ambientales como de sismos, obtenidos a la fecha en el puente Marga-Marga de Viña del Mar, en el tramo elevado de la Línea 5 del metro de Santiago y en el puente Amolanas, ubicado en el kilómetro 308 de la carretera Panamericana Norte. Además, se presentan modelos de elementos finitos que reproducen las características dinámicas obtenidas experimentalmente.(AU)

Características ingenieriles del terremoto de Ocoña del 23 de junio de 2001

Los Departamentos de Ingeniería Civil y Geofísica de la Universidad de Chile en conjunto con instituciones internacionales poseen redes sismológicas y de movimiento fuerte en el norte de Chile. Estas redes registraron el terremoto del 23 de junio del 2001 de Magnitud Mw=8.4 ocurrido en el sur de Perú que es a su vez el mayor detectado en los últimos 25 años en la zona. El evento en la zona norte de Chile presenta importantes aceleraciones y velocidades máximas considerando que la zona está a más de 400 km de distancia del epicentro y 200 km de la zona de ruptura y espectros de respuesta muy cercanos a la demanda elástica establecida en la norma chilena de diseño NCh 433 of 96.(AU)

Soil structure interaction of bridges for seismic analysis

This report documents the current state-of-practice in soil-structure interaction analyses for seismics desing of bridges. It covers several relevant areas such as ground motion aspects, various issues on soil-structure interaction for typical foundations and methods of substructuring to reduce the number of degrees of freedom for foundation elements. The ground motion topic includes seismic hazard analyses, seismic perfomance criteria, spectrum compatible time history, spatial variation of ground motions, effects of local soil condition, and the recent ATC-32 recommendations on standard ARS (Acceleration Response Spectrum) design criteria. The soil-structure interaction area discusses modeling of foundation stiffness and damping for spread footing, gravity caisson, large diameter drilled shaft, and pile group. The concept of substructuring technique is described fully. The technique offers two approaches: one bases on kinmatic soil-structure interaction and the other based on inertia interaction. Both are intented to reduce the number of degrees of freedom for the foundation to be used in the global bridge analyses. (AU)

Development of measurement capability for micro-vibration evaluation with application to chip fabrication facilities

In this project, Multidisciplinary Center of Earthquake Engineering Research (MCEER) researchers conducted vibration tests at a site in West Seneca, New York to determine its suitability for attracting and supporting a ChipFab facility. ChiFab, a short name for a semiconducto chip fabrication facility, is high-tech manufactuing facility where the electronic chips for items ranging from computers to cellular phones to automobiles are manufactured. The industrial park site (North America Park) is located near a railroad, a major expressway and an active mining operation. The level of micro-vibrations of ground motion is critical for this type of facility. Several locations were instrumented within the industrial park. Three direction acceleration components were measured at each location, during the period between November 1 and December 1, 1998. These acceleration data were subsequently converted into RMS velocity (one-thrid-octave band) through specially derived analytical relationships. It was found that the proposed ChipFab site in the northen section of the industrial park was suitable for the manufactuting facility. The measurement system used to conduct this testing was developed specifically for this project. This report describes the measurement system detail, including its sensory system, data acquisition and recording, sensor installation and distribution of the measurement locations. The procedure to obtain measurements, data evaluation, and results and analyses related to the West Seneca site are also described in the report. In addition to the encouraging results at the specific site (North America Center, West Seneca, NY), the ground vibration measuring procedure developed can potentially be used as an industrial standard for delicate manufacturing site evaluation. The report also introduces the theorical development for the relationship between frequency spectra and RMS values, which can be adopted for a wide range of applications on interpretations of the data obtained from up-to-date data acquisition systems

Design and retrofit methodology for building structures witn supplemental energy dissipating systems

The study described in this report on focuses on fundamental issues related to the design and use of supplemental damping devices in building structures. The principle objective is to develop a generic/practical analysis and design methodoly for structures that considers structural velocities and equivalent viscous damping of the devices. These two issues are explored in depth. Tools to transform the spectral velocity to an actual relative structural velocity are provided, and simple design procedure which incorporates power equivalent linear damping based on actual structural velocities is presented. The effectiveness of the design methodology is demonstrated with a retrofit design example using a supplemental load balancing tendom configuration

Property modification factors for seismic isolation bearings

The overall objective of this task was to develop an improved understanding of the expected performance and behavior of sliding isolationsystems;evaluate their functionality, reliability, and longevity; and assist in the development of improved codes and specifications for their use. This report deals with the problem of establishing upper and lower bound values of properties of seismic isolation bearing for use in the analysis and design of seismicallyisolated bridges. These bounding values of properties are determined by using system property modification factors. The concepts and the values presented represent the basis on which bounding analysis is described in the new 1999 "AASHTO Guide Specifications for Seismic Isolation Design"

Restrainer design procedures for multi-span simply-supported bridges

The overall objective of this task was to review and compare the methods currently in use for the desing of cable restrainers used to tietogether simple spans in multiple-span, simply-supported bridges and to recommend improvements which will provide better performance while maintaining ease and efficiency of desing. Two existing methods, one each developed by Caltrans and AASHTO, were compared and evaluated. Three new methods were also proposed and evaluated. All five procedures were found to be effective in preventing spans from unseating in most bridges. However, the authors recommend that the procedure known as the "proposed" method be used for future desing, as it provided the best overall performance under moderate-to-large earthquakes. A companion MCEER report, "Design Procedures for Hinge Restrainers and Hinge Seat Widht for Multiple-Frame Bridges," by R. Desroches and G.L. Fenves, MCEER-98-0013, provides similar evaluations and recommendations regarding the design of cable restrainers for multiple continuous span bridges

Funcionabilidad del programa médico arquitectónico en la remodelación de hospitales en zonas sísmicas de Venezuela

El colapso funcional de un hospital se produce cuando la institución, ante un sismo, aunque no haya sufrido ningún daño en su estructura física, se ve incapacitada de brindar los servicios para la atención inmediata de víctimas y la posterior recuperación de la comunidad afectada. Este colapso se ocasiona, no sólo por daños en los elementos no estructurales, sino por un plan funcional inapropiado originado por un diseño rígido de los ambientes, una inadecuada ubicación y relación entre éstos y falta de coordinación del hospital con los servicios externos a éste. Los esquemas médico arquitectónicos usualmente utilizados en el diseño de los hospitales en los países occidentales, no incluyen los aspectos funcionales para la atención después de un sismo. Esta carencia debe subsanarse, por lo que hay que reestudiar el programa médico arquitéctonico e incluir estos nuevos conceptos en los proyectos de remodelación. Así, un plan para reducir la vulnerabilidad sísmica en hospitales debe incluir tanto el estudio de los componentes estructurales y no estructurales, como una remodelación que garantice la apropiada funcionalidad del esquema médico arquitectónico al ocurrir un sismo. Esta ponencia presenta el avance de una análisis de los hospitales de mediana y alta complejidad de Venezuela y una breve descripción de un método para el establecimiento de parámetros y sus valores, para la evaluación de funcionalidad del esquema médico arquitectónico, para determinar los parámetros a remodelar. (AU)

Effect of vertical ground motions on the structural response of highway bridges

The Multidisciplinary Center of Earthquake Engineering Research (MCEER) is a national center of excellence in advanced technology applications that is dedicate to the reduction of earthquake losses nationwide. Headquartered at the University at Buffalo, State University of New York, the Center was originally established by the National Science Foundation in 1986, as the National Center for Earthquake Engineering Research (NCEER). Response spectrum analyses are perfomed on all six bridges usinga all of the above ground motion parameters for the cases of (a) two-component horizontal only input and (b) three-component input. Results for the two cases are compared. The accuracy of these resultus is validated by linear time history analyses of three bridges using spectrum compatible records. The additional effect of including the vertical component of motion is presented as a ratio of the dead-load only response. Records with early-arriving short period motion in the vertical component are shown to produce similar structural response to records that do not have these caracteristics. Results from response spectrum analyses using vertical spectrum with a spectral amplitude 2/3 of the horizontal spectrum showed that the response can be up to 40

greater or less than those from empirical vertical spectra

Seismic reliability assessment of critical facilities : A handbook, supporting documentation, and model code provisions

This document summarizes a multi-year research project in the development of a detailed methodology to assess and improve the functional reliability of equipment systems in critical facilities following earthquakes. It is inended to be used by engineers, building officials, owners and other individuals interested in assessing and impoving the capability of a facility to provide critical services. The methodolgy described intends to improve the reliability of equipment systems and make it flexible enough to be used in many types of facilities and does not require personnel with seismic expertise. The approach to this methodogy is simple: 1. Systems definition. 2.Evaluation of individual components. 3. Systems evaluation. 4. Risk management, make decisions

Critical seismic issues for existing steet bridges

This report assesses the perfomance of existing steel bridges in the past earthquakes. There is an identification of the areas in existing steel bridge structures that are seismically vulnerable. Among the examined components there are: steel columns, steel tower bents, steel superstructures (particularly steel trusses), girder cross-frames, and steel connections. Vulnerable areas and details are identified, and recommendations for improved designs and retrofit techniques are made. Research needs are identified where existing knowledge is lacking. There is an examination of the three most common lateral force existing systems: MRF's: moment resisting frames; CBF's: concentrically braced frames and EBF's; eccentrically braced frames. It indicates that any of them can provide adequate seismic structural ductility. There is also an analysis of X-braces and X-braces and V-braced bridges piers as a way of getting potential structural ductility. It has a lis of illustrations, which include configurations, pier designs, axial loads and analytical models of connections, among others