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2001 | Buch

Strong Motion Instrumentation for Civil Engineering Structures

herausgegeben von: M. Erdik, M. Celebi, V. Mihailov, N. Apaydin

Verlag: Springer Netherlands

Buchreihe : NATO ASI Series

insite
SUCHEN

Über dieses Buch

Most of the existing strong motion instrumentation on civil engineering structures is installed and operated as federal, state, university, industry or private applications, in many cases operated as a closed system. This hampers co-operation and data exchange, hampering the acquisition of strong motion and structural data, sometimes even within a single country. There is a powerful need to inform engineers of existing strong motion data and to improve the accessibility of data worldwide. This book will play a role in fulfilling such a need by disseminating state-of-the art information, technology and developments in the strong motion instrumentation of civil engineering structures. The subject has direct implications for the earthquake response of structures, improvements in design for earthquake resistance, and hazard mitigation.
Readership: Researchers in earthquake engineering, engineers designing earthquake resistant structures, and producers of strong motion recording equipment.

Inhaltsverzeichnis

Frontmatter
State-of-the-art technology for data storage and dissemination

Seismology presents unique challenges in data storage requirements and the need to rapidly access data and disseminate information. This paper will briefly summarize some current technological trends in each of these areas.In general, seismological data sets can vary in size from minute to massive. Seismology is somewhat unique in that, not only can the data volumes be large, there still exists a requirement to recover and manipulate data at the level of individual samples. These competing requirements make data storage solutions more complicated. This paper will review some of the current technologies that exist and how they can be applied to seismological data archives.There exists a need to access data from remote seismological data recorders in real time. Often the telecommunications infrastructure at these remote sites does not exist and this presents unique challenges to operators of seismic networks. This paper will discuss several communication techniques including use of telephone circuits, Internet Service Providers (lSPs), and satellite systems that can be exploited to benefit seismology on local, regional and global scales.New opportunities have emerged that allow easy dissemination of data and information to outside users. This paper will also discuss some of the efforts taking place within the Comprehensive Test Ban Treaty Organization and the Federation of Digital Broadband Seismographic Networks in this area.

Timothy K. Ahern
Structure Instrumentation in the California Strong Motion Instrumentation Program

In the last 27 years the California Strong Motion Instrumentation Program (CSMIP) in the California Department of Conservation, Division of Mines and Geology has instrumented over 240 structures, including 160 buildings, 58 bridges, and 20 dams. In addition to these structures, CSMIP has installed over 500 ground response stations. Many of these stations have been installed since the 1994 Northridge earthquake. These modern stations have modem digital recording and communication systems that can transmit the recorded data to a central facility in Sacramento within a few minutes after the shaking occurs. The recorded data are automatically processed in the central facility and then disseminated rapidly to the users. These near-real-time data include acceleration, velocity, and displacement time series and response spectra.The near-real-time strong-motion data provide information on ground shaking and response of instrumented structures, and are useful not only for improving seismic design practices but also for post-earthquake damage evaluation of structures. This paper describes the current status and future plan of CSMIP structure instrumentation projects, and discusses quick application of strong-motion data to post-earthquake response and damage evaluation of structures.

Moh J. Huang, Anthony F. Shakal
Learning From Seismic Response of Instrumented Buildings During the 1994 Northridge Earthquake

In the aftermath of the January 17, 1994 Northridge earthquake hundreds of strong ground motion and building response accelerograms were retrieved from stations throughout the greater Los Angeles basin. Particularly important among the building response records were the data obtained from instrumented buildings which experienced relatively large ground motions. This paper provides a summary of the results obtained from an elaborate two-year project which included inspection of the buildings, damage assessment, performance evaluations. The forces, displacements, and dynamic characteristics interpreted from recorded data are contrasted with those suggested by building codes. Key response parameters and characteristics of each building are studied and where necessary observations are provided which may be used to improve future editions of the building codes.

Farzad Naeim
New Developments in Health Monitoring for Civil Structures

Practical examples of health monitoring of civil structures now exist, and recent or coming improvements in technology will likely add more examples. This paper discusses several health monitoring projects, both commercial and research. Some new technologies in instrumentation, communications, and analysis are then briefly listed. However, technology alone cannot improve the “market” for structural health monitoring. The decision process for monitoring must be studied, and developers of monitoring technology must realistically compare the costs and benefits. Barriers to wider adoption and implementation are discussed and some needs expressed.

Robert Nigbor, John Fort
Experimental Dynamic Analysis of Historic Monuments and Buildings

The earthquake effect on monumental heritage is a critical issue in areas of ancient civilisation. Monumental buildings require specific strengthening techniques, related to a clear understanding of all factors affecting its vulnerability.

Dario Rinaldis
Utilization of Rapid Post-Earthquake Data by utilities

When a potentially damaging earthquake occurs, utilities (electricity, gas, water, and telecommunications) have an urgent need for information about the effects of the event so that they can make optimal decisions regarding safety and maintaining and restoring utility functionality. Modern earthquake instrumentation systems, including strong-motion recorders and regional seismic networks, can collect data and provide information products that can greatly improve this decision-making and action-taking process. Four areas of utility response to earthquakes illustrate the utilization of these data: (1) Rapidly available network and strong-motion data can provide an earthquake alert that will make utility personnel aware that an earthquake is occurring, what area of the utility’s service territory is affected, and the likely extent of damaging ground motions. This alert will focus the earthquake response attention of the utility and may permit quick operational and life-safety actions. (2) Within 10 to 30 minutes after the earthquake, analysis of strong-motion data from key utility sites can provide assessments of the likelihood of damage that can be used to prioritize deployment of field personnel and guide the initial operational control and recovery plans. (3) In the same time frame, similar strong-motion-based damage assessments of transportation routes (e. g. freeways, bridges, and overpasses) along with reported damage and disruption can help the utilities plan how to get inspection and repair crews to key facilities. In addition, damage likelihood assessments of commercial, industrial, and residential buildings can indicate where utility service connections may need rapid responses to safety and secondary damage threats. (4) Within a few hours of the earthquake, pre-arranged building inspectors can use building response strong-motion measurements to help evaluate the safety of continued occupancy of structures housing critical post-earthquake response functions.

William U. Savage
Analysis of Earthquake Records from Structures: An Overview

The paper presents an overview of the methods that are available to analyze seismic records from structures. A typical analysis involves data processing, system identification, and damage detection. Data processing aims to minimize the ambient and instrument noise in the data, as well as possible low-frequency drifts, outliers, and other unwanted signals. System identification deals with determining the dynamic characteristics of a structure from its recorded response. There are a large number of methods available in the literature for system identification, varying from simple Fourier analysis to stochastic adaptive filtering. Unless data require otherwise, simple methods should be preferred for identification, because they are more robust and results are easier to interpret. Modal identification is the most widely used form of system identification. An alternative is the discrete-time filters, which provide a convenient model for identification of linear as well as nonlinear structures. Special techniques can be developed to identify a particular component of response, such as torsion, soil-structure interaction, and inter-story drift. Damage detection is a subject that is closely related to nonlinear system identification. Since a damaged structure almost always behaves in a nonlinear fashion, the problem of damage detection becomes equivalent to identification of the nonlinear behavior in the structure. The standard method for damage detection has been to observe the changes in the frequencies of the structure, However, unless it is a major damage, frequencies are not very sensitive to damage, particularly to localized damage. More reliable methods for damage detection can be developed by using time-frequency analyses and wave propagation techniques.

Erdal Şafak
Structural Monitoring of Bridges — An Overview

The author’s experience is used to describe two kinds of monitoring of suspension and cable-stayed bridges. These include the Humber and Bosporus suspension bridges and the Second Severn cable-stayed bridge. Special attention is paid to a very detailed study at Humber of correlation between wind speed/direction and response. Use of a new video vision system for measuring dynamic displacement is described. The importance of wind speed/direction and rain is noted for cable-stayed bridges, as well as cable/deck interaction. Mention is made of monitoring studies on highway bridges.

R. T. Severn
Recording and interpreting earthquake response of fullscale structures

Earthquake resistant design (or retrofit) of structures requires realistic and accurate physical and theoretical models. Validation and further improvement of these models can be done only by comparison with full-scale, in situ measurements of the response to earthquake excitation. This paper presents (a) a review of the principles this validation process is based on, (b) discussion of selected examples of past contributions to modeling of structures, and (c) an outline of some of the current research needs. It is concluded that, in the education of future engineers, the art of modeling full-scale structures, and breadth of knowledge in classical mechanics have been neglected, and that this trend should be reversed.

M. D. Trifunac, M. I. Todorovska
The U.S. Army Corps of Engineers Seismic Strong-Motion Instrumentation Program

The U.S. Army Corps of Engineers (USACE) currently operates a seismic Strong-Motion Instrumentation Program (SMIP) throughout the United States to provide a measure of project performance, provide insight into the safety of USACE projects, and establish a data base for earthquake research. Strong-motion instruments used for SMIP consist of digital and analog accelerographs, peak acceleration recorders, and seismic alarm devices. These instruments have been placed at earth, rock, earth and rock, arch, and gravity dams owned and operated by the USACE. At present, 123 projects located in 32 states and Puerto Rico are monitored with more than 500 strong-motion instruments. The USACE network is second in size to that operated by the California Division, of Mines and Geology.The purpose of this paper is to present various aspects of the USACE SMIP including criteria for design of installations, recording equipment, operation, maintenance, performance to date, upgrades, future goals and the importance of interagency cooperation. Particular attention is focused on economics and advantages associated with ultimate conversion to remotely accessed digital instrumentation.

Robert F. Ballard Jr.
Integrated Surface and Borehole Strong-Motion, Soil-Response Arrays in San Francisco, California

An integrated set of four borehole arraysand ten surface installations is installed in the city of San Francisco, California to measure the response of soft-soil deposits to strong earthquake ground motions. The borehole arrays extend through thick layers of softwater-saturated soils of Holocene age and older more consolidated soils of Pleistocene age into bedrock at depths up to 100 m. The surface installations are configured in pairs to provide simultaneous comparative surface measurements of soft soils and nearby rock. The rock locations also permit comparative measurements of rock as observed at the surface and in nearby boreholes. Complementary structural response arrays alsoare installed near each array.The arrays are designed to address a wide variety of scientific and engineering issues, and especially the issue of anelastic and nonlinear soil response at high strain levels. Exact anelastic models have been developed to account for contrasts in anelastic properties at boundaries and the resultant inhomogeneity of propagating wave fields. These models predict that significant amounts of energy may be trapped in soil basins with resultant larger amplifications than can be predicted using conventional homogeneous wave-field models with damping. Results of these models are discussed.

R. D. Borcherdt, H. P. Liu, R. E. Westerlund, C. Dietel, J. F. Gibbs, R. E. Warrick
Current and New Trends in Utilization of Data from Instrumented Structures

The many uses of seismic response data from instrumented structures include assessment of design and analysis procedures, improvement of code provisions, and correlation of system response with damage. A preliminary list of applications of response data with sample references is provided. Three examples of recorded data and summary analyses are provided to illustrate uses of response data.

Mehmet Çelebi
Instrumentation of Dam Structures in Switzerland

A dam network was created in 1992 and 1993 in Switzerland. It encompasses 29 accelerographs placed in the dams of Mauvoisin (250.5 meter high arch dam, 12 instruments), Punt-dal-Gall (130 meter high arch dam, 7 instruments), Grande-Dixence (285 meter high gravity dam, 6 instruments) and Mattmark (120 meter high embankment dam, 4 instruments). The aim is to observe the free-field motions at the dam sites, the motions at the abutments and the dams’ dynamic responses and characteristics. Array configurations and instrument specifications were developed based on the stated objectives. Earthquake events have been recorded at the dams.

G. R. Darbre
Strong Motion Networks: A Tool For The Assessment of Earthquake Response of Historical Monuments

Strong motion networks installed in two historical monuments in Istanbul, Turkey, namely in Hagia Sophia Museum and in Süleyrnaniye Mosque, yielded valuable information regarding their time-domain and frequency-domain dynamic characteristics. The existing information was enhanced by recordings obtained during the recent August 17, 1999, Kocaeli (Mw=7.4) and November 12, 1999, Düzce, Turkey (Mw=7.2) earthquakes and during the following aftershock activity. Analysis of data yielded following results: The two buildings with similar structural support systems have different vibration characteristics. There is an earthquake specific variation of modal frequencies in the two structures which exists during low amplitude events as well. Local problems in terms of excessive vibrations exist in the southwest main pier of Hagia Sophia and possibly in the west main arch of Süleyrnaniye. Significant vertical vibrations at the crowns of the east and west main arches in Hagia Sophia are probably indicating locations where most of the damage are to be expected during a major earthquake close to Istanbul. The strong motion accelerometer networks are valuable tools for monitoring of historical structures and help to identify potential problems and/or to explain past/present structural problems. It is expected that such networks will become a standard tool for investigations towards the preservation of historical buildings in seismic areas in the future.

E. Durukal, M. Erdik, S. Cimilli
Wireless Monitoring and Low-Cost Accelerometers for Structures and Urban Sites

New technologies in wireless telemetry and low-cost micromachined silicon accelerometers enable lower cost and denser instrumentation of both structures and the urban environment. Applications include any site where robustness, capital or maintenance costs, spatial density, or ease of communication are controlling issues. This paper reviews these new implementing technologies and gives two practical examples.Recently introduced techniques have vastly expanded the palette of practical telemetry options. These include unlicensed spread-spectrum, cell-phones in several variants, two-way paging, and a rapidly growing set of satellite services. Many products are available for each technique, so off-the-shelf solutions are routinely achievable. Relevant issues when selecting telemetry for a particular project include whether the service is offered in that region and how complete their coverage is, access from inside structures and urban canyons, capital and recurring costs, ease of installation, and viability after an earthquake. These issues vary greatly from one technique to another. However, an attraction shared by most is the elimination of most hard wiring, which can greatly ease installation and reduce the number of failure modes, both in routine maintenance and during an earthquake.Low-cost micromachined accelerometers have reached price and performance levels of interest for structural and free-field monitoring, particularly to augment the spatial density of more expensive instruments in urban areas. For example, one can find dynamic ranges reaching from typical urban background noise levels to ±2g for under US$100 per channel, or better the resolution of an SMA-l for a few tens of dollars per channel. This paper includes performance details from USGS tests of the high-dynamic-range accelerometer. Most micromachined accelerometers exhibit small physical size, low cost, and great robustness and stability. In combination, these characteristics yield low capital and maintenance costs.The new wireless technologies and micromachined accelerometers can contribute separately to structural monitoring, and they may be used separately in many situations. Additionally, the two technologies can be combined to sharply reduce the cost of arrays, and to permit arrays of unprecedented spatial density. The two examples presented here combine both technologies. In the first, spread-spectrum transceivers and micromachined accelerometers were used to monitor a New Mexico highway bridge for structural integrity. In the second, micromachined accelerometers and cell-phone Internet links (CDPD) are being used for a regional urban freefield array in Oakland, California.

John R. Evans
The Need for Data from Instrumented Structures for an Optimal Control Approach to the Seismic Interaction between Adjacent Buildings

The paper deals with an optimal control numerical treatment of the dynamic inequality problem concerning the elastoplastic-fracturing unilateral contact between neighboring structures during earthquakes. The numerical procedure is based on an incremental problem formulation and on a double discretization, in space by the finite element method and in time by the Houbolt method. It is emphasized that the generally nonconvex constitutive contact laws can be simulated numer ically by using data derived from response records of instrumented civil engineering structures. These interface laws are piece-wise linearized, and in each time-step a nonconvex linear complementarity problem is solved with a reduced number of unknowns, Finally, the method is applied to a civil engineering example of adjacent frames.

Asterios A. Liolios
Wireless Sensors for Structural Monitoring

A wireless sensor system is developed for structural monitoring purposes. This experimental system includes 5 monitoring stations and a main data collection and system control station. Each monitoring station has an accelerometer of 3-axis. Total number of channels is 15. This system uses 900 MHz ISM band spread spectrum digital radio transceivers for data transmissions. At each monitoring station, the analog signal from sensors is digitized using a 16-bit AID. A custom microcontroller (80C251 series) is designed and implemented to control the data collection and data transmission. A software for the sensor control, data collection, processing, coding, and transmission is inbedded into the microcontroller. A communication protocol is developed for the system. The central station is a PC with a radio module attached. Each monitoring station continuously collects data from the accelerometer, processes the collected data, and transmits processed data to main station when the monitoring station receives a data request command from the main station. The central station receives the data from each substation and stores them in a data file. The received data is analyzed by the main station. If one or more events exist in a period of time (e.g. 10 minutes), the data within this period will be stored. If no event is found, the data will be dropped. Received data can be analyzed using graphic display or computerized analysis. Initial lab tests show that this system is very efficient and reliable. The dynamic range of the wireless sensor is +/−4g, sensitivity is about 5 mg, and transmission distance is about 1000 ft indoor and 5 miles outdoor.

C. Richard Liu, Lanling Zhou, Xuemin Chen, S. T. Mau
Puerto Rico Strong Motion Network and Instrumented Buildings

Puerto Rico is the smallest of the four Greater Antilles. It is located between the Atlantic Ocean and the Caribbean Sea, approximately in the latitude 18.25N, longitude 66.50W. The population of the Island is about 3.52 millions (1990 census), while its area is of 8,875 km2 (1990 census). The capital and the largest city is San Juan, located in the northern part of the Island. Puerto Rico is a self-governing Commonwealth in union with the USA.

José A. Martínez-Cruzado, Esteban L. Llop-Ramirez
Strong Motion Instrumentations of Dams in Macedonia Some Experience and Results

A high dam is a particularly important element in seismic risk evaluation of the wider dam site area, i.e., in the definition of the seismic risk of the area in which a dam is planned to be constructed. A large number of high dams in the world and in our country are located within high seismicity zones or in zones close to areas which were affected by string earthquakes in the past.

Vladimir Mihailov, Dragi Dojcinovski
An Effective Earthquake Monitoring Process for Emergency Response

There is no doubt that, investigation of durability of surface ground and dynamic characteristics of structures are important steps to estimate damage that will be caused by earthquakes. Together with this, it has been widely recognized that, systematical and continuous monitoring of earthquakes is indispensable factor for early warning systems.Japan has 10% of global seismic energy and suffers severely from earthquakes. There have been many efforts including early warning system since 1960’s. For the important infrastructures and automated systems, having an early alarm and earthquake information, even a few seconds before the destructive wave arrives, is still an important issue for many countries. Starting with conventional alarm seismometers and continuing with UrEDAS (Urgent Earthquake Detection and Alarm System), early warning system has been extensively used in Japan Railways for stopping high speed trains. This early warning system has been improved recently and this new effective real time monitoring approach is proposed in present study.Basic concept of this system is to catch earthquake motion by P waves in and around the earthquake occurring area. For this purpose, new characteristic parameters, named as PI (P wave index) and DI (Damage Intensity) of seismic motion are proposed to be able to define destructiveness of the earthquake and effectively realize P wave alarm system. DI is defined as an inner product of acceleration and velocity vectors, at each time step. Multiplication of DI with mass received seismic motion indicate a power of motion acting to the object. With a P wave arrival, DI increases drastically and after S wave arrives it reaches to its maximum value. This value (maximum of DI) is named as DI value. PI is defined as maximum of DI calculated at the time step around P wave arrival and this value is suggested to be used for realizing P wave alarm. DI value is directly related to the seismic intensity and earthquake damage. With a continuous calculation of DI, P and S wave alarm can be issued (when PI exceeds the preset level P wave, and when ordinary monitored values or DI value exceed preset level S wave alarm can be issued). Detailed explanation of P wave detection methos was described in Nakamura (l996). This system is very simple and it works with single station. Because of this, it is easy to apply it to all important lifeline structures like pipelines, power plants, railways and bridges. Combination of this alarm system with vulnerability information of the ground and structures estimated with other methods is promising for future early warnings, since it makes possible to understand the areas that will be vulnerable during the earthquakes.

Yutaka Nakamura
Estimation of dynamic characteristics of ground and structures with microtremor measurements- A supportive tool for strong ground motion instrumentation

Degree of damage during earthquakes strongly depends on dynamic characteristics of buildings as well as amplification of seismic waves. Determining these characteristics in advance and increasing durability of ground and structures beyond the presumed seismic force become a fundamental of earthquake disaster prevention.One way of investigating dynamic characteristics is to install strong motion seismometers and monitor structure continuously. For the effectiveness of this installation, vibration mode characteristic of the structures be clearly understand in advance. In this paper, usage of microtremor method as a supportive tool for strong ground motion instrumentation is presented. Since there is a growing interest to protect historical monuments, application of this method was made to the microtremor measurements performed at Suleymaniye Mosque located in Istanbul. In a short period of time present method provided several information including natural frequency, amplification factor and vibration mode characteristics of the mosque as well as its ground. Data showed that movement in longitudinal(NS) direction is larger than transversal(EW) direction. Vulnerability index, K values (Nakamura, 1997) is also calculated and several weak points of the mosque could be investigated. This approach help to understand the behaviors of old monuments as well as new buildings and can serve for retrofitting purposes.

Yutaka Nakamura, Dilek E. Gurler
Strong Motion Instrumentation of Buildings
A Study on the Linear and Nonlinear Response of an Instrumented 52-Story Building

A comparison of the recorded structural earthquake response of a building and its predicted response by dynamic analysis provides vital information to structural designers on the effectiveness of current methods of dynamic analysis. There have been a number of previous studies of this nature, but only a few have paid attention to investigating the three-dimensional nonlinear dynamic behaviour of instrumented tall buildings. The purpose of this paper is to study the seismic behaviour of a well-instrumented 52-storey steel frame building in Los Angeles, California. This building has been subjected to ground motions from several earthquakes among which the 1991 Sierra Madre earthquake and the 1994 Northridge earthquake were selected in this study. During both earthquakes the building responses appeared to be in the linear range. Frequency domain analyses of the recorded motions from these two earthquakes were conducted to determine the dynamic characteristics of the structure. Three-dimensional nonlinear dynamic computer analyses were then employed to evaluate the response of the structure induced by severe shaking. The results of this study show that by performing a linear three-dimensional analysis, the real response of a building during past earthquakes can be reproduced with confidence. By further performing a nonlinear three-dimensional analysis, the state and sequence of damage can also be predicted. The Nonlinear Static Procedure (pushover analysis) generally excludes higher mode participation, which can be important for high-rise buildings subjected to certain types of ground motions. Improvements to this procedure were explored.

Carlos E. Ventura, Yuming Ding
Current Status of Strong-Motion Monitoring and Notification at the United States Bureau of Reclamation

Acquisition of strong motion data at the Bureau of Reclamation provides near real time notification of strong shaking at our structures as well as recordings of earthquakes for use in the dynamic analyses of large, engineered structures. To facilitate rapid notification following strong ground shaking, we have developed a low-cost, automated system to retrieve event-triggered seismic waveform data from digital data loggers at remote sites. Only a modest infrastructure investment is required. The method relies on standard dial-up telephone circuits, a custom-designed serial interface device, and communications software that runs under a UNIX operating system. Event wave- forms can be retrieved in near real-time from strong-motion accelerographs as well as from general-purpose seismic data loggers. The system can perform automatic remote configuration and periodic state-of health monitoring of the field instrumentation. The system presently retrieves data from 70 digital strong-motion instruments at 49 dams and other lifeline facilities located throughout the western United States. It has also been successfully used in temporary site-response and aftershock studies to provide remote access to seismic data loggers with broadband seismometers. Deployment of instrumentation is also focused on acquiring the detailed recordings necessary for validating the increasingly sophisticated dynamic analyses of dams.

Chris Wood, Andy Viksne, Jon Ake, David Copeland
Structural Vibration Monitoring System for the Bosporus Suspension Bridges

The study will describe the structural health monitoring system installed on the Bosporus Suspension Bridge. The bridge, commissioned in 1973, has a main span of 1074 m. The bridge deck has a total width of 33.4m. The deck is supported by four steel towers of 165 m height. The ambient vibrations of the Bosporus Bridge has been investigated. For the structural health monitoring system, the following sensors are installed in the system: One wind speed transducer at the mid-span; Four vertical, three transverse and two longitudinal acceleration transducers at the mid-span, one-fourth of the span and at the top of Beylerbeyi tower; Four seismometers at the foundation of towers and cable anchorages; Two relative displacement transducers at the Ortaköy joint and; One optical displacement transducer at the mid-span. The response of these transducers, digitized at the source is transferred to central recording/monitoring system located at the control building. The triggering is based on the exceedance of the appropriately set threshold levels.A new vibration monitoring system has been designed for Fatih Sultan Mehmet Suspension Bridge. Various techniques will be studied to optimally place 32 triaxial solid-state acceleration monitoring sensors. The data, digitized at the source will be monitored by two parallel PC systems operating under the “SEISLOG“ data acquisition software, developed by University of Bergen. Damage to bridge will be inferred from the response of distributed sensors (vibrational data) and the analytical modeling of the structure through the use of system identification techniques. The structural models or properties (generally modal parameters) will be systematically determined by using the measured response and, if available, the corresponding excitation (ambient or transient) of the bridge through an integrated approach of experimental, analytical and computational techniques.

Nurdan Apaydin, Mustafa Erdik
Soil-Structure-Interaction And Seismic Isolation, An Interdisciplinary Investigation At the multidisciplinary Seismic Test Site Incerc, Bucharest, Romania

The Collaborative Research Center 461 (CRC 461) “Strong earthquakes: A Challenge for Geosciences and Civil Engineering” (Germany) and the Romanian Group for “Strong Vrancea Earthquakes” work on a multidisciplinary attempt towards the mitigation of the impact of the next strong Vrancea earthquake (Romania). The recently installed Multidisciplinary Seismic Test Site INCERC (MSTS) located in the eastern part of Bucharest serves as focus to study the entire sequence relevant in engineering seismology including structural dynamics, seismology, soil mechanics, and engineering geology. Within this co-operation, the complete chain for seismic hazard and seismic risk analysis and can be checked and verified. For this purpose a base isolated test building was constructed, where acceleration will be measured at the base and at the top. Additionally, free field accelerometers in various depths were installed. Thus, free field accelerations and the response of the test building can be measured simultaneously. In this paper we want to focus on the test building. One mainly task, among others, is to investigate the dynamic behaviour of rubber bearings under seismic loading, including soil-structure-interaction. Geotechnical parameters which will be available to a depth of 180 m ensure that the soil-structure-interaction incorporating the seismic behaviour of rubber bearings can be computationally studied with FE methods. These calculations include constitutive laws describing non-linear behaviour of rubber and soil material under cyclic loading. M. Erdik et al. (eds.), Strong Motion Instrumentation for Civil Engineering Structures, 369–381.

M. Baur, O. Novak, J. Eibl, D. Lungu
GPS in Dynamic Monitoring of Long-Period Structures

Global Positioning System (GPS) technology with high sampling rates (~10 sps) allows scientifically justified and economically feasible dynamic measurements of relative displacements of long-period structures … otherwise difficult to measure directly by other means, such as the most commonly used accelerometers that require post-processing including double integration. We describe an experiment whereby the displacement responses of a simulated tall building are measured clearly and accurately in real-time. Such measurements can be used to assess average drift ratios and changes in dynamic characteristics, and therefore can be used by engineers and building owners or managers to assess the building performance during extreme motions caused by earthquakes and strong winds. By establishing threshold displacements or drift ratios and identifying changing dynamic characteristics, procedures can be developed to use such information to secure public safety and/or take steps to improve the performance of the building.

Mehmet Çelebi
Real Time Large Structure Monitoring Using The Inclination Sensor

This paper gives the brief information about the precise inclination-sensor called NIVEL20. Thereafter fields that the sensor might be used to determine flatness, torsion, deformation and etc are mentioned. A test carried out to determine the movements of a building and a pillar built on this building are examined using continuously collected data by two NIVEL20s. Therefore movements of the building and the pillar are simultaneously be monitored and effects of building movements onto pillar are investigated in micron level. Results obtained are expressed and interpreted.

R. N. Celik
Monitoring Deformation on Karasu Viaduct Using Gps & Precise Leveling Techniques

A project has been carried out to investigate the performance of GPS for determining deformations of large strong structures. As a test structure, a viaduct has been chosen 40 km away from West of Istanbul and built in a marsh area. Four epochs of GPS and levelling measurements have been done. Results obtained from epoch measurements are investigated and expressed in this paper. Also the needs of a special force centring equipment to achieve the accurate results are emphasised.

R. N. Celik, T. Ayan, H. Denli, T. Ozludemir, S. Erol, B. Ozoner, N. Apaydin, M. Erincer, S. Leinen, E. Groten
Seismic Monitoring of Nuclear Power Plants; An Approach to Optimal and More Accurate Seismic Data Processing and Interpretation Procedure

The seismic monitoring systems on NPP-s have two main functions: (1) to provide recorded accurate data on seismic input and dynamic behaviour of structures and the vital hardlines and processing control and protection systems, and (2) to enable automatic alarm, and, in some cases, automatic stoppage of the processes that go on in NPP-s in case of earthquakes with intensities higher than the previously defined values. The exact records of the seismic input and dynamic response are important from two aspects: (1) they should enable fast inspection of NPP-s after earthquakes and (2) they should enable checking of the previous design and analytical models for definition of the seismic safety of the NPP-s.The new regulations for seismic design of NPP-s anticipates a complex concept for definition of intensity of seismic motion. Apart from amplitudes (peak acceleration) and frequency characteristics (dominant frequencies), the new regulations consider also the energy characteristics (cumulative absolute velocity).Presented in the paper is a concept for processing of accelerogrammes based on comparative analysis of two software packages: Kinemetrics SWS (Seismic Work Station) and the procedure developed at the Institute of Earthquake Engineering and Engineering Seismology. Both concepts are based on the same theoretical basis and represents derivatives of the main procedure developed at CALTECH Institute from Pasadena, USA.Elaborated is a concept for definition of the input parameters; band-pass filter comer frequencies and slopes, elimination of DC components in the recorded accelerograms and calculation and selection of 100 most relevant values of frequencies for calculation of response spectra. Used as seismic input were two types of data: recorded accelerogrammes generated by biaxial shaking table (the applied acceleration and displacement time histories were used as reference and comparative signals) and “in situ” record of blast experiments.

D. M. Dojcinovski, D. J. Mamucevski, V. P. Mihailov
Analysis Of Data From Strong Motion Network in Fraser Delta, British Columbia, Canada

The 1996 Duvall earthquake in Washington State triggered ground motion stations in the Fraser Delta, British Columbia, Canada. Recorded ground motions were used to examine the applicability of 1-D and 2-D site response analyses for amplification studies in the Delta. 1-D response analysis gave a good indication of the period of peak response, but response spectra were generally not satisfactory for engineering purposes. The use of 2-D analyses which included buried topography generally improved the predictions of site response spectra.

W. D. L. Finn, E. Zhai, T. Thavaraj, X-S. Hao, C. E. Ventura
On identification of Damage in Structures Via Wave Travel Times

The traditional identification methods for detection of damage and for health monitoring of structures are based on detection of changes in the system natural frequencies. These changes tend to be small in the early stages of damage, and therefore may be difficult to quantify, even from accurately processed recorded motions. Other difficulties arise from the nonuniqueness in the model representation. Unless the model accounts for the soil-structure interaction, and it has been carefully validated and calibrated, it is very difficult to identify the true causes and sources of observed nonlinearities in the response. In this paper, it is suggested that the formation of damaged zones in structures could be monitored (identified) via the delays in travel times of seismic waves through these zones. This approach needs further development and testing. A preliminary analysis presented in this paper (of a building damaged by the 1994 Northridge, California, earthquake) shows that this method (1) can lead to detectable changes in the travel times of the waves passing through the areas known to have experienced damage, and (2) in its simplest form does not to require detailed modeling or analysis of soil-structure interaction.

S. S. Ivanovic, M. D. Trifunac, M. D. Todorovska
Earthquake Motion Observation In And Around 8-Story Src Building

Building Research Institute (BRI), Ministry of Construction, Japan, started the strong motion observation project in 1957. The observation network has been enriched and enlarged in the past forty years. BRI is now operating several networks with a number of strong motion instruments. In this paper, we are introducing a new system that is installed to buildings and underground at BRI, and some observation results.

Toshihide Kashima, Izuru Okawa, Shin Koyama
Instrumentation, Measurements and Numerical Analysis of Bridges: An Example of the Cable-Stayed Bridge on Evripos Channel, Greece

The instrumentation of special structures such as large bridges, tunnels, monuments etc., contributes towards a better understanding of their dynamic performance, as well as a more accurate and reliable prediction of the earthquake resistance of such large-scale structures. In experimental analysis the classical ways to estimate the modal parameters of the whole structural system, as well as of its structural elements, is either to excite the structure artificially (using, e.g. vibrators, heavy vehicles) or to evaluate the recordings obtained from a weak or strong ground motion. In modeling the behaviour of a civil engineering structure in a realistic way, among the important parameters to be defined are the mass distribution, the damping characteristics, the stiffness of the main load resisting system, the influence of secondary elements and interaction phenomena. Large vibration tests provide reliable data for the evaluation of the influence of such modal parameters. The effective analytical evaluation of the bridge through reliable and effective numerical models is necessary in order to verify the experimental data. By comparing the results of both experimental and analytical approaches and adequately updating the analytical model, a more realistic modeling of the bridge can be obtained. Changes in the modal parameters during the time-life of the bridge can contribute towards detection of damages, such as crackings or any other reasons reducing the stiffness of the structural system. The cable-stayed bridge in Evripos channel (Greece) was selected to apply the aforementioned methodology. The main ambient vibrations recorded are due to traffic, wind and moderate earthquakes at small distances from the bridge. Three-dimensional finite element models of the bridge were created and the dynamic behaviour of the bridge was analysed for both a small and a strong earthquake with high frequency content. Results of the experimental estimation of eigenvalues of the vibration modes are also presented. Finally, comparisons between experimental and analytical values have been performed,

V. A. Lekidis, C. Z. Karakostas, D. G. Talaslidis
Damage Detection in Semi-Rigid Joint, RC Frames Subjected to Strong Motion Excitation

A new approach to fault detection and prediction in RC frame resistant structures subject to strong ground excitation, considering both input uncertainty and material non-linearity, is presented. It could also serve as a basis for developing a near-real-time structure health assessment procedure.

J. Leonov
Assessment of Seismic Hazard in Romania Based on 25 Years of Strong Ground Motion Instrumentation

The first and the most important free-field strong ground motion in Romania was recorded in Bucharest, at INCERC seismic station, during March 4, 1977 Vrancea earthquake (M w =7.5, h= 109 km, epicentral distance to Bucharest 105 km).

D. Lungu, C. Arion, A. Aldea, S. Demetriu
Measurement of Lateral Earth Pressures on an Embedded Foundation During Earthquakes

The dynamic earth pressures during earthquakes have been observed on both sides of an embedded foundation for about 30 events. Some characteristics of dynamic earth pressures were extracted from the observations. The main findings obtained in this study can be summarized as follows. (1) The phase characteristics of earth pressures between both sides of the foundation show remarkable dependence on the frequency components of acceleration motions. (2) The earth pressures on lateral sides of the foundation are strongly related with horizontal velocity motions of the foundation. (3) The peak values of earth pressures have shown a tendency to increase with increase of lower frequencies contained in accelerograms on the ground surface. (4) The fact that the earth pressure has strong relation with the velocity motions of the foundation may be roughly explained by means of a simplified one-dimensional wave propagation theory for a soil rod model.

Chikahiro Minowa, Michio Iguchi, Masanori Iiba
Seismic Instrumentation of the I-40 Mississippi River Bridge in Memphis, Tennessee

The purpose of this paper is to describe installation of a seismic instrumentation system which is proposed to be deployed on and in the vicinity of the I-40 Hernando DeSoto Mississippi River Bridge in Memphis, Tennessee. This bridge is planned to be retrofitted to withstand a magnitude (mb) 7 event at 65 km distance from the site with a depth of 20 km. The goal of the retrofit is to have this bridge fully operational following the maximum probable earthquake (2500 year return period). As part of the I-40 bridge retrofit, Friction Pendulum™ Isolation Bearings will be used to insure the integrity of the main spans of the bridge.The I-40 bridge is scheduled to be retrofitted in several phases. The first phase of the retrofit is scheduled to begin in year 2000. Therefore, there is a window of opportunity to install an integrated system of seismic strong-motion instruments on and around the vicinity of the bridge during the retrofit construction phase. A strong-motion instrumentation with 65 data channels at 25 different locations on the bridge and at the free-field in the vicinity of the bridge is proposed to be installed. This will provide needed data to better understand the ground motion and ground failure and the response of the retrofitted bridge in a strong earthquake. In addition. the instrumentation will strengthen the free-field strong-motion network in the metropolitan Memphis area.

Shahram Pezeshk, Mehmet Celebi, Greg Steiner, Charles V. Camp, Howard Hwang
Engineering and Seismometric Service in the Buildings of Tashkent and Tashkent Regions

Tashkent city is located in the zone where I=8–9 (Mercalli intensity scale) and some faults are in the adjoining regions. Microseismozoning carried out with due regard for the soil conditions showed that there are areas on the city territory where I=7,8,9 and areas exposed to landslides and dilution of soil under earthquakes. The buildings constructed in Tashkent are of different constructive schemes. Stations of engineering and seismometric service (SESS) are located in the 20-storeyed panel administrative building, in the 9-storeyed dwelling house of a special construction, in the 4-storeyed brick building of the Hotel Tashkent, in the 5-storeyed brick buildings of research institutes, in the 17-storeyed building of the Hotel Uzbekistan. Seismodetectors are installed in ground and on different levels inside these constructions.The stations record ground motions caused by earthquakes if I>4. Equipment of these stations was constructed in the former Soviet Union and is obsolete at present. Besides that tracking of underground communications and the Metro where SESS has been installed is also carried out. The Charvak reservoir whose water storage reach 2 milliard cubic metres is at 60 km distance from Tashkent. Dam of the reservoir is in the vicinity of a seismic fault. If the dam whose altitude is 167 m is destroyed the Tashkent oasis will be flooded. Detectors have been incorporated into the dam and seismometric service was organised. At present equipment of the station is obsolete but is in a serviceable condition.Ground motions recorded by these SESS were used for improvement of the map of microseismozoning, Constructive Standards and Regularities and for calculation of city buildings for seismic stability. Now organisation of common network for seismometric control in Tashkent and Tashkent regions, use of new-type machinery for registration of strong ground motion caused by earthquakes are actual.

T. Rashidov
Stress Wave Propagation Due to A Moving Force: Comparison of Fem and Bem Solutions

In this paper the performance of two numerical methods of solving the problem of a time dependent moving force on the surface of an elastic continuum will be evaluated. One method is the finite element method (FEM) formulated in convected coordinates coupled with an absorbing boundary condition of the impedance type. The other method to be considered is the boundary element method (BEM), where a new formulation using Green’s functions transformed to a moving coordinate system is introduced. The methods are tested by the classic wave propagation problem of a Ricker pulse propagating from the surface of an elastic halfspace. The time integral net impulse of the considered loading must be null for the considered FEM to work. Further, the FEM is unable to absorb Rayleigh waves, since the considered impedance condition has been tuned to P- and S-waves. By contrast the BEM is able to handle also these cases. The disadvantage of the BEM is the increased calculation time.

K. M. Rasmussen, S. R. K. Nielsen, P. H. Kirkegaard
Strong Motion in Absorbing Nonlinear Medium and Problems of Their Registration

In the paper some physical phenomena in natural soils are considered, provided by intensive seismic excitation. On the basis of regressive analysis of Racha earthquake instrumental data and so-called “dimensionality method”, the new parameters, which are tightly connected with absorbing indexes and non-linearity of natural soils have been obtained. The consideration of corresponding correlation links has shown that in epicentral zone of earthquake (30–40 km) the absorption of seismic energy in soft soil is inversely proportional to earthquake magnitude and not significantly depends on acceleration. In rocks the absorption is directly proportional to the acceleration and slightly depends on magnitude. This fact explains considerably the difference degree of buildings’ and constructions’ damage on soft and rock soils.It was detected the degrees of non-linearity and non-elasticity of soils. Also, it was considered the usage of offered parameters during solving of practical issues of seismic microzonation.It was shown the uncertainty of differentiation of strong and weak motions. The properties of strong motion is being analyzed, based on corresponding behavior of geomaterial at linear-elastic, nonlinear-elastic, non-elastic deformation.Partially, it was obtained the empirical quantity for account of intensity level of seismic impact. Following leads to a conclusion about necessity of registration strong motion not only in maximum narrow band of spectrum, but also in wide frequency band of spectrum.

V. Zaalishvili
Seismic Response Study of Two-Storey Building in Eilat Using Weak and Strong Motion Data

A two-storey building was temporarily instrumented with two horizontal seismograph stations installed on the roof, basement and at the free field. Local earthquakes with magnitude 3.0–4.0 at a distance of 45–80 km were recorded. These week records are utilized to derive the building transfer function. The fundamental frequencies of the longitudinal and transverse vibrations of the buildings are found to be within 8–10 Hz and the corresponding damping ratios between 6–7%. The ambient vibration data were not used since the low-intensity ambient excitations do not put the building into resonant motion. The estimated parameters were then checked by cross-wise convolution — the input from one earthquake record is convoluted with the transfer function derived from the other in order to derive the building response caused by the former earthquake.The linear dynamic characteristics, determined from the low-amplitude test, are used to forecast the buildings response, convoluting them with selected strong ground motion (the available accelerograms from Eilat/Aqaba Gulf earthquake with magnitude MW=7.1). The building response is assessed from the derived accelerograms. The values obtained are compared with their counterparts, as determined from structural analysis, according to the guidelines of the Israeli Design Code for this type of structure.

Y. Zaslavsky, J. Leonov, A. Shapira
Strong Motion Instrumentation for Structures of Civil Engineering and Economical Aspects of Planning of Territory of Big Cities

A number of strong earthquakes have taken place in last several years, and they were characterized by suddenly high peak values of accelerations (0.4–2.0 g). The existing position of structural engineers and scientists at the usage of so-called design accelerations is based on rather formal connection between acceleration and seismic intensity. So, according to Mercalli seismic scale (MMI), the design acceleration, which corresponds to earthquake intensity 9 degrees, has changed 5 times (from 0.1 to 0.5g) over the last 40 years. From the other side during high accelerations (2.0g, Nortridge, 1995 etc.) the intensity has reached even above-mentioned intensity of 9. At the same time a buildings designed at the intensity of 7 (e.g. 0.1g), very often can endure the seismic intensity of 9 degrees (0.4g, Sakhalin, 1995).The existing factors of seismic hazard are correlated badly with instrumental characteristics of earthquakes. All above-mentioned sets the problem for selection of parameter. which is directly connected with destructive seismic effect.Based at this and other views, the paper shows necessity of such type of equipment (strong motion instrumentation) which will give opportunity to test the reaction of buildings at seismic effect accurately, based on direct energy parameters or more closely on parameter which characterizes seismic effect (acceleration, velocity etc.),In the regions with low seismic intensity (Georgia), which means the country where the return period of strong earthquakes is rather long, it should be used the equipment (strong motion instrumentation) which would have widen working characteristics, in order to accept the weak signals.The paper contains economical aspects of planning of urban areas, based on hazard mitigation and vulnerability of buildings and structures in the case of their provision by corresponding strong motion instrumentation. The following part contains considerations about the creation of monitoring instrumental systems in buildings and at major structures of urban areas of Georgia.

V. Zaalishvili, I. Timchenko, V. Kacharava, Z. Zaalishvili
Backmatter
Metadaten
Titel
Strong Motion Instrumentation for Civil Engineering Structures
herausgegeben von
M. Erdik
M. Celebi
V. Mihailov
N. Apaydin
Copyright-Jahr
2001
Verlag
Springer Netherlands
Electronic ISBN
978-94-010-0696-5
Print ISBN
978-0-7923-6917-2
DOI
https://doi.org/10.1007/978-94-010-0696-5