Sami F. Masri - US grants

The research will focus on two major areas of research: first, a preliminary investigation of the performance of transportation systems subject to earthquake ground motions; and second, the assessment of impacts of travel behavior on the physical environment using theoretical and operational models of complex travel behavior previously developed by the researcher.

The objective of this project is to validate the present dynamic characteristics of typical Mexico City buildings and to measure the damping characteristics of these buildings. One steel and four reinforced concrete buildings are chosen and their ambient responses are monitored using seismometers and analog data recorders. These analog measurements of ambient data are uniformly processed and analyzed for spectral characteristics and modal properties. Further, correlation of analytical and experimental results is made to identify good design features, stress distribution in critical elements, torsional effects, effects of in-plane flexibility, and relationship between observed damage and stress intensity.

Highway bridges in the United States are experiencing the problems of aging, corrosion, and excessive cracking of concrete. It is important to evaluate these deficiencies in terms of the remaining strength of the bridge structure. The problem of determining the current capacity and remaining life of the bridge is very complex because of the many and varied factors involved. This project will investigate the development of a computer program which will take into account the various defects and aging parameters of the material estimate its strength and rate of decay. The study will concentrate on the behavior of a scale model bridge with various intentional defects added to it to develop an appropriate methodology for future full-scale use by bridge engineers.

In order to determine the existing conditions, strength and safety of structures, nondestructive evaluation (NDE) techniques are required for field examinations. There are many types of NDE equipment available with varying precision, convenience of use, limitations in application, and economy of use. The objective of this project is to conduct a combined conference and workshop in order to assimilate existing information on the current uses of nondestructive evaluation and to project plans for subsequent research activities. Researcher is qualified to perform this project. Project is recommended for an award. This is a one time award.

Masonry construction comprises a large portion of building construction in the U.S. and the world. Reinforced masonry construction use is increasing in moderate to higher seismic zones because of its apparent features of economy, fire safety, architectural flexibility and ease of construction. The present state of masonry structural analysis and design and materials and construction technologies does not enable an accurate prediction of building behavior under lateral loads such as seismic loads. In the U.S., masonry buildings are designed and built with methods, codes, and standards that rely upon a mixture of working stress methods, empirical rules, and questionable methods for determining allowable stress values. Masonry is also a complex building material because of the large number of design and construction variables which influence the final product configuration and its response under seismic loads. In order to describe the seismic response of masonry buildings it is necessary to develop the fundamental knowledge base to determine basic design methodologies consistent with safety and economic requirements. This research project will investigate and provide basic data for verification of analytical models that describe the out-of-plane response of masonry walls. It is focused on reinforced clay masonry walls. The experimental portion of this program will consist of quasi- static, cyclic testing of reinforced clay masonry walls subjected to out-of-plane loadings. The data produced will include force- displacement load paths and hysteretic loops, as well as strain data in the masonry and reinforcement. The analytical portion will utilize the mathematical models developed by others in the TCCMAR program. The final research results will then be used to establish rational limit state design methodologies to resist seismic loadings. The principal investigator is highly qualified to conduct this research project and the institution provides excellent facilities. An award is recommended for this twelve-month research project. This research project is part of the U.S.-Japan Coordinated Program for Masonry Building Research and the Technical Coordinating Committee for Masonry Research (TCCMAR) Program.

This project is a coordinated effort of experimental work analysis in order to be responsive to two major problems: verification mathematical modelling and prediction of the capacity of actual structures. The emphasis of this project is placed on steel structures and components. The experimental and analytical laboratory studies to be carried out can be conveniently grouped under three main headings: (1) equipment, (2) frames, and (3) joints. These studies complement the scale field tests on existing motion earthquakes which are underway or being proposed. The study of equipment includes investigation of the failure modes supported correlation equipment response. For the steel frame study a 4' x 6' shaking table will be used to study the response due to the horizontal motion and the effects of vertical irregularity of frame stiffness. Detailed nonlinear models will be developed for selected structures. For joint study biaxial full-scale steel-moment connection tests will be conducted and compared with the analytical prediction. The investigators are all competent researchers of proven track record. The Principal Investigator is a leader in the field and is highly experienced in the practical problems of seismic-resistant design. This research will fill some of the gaps in the current knowledge base about the nonlinear structural behavior and will lead to techniques for improved reliable design of structures subjected to strong earthquake shaking. A two-year continuing grant is recommended.

In this project the strong motion records taken from the 26 accelerographs located on and in the vicinity of the Vincent Thomas Bridge during the 1987 Whittier Earthquake will be studied. The study will: (i) define representative and appropriately correlated non-synchronous support motions, (ii) validate existing analytical modelling and seismic analysis, (iii) develop system identification techniques that deal with multiple-input multiple-output models (both linear and nonlinear), (iv) evaluate the bridge performance during the earthquake, (v) optimize the return on the instrumentation investment and improve the usefulness of the recorded-response data, (vi) propose a general program for strengthening or retrofitting of existing cable-supported bridges, (vii) obtain information on damping values as a function of the vibrational amplitudes, (viii) obtain information on the soil-structure interaction of this massive structure, (ix) develop elastic stoppers or other special devices to dampen the effects of seismic and wind forces. The study will fulfill an urgent need for comprehensive investigations of these unique and historical response records to insure the safety of suspension bridges which have been widely in use across the nation's seismic zones. The research results will be of extreme importance to strengthen existing cable-supported bridges (as well as to design new structure, and for up-grading and installing new monitoring instrumentation).

This proposal requests funds to permit Dr. Mihran S. Agbabian, Dr. Sami F. Masri, and Dr. James C. Anderson, Department of Civil Engineering, University of Southern California, to pursue with Dr. Seng-Lip Lee, Dr. Somsak Swaddiwudhipong, Dr. Ser-Tong Quek, Dr. Chi Young Liaw, and Dr. Thambirajah Balendra, Department of Civil Engineering, National University of Singapore, for a period of 24 months, a program of cooperative experimental and analytical research on nonlinear structural systems under earthquake loads. The following three research topics will be studied: ductility demand for short period steel frames; behavior of steel frames subjected to earthquake motions in both vertical and horizontal directions; and beam-column moment connections for severe earthquakes. The main goals of this project are to evaluate the need to include stiffer plates in box columns at the connection to beams, to evaluate the ability of current element codes to predict the nonlinear behavior occurring at the joint under limit loads, and to accurately predict the capacity of building structures to resist damaging earthquake motions without failure or collapse. The research will add an international cooperative dimension to ongoing research at the University of Southern California (USC) supported by the National Science Foundation under Grant No. ECE8617623. The proposed cooperative research should provide valuable data to the earthquake engineering profession on structural response to severe earthquake shaking. This cooperative project will make available to the USC team a large scale test facility on which full-size building components can be tested rather than half-scale, as at USC. Comparison of results obtained at the two facilities would provide valuable information on scaling effects in such tests. This project is relevant to the objectives of the Science in Developing Countries Program which seeks to increase the level of cooperation between U.S. scientists and engineers and their counterparts in developing countries through the exchange of scientific information, ideas, skills, and techniques and through collaboration on problems of mutual benefit. Both groups of collaborators are highly respected scientists who have productive publication records in the field of the proposal.

This is a post Loma Prieta earthquake (Oct. 1989) investigation project in learning from this damaging event. This project is directed toward the evaluation of the performance, including interpretation and analysis of earthquake-response records, of the well-instrumented six earth dams which were shaken by the Loma Prieta, California earthquake (M=7.1) of October 17, 1989. The shaking during the main and after shocks triggered most of the accelerographs on the six dams (one of them is partially damaged) providing the most extensive array of earthquake response measurements yet obtained in the U.S. and abroad. The data obtained will be used to (1) study the effects of sequential earthquakes on the safety of earth dams, (2) correlate dynamic properties (shear modulus and damping) extracted from field performance during earthquakes, via system identification techniques, with existing laboratory-measured properties of the dam materials, (3) verify the adequacy of existing procedures for seismic analysis of earth dams by applying them to observational data and by comparing predicted results with measured responses, (4) disseminate research findings, and (5) document and improve capability to assess the safety of earth dams. The study will provide a comprehensive knowledge base for evaluation of seismic safety of earth dams.

This project presents an analytical and experimental study of the problems associated with seismic damage mitigation measures for museum art objects. The proposed research will address the problem of developing design guidelines to handle the following situations relative to the performance of art objects: 1. Sliding of rigid systems 2. Rocking of small rigid systems 3. Multiple support response In view of the difficult analytical aspects of the underlying problems, newly acquired USC seismic shaking equipment will be used to study the enumerated problems and develop design charts for use by museum curators, conservators, or individuals caring for art objects, in establishing sound seismic damage mitigation measures for art objects under earthquake inputs.

This project concentrates on general key research issues pertaining to lifeline earthquake engineering systems using active control techniques. A consortium consisting of four research universities and multidisciplinary investigators will conduct a sequence of well coordinated analytical and experimental investigations designed not only to produce results of immediate usefulness, but also to lay the groundwork for future needed developments in the technological areas. The objectives of the proposed major tasks are to: 1. Develop, design, fabricate and assemble a medium-sized laboratory model of a distributed system representing a generic lifeline system such as a long-span bridge. 2. Design and implement a distributed fiberoptic sensing system for monitoring the deformations of test specimen. 3. Perform supporting analytical studies to (i) evaluate the control energy requirements for various active control schemes, (ii) establish performance bounds on instrumentation and actuator hardware, and (iii) investigate the performance limits of vibration sensing techniques utilizing fiberoptic approaches. 4. Perform a systematic series of active control experiments to (i) correlate the experimental measurements with predictions on the basis of suitable mathematical models, and (ii) identify technology issues that may impede the full-scale field implementation in the future. The multidisciplinary research team will ensure that the practical implementation issues for future field applications are clearly identified and addressed.

9703805 Masri Presently used actuators to generate control forces are generally inadequate for limiting the response of civil structures under strong earthquake shaking. There is a critical need for a new generation of actuators that have the capability of adequately performing under strong ground motion which may induce significant nonlinear deformations in structures. The objective of this research is to develop an innovative semi- active damping augmentation device for controlling the seismic response of dispersed civil structures. The control procedure uses nonlinear auxiliary mass dampers with adjustable (adaptive) motion-limiting stops, located at selected positions throughout the structure, to inject an optimum amount of "chaos" in the structures dynamic response by disorganizing the orderly process of amplitude buildup. The degree of the structure's oscillation in the vicinity of each semiactive nonlinear actuator determines the actuator's actively-controlled gap size and activation time. By using control energy to adjust the actuator's critical parameters instead of directly attenuating the motion of the structure (which conventional active control methods do), a significant improvement is achieved in the total amount of energy expended to accomplish a given level of vibration control. A sequence of analytical and experimental studies by means of a bridge model to be provided with several innovative nonlinear actuators and subjected to multiple-support earthquake excitation by seismic shakers will also be conducted. ***

Novel health monitoring strategies for Highway Bridges and Constructed Facilities are of
primary significance to the vitality of our economy. Using latest enabling technologies, the objectives of health monitoring are to detect and assess the level of damage to the civil infrastructure due to severe loading events (caused by natural loads or man-made events) and/or progressive environmental deterioration. Damage identification is performed based on changes in salient response features of the structure, as measured by deployed sensor arrays. Due to the challenging nature of the technical problems associated with this topic, substantial research efforts during the past thirty years were undertaken by many researchers in many areas related to this broad interdisciplinary topic. The proposed research will build on these developments, and address a number of fundamental and basic research challenges towards a next-generation, versatile, efficient, and practical health monitoring strategy. In such a strategy, data from thousands of sensors will be analyzed with long-term and real-time assessment decisionmaking implications. A flexible and scalable software architecture/framework will be developed to integrate real-time heterogeneous sensor data, database and archiving systems, computer vision, data analysis and interpretation, numerical simulation of complex structural systems, visualization, probabilistic risk analysis, and rational statistical decision making procedures. This development will be undertaken in a concerted and focused comprehensive approach by an inter-disciplinary team of Computer Scientists (CS) and Structural Engineers (SE). It is believed that this inter-disciplinary
approach will synergize the resolution of basic technical challenges and allow development of the
framework for future applications in this field. The new framework will also speed up the discovery of new knowledge related to the progressive or sudden deterioration of civil infrastructure systems and the corresponding damage mechanisms. The planned research activities will not only culminate in the deployment of a robust, field-implementable monitoring system, but it will also advance the research frontiers in several active, cutting-edge research areas involving grid storage (curated databases, filesystems, database systems), knowledge-based data integration and advanced query processing, information extraction (data mining, modeling, analysis and visualization), knowledge extraction (reliability/risk analysis, structural health assessment, physics-based model development), and decision support systems (e.g., emergency response, preventive maintenance, rehabilitation).

The entire project will be developed around actual Bridge Testbeds in cooperation with the
California Department of Transportation (Caltrans), and Industry Partners. These Testbeds will be
densely instrumented and continuously monitored, and the recorded response databases will be made available for maximum possible use by interested researchers and engineers worldwide. The actual recorded data streams from both laboratory models and bridge testbeds will be a major component for all phases of this research effort. An Internet Portal will integrate all elements and act as a Gateway for the Project.

The proposed 5 year project duration will allow the opportunity for resolving key basic research issues of relevance to Structural Health Monitoring, and collaboration between CS and SE
is simply a necessity. State-of-the-art data acquisition, transmission, and management, involvement of computer vision, refinement of nonlinear system identification and modeling, and practical
implementation constitute the basic research framework. Applications include long-term condition
assessment and emergency response after natural or man-made disasters and acts of terrorism for all
types of large constructed facilities. From a broader perspective, the proposed effort will be a major boost in defining and shaping additional long-term interaction and collaboration opportunities between CS and SE, with wide national and international implications, as well as strongly benefiting from leveraging resources and ongoing monitoring activities.

Structural Health Monitoring (SHM) is a highly interdisciplinary area of research focused on developing techniques to detect damage in structures such as buildings, bridges, aircraft, ships and spacecraft. Most SHM research to date has focused either on global damage assessment techniques using low-resolution measurements of a structure's response to ambient excitation, or on limited local independent damage detection mechanisms.

This proposal advocates a paradigm shift in SHM, using decentralized local excitation and high-resolution measurements of response to these excitations, detected and collaboratively analyzed through a spatially
dense wireless network of devices. This shift promises simpler and more accurate techniques to identify and even localize damage within the structure.

The goal of the proposed research is the design of a networked computer system, with distributed actuation and sensing, for SHM. The term "networked SHM" denotes the class of monitoring systems that will
be enabled by this research. By combining local excitation with high-resolution sensing, networked SHM is quite distinct from other sensor network applications being examined today. Networked SHM promises a future where, for example, buildings are constructed using concrete mixed with several tens of thousands of embedded sensor devices as well as low-power local exciters. The network of sensors will be able to continuously monitor the structure, trigger alarms that identify the onset of damage, precisely pinpoint the location of damage and also provide a long-term history of ambient stresses imposed on the building.