Computational Elements of Robust Civil Infrastructure

White paper by:

G. Cybenko, K. Fuchs, A. Grama, C. Hoffmann, A. Sameh, N. Shroff, M. Sozen, and B.F. Spencer

September 17, 2002

Motivation for Study

• The country has an investment of $20 trillion in civil infrastructure.

• Much of this civil infrastructure is “mission-critical”, e.g.,– bridges– power plants and power grid towers– telecommunication centers– water purification plants

Motivation for Study• Monitoring the health of such infrastructure

through sensing technology can:– assure timely service,– detect the onset of catastrophic failure,– mitigate catastrophic failure, or– allow for effective contingency plans (crisis management).

• Actuation based on sensing infrastructure can:– increase the robustness of such structures very significantly,– enable economical construction of critical infrastructure,– in the event of imminent failure, direct the structure to desirable

failure modes.

Targeted Hazards• Earthquakes• Explosions• Fire• Rust• Wind• Terrorist events

State-of-the-art in Controlled Structures - Passive Control

Focus of the study1. Develop the communication, data integration,

and computational, infrastructure that enables:– Effective design and economical construction of highly

robust “smart” structures that sense and react to external stimuli; and

– Transformation of existing structures into active structures that sense, discriminate, and act in defense.

2. Off-line use of data collected to “solve the inverse problem” – determine actual structural characteristics and specific stimuli leading to failure. This can be done through a series of scenario simulations.

Research and Development Highlights

1. The design and implementation of a low-power/ low-cost smart sensors-actuators complex (SAC) consisting of:1. smart sensor networks2. data receptors3. computational elements4. real-time control

algorithms

Sensing/Computation/Communication elements - designed by part of our research team at Dartmouth. These units cost under $200 and are the size of a deck of cards. Efforts are on to develop the next generation of such devices at Purdue.

Research and Development Highlights

• Integrate the SAC with a strut system containing controllable dampers (to change the stiffness characteristics of the structure).

– a magnetorheological (MR) device, also referred to as a smart-strut-device (SSD).

Magnetorheostatic dampers can change their load bearing characteristics from fully solid to fully damping in milliseconds when exposed to magnetic fields.

Research and Development Highlights

• Develop distributed strategies for computing control vector from sensed signals in real time.

• Develop detailed simulation methodologies for validating control strategies and examining a variety of what-if scenarios for a range of stimuli.

Research and Development Highlights

• Detailed methodologies for design of structures, including placement and capability of sensors and actuators, precise calibration of impact bearing capacity of the structure.

• Real-time visual information infrastructure to support status checks, and rescue and relief efforts.

Research and Development Tasks

a) Development of self-configuring, self-calibrating wireless sensor networks and low-latency sensor data management techniques.

b) Development of algorithms and software for continuous real-time testing, diagnosis, and maintenance for all communication and computational components of the sensor/actuator networks.

c) Fault-tolerant operation of the SAC-SSD complexes.

Research and Development Tasks

• Model reduction of the large-scale dynamical system representing the structure (off-line).

• Development of distributed, real-time (on-line) algorithms for determining the structure’s response to dynamic impulses using the reduced low-order model, together with a real-time visualization environment.

• Development of rapid simulation and visualization infrastructure for exploring (off-line) a range of “what-if” scenarios for real-time disaster management and control strategies.

Research and Development Tasks

• Validation of the entire computational paradigm on well-instrumented model structures, as well as actual instrumented structures in Puerto Rico (wind effects), and Japan (earthquakes).

Unique Qualifications of Research Team

• Extensive experience building and applying sensor networks (Cybenko, Dartmouth, Shroff, Purdue).

• Pioneered the development and use of smart-strut devices (Sozen, Purdue, Spencer, Illinois).

• Fundamental work in fault tolerance, testing, and system validation (Fuchs, Cornell).

• Experts in geometric modeling, large scale simulation, and visualization infrastructure, more recently, applied to the Pentagon crash simulation (Hoffmann, Purdue),

• Parallel and distributed algorithms for structural modeling, model reduction, and control (Sameh, Grama, Purdue).

Relation of Project to Other Sensor Network Efforts

• The fundamental goal of this project is to build robust civil infrastructure.

• From this point of view, the aim is one of integrating a range of existing technologies, and where needed, to develop new technologies.

• Its primary aim is not to build a new class of sensors or RF communication devices. It is our belief that these technologies have matured to a point where they can safely be used for solving the critical task of securing civil infrastructure.