Computational Elements of Robust Civil Infrastructure

1. 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

2. 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

3. 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.

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

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

6. Focus of the study • 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. • 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.

7. Research and Development Highlights • The design and implementation of a low-power/ low-cost smart sensors-actuators complex (SAC) consisting of: • smart sensor networks • data receptors • computational elements • 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.

8. 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.

9. 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.

10. 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.

11. Research and Development Tasks • Development of self-configuring, self-calibrating wireless sensor networks and low-latency sensor data management techniques. • Development of algorithms and software for continuous real-time testing, diagnosis, and maintenance for all communication and computational components of the sensor/actuator networks. • Fault-tolerant operation of the SAC-SSD complexes.

12. 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.

13. 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).

14. 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).

15. 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.