Future Forward: Structural Health Modeling as a Multidisciplinary Pursuit
Michael D. Todd is a professor of structural engineering at the University of California, San Diego (UCSD), and co-director of the UCSD Engineering Institute at Los Alamos National Laboratory. He has combined the coursework of several disciplines to create a graduate program in Structural Health Monitoring, Damage Prognosis and Validated Simulation, and he is focusing his specific research on structural dynamics, nonlinear vibrations, time-series modeling, fiber-optic sensor-system design and uncertainty quantification in monitoring processes.
Todd founded the country’s first graduate-degree program in structural health monitoring, damage prognosis and validated simulations—the UC San Dieogo program is the only such graduate program that combines the diverse set of disciplines needed to address problems in the monitoring of structures of all kinds. Students take equal numbers of courses in structural engineering, mechanical/aerospace engineering, computer science and electrical engineering.
“To solve the kinds of problems in structural health monitoring to create ‘smart structures’, you need knowledge in all those domains,” says Todd. “Students take classes to know the mechanics and physics, data analytics and sensing technologies, and then integrate the technologies to make a useful solution.”
The Three Disciplines
Structural health monitoring measures structures in-situ performance (e.g., buildings, bridges, aircraft, automobiles, etc.) and infers from the data, using both data- and physics-based analytic techniques, whether they’re successfully performing design functions.
“There’s no such thing as a sensor that tells you exactly the damage or where it is,” notes Todd. “Sensors give you indirect clues, so we have to develop the data-interrogation algorithms that know how to mine data to look for subtle changes that reflect what we’re interested in.”
Damage prognosis feeds the information from structural health monitoring into physics-based models that predict how damage in a structure will evolve. The goal is to perform predictive planning that anticipates when it reaches a critical point necessary for an inspection, maintenance or removal of service. Validated simulation ensures that models are validated with reality by making sure those models and any available test data match.
“The Holy Grail is to understand where a structure is going to be in the future,” adds Todd. “When do we expect, with quantified certainty, that something critical will happen to the structure? When will we have a failure, or when will we have to do maintenance, or when do we have to mitigate the problem? Nobody is doing that now in a comprehensive way. We’re trying to develop capabilities to match this vision.”
The analogy to health is an important one, swapping the patient with a structure and the doctor with an engineer. The three disciplines come together to create infrastructure that can sense and reason and tell engineers when it’s sick and what its symptoms are as well as where it’s “feeling pain.”
“You can imagine a bridge learning through sensor data, data mining and analytics, and then sending alerts to engineers when and where there’s a problem and the most likely cause,” says Todd. “To me that’s truly a smart structure, when the patient we’re trying to diagnose calls the doctor.”
The coursework is designed to train multidisciplinary problem solvers and not specialists. Contrary to a traditional Ph.D. approach that’s a deep dive in a narrow topic, the multidisciplinary program teaches students to speak all the languages of the sub-disciplines and understand the “big problem.”
“Our students have to demonstrate expertise in an area, but they really have to be solving system-wide problems,” says Todd. “That’s what our program does, and I think employers appreciate that.”
Todd’s team demonstrated the use of simple unpowered sensors to test a bridge for a seismic event, using RFID sensors that communicate via cellular networks as well as an unmanned aerial system to fly out and take readings from the sensors without putting a person in harm’s way.
“If a moderate earthquake hits a bridge or building, if it isn’t destroyed or hasn’t collapsed, does that mean it’s safe,” notes Todd. “With all these readings, you could get a picture of the bridge’s performance without sending inspectors.”
Such monitoring of structures now is happening at large scales in China and South Korea, where they mandate that new construction includes monitoring technology. Requiring designers to install the technology is driving innovation.
“We’re a fundamentally reactive culture when it comes to infrastructure and asset management,” says Todd. “These countries will catch up and pass us if the United States doesn’t make an investment.”
Read the full interview here.