Structural health monitoring, or SHM, is the process of using sensors installed on structures like bridges, buildings, and aircraft to continuously measure their condition and detect damage before it becomes dangerous. Think of it as a real-time diagnostic system for infrastructure, similar to how a fitness tracker monitors your heart rate and flags irregularities. The global SHM market was valued at $4.35 billion in 2025 and is projected to reach $17.77 billion by 2033, reflecting how quickly this technology is being adopted worldwide.
How Structural Health Monitoring Works
An SHM system collects data from an array of sensors mounted on or embedded within a structure. These sensors measure physical changes: vibrations, strain, tilt, temperature shifts, and acceleration. The data flows to a dedicated server that processes and compresses it into useful information about the structure’s condition. The U.S. Geological Survey describes SHM as measuring structural response, often in near real-time, to assess conditions after severe loading events like earthquakes and to track progressive deterioration over time.
The process generally follows four stages. First, sensors capture raw physical measurements. Second, a data acquisition system collects and transmits those measurements. Third, software extracts meaningful features from the data, filtering out noise and identifying patterns that matter. Fourth, statistical models compare those patterns against baseline readings to determine whether something has changed, and if so, how serious it is. The goal is to move from raw numbers to a clear picture of whether a structure is safe, degrading, or in need of immediate attention.
Types of Sensors Used
Different structures and hazards call for different sensing technologies. Accelerometers are among the most common, measuring vibrations and movement. They’re used on everything from bridge decks to wind turbine blades, where they can track bending patterns during operation. Strain gauges measure how much a material is stretching or compressing under load, which helps locate stress concentrations in beams and joints.
Piezoelectric sensors generate an electrical signal in response to mechanical pressure, making them useful for detecting cracks and delamination in materials like composites. They’re lightweight, inexpensive, and can both send and receive signals, which allows them to actively “ping” a structure and listen for changes in how waves travel through it. One limitation: temperature changes can cause false readings with piezoelectric sensors, so systems need to account for environmental conditions. Fiber optic sensors, GPS receivers, and imaging technologies round out the toolkit, each chosen based on what needs to be measured and how harsh the environment is.
Where SHM Is Used
Bridges and Civil Infrastructure
Bridges are one of the most prominent applications. They face a long list of threats: earthquakes, typhoons, flooding, vehicle overloading, and collisions with ships passing beneath them. SHM systems on bridges typically monitor wind speed, load, acceleration, temperature, and structural deflection. Early warning capabilities fall into two categories: detecting structural damage through changes in static and dynamic responses, and detecting external disasters like seismic events or floods that could compromise the bridge.
The scale of bridge monitoring varies enormously. In California, only 61 of the state’s 22,000 bridges have been instrumented with wired monitoring systems, partly because costs have exceeded $300,000 per toll bridge for a 60-channel setup. The Tsing Ma suspension bridge in Hong Kong cost more than $16 million to outfit with over 600 sensing channels, roughly $27,000 per channel. These figures illustrate both the value placed on monitoring critical structures and the cost barriers that have historically limited adoption.
Aircraft and Aerospace
In aviation, SHM focuses on continuously inspecting maintenance-critical components of the airframe. Sensors permanently installed on or embedded within the aircraft structure provide real-time feedback about its condition. Over an aircraft’s lifetime, this data can reveal anomalies, pinpoint their location and severity, and help estimate how much useful life remains in a component.
The payoff is significant. Detailed visual inspection currently accounts for 80 to 90 percent of aircraft maintenance downtime. If an SHM system can reliably detect damage below the allowable limit, airlines can shift from rigid scheduled inspections to more flexible, on-demand maintenance. This means less time grounded and faster turnaround. One study on composite aircraft structures found that integrating SHM allowed safety factor reductions from 2.0 to 1.75, translating to a 50 percent decrease in maintenance costs and direct operating cost reductions between 2 and 5 percent. A separate estimate suggested potential weight savings of 5 percent from designing with less conservative margins, since the monitoring system catches problems that would otherwise require built-in safety buffers.
Wired vs. Wireless Systems
Traditional SHM systems use wired sensors connected by cables to a central data acquisition unit. These systems are reliable and allow frequent, high-quality data collection. But they don’t scale well. Installation of a moderate-size wired system can consume over 75 percent of total testing time, with installation costs approaching 25 percent of total system cost. On bridges, just laying the protective conduits for wiring can cost $10 per linear foot.
Wireless sensor networks have emerged as a lower-cost alternative. Installation costs can drop to less than half of a wired system. Wireless networks also allow far higher sensor density, with deployments potentially reaching hundreds or thousands of nodes, which improves the resolution of damage detection across large structures. The tradeoff is performance: wireless systems face challenges with limited bandwidth, synchronization accuracy (some SHM applications need microsecond-level precision), packet loss, and power supply for remote nodes. For now, many projects use a hybrid approach, combining wired systems in critical areas with wireless networks for broader coverage.
Technical Challenges
Temperature is one of the biggest confounding factors in SHM. Both strain readings and vibration-based analysis shift with temperature changes throughout the day and across seasons. A bridge expanding on a hot afternoon can look, to the sensors, a lot like a bridge under excessive load. Any reliable SHM system needs compensation methods to separate temperature effects from actual structural changes, and developing those methods remains an active challenge.
Sensor durability is another concern. Sensors mounted on outdoor infrastructure endure rain, ice, UV exposure, and temperature extremes for years or decades. Maintaining consistent performance over that lifespan, especially for wireless nodes that rely on batteries or energy harvesting, is difficult. Data storage and processing also scale up quickly when thousands of sensors are sampling at high frequencies around the clock. Turning that firehose of raw data into actionable assessments requires sophisticated software and computing power at the monitoring site.
Why It Matters for Aging Infrastructure
Much of the world’s critical infrastructure is aging. Bridges, dams, tunnels, and high-rise buildings degrade over decades from weather, use, and seismic activity. Traditional inspection relies on periodic visual checks and scheduled maintenance, which can miss problems developing between inspections or waste resources replacing components that still have useful life. SHM fills that gap by providing continuous or near-continuous data, catching deterioration trends early and allowing maintenance to be targeted where it’s actually needed rather than applied on a fixed calendar.
The 19.4 percent annual growth rate projected for the SHM market through 2033 reflects how broadly this shift is happening, driven by a combination of aging infrastructure, stricter safety regulations, and sensor technology becoming cheaper and more capable. As wireless systems mature and data processing improves, monitoring is becoming practical for a much wider range of structures, not just marquee projects like suspension bridges and commercial aircraft.