How Structural Health Monitoring Works for Cranes
📋 Key Summary
Human health is tracked through pulse and checkups — but what keeps tabs on a steel structure? Structural health monitoring. Strain gauges and optical fiber sensors installed at critical points like the main girder and weld seams measure stress and deformation in real time, triggering alarms the moment limits are exceeded. This article explains how structural health monitoring works, turning the crane's main girder from "silent steel" into "equipment that talks."
📌 Core Logic
The structure can't speak — the sensors speak for it.
Measure stress and deformation in real time, alarm on over-limit conditions, and expose hidden risks before they become accidents.
The main girder of a crane carries tens of tons day in and day out, yet no one truly knows its "physical condition." Cracks grow silently inside weld seams, stress accumulates quietly at critical points — until one day, a failure reveals what was hidden all along.
Structural health monitoring changes that: it fits the steel structure with a "pulse monitor," measuring stress and deformation in real time, so the structure evolves from silent steel into equipment that communicates its condition.
Here's how structural health monitoring is implemented.
What Structural Health Monitoring Measures: Stress, Deformation, Cracks
Structural health monitoring centers on three key measurements.
Stress is the force the structure endures. Measuring stress at load-bearing points reveals whether the structure is actually being overstressed. Stress is the core indicator of structural health.
Deformation is the deflection of the structure under load. When main girder deflection exceeds allowable values, it signals reduced stiffness and possible damage.
Cracks are the most direct sign of structural damage. Crack propagation causes a sharp drop in structural strength — the most dangerous signal of all.
Together, stress, deformation, and cracks form the "health check indicators" of a steel structure. GB/T 28264-2017 Safety Monitoring and Management System for Lifting Appliances sets requirements for structural condition monitoring.
Sensor Installation: Strain Gauges and Optical Fiber Sensors
Two types of sensors measure stress and deformation.
Strain gauges are resistance-based sensors bonded to the structure's surface. When the structure deforms under load, the gauge deforms with it, changing its electrical resistance — this resistance change is converted into strain and then stress readings. Strain gauges are economical and well-proven, making them the workhorse of structural monitoring.
Fiber Bragg grating sensors measure strain through optical fiber. They resist electromagnetic interference and corrosion, offer long service life, and support series-connected multi-point measurement — ideal for long-term monitoring.
Both sensor types are installed at critical load-bearing locations on the main girder — mid-span, supports, and near weld seams — for real-time stress data acquisition. Kelude Heavy Industry determines monitoring points through force analysis and installs sensors only at these keypoints. ISO 24445 Technical Specification for Smart Sensors of Cranes governs sensor selection.
Using Monitoring Data: Over-Limit Alarms and Health Assessment
Raw sensor data must be turned into actionable information.
Over-limit alarming triggers an alarm when stress or deformation exceeds allowable values. If main girder stress or deflection goes beyond limits, the structure may be overloaded or damaged — an immediate alarm prevents accidents.
Health assessment tracks structural condition over the long term. Trends in stress and deformation over time reveal how the structure's health is evolving — a deteriorating trend means the structure is degrading and needs inspection or overhaul.
Over-limit alarms address "immediate safety," while health assessment manages "long-term integrity." Only when both work together does structural health monitoring deliver real value.
Value of Structural Health Monitoring: Extending Old Equipment, Securing New
Structural health monitoring delivers the greatest value for two categories of equipment.
For aging equipment, monitoring extends service life. Installing sensors on cranes that have operated for years provides real-time visibility into structural condition. If the structure remains sound, the crane can continue operating with confidence; if degradation is detected early, it prevents continued operation with hidden defects.
For new equipment, monitoring provides peace of mind. Large-tonnage and mission-critical cranes fitted with monitoring from day one give operators full visibility into structural condition, catching overloads and anomalies as soon as they occur.
Kelude Heavy Industry offers structural health monitoring as a premium configuration, installed on critical equipment and cranes undergoing life-extension overhauls — keeping structural condition transparent at all times.
Most Common Structural Health Monitoring Mistakes
Mistake one: wrong monitoring points. If sensors are not placed at the most critical load-bearing locations, the data collected will not reflect the structure's true condition. Monitoring points must be determined through force analysis.
Mistake two: monitoring without alarms. Data is collected and stored, but no over-limit alarms are configured — so excessive stress goes unnoticed. Monitoring must be linked to early warning systems.
Mistake three: installing sensors and forgetting them. Sensor drift or failure produces inaccurate data, making the entire installation pointless. Kelude Heavy Industry performs periodic calibration and periodic maintenance on all sensors to ensure data reliability.
Structural Health Monitoring: Key Elements at a Glance
| Monitoringquantity | Sensor | indication | early warninglogic |
|---|---|---|---|
| Stress | strain gaugeoptical fiber | actual load | exceeding allowable valuealarm |
| Deformation | Displacement Sensor | Stiffnessdamage | Deflectionover-limitalarm |
| Crack | acoustic emissionFlaw detection | damage propagation | abnormal propagationalarm |
Quick Reference of Standard Clauses for Structural Health Monitoring
| Standard | clause essentials | versusMonitoringrelationship |
|---|---|---|
| GB/T 28264 Safety Monitoring and Management System | structureCondition Monitoring | Monitoringrequirementsbasis |
| ISO 24445 | smart sensortechnical specification | sensor selectionreference |
| FEM 1.001 Crane Design Standard | structuredesign specification | allowableStressreference |
Structural Health Monitoring: FAQ
Q: Which cranes are best suited for structural health monitoring?
A: Large-tonnage cranes, those used in key processes, and aging equipment. Large-tonnage units carry higher structural risk, downtime in critical operations is costly, and older cranes benefit from continuous insight into their structural condition to extend service life. These are the scenarios where structural health monitoring delivers the most value. For small- to medium-capacity cranes with lower risk profiles, periodic inspection is generally sufficient—monitoring isn't necessary across the board.
Q: How does structural health monitoring differ from periodic inspection?
A: Think of periodic inspection as an annual physical exam—it assesses the crane's condition at a single point in time. Structural health monitoring, by contrast, works like a continuous pulse monitor, tracking the structure in real time. It catches overloads or anomalies the moment they occur, even between scheduled inspections. In short, it's the difference between checking periodically and watching constantly—monitoring captures issues that arise in the intervals between inspections.
Q: How is the accuracy of monitoring data ensured?
A: Through sensor calibration and diligent maintenance. Sensors must be calibrated after installation to establish a reliable correlation between measured values and actual conditions. Over time, sensors drift, so periodic calibration and checks for sensor failure are essential. The key is calibrating after installation and rechecking on a regular schedule—without this, the data you collect is unreliable, and the entire system provides little value.
Structural health monitoring and Digital Twin technology go hand in hand. For a closer look at how they work together, see the Digital Twin platform described in "University Collaboration Drives Development of Crane Digital Twin Simulation Platform, Cutting New Product Development Time by 40%".
When you give a steel structure a pulse monitor, it's no longer silent. Kelude installs strain and optical fiber sensors at critical load-bearing points to measure stress and deformation in real time, issue early warnings when limits are exceeded, and assess structural trends—giving you a clear, continuous picture of the Main Girder's health.
