Acoustic Emission Monitoring for Detecting Cracks in Steel Bridges

The safety and longevity of steel bridges are vital for transportation infrastructure. Continuous exposure to traffic-induced vibrations, thermal fluctuations, and environmental stresses can lead to structural degradation over time. Acoustic Emission Monitoring (AEM) provides a real-time, advanced approach to detecting and tracking crack propagation in steel bridges, enabling early maintenance and extending service life.

Æmission Digitizer/Recorder: The Core of Our AEM System

At the heart of our monitoring solution is Æmission, a state-of-the-art acoustic emission monitoring system designed for high-speed data acquisition and real-time signal processing.

  • High-Speed Data Acquisition: Operates at 1.25 MSps @ 18-bit resolution or 5 MSps @ 16-bit resolution, ensuring high-fidelity signal capture.
  • Patented FPGA Algorithms: Developed in collaboration with the Polytechnic University of Turin, enabling onboard processing of acoustic emission waves.
  • Localized Data Processing: Extracts key crack progression indicators, such as βt, b-value, and cumulative count, facilitating predictive maintenance strategies.
  • Proven Performance: Validated through the MONFRON project, a large-scale experimental initiative funded by Regione Toscana in Italy.

Acoustic Emission (AE) Technology for Structural Health Monitoring

Acoustic emission (AE) is the release of stress waves within a material caused by internal structural changes or external mechanical loads. These waves propagate through the material and can be detected to assess its condition, revealing cracks or other forms of damage.

AE testing is a non-destructive technique used to identify and monitor crack development in structures, including metals, concrete, and composites. When subjected to mechanical stress, temperature variations, or environmental changes, a structure generates acoustic emissions that sensors capture on its surface.

The recorded signals are processed using advanced software and hardware to pinpoint the AE source and locate potential damage. Continuous monitoring allows engineers to track crack progression, evaluate structural integrity, and make data-driven decisions regarding maintenance, repairs, or replacements. AE testing is a crucial tool for ensuring the safety and longevity of critical structures across industries such as aerospace, civil engineering, and manufacturing.

Application of AEM in Steel Bridges

Steel bridges experience constant mechanical and environmental stress, making them susceptible to fatigue cracks and localized failures. Implementing an AEM system on existing steel bridges provides real-time insights into structural integrity and ensures early intervention before catastrophic failures occur.

Use Cases:

  • Traffic-Induced Vibrations: AE sensors monitor crack initiation and progression in high-stress zones such as welds and riveted connections.
  • Thermal Fluctuations: Seasonal temperature changes cause expansion and contraction, exacerbating material fatigue.
  • Corrosion Monitoring: Detects stress-corrosion cracking, an insidious form of material degradation.
  • Emergency Event Detection: Sudden impacts (e.g., vehicle collisions, seismic activity) introduce immediate damage, with AE-based monitoring aiding rapid response.
  • Predictive Maintenance Planning: Engineers analyze AE data trends to forecast maintenance needs, minimizing costs and avoiding unscheduled repairs.

Æmission System Architecture

Æmission is supplied with eight piezoceramic sensors, selected and characterized with assistance from the Polytechnic University of Turin for optimal civil structure monitoring. These sensors are strategically placed around the monitored area and connected via 10-meter cables.

Key Features:

  • Analog Signal Processing: The analog signals from the piezoceramic sensors are conditioned and level-adapted by a cascade of analog filters before digital conversion.
  • High-Speed Data Conversion: Eight high-speed ADCs (1.25MSps@18bit or 5MSps@16bit) continuously convert analog signals into digital format, synchronized to the same clock source.
  • Parallel Processing with FPGA: Digital signals are acquired and processed in parallel by the FPGA, with only relevant events transferred to the Linux CPU.
  • Data Storage & Remote Sharing: Events are stored locally within the Linux CPU and can be shared remotely via WiFi or 3.5G connection.
  • Integrated GNSS Receiver: Synchronizes multiple Æmission units, enabling scalable monitoring across extensive infrastructures.
  • Comprehensive Data Analysis: After sufficient monitoring, parameter plots help analyze cracking patterns and structural health trends.

Real-World Monitoring Example

The following graphs represent an ongoing acoustic emission survey in a marble quarry:

  • AE Cumulative Count
  • AE/hour Trends
  • Event Frequency Distribution
  • Amplitude Variations
  • βt and b-value Progression
  • 3D Localization of Emission Sources

In the 3D representation, blue squares denote AE sensors, while red dots indicate the localization of emission sources.

Implementation Plan

Our proposal outlines a comprehensive approach to designing, installing, and maintaining an AEM system for steel bridges:

  1. Site Assessment & Sensor Placement: Identify high-risk zones and strategically install AE sensors.
  2. Real-Time Data Collection & Processing: Utilize the Æmission digitizer/recorder for continuous monitoring.
  3. Data Interpretation & Reporting: Implement advanced algorithms to analyze AE parameters and generate actionable insights.
  4. Predictive Maintenance & Intervention: Leverage AEM data to schedule repairs before structural failure occurs.

Why QuakeLogic’s AE Monitoring System?

QuakeLogic’s AE monitoring system is a cutting-edge solution for steel bridge health assessment. Our system is designed for high-performance data acquisition, real-time crack detection, and predictive maintenance planning. By investing in our AE monitoring technology, bridge owners and engineers can ensure structural safety, extend service life, and reduce maintenance costs.

Buy Our AE System Today!

Visit our website to explore our state-of-the-art acoustic emission monitoring hardware and equip your infrastructure with the latest technology for proactive maintenance.

BUY ACOUSTIC EMISSION SYSTEM NOW!

About QuakeLogic

QuakeLogic is a global leader in monitoring solutions, offering innovative technologies for accurate seismic data acquisition and analysis. Our solutions empower organizations worldwide to predict, understand, and mitigate risks effectively.

For more information or inquiries, reach out to our sales team today!

Ensuring Effective Vibration Isolation for Shake Table Experiments

Shake tables are powerful tools for simulating earthquakes, studying structural dynamics, and testing critical infrastructure components. However, operating a shake table inside a building presents a unique challenge: how to isolate vibrations effectively to prevent any impact on the surrounding structure.

In this blog, we’ll explore the importance of vibration isolation, the role of an inertia mass block, and the key considerations for achieving precision and stability during shake table experiments.

Why Vibration Isolation Matters for Shake Tables

Shake tables generate high dynamic forces and vibrations during testing. If not properly isolated, these vibrations can:

  • Transmit through the building’s foundation.
  • Cause damage or wear to surrounding infrastructure.
  • Create feedback vibrations, reducing experimental accuracy.
  • Compromise the safety of personnel and equipment.

The Challenge of Isolation: Precision vs. Power

Shake tables must simulate real-world earthquake scenarios with precision while ensuring vibrations remain fully decoupled from the building’s structural slab. Achieving this balance requires a carefully engineered vibration isolation system.

The Role of an Inertia Mass Block in Vibration Isolation

One of the most effective ways to isolate a shake table is by placing it on an inertia mass block. This intermediate concrete foundation acts as a dynamic buffer between the shake table and the building slab.

Key Benefits of an Inertia Mass Block:

  1. Increased Stability: Prevents rocking and tilting during high-amplitude experiments.
  2. Energy Dissipation: Absorbs and dampens dynamic forces generated by the shake table.
  3. Load Distribution: Spreads the shake table’s weight evenly across air springs.
  4. Reduced Resonance Effects: Lowers the natural frequency of the system, minimizing unwanted vibrations.
  5. Long-Term Durability: Reduces fatigue on isolation components, ensuring reliable performance over time.

Without an inertia mass block, air springs may experience uneven loading, excessive deflection, or reduced isolation efficiency.

Air Springs: Fine-Tuning Vibration Isolation

Underneath the inertia mass block, air springs play a critical role in vibration isolation. These components are designed to:

  • Absorb vibrations across a wide frequency range.
  • Provide adjustable stiffness and damping characteristics.
  • Maintain stability under varying loads.

Key Considerations for Air Springs:

  • Load Capacity: Each air spring must support a specific portion of the total system weight.
  • Stiffness: Proper stiffness tuning ensures a natural frequency below 2 Hz for effective isolation.
  • Static Deflection: Optimal deflection ensures air springs operate within their designed range without excessive compression.

When combined with an inertia mass block, air springs deliver precision and reliability, keeping vibrations isolated and the surrounding building safe.

Designing an Optimal Vibration Isolation System

Step 1: Build a Stable Inertia Mass Block

  • Construct a concrete block, typically 2 to 3 times the weight of the shake table.
  • Ensure a minimum 5 cm isolation gap around the block.

Step 2: Use Proper Air Springs

  • Select air springs capable of supporting the total system weight (shake table + inertia mass block).
  • Ensure the natural frequency remains below 2 Hz.

Step 3: Isolate Utility Connections

  • Use flexible hoses and conduits for hydraulic, pneumatic, and electrical connections to avoid creating vibration pathways.

Step 4: Monitor and Fine-Tune the System

  • Install vibration sensors to monitor performance.
  • Adjust air pressure in the springs to maintain optimal isolation.

What Happens Without Proper Isolation?

Neglecting proper isolation can lead to:

  • Vibrations transmitting through the building slab, causing unintended structural stress.
  • Inaccurate experimental results due to feedback vibrations.
  • Excessive wear and reduced lifespan of the shake table and air springs.

In severe cases, it can even invalidate test results, rendering experiments ineffective.

Key Takeaways for Shake Table Vibration Isolation

  1. Inertia Mass Block: Provides stability, uniform load distribution, and energy absorption.
  2. Air Springs: Fine-tune vibration isolation and ensure dynamic forces are not transmitted to the building.
  3. Isolation Gap: Prevents secondary vibration paths.
  4. System Monitoring: Real-time monitoring ensures ongoing performance and reliability.

When properly designed, these components work together to create a robust vibration isolation system that protects both the experiment and the surrounding environment.

Consult QuakeLogic:

At QuakeLogic, our solutions ensure accurate, repeatable experiments while maintaining complete structural safety.

Interested in designing an isolation system for your shake table project?
Reach out to us today at sales@quakelogic.net, and let’s build a solution tailored to your needs.

Because in vibration isolation, precision isn’t optional—it’s essential.

Understanding Linearity, Repeatability, and Phase Lag in Digital Sensors

QL-mini-shm sensor

Digital sensors are the backbone of effective real-time monitoring systems, especially in fields where accuracy and responsiveness are crucial, such as seismic monitoring, structural health assessment, and environmental monitoring. Key performance characteristics—linearity, repeatability, and phase lag—define a sensor’s accuracy, consistency, and responsiveness. Understanding these factors and how they are measured can help ensure the reliability of monitoring systems and the quality of data collected.

Linearity: What It Is and How to Measure It

Definition: Linearity indicates how accurately a sensor’s output follows a straight line relative to the input. Ideally, a sensor should have a direct, proportional relationship between input and output across its full range, meaning that changes in the input yield corresponding, linear changes in the output. However, sensors often deviate from this ideal, impacting their linearity.

Measurement: To measure linearity, test the sensor across its entire measurement range and compare its output to the ideal linear response. Deviations from this line can be quantified as a percentage of the full-scale output. Lower deviation percentages signify higher linearity, making the sensor more reliable for precision measurements.

Importance for Real-Time Monitoring: Linearity ensures the sensor output consistently reflects the actual value of the measured phenomenon, which is crucial in applications like seismic monitoring. Accurate linearity enables sensors to capture ground motion amplitudes precisely, providing essential data for analyzing seismic waves and predicting potential impacts.

Repeatability: What It Is and How to Measure It

Definition: Repeatability is the sensor’s ability to produce the same output under identical conditions over multiple measurements. High repeatability signifies consistent, reliable data collection, which is vital for any monitoring application.

Measurement: To assess repeatability, the sensor is exposed to the same input several times while recording each output. The variations in these measurements are quantified, often using standard deviation. Smaller variations indicate higher repeatability, demonstrating the sensor’s ability to provide consistent results under similar conditions.

Importance for Real-Time Monitoring: High repeatability ensures consistent data, vital in real-time monitoring applications like earthquake early warning systems or structural health monitoring. Reliable, repeatable data builds confidence in the monitoring system’s accuracy, supporting timely and well-informed decision-making.

Phase Lag: What It Is and How to Measure It

Definition: Phase lag, or phase delay, is the time delay between a sensor’s output and the occurrence of the measured event. A low phase lag indicates that the sensor can quickly respond to changes, an essential trait for systems monitoring dynamic or rapidly shifting environments.

Measurement: Phase lag can be measured by applying a known waveform, such as a sinusoidal signal, to the sensor and recording the output’s response time. The phase difference between the input and output is quantified in degrees or time units. A smaller phase lag value indicates a faster response, ensuring the sensor’s output stays in sync with real-time changes.

Importance for Real-Time Monitoring: For critical monitoring applications, phase lag can compromise the reliability of data. In seismic monitoring, a delay in sensor response can affect wave propagation analysis, making low phase lag essential to real-time applications. When phase lag is minimized, data more accurately reflects real-world events, supporting rapid response actions during emergencies.

QuakeLogic’s New QL-MINI and QL-MINI-SHM Sensors

At QuakeLogic, we are excited to introduce our latest additions to our seismic and structural health monitoring (SHM) product line: the QL-MINI and QL-MINI-SHM sensors. These compact, high-performance digital sensors are engineered to offer unmatched precision in real-time monitoring applications, making them ideal for infrastructure, geotechnical, and environmental monitoring.

QL-MINI: Designed for versatility and efficiency, the QL-MINI combines compactness with high accuracy, making it ideal for a range of monitoring applications. With its exceptional linearity and repeatability, the QL-MINI provides consistent data and minimal phase lag, ensuring precise, real-time insights for critical applications.

QL-MINI-SHM: Tailored specifically for structural health monitoring, the QL-MINI-SHM sensor provides advanced data fidelity with ultra-low phase lag and superior repeatability. It’s ideal for monitoring structural integrity, ensuring safety and resilience in buildings, bridges, and other critical infrastructure.

QL-mini-shm sensor

Both QL-MINI and QL-MINI-SHM models are designed to meet the rigorous demands of real-time monitoring, providing the highest levels of accuracy, consistency, and responsiveness. By choosing QuakeLogic’s sensors, you’re investing in state-of-the-art technology that supports proactive maintenance and risk mitigation, offering peace of mind through high-quality, reliable data.

About QuakeLogic

QuakeLogic is a leading provider of advanced seismic monitoring solutions, offering a range of products and services designed to enhance the accuracy and efficiency of seismic data acquisition and analysis. Our innovative technologies and expert support help organizations worldwide to better understand and mitigate the impacts of seismic events.

Contact Information
Email: sales@quakelogic.net
Phone: +1-916-899-0391
WhatsApp: +1-650-353-8627
Website: www.quakelogic.net

For more information about our products and services, please visit our website or contact our sales team. We are here to help you with all your seismic monitoring needs.

Thank you for choosing QuakeLogic. We look forward to assisting you with your seismic monitoring projects.