Structural Testing & Monitoring

Sensing Systems plans and conducts testing programs to measure and monitor parameters critical to the health and well being of structures.  We also install permanent monitoring systems to continuously acquire structural data.  Typical measurements include stress, strain, vibration, temperature, deflection, displacement and tilt.  Our testing services are sought by industry, government and universities.  Structural measurements are used to determine operating stresses, vibration levels, diagnose problems, confirm and fine tune analytical models, determine compliance and plan corrective actions.

We have tested structures of all shapes and sizes.  We have acquired structural data on bridges, tunnels, power plant buildings and equipment, containment buildings, ship superstructures, roof joists, concrete piers, seismic restraints and many others.  Our permanent monitoring systems continuously acquire, store and transmit data locally and to remote locations.

Structural tests may include a wide variety of measurements.  In addition to the measurements mentioned above, the testing objectives may require that some of the following measurements be included:

• Force
• Pressure
• Torque
• Power
• Soil Pressure
• Humidity
• Flow

All sensors in our testing programs are installed in the field and connected to state of the art data acquisition equipment.  Our systems can acquire data at very high sampling rates using high quality signal conditioning equipment and filtering and analysis capabilities.  The quantity of measurements may start at 1 or all the way up to 500+ channels using all types of sensors.

Experience

Sensing Systems has completed structural testing projects for a wide variety of industries including power generation, oil and gas, marine, construction, nuclear, steel, packaging, wood processing, infrastructure and many others.  Our field staff has operated throughout the world in a wide range of industries and field conditions.

We have developed unique and innovative methods and procedures to install and operate all sensors under challenging conditions such as underwater, cryogenic and high temperature, high magnetic field and corrosive environments.  We have performed testing in temperatures ranging from -452 ˚F to +1,300 ˚F and in magnetic fields up to 7 Tesla.  Following is a sampling of structural testing and monitoring projects.

Stress Monitoring of Bridges

Sensing Systems has conducted several short and long term structural monitoring projects on bridges.  Stresses are measured on steel or concrete load bearing members using bonded or welded strain gages.  Analyses such as rainflow are performed real time and data downloaded using telephone connections.  Major bridges such as the Triborough and Cross Bay in New York City have been monitored using this approach to confirm and/or adjust analytical models.

Roof Monitoring

Most commercial buildings in the United States utilize steel joist construction to support the roof.  Sensing Systems has installed strain gages to monitor dynamic loading of the roof by external agents such as snow or rain.  We have also used optical measurements to measure deflection due to static loading of the steel joists.  The sensors can be connected to temporary or permanent monitoring systems to alert the business owner of unusual or excessive loading conditions and to take corrective action.

Measurement of Hull Stresses, Vibration and Shock

A large operator of cargo ships discovered cracking in several areas of the cargo hold in brand new 980 ft ships.  Sensing Systems personnel instrumented the structural sections where cracking occurred with strain gages to measure operating stresses.  In addition, accelerometers were used throughout the same area to measure vibrations and on the bow of the ship to measure high acceleration and shock loading.  Data were acquired for one month during regular ship operation and then turned over to the owner’s consultant for analysis.  

Structural Integrity Tests

Sensing Systems personnel have performed over 30 Structural Integrity Tests (SIT) at Nuclear Plants throughout the United States.  SITs must be performed to certify the structural integrity of the Containment Building at Nuclear plants.  The Containment Building is internally pressurized and parameters such as stress and displacement are measured throughout the structure and compared to acceptable values.  Each test may include up to 150 individual measurements to ensure regulatory compliance.

Balancing Movable Bridges

Lift bridges require a proper weight balance between the movable roadway and counterweights.  Sensing Systems has balanced a multitude of bridges by measuring the torque experienced by the drive train when the bridge is opened and closed.  Torque is measured using bondable strain gages and connected to a data acquisition system.  Counterweight adjustments are performed based on the acquired data until the desired condition is achieved.

Tunnel Stress Monitoring

Sensing Systems personnel installed 298 strain gage installations on the Ted Williams tunnel to monitor stresses throughout the structure.  The outer and inner steel shells were instrumented as well as rebar encased in concrete.   All of the installations were surrounded by water or concrete once the tunnel was set in place.  A portable data acquisition system was provided to read all the sensors. 

Vibration-Stress Monitoring

Using accelerometers and strain gages, Sensing Systems has instrumented bridges and infrastructure to measure vibration induced stress on several structural components.  Our measurements have been used to create Specifications for all equipment to be installed on the structure to ensure survivability under operating conditions.

Special Sensors

Sensing Systems has developed special sensors to be used in field testing projects where no existing device is commercially available.  Examples include soil pressure sensors to measure the pressure applied by settling or moving soil over time.  We have instrumented sections of reinforcing bars used in construction to measure strain/stress in concrete structures over time.  We refer to these sensors as “Sister Bars”.  In several projects we have removed and instrumented existing components, calibrated them in the laboratory and re-installed them prior to field testing.

Data Acquisition Systems

Testing programs require that data be collected using data acquisition systems connected to all the installed sensors.  Data acquisition systems must acquire, store and make data available for further analysis.

Sensing Systems utilizes state of the art computer based data acquisition systems.  Our equipment can sample at rates as low as once per day and up to 1,000,000 samples per second.  Data may be acquired and submitted in different formats for further review and analysis by our customers.  Filtering may be performed during acquisition or digitally following data acquisition.  Data analysis such as rainflow may be performed real time by our equipment. 

Signal conditioning equipment is used to convert low level signals to high level signals or, depending on the application, to convert analog data to digital data for transmission to a computer.  Field equipment configurations are optimized on the basis of number of measurements in the test program, distance between sensors and equipment, required sampling rates, available power and environmental considerations. 

Permanent Monitoring Systems

Sensing Systems also installs permanent monitoring systems in the field.  Installation, planning and implementation of permanent systems are usually combined with field testing projects.  The data acquisition equipment selected for permanent systems typically has communications capabilities using telephone connections or wireless systems for downloading data to computers at the customer facilities.

Our equipment has been left to operate unattended for years at a time while being able to download data to a remote computer using telephone connections. 

Accuracy

The accuracy of field measurements varies according to the sensors being used.  For most sensors that have been calibrated in the laboratory and installed in the field, accuracies in the range of 0.1 % to 1 % of full scale are typical.  Strain and stress measurements require sensors such as strain gages which depend on the installation material for their accuracy.  Field accuracies range from 3% to 5% of full scale.

Sensing Systems has pioneered the use of in-situ calibrations for strain gage measurements.  We design and manufacture the required fixtures and apparatus to apply a known load to the structure and measure the corresponding output.  Using this approach the accuracy may be improved to 0.5% to 1% of full scale.

Technical Assistance

Please contact our engineering department to discuss your specific testing requirements. 

Contact Us now to discuss your application.