Low-cost technology for structural health monitoring of civil infrastructures with measure of strains and temperature embedded in ordinary reinforcing steel bars for reinforced concrete structures. It is possible to instrument structures with a higher number of sensors for a more efficient control of structures during construction, in service or after extreme events such as earthquakes. The technology is robust, easy to use and particularly effective for both new and existing structures.
Patent Status
SUBMITTED
Priority Number
2016IT-0118077
Priority Data
22/11/2016
License
INTERNATIONAL
Market
The technology can be used for all reinforced concrete structures under construction and in particular: geotechnical structures such as tunnels, foundation piles, water and earth retaining structures; bridges and viaduct, buildings and precast structures. The technology is affective for existing structures for which it could be valuable to monitor the structural behavior even after repairing works in order to evaluate its effectiveness.
Problem
The recent two decades have been demonstrated that the structural health monitoring can give precious data on loads, environmental effects, performance and residual structural conditions without scale and model errors. These data are of extreme importance to validate the design assumptions and theoretical/numerical models, other than for complex structural behavior for the evaluation of structural condition after an extreme event (earthquakes, impacts, fire,….), for condition evaluation during service and for the management of the structure: data from monitoring are used for structural control and for decision making even in case of emergency. The awareness of the importance of monitoring has been obtained through ordinary devices that are not suitable for a variety of applications for civil structures due to their cost and a limited integration capacity with other systems currently used in construction sector. With the present device it will be possible to overcome current limits of traditional devices for a safer structural and infrastructural heritage.
Current Technology Limits
The devices currently available, such as vibrating wire extensometers, are based on physical principles that require mechanical elements with a cost that is generally determined by machining of the components. Currently some systems IoT based are available on the market but they are a reproduction of traditional systems in terms of functioning principles but using new generation sensors. This generally does not change the cost of the devices but gives an improvement on signal management thanks to the digital nature. For traditional devices the initial cost should be added to an expensive installation phase; furthermore an early dead is registered during the first phases after installation (cast of concrete). These limitations bring to a monitoring frequently based on a extremely limited number of devices that does not ensure an adequate robustness of the system and an appropriate control of structural conditions.
Killer Application
The first application is the monitoring of a structural foundation specifically a foundation pile. Currently an instrumented pile is equipped at 3 sections with 3 or 4 devices for each section. S3T reinforcing bar will be instrumented with 1 device for each meter for the entire length of the pile for a total of 4 bars. This allow to have a number more than doubled compared to traditional systems at a similar cost and therefore it will be possible to verify in a more effective way the strain pattern of the pile and then its actual behavior
Our Technology and Solutions
The monitoring system for strains and temperatures designed for reinforced concrete structures exploit a patented technology with number WO 2018/096443. The system uses the volumetric strain of steel subjected to tensile actions and correlate it to the axial deformation of the reinforcing bars embedded in concrete by means of pressure variation of a fluid contained into a sealed cavity located into the same reinforcing bar. The sensors for the measurement are taken from the consumer MEMS market and therefore they are low-cost. The system is completely integrated into common steel reinforcing bars and is protected from the aggressive environmental effects and from actions generally present in construction sites. Reinforcements S3T are definitely similar to reinforcing bars used for reinforcement and their positioning does not require skilled personnel. The position of the sensing devices is fixed into the reinforcing bar and this prevent from errors and speeds up S3T placing phase. The devices communicate with wired connections within the reinforcing bars and then with datalogger with wifi systems. The cost reduction for single point of measure on the structure allow to increase the number of devices and obtain a more effective control for monitored structure in a new paradigma with important advantages during all stages of service life of the structure.
Advantages
The technology is able to reduce the construction costs in comparison with traditional devices; the sensors are embedded in common reinforcing steel bars whose installation can be done by unskilled personnel. It is not necessary to stop the construction during the S3T device installation. Errors of placing are minimized. The characteristic to be embedded in steel bars makes the solution very robust for each phase during installation. The low-cost allows to increase the points of device placing improving the effectiveness of monitoring.
Roadmap
Technology development will require an extension of validation for long term measurements in thermal chamber for calibration and operational activity with high frequency values in order to be useful even for measures with moving loads on bridges. Furthermore it will be important to implement configurations to enable a further increment of sensibility of the system to be sensitive to the effects of strain variation on existing structures. Finally, it will be necessary to perform electromagnetic compatibility tests.
TRL
Il team
