Caso di studio di monitoraggio strutturale: Resensys

Fornire la soluzione di monitoraggio wireless più efficiente al mondo in termini energetici con l'aiuto dei sensori elettrolitici di inclinazione di Fredericks

Introduzione

There are over 612,000 bridges in the United States and as of February 2017, almost 10% of them need to be repaired or replaced according to The American Road and Transportation Builders Association. That means that there are currently over 55,000 bridges that require real-time monitoring in order to avoid a catastrophe like the 2007 bridge collapse in Minneapolis, Minnesota.

Che cos'è Resensys?

Resensys offre soluzioni economiche e scalabili per aiutare a valutare la stabilità strutturale di questi e di altri ponti autostradali in modo da individuare i problemi strutturali e pianificare la manutenzione e le riparazioni necessarie per garantire la sicurezza e la longevità del ponte.

La loro soluzione wireless per il monitoraggio strutturale della salute, SenSpot™, è per ponti esistenti e ponti in costruzione ed è dotata di sensori wireless piccoli, economici e facili da installare che misurano una varietà di variabili che influenzano le prestazioni di un ponte.

Nato dalla ricerca condotta dal Presidente e CTO Dr. Mehdi Khandani dell'Università del Maryland, Resensys è leader nel monitoraggio geostrutturale in tempo reale e offre il più durevole sistema di monitoraggio dei ponti wireless con una durata minima prevista di 10 anni. Per maggiori informazioni visitate il sito http://www.resensys.com.

La sfida

Anche se esistono altri sensori sul mercato per il monitoraggio delle infrastrutture, ciò che differenzia un dispositivo Resensys è il suo bassissimo consumo energetico, che utilizza solo circa 4 microwatt, o circa 100 milioni di volte meno di una tipica lampadina. Questo significa che un sensore SenSpot ha una durata minima di 10 anni utilizzando solo una piccola batteria da ½-AA.

Per offrire un sistema di monitoraggio così efficiente e preciso, Resensys aveva bisogno di trovare un sensore di inclinazione con una risoluzione fino a un millesimo di grado, offrendo al tempo stesso un basso consumo energetico, una lunga durata e una durata del prodotto di almeno 10 anni.

La soluzione 

Dr. Khandani and his team thoroughly evaluated a variety of MEMS and other electrolytic tilt sensors and concluded that the Fredericks Single-Axis Narrow-Range Electrolytic Tilt Sensor (PN 0703-0711-99) significantly outperformed competing products in terms of long term repeatability and resolution.

“Qualitatively, Fredericks’ devices were an order of magnitude better than both MEMS and competing electrolytic sensors,” says Dr. Khandani. “In our application, repeatability is very important and none of the competing products did as great as Fredericks products did.”

I risultati 

With the help of Fredericks’ electrolytic tilt sensors, Resensys is able to offer the world’s most energy-efficient wireless monitoring solution that helps keep travelers safe with around 5,000 SenSpot™ tilt units in use in the US and around the world.

“Our decision to use Fredericks products was driven by the excellent accuracy and durability of their tilt sensors,” Dr. Khandani adds. “Such long term and high-quality measurements help capture the smallest movement and instability on critical bridge components.”

SenSpot™ in azione: Ponte sul fiume Patapsco

In the Spring of 2014, cracks were spotted in the girders and piers of the I-70 Patapsco River Bridge near Baltimore, Maryland. Engineers found that non-responsive bearings had caused damage to piers and steel girders of the bridge, which led to its closure in June 2014.

Repairs were made, retrofits were applied, and a SenSpot™ monitoring system was installed in July 2014 to detect any further changes. More than 40 SenSpot™ units were mounted on the bridge, including 12 tilt sensors located on the bridge’s rocker bearings to monitor the movement pattern and detect non-responsiveness or over-responsiveness. In addition, six high-resolution tilt sensors were mounted on the bridge’s piers to monitor the deflection and rotation of the bridge rocker bearings caused by cold temperatures.

Early results from August to November 2014 found that the bearings on two piers were non-responsive to temperature changes and an additional bearing saw only 20% of expected movement. Data collected through Spring 2015, however, showed that the bearings had an unprecedented response to the robust retrofits (combined with especially cold winter), and by March 2015 all piers and respective bearings were fully responsive.

 

Prior to February 2015, the bearings and retrofits weren’t responding properly to changes in temperature, but by mid-Spring, they proved to be fully responsive and have seen continued success in the years since.

 

Dr. Khandani notes, “After more than four years of continuous monitoring, we are pleased that the Fredericks devices used in SenSpot™ sensors produce very consistent, repeatable, and high-quality measurements of tilt and inclination at sub-arc-second resolution.”

Before alerting the Maryland State Highway Administration, the Resensys team worked with engineers at Fredericks to confirm the data. At Fredericks, we take a partnership approach to our relationships with customers, and customer satisfaction is a priority. We have dedicated representatives and engineers committed to providing highly responsive service, and our customers have anytime-access to our leadership team, made possible in part by our “not too big, not too small” operation.