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Sensor technology boosts concrete piles’ competitiveness

After several years of successful project completion in the Southeast, Smart Structures has begun expanding the use of its SmartPile System nationally and internationally. The system represents what developers note is the first step in an ambitious plan to instrument and monitor transportation infrastructure. It combines concrete, steel, electronics and software to create a product intended to increase construction productivity and reduce foundation costs.

A SmartPile is a precast concrete structure that has been “wired” with sensors and wireless radio. Installed at the casting yard, the system’s sensors are immediately testable when the pile arrives at the construction site. Based on technology licensed from the University of Florida, Smart Structures has perfected the process of casting electronics into prestressed concrete piles with upwards of 100 percent reliability. Soon, precast plant crews can install sensors (temperature, strain gages, accelerometers), alignment assemblies and a wireless radio that transmits data from the pile.

Once installed, the SmartPile system software connects to the pile while being driven and reports real-time capacity and health/integrity information. True to its engineering, the system has proved to withstand impacts of the driving process, thereby enabling testing of every pile in a foundation. Armed with data from a test or preliminary installation, engineers can optimize pile dimensions according to AASHTO Resistance Factor provisions.

While shipping less concrete may not sound promising to producers, Smart Structures officials note, the ability to instrument and test every foundation element opens up opportunities for prestressed concrete piles to replace steel or cast-in-place alternatives. When measured against competing structure types, the SmartPile technology has the potential to reduce quality assurance testing costs by 90 percent, system developers contend.

A key SmartPile benefit—the ability to monitor and report on tip integrity and (end bearing) capacity—is possible only by protecting the sensitive electronics with the concrete and steel that make up the pile. This feature is recognized in ASTM D4945 as improving pile capacity benefits as end bearing is measured. Given the accuracy and precision provided by SmartPiles, the expectation is that prestressed concrete piles will soon become the choice for foundation design.

The sensors embedded in the material provide unique insight in the static and dynamic health of the concrete pile and have led to the introduction of highly accurate monitoring capabilities (Measured Pile Integrity). These embedded gages have been designed to monitor the health of the pile from the point of casting through long- term, post-driving observation.

Notes John Jarrett, Bridge Division Manager at Dura-Stress Inc. in Leesburg, Fla., “Dura-Stress has been coordinating production of concrete piles with installed EDC devices since they were first developed (Product R&D in 2004). Through that time, the installation process and coordination has been prompt, professional, and with no impact to our production (casting) schedule. We look forward to working with Smart Structures on their efforts to instrument other pre-cast bridge elements.”

How does it work?
The SmartPile Electronics are set directly into the wet concrete. The process is fully documented and has been “kitted” for the installer. The only selections required are the length of the pile and the number of sensors. “Our goal is to provide casting yards with a variety of installation kits, similar to SmartPile, that would enable other precast concrete bridge elements to be instrumented,” says Smart Structures CEO Tom Chiarella. “In the future, prefabricated bridge elements will arrive ready for testing, with built in Quality Assurance and item logistics details, and the ability to provide long-term monitoring with little to no additional installation costs…a compelling value proposition for prefabricated concrete elements and systems.”

The SmartPile Embedded Data Collector can support up to six channels of sensor data: temperature sensors, strain gages and accelerometers. The system can be tailored to support different structural elements using the appropriate sensors to aid in assessing the curing profile, stresses and strains being applied to the element. The unique quality control and quality assurance the prestressed producer provides carries over to installed piles’ quality and accuracy. Soon yards will be able to offer customers “smart” structural elements that add further to their value proposition.

 

— Smart Structures Inc., Southampton, Pa.; 267/983-6106, x601; www.smartpile.com