Driven Concrete Pile Foundation Monitoring with Embedded Data Collector System
Florida Department of Transportation (FDOT) sponsored research performed at the University of Florida resulted in developing a wireless monitoring and real time static capacity estimate technology for driven piles. This new technology, Embedded Data Collector (EDC), uses two levels of instrumentation, embedded in the body of precast prestressed concrete piles near the head and tip. Strain and acceleration measurements obtained at these instrumentation levels during driving are sent wirelessly to a receiver in the field, and analyzed in real time to provide the operator with estimates of static capacity, stresses in the pile, transfer energy, damping factor, stroke height, and other relevant parameters used to evaluate the pile driving process and the driving system. The EDC system is currently undergoing phase one of a two phase field evaluation program planned by the FDOT to determine the level of reliability that can be anticipated by its use. The first phase consists of monitoring piles with EDC instrumentation and concurrently monitoring them with the Pile Driving Analyzer (PDA), given that there is ample data supporting the reliability of PDA. Measurements of strain and particle acceleration converted to force and velocity traces can then be compared between the two systems, along with the corresponding calculated magnitude of downward and upward traveling stress waves as they move along the pile at any point in time. Selected hammer blows recorded by PDA equipment are analyzed by means of signal matching software (CAPWAP) and the estimated static skin, end bearing, and total resistance obtained are compared against EDC static resistance predictions. The second phase of the evaluation will compare EDC estimates of static capacity against instrumented static load test results. The purpose of this paper, is only to present a summary of results obtained thus far in phase one, and compares EDC estimates of static capacity results with those from PDA and CAPWAP.
A BRIEF HISTORY OF THE APPLICATION OF STRESS-WAVE THEORY TO PILES. IN: CURRENT PRACTICES AND FUTURE TRENDS IN DEEP FOUNDATIONS
A summary of the early scientific research that forms the basis of the development of one-dimensional wave mechanics is first summarized. Beginning with the work of Donnell in the early 20th Century the subsequent analytical and computational research is reviewed in some detail. The early "wave equation" computer programs beginning in the 1940's are described and discussed including the applications that motivated the entire development up to the present. Early measurement techniques are reviewed briefly up to the development of the resistance strain gage. This device made possible routine measurements of the force wave in the pile. The development of an accurate and reliable accelerometer was somewhat slower than the force measurement capability but usable devices were available by the time of the Michigan pile tests of 1960. The modern era of pile measurements and analysis began in earnest with the research at Case Western Reserve University. The method of dynamic pile capacity predictions are summarized up to the present. It is estimated that today over 5000 job sites are tested and analyzed annually. The history of low strain integrity is presented briefly and the history of the International Stress Wave Conferences is summarized. Finally a list of American codes and standards relating to this topic is included.
Improving the Nutritional Intake and Physical Activity of Children from Low-Income Households via Family, School, and Workplace Policy
Childhood obesity remains high, especially among children from racially and ethnically diverse and low-income households, and it is associated with numerous negative health consequences in adulthood. Family, home, school, and workplace environments are recommended areas for expanding policies and implementing strategic interventions for child obesity designed to improve nutritional intake and increase physical activity. Family-based interventions offer a variety of strategies to lower the incidence of obesity. Programs such as the federally funded Child and Adult Care Food Program can be extended to work with families and caregivers in schools. Further workplace wellness programs could use federal programs such as the USDA Expanded Food and Nutrition Education Program to establish policies and initiatives that extend obesity interventions to employees’ families.