NIOSH 1998 Feb; :1-36
Over the past 25 years in the US there have been more than 85 collapses of structures under construction that have been directly attributable to formwork failure. Sensing systems and techniques applicable to the monitoring of construction site shoring and scaffolding are designed and implemented with preliminary systems being used in the field and in the laboratory. Such a sensor network can provide significant information about the load distribution on shoring systems information that is currently not available. This information can allow dangerous situations to be quickly identified so that corrective action can be taken. The principal task of this project was to investigate whether or not it was possible to detect potentially dangerous changes in load distribution of construction framework. Laboratory measurements were taken in controlled situations, which included weak supports, loose footings, and uplifting of the supports, to ascertain the applicability of instrumented shoring at realistic construction venues. The next step was to design, fabricate, and test an overall system that is capable of providing advanced and early warning capabilities to onsite construction crews working in situations where shoring accidents could happen. The end goal was to have such a sensing and alarm system be used in a large-scale construction site to verify system performance as well as provide a working environment where the alarm warning system could be fully tested and enhanced if necessary. In order to meet these goals, initially a ruggedized system composed of load and tilt sensors, wireless telemetry capabilities, microprocessor based data acquisition and signal processing, and comparative software schemes was designed and fabricated. This system was iteratively tested and modified in multiple laboratory and field settings under ambient conditions ranging from outside mid-winter conditions in Vermont (temperatures ranged from -21 to +37 degrees Fahrenheit) to summer conditions in Boston (the maximum was 101 degrees F). The culmination of this project was the in-service utilization of the load monitoring system at a 26- story building under construction in Boston. This field effort, which began in early May 1997 and continued until December 1997 (subsequent data analysis continued until mid-February 1998), represented the integration of a load monitoring system into the largest multistory building being constructed in North America with substantial reinforced concrete construction. In addition, a rapid shoring system developed in Europe was used by Beekman and Associates during teh construction phase. This PERI system meant that the shoring crews had to learn how to quickly and efficiently install this type of shoring member, which in turn led them to be quite amenable to the utilization of a load monitoring system within the shoring arrangements. Specifically, instrumented shoring was placed beneath key concrete forms throughout the construction process. Data was taken at short intervals immediately before and after concrete pouring on upper levels. Subsequent data acquisition would occur on a less frequent interval (hourly) with the microcomputer continually examining load distributions obtained from the sensors. The information gathered via this sensor monitoring clearly demonstrates how the load on the shoring changed over time. We have developed a multiplexed load cell system to sense load distribution changes on shoring systems used at construction sites. Laboratory and field measurements taken at a multistory building under construction shower that this system can quickly identify dangerous situations where the shoring may collapse. Laboratory demonstrations of simulated failure mechanisms verified that this unique system may even identify "shoring uplift" at its earliest onset. An alarm system was implemented during the construction site testing. This alarm could consistently detect dangerous shoring load distribution changes and relay that information to key personnel via wireless communication. Discussions with numerous construction site managers, company officials and insurance underwriters shows that use of this simple, low cost system may allow dangerous situations to be quickly identified allowing corrective action to be taken.
Scaffolds; Construction; Construction-industry; Construction-workers; Construction-equipment; Control-technology; Safety-equipment; Safety-monitoring; Safety-measures
Peter Fuhr, PhD, VT Sensing, Inc., RD 2, Box 978, Underhill, VT 05489
Final Grant Report
NTIS Accession No.
National Institute for Occupational Safety and Health
VT Sensing, Inc, Underhill, Vermont