STRENGTH VARIABILITY OF CONVENTIONAL SLAB FORMWORK SYSTEMS

Wooden formwork design is currently based on the criteria developed fo r the design of wood in new condition. To develop formwork design crit eria that include the effect of material reuse and formwork installati on workmanship, data on actual formwork member resistances and install ation inaccuracies are required. In this paper, wooden slab formwork i nstallation inaccuracies and strength variabilities are investigated. The formwork structural properties presented are based on laboratory e xperiments on formwork members collected from eight construction sites located in Chicago, Illinois, Milwaukee, Wisconsin, and Minneapolis-S t. Paul, Minnesota. From each construction site, samples of shores, st ringers, and joists were collected. In addition to formwork member sam ple collection, during site visits, installed shore out-of-plumb angle s and stringer, joist, and sheathing spans were also measured. In this paper the observed formwork member physical conditions, installation inaccuracies, shore compressive strengths, and bending and shear stren gths of the stringers and joists are presented. The observed structura l properties are summarized with appropriate probability distributions .