A parking garage, owned by St. Louis County, scheduled for demolition during the summer of 2002 was used as a research test bed before decommissioning. This structure, a two-story steel and reinforced concrete (RC) - frame with one-way RC slabs built in 1970's, was ideal, in terms of size and construction system, for performing comparative field experimentation on load testing.

Investigation and validity of acceptance criteria of existing and proposed testing methods was preformed. Two identical RC slabs were tested, using a closed loop method with load applied by hydraulic jacks, according to both the standard procedure (ACI-318) and the proposed diagnostic load testing. In both instances, the applied total test load was such that the slab did not pass the load test. This allowed characterizing the critical test parameters that govern acceptability and drawn conclusions on their values. After load testing, both slabs were loaded until member failure was reached allowing making observations on the margin of safety with respect to collapse, a determination that is not generally possible in a proof test. The analysis of the experimental data is presented and discussed to provide practitioners with evidence on the validity of in-situ assessment of the adequacy of structural members.