In Situ Load Testing of Parking Garage Reinforced Concrete Slabs: Comparison between 24 h and Cyclic Load Testing

This paper reports on the results obtained on the applicability of the diagnostic cyclic load test method in comparison with the existing 24 h test procedure adopted in ACI-318. A parking garage, owned by St. Louis County, St. Louis, Missouri, scheduled for demolition during the summer of 2002 was used as a research test bed before demolition. 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 were performed. Two identical RC slabs were tested, according to both the standard procedure (ACI-318-02) 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 draw conclusions on their values. After load testing, both slabs were loaded until partial collapse was reached. This allowed 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 provides professionals with evidence on the validity of in situ assessment for the adequacy of structural members.