Unbonded post-tensioning tendons are an efficient and cost effective method of reinforcing concrete floor slabs, slabs-on-grade, parking garages, and bridge structures. However, the behavior of these structures is not well understood. There is concern that due to the lack of a significant amount of reliable research data on specimens reinforced in this manner, the commonly used design methods tend to significantly under-predict the strength. Four large, scaled, floor slab sections were constructed and destructively tested with the intent of more accurately understanding the strength of specimens reinforced with this method. Four test specimens represent a significant percentage of the current body of reliable research in this field. In order to accurately predict the design strength of these members, it is necessary to predict the increase in the reinforcing strand stress when the member is loaded to a flexural failure. This increase in strand stress was measured on each of the four laboratory tests which were performed. This allowed the strength of these concrete members to be more accurately predicted, and it was observed that the current design methods are significantly under-predicting this increase in strand stress as well as the flexural capacity of the members. The behavior of the deflection of the slabs in relation to the applied load was also analyzed, as well as the cracking behaviors. The four test specimens were combined with the available body of research data to complete the largest known database of members reinforced in this manner.