PTI DC20.5 PDF

INTRODUCTION

In the summer of 1989, a parking structure adjoining an office building in the Inner Harbor area of downtown Baltimore, Maryland, was demolished to make room for an expansion to the existing office tower. This post-tensioned concrete parking structure was built in 1974, and thus, had been in service for 15 years prior to demolition.

There has been much concern in the profession with respect to the behavior and corrosion susceptibility of prestressing steel that has been exposed to chlorides in service, such as from deicer chemicals. PTI responded to these concerns for unbonded tendons used in aggressive environments in the "Specification for Unbonded Single Strand Tendons" published in 1985.' The demolition of this structure provided a rare opportunity to directly inspect the condition of unbonded single strand post-tensioning tendons fabricated and installed in accordance with the less demanding accepted practices of 1974. The tendons had been in service for 15 years in what could be considered a moderately aggressive environmental exposure.

This report summarizes the observations and evaluation of the general condition of the parking structure prior to demolition and of the unbonded monostrands which were inspected after demolition.