INTRODUCTION

Several references are available which describe the demolition of bonded post-tensioned concrete structures (Felstead et al, 1981, Buchner et al, 1985). The National Association of Demolition Contractors (NADC. 1981) has issued a demolition safety manual for special structures including post-tensioned members. The Federation International Precontrainte (FIP, 19S2) has compiled a comprehensive summary of demolition methods for prestressed structures. Additional information is given in references listed at the end of this report.

The published information available today for the controlled demolition of unbonded post-tensioned structures is meager, In view of the fact that, during the last two decades most of the elevated concrete slabs in the United States are post-tensioned using unbonded tendons, and that changes in function or occupancy may require partial or entire removal of a slab, controlled demolition of unbonded post-tensioned slabs is of particular importance.

The purpose of this report is to document a specific controlled demolition procedure of an unbonded post-tensioned concrete slab, which was executed successfully on a large project. During the demolition process the response of the tendons being neutralized was monitored and documented. The observations made arc categorized and presented. The report concludes with a summary and recommendations.