Comprehensive Strain-based Methods for Monitoring Prestressed Concrete Beam-like Elements

Abstract

Structural Health Monitoring (SHM) is defined as the process of periodically or continuously measuring structural parameters for the purpose of assessing the performance of a structure. Successful SHM depends, to a large extent, on the analysis of acquired data. This thesis presents methods of analysis created specifically for prestressed concrete structures. The interest in prestressed concrete stems from the recent increase in its use for the construction of major infrastructure elements such as bridges, tunnels, and nuclear containment vessels.

This thesis identifies three structural parameters as key indicators of the structural performance of prestressed concrete structures: (1) the distribution of prestressing forces at transfer, and (2) the status of pre-release cracks that often occur in prestressed concrete structures (due to shrinkage) prior to the release of prestressing forces, and (3) the magnitude and distribution of time-dependent prestress losses. Methods for the assessment of these parameters using strain measurements from long-gauge fiber optic sensors are created and validated using field measurements from Streicker Bridge, a post-tensioned concrete pedestrian bridge on the Princeton University campus.

Results from the Streicker Bridge project indicate that: (1) pre-release cracks do occur in prestressed concrete structures, (2) the occurrence and severity of pre-release cracks, as well as the extent of crack closure due to prestressing, can be determined using strain measurements (3) the distribution of prestressing forces at transfer and in the long term can be determined using strain measurements, including at cracked cross-sections, and (4) design codes can underestimate prestress losses.