Evaluation of Fire Damage to a Precast Concrete Structure Nondestructive, Laboratory, and Load Testing

This article discusses the use of nondestructive and laboratory testing techniques and load testing in evaluation of fire damage to precast prestressed concrete members in a parking structure. The in situ evaluation phase consisted of nondestructive testing of concrete using ultrasonic pulse velocity and radiographic exposures to locate tendons prior to the removal of cores. Flexural strength of concrete and dynamic Young’s modulus of elasticity and air permeability index of $25\mathrm{mm}$ $\left(1\mathrm{in.}\right)$ thick disks sawed from the cores were determined in the subsequent laboratory testing phase. Analysis of concrete properties at small depth increments permitted assessment of whether a damage gradient was present and the nature of any gradient found, as expressed by changes in these properties. Based on the compromise in material properties indicated by nondestructive and laboratory testing, two affected double-tees were load tested. The deflection pattern observed during load testing confirmed the compromise indicated by the findings of the testing program.