Volume-change response of precast concrete buildings

Abstract

This paper summarizes the findings of the authors' recent study on the volume-change response of precast concrete buildings. The objective of this research was twofold: to develop a better understanding of volume-change movement and forces based on measured performance of precast concrete parking structures and calibration to analytical models and to recommend revised design procedures that reflect this understanding and account for the influence of flexible connections. The primary research tasks included field monitoring and finite-element analyses of actual structures as well as evaluation of the predictability of volume-change forces. The research revealed that deformations of flexible deck and spandrel connections change the deformation pattern and thereby substantially reduce volume-change movement and force at the lowest supported level, where volume-change forces are most significant. The study also developed new findings with respect to other volume-change parameters, including the thermal-expansion coefficient, the design temperature range, the degree of member softening due to creep and microcracking, and the load factor for volume-change effects. Design recommendations are provided for qualitative consideration of volume-change effects as well as quantitative analysis. Although the new research indicates that the procedures recommended in the PCI Design Handbook: Precast and Prestressed Concrete result in a conservative estimate of volume-change force, certain aspects of the PCI Design Handbook procedures were found to be unconservative. Therefore, the research findings should be considered in their entirety. The full research report is available from PCI.