Shrinkage and Creep Predictions Evaluated using 10-Year Monitoring of the North Halawa Valley Viaduct

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Title: Shrinkage and Creep Predictions Evaluated using 10-Year Monitoring of the North Halawa Valley Viaduct

Author(s): I. N. Robertson and X. Li

Publication: Special Publication

Volume: 227

Issue:

Appears on pages(s): 143-162

Keywords: bridge monitoring; creep; instrumentation; long-term deflection; prediction; shrinkage

Date: 3/1/2005

Abstract:
This paper presents the results of a 10-year instrumentation and monitoring program on the North Halawa Valley Viaduct, a major prestressed box girder viaduct on the Island of Oahu, Hawaii. The long-term monitoring program was initiated in 1994 during construction of the long-span post-tensioned box-girder viaduct. Over 200 electrical strain, displacement, temperature and load sensors were installed in one unit of the structure and have been monitored continuously since. These instruments monitor vertical deflections, span shortening, prestress loss, longitudinal strains and temperature in the box-girder concrete. The long-term response of this structure is presented and compared with the initial predictions made during the design process. Modified material properties based on short-term shrinkage and creep tests were incorporated into the long-term prediction model to produce significantly improved comparisons. A procedure is proposed for prediction of upper and lower bounds for the long-term response of long-span prestressed concrete bridges. This improved prediction model is applied to the other five units making up the NHVV to verify its performance as a design tool. The results of this study were then incorporated into the development of an instrumentation system for the planned Kealakaha Bridge on the Island of Hawaii. Application of the prediction model is demonstrated using shrinkage and creep data determined from short-term tests performed on the concrete mixture proposed for this new long-span box-girder bridge structure.