Report on the Investigation of the Contraction of Prestressed Concrete Bridges.

摘要

The general nature of the deterioration of prestressed concrete bridges through contraction in Nebraska is discussed and clearly illustrated through the use of photographs taken from a previous field study involving 82bridges. The test program,formulated to determine the actual nature and cause of the deterioration process,involved continued study of 90existing bridges,two new instrumented field structures in a natural environment,and a new full-scale model structure in a partially controlled environment. The new structures were heavily instrumented with mechanical and electrical types of strain measurement devices,thermometer and humidity wells,and other deformation references. The devices were pre-embedded using tape-in-place techniques to avoid damage to the steel forms for the girders. This technique gave quick access to ready-to-read installation points after girder forms were stripped. Readings were taken over a 4-year period. The computer was used to store and analyze the data. A high-speed plotter was used to plot the curves. An analysis is presented and remedial recommendations are outlined.