When completed in 1977, the Koror-Babeldaob Bridge in Palau held the world-record span of 241 m (790 ft) for segmentally erected prestressed concrete box girders. Within 18 years, its total deflection, compared with the design camber, reached 1.61 m (5.3 ft.) and the prestress loss was measured as 50%. In 1996, the bridge was retrofitted, but three months later the bridge suddenly collapsed. It wasn’t until 2008 that the technical data necessary for complete analysis were released. This article shows that the existing models for creep and shrinkage prediction grossly underestimate the deflections and prestress loss, although one model, model B3, does so much less than the others and, if calibrated by the 10-year tests of Brooks, matches the observations.

A research project was undertaken with the aim of developing expertise and guidelines for predicting lateral formwork pressures associated with self-consolidating concrete (SCC). Lack of information regarding formwork pressure variations during casting and pressure decay following placement has prompted contractors and engineers to design for full hydrostatic pressure as recommended by ACI Committee 347. Unfortunately, this leads to increased costs for formwork systems—compromising profitability by offsetting cost savings associated with rapid placements and labor savings associated with SCC. This article reviews the study and discusses a pressure column device for predicting lateral pressure exerted by SCC; empirical test methods for evaluating the at-rest structural buildup of SCC—a phenomenon that has been shown to significantly affect formwork pressure; and proposed design equations