ANP Model for Evaluation of False-work Systems for Cast-in-place Cantilever Bridges

The terrain of Taiwan is characterized by large areas of mountains, while lands in urban areas have become increasingly difficult to acquire for developing infrastructures. To reduce environmental impacts and to improve traffic conditions, highway projects have adopted more and more bridges over the years and many advanced bridge construction methods have been introduced. In terms of construction of bridge superstructures, the cast-in-place cantilever method has seen wider use with many successful examples. This study investigated the false-work systems that may be selected for use in implementing the cast-in-place cantilever method in Taiwan, with the objective of developing a model for evaluating possible options. Based on a review of related researches, an evaluation framework for the false-work systems has been proposed first, which consists of six factors: system controllability, structural stability, initial cost, operating cost, segment cycle time, and closing segment construction time that are categorized into three aspects: reliability, cost, and speed. Because of the interdependencies among the factors, the model uses the analytic network process (ANP) to produce the weights of the factors and the ratings of the options in given project conditions. An illustrative example is provided, in which three false-work systems considered for a hypothetical box-girder bridge project are evaluated. The rankings of the options obtained for the example from best to worst were triangular truss, diamond truss, and suspension truss. Practitioners may use the model as a decision aid in evaluating and selecting false-work systems for the cast-in-place cantilever method for construction of bridge superstructures.