ABSTRACT
The construction of bridge deck often introduces torsional moments acting on the exterior girder. To resist these torsional moments and limit the maximum exterior girder rotation, diaphragms are commonly used as transverse bracing system. However, the unbraced lengths of diaphragms are typically not designed for torsional moments introduced by construction loads, which may lead to excessive rotation on bridge exterior girders during bridge deck construction and cause many safety and maintenance issues. In this study, 1457a parametric study was conducted to evaluate the significance of different parameters. Around three thousand finite element models were built to find the relation between the rotation and the ratio of the unbraced length (B) to girder depth (D). Then a simple method, which combines primary curves of B/D ratio in term of rotation and tables of section modification coefficients, was developed for engineers to easily determine the maximum allowable B/D ratio.
