Complete stress indicator system for the design of concrete box-girder bridges. (April 2022) - Sun, Yuan
Highlights: CSIS indicators for a concrete thin-walled box-girder is proposed. Common spatial cracks are explained by CSIS at a stress level. Updated design methodology based on CSIS is proposed. Practical examples are used to validate the effectiveness of the CSIS. Abstract: Stress checking is a crucial step in the design of concrete bridges to ensure certain safety and application demands of structures. The categories of the checking-stress indicators account for the main cracks that should be controlled under the limit state design method to guide the design objectives. However, as the spatial complexities of concrete box-girder bridges become prevalent, new structure cracks that cannot be related to any of the currently dominant indicators are constantly discovered. This leads to the necessity of reorientating the existing indicator system, which originally starts from the design methodology of a thin-walled narrow beam. This paper intends to establish a complete stress indicator system (CSIS) for perfecting the design of these structures. For the first time, cracks from practice surveys, far from discontinuity regions, are classified with the total spatial effects of a box girder. These effects are deconstructed into in-plane and out-of-plane effects of flanges and webs to correlate with crack morphologies. On the basis, three-layer stress indicators of slabs are constructed to contain the missing items in codes and to provide unified explanations for all structure cracks. The CSIS-directed design methodology is then established and the effectiveness of this methodology is validated through examples with field investigations.