Live load moment distribution effect of intermediate diaphragms in precast concrete I-girder bridges

The utilization of intermediate diaphragms (IDs) in precast concrete (PC) I-girder bridges has been a topic of debate among researchers for decades, with its effectiveness remaining a subject of controversy. Nevertheless, the consideration of IDs is an essential aspect of engineering practice, making it crucial to explore their role in live load moment distribution. This study delves into the application of concrete IDs, examining the impact of various finite element modeling practices and key parameters on their effectiveness. A sensitivity study was conducted to compare the efficacy of grillage, planar, and solid models in determining the suitable modeling approach for straight, skewed, and curved deck bridges equipped with IDs. To optimize modeling practices, a further investigation was undertaken to evaluate the influence of different parameters on the role of IDs, including the presence of IDs, the rigidity of connections between IDs and girders, and several geometric parameters related to the bridge span layout. The live load moment envelope of girders was chosen as the response indicator to evaluate the role of IDs. The findings of the parametric study revealed that the removal of IDs leads to an increase in the midspan moment of the interior girders, while the midspan moment of the exterior girders decreases. Furthermore, it was found that the rigidity of connections between IDs and girders, girder spacing, and span length significantly influence the role of IDs in PC I-girder bridges.