Multiscale analysis of non-contact splices at drilled shaft to bridge column interface

The contact and non-contact splices of the longitudinal steel bar and dowel bar have been widely adopted as the interface connection between pier columns and drilled shafts in bridge engineering. With the popularization and application of bridge substructures composed of the rectangular column and circular drilled shaft, the suitability and accuracy of the design provision specified in the current codes, which is derived from the investigation of the uniform circular components, are becoming the research hotspots in engineering and academia. In order to further study the mechanical behavior of the pier column-drilled shafts interface with inconsistent geometrical shapes, the experimental and numerical analysis of the interfaces with the overlap spacing of 0, 4, 6 and 8 in. are carried out systematically. The experimental results indicate that with the increment of lap spacing, the load-bearing capacity of the components will be consistently reduced, and the material strength also plays an important role in the structural performance. Compared with the specimen with the contact splice, the non-contact lap splice between the longitudinal bar and dowel bar will lead to additional shearing cracks and splitting cracks, and the inclination angle of the shearing cracks gradually increases with the enlargement of lap spacing as well. The relationship of the lateral displacement at the top of the column and the vertical reaction agrees well with that of the numerical analysis. Moreover, the fracture distribution and the interface separation can be explicitly depicted by 3D/2D numerical models based on homogeneous concrete assumption, which fully validates the rationality of the experimental observations. In order to exclude the influence caused by the variation of the concrete strength in tested specimens, the material properties in 3D and 2D simulation are uniformly specified according to the measured material strength of Specimen 1 and the numerical findings show that the structural stiffness of Specimens 1-4 decrease with the increment of lap spacing. However, the ultimate bearing capacity of the component is not apparently affected while using non-contact splices, accompanied by satisfied ductility. The detailed failure pattern and the crack evolution between overlapped steel bars are explicitly revealed by the 2D multiscale models. The maximum angle of diagonal cracks can be detected at the end of the overlap area, which is about 45°. The inclination of shearing cracks within the overlap area is slightly smaller and deteriorates with the enlargement of lap spacing. Meanwhile, the microcracks located in the non-overlap area are typically horizontal bending fractures. The research conclusion of this study based on large-scale experimental and numerical investigation is highly referential for the practical application of the interface connection of bridge column to drilled shaft with inconsistent geometry using non-contact splices.