Non-Contact Lap Splices in Geometrically Dissimilar Bridge Column to Drilled Shaft Connections

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Contact lap splices are widely used for the construction of reinforced concrete structures. But, it is often required to provide a reinforcing steel splicing arrangement with non-contact lap splices due to the limitation of internal space or geometric irregularity for the connection of non-circular bridge columns interfacing directly with circular drilled shafts. However, there is a concern on the safety and cost-effectiveness of such non-contact lap splices because the guidelines in the current AASHTO LRFD code and studies on this type of connection are limited. This study presents an experimental and analytical investigation of non-contact lap splices in non-circular bridge column to circular drilled shaft connections. Eleven large-scale column-drilled shaft specimens were tested to investigate the effects of the critical parameters affecting the performance of non-contact lap splices: the non-contact distance between the spliced bars, the lap splice length and the amount of transverse reinforcement in the non-contact lap splice zone. The specimens were subjected to flexure action with both monotonic and cyclic loading. The test results showed that the specimens with larger non-contact splice distance generally exhibited lower lateral stiffness and lower capacity. The increase in the non-contact splice distance yielded significant inclined cracks and splitting cracks in the non-contact lap splice zone. The angle of inclined cracks was observed to increase with increasing the non-contact splice distance. Furthermore, a three-dimensional finite element analysis (FEA) was performed on the test specimens, and the finite element simulated results were compared with the test outcomes. Using the validated FEA models, a thorough parametric study was performed to understand the effect of the critical parameters. The results of this study provide a basic understanding of the behavior of non-contact lap splices in non-circular columns to circular drilled shaft connections. Based on the findings from the experimental and analytical investigation, a set of design recommendations is provided for the design of non-contact splices in geometrically dissimilar bridge column to drilled shaft connections. In conclusion, with the consideration of the current AASHTO LRFD code and the proposed guidelines, a safe and efficient non-circular column to circular drilled shaft connection can be constructed.

Bridge substructure, Non-contact lap splices, Bridge column to drilled shaft connections, Large-scale testing, Non-contact splice distance, Splice length, Splitting cracks, Finite element analysis, Parametric study, Design recommendations
Portions of this document appear in: Chen H, Masud M, Sawab J, Huang HW, Xu B, Mo YL, Hsu TT. Multiscale analysis of non-contact splices at drilled shaft to bridge column interface. Engineering Structures. 2018, 176: 28-40.