Determination of Reduction Factor of Shear Key Configurations for Calculating Direct Shear Strength of Precast Concrete Dry Joints Using Parametric Finite-Element Simulations

Direct shear strength (DSS) of the precast concrete dry joints (PCDJs) is one of the critical issues for ensuring the structural integrity and performance of the precast segmental concrete bridges (PSCBs). However, the effects of shear key configurations, such as size, shape, spacing, and number of the PCDJs, were studied within narrow value ranges and were not well considered in the widely used AASHTO formula, resulting in unconservative predictions of the formula for multiple-keyed PCDJs. This study investigated the effect of shear key configurations within wider value ranges and incorporated a reduction factor into the AASHTO formula through a newly established parametric finite-element (FE) simulation. The simulation included an automatic procedure of model generation and calculation to derive the DSS of PCDJs based on 13 input parameters of the joint and was validated by a comprehensive database including 111 DSS results of PCDJs collected from existing literature. A parametric study was then conducted on a customized joint, which allows for exploring the PCDJs with large key sizes or numbers. Finally, a reduction factor was proposed to the AASHTO formula based on the test and simulation data considering the effects of key configurations. Results demonstrate that the proposed FE simulation is able to consider the reduction effect from the key configurations and reaches an excellent agreement in predicting the DSS of PCDJs in the database with more accurate mean values (MVs) (0.95 and 0.98), higher R2 values (0.63 and 0.69), and lower root-mean-squared error (RMSE) values (1.00 and 0.79 MPa) for both single-keyed and multiple-keyed joints compared with the results of the AASHTO formula. The parametric study revealed that the ASSHTO formula becomes increasingly unconservative with the increase of key numbers. The reduction factor needs to be included in the formula when multiple-keyed or large-size keyed joints are considered. The AASHTO formula with the reduction factor leads to a conservative prediction performance in the multiple-keyed joints, which is similar to that in the single-keyed joints.