Analysis of the AASHTO LFRD Horizontal Shear Strength Equation

The composite action of a bridge deck and girder is essential to the optimization of the superstructure. The transfer of forces in the deck to the girders is done across a shear interface between the two elements. The transfer occurs through the cohesion of the concrete at the interface and then through the shear reinforcement across the interface. Adequate shear strength is essential to the success of the superstructure.

A collection of 537 horizontal shear tests comprised the database for the study of various concrete types and interface surface treatments. The predicted horizontal shear strength calculated from the AASHTO LFRD bridge design code was compared to the measured shear strength. The professional bias was computed for each specimen. The professional biases, standard deviations, and coefficients of variation for each category were calculated. The material properties factor along with fabrication factor was researched. The loading factors were researched and calculated for use in calculating the reliability index. The final step was to compute the reliability index for each category. The process was repeated to learn the reliability of the equation proposed by Wallenfelsz. The results showed that the reliability index for the AASHTO LRFD horizontal shear strength equation wash much lower than the desired target reliability index of 3.5. The reliability index for the Wallenfelsz equation was higher but still not close to the target reliability index.