Date of Award


Degree Name

Doctor of Philosophy


Engineering Science

First Advisor

Hsiao, J.


The degree of footing fixity G value of a column is a parameter which represents the rotation restraint at the base of a column. By using G values, the effective length factor K of the column can be calculated. The K value is used to check if the effect of slenderness needs to be considered for the column design. Moreover, the rotation of structural members is a major factor in determining the deflection of structures. The magnitude of structure deflection due to the rotation and elastic deformation are used to check if the second-order effect (P-delta effect) needs to be considered. When large axial loaded compression members, like bridge piers, are under lateral load impacts, the rotation at the base of the pier may cause a significant effect on the lateral deflection of the pier. However, traditionally the computation of slenderness ratio and the structure deflection due to the lateral loads is carried out by considering that the pier footing is rigidly fixed on the ground. AASHTO recognized the significance of the footing fixity effect on bridge piers and recommended an approach to account those considerations and suggested some footing fixity G values for different footing conditions. The purpose of this study is to verify the accuracy of the G values recommended by AASHTO for the pier footing on multiple rows of end-bearing piles case. A comprehensive study using 20 models derived from the pier-pile design example presented by FHWA is developed for the finite element analysis using computer software. In order to investigate the difference of G values for different pile foundations, these models are generated using various pile lengths, soil contents, pile arrangements and pile head boundary conditions. Also, the computations of the slenderness effect check, pier deflections and the G values obtained from finite element models are provided for the comparisons with that recommended by AASHTO.




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