Dynamic response of batter piles considering soil-structure interaction

Abstract

Batter pile groups application has been increased in recent years due to its considerable resistance against lateral loading condition. Actually batter pile groups are more appropriate choice to resist lateral forces due to seismic excitations and inertial forces, because vertical pile group perform much weaker while seismic motions affect these structures. The objectives of the present study are to evaluate modal behavior of Batter piles at various Batter angles and also to evaluate pier top deformations of Batter pile with respect to free field deformations at different batter angle with different frequencies. In this study, the pile head stiffness will be determined by the Thin Layered Element Method (TLEM) considering semi-infinite layered soil profile. The substructure i,e. the pile cap along with the pile soil system will be considered such as pile to pile interaction will be ignored. The individual pile stiffness will be considered as complex stiffness. Only stiffness and damping properties will be considered from the substructure. Modal analysis of a viaduct-pile system will be conducted by Mathmatica 5.0 and the kinematic interaction between a viaduct and the pile foundation will be investigated by sub-structure method. In the present study it has been observed that for low batter angle pier top deformation are in phase and pier top rotation & pile top rotation are out-of-phase but for greater batter angles, the pier top deformation is out of phase and rotations are in phase and anti-clockwise rotations at both pier top and pile cap occur. In the present study it has been observed that in lower frequencies pier goes through almost rigid body motion. Frequency greater than 3.5 Hz, pier top deformations increase. But the rate of change of pier top deformation increases with the increase of batter angle. It has been also observed that in lower frequencies pier top deformation are out of phase and in higher frequencies the same are in phase. It has been also observed that at resonance frequency there have no significant effect of batter angle on phase difference between pier top and pile cap rotation.