The P-multipliers of Pile Groups Supported Large Billboard Signs in Bangkok Area

Abstract

The purposes of this research were 1) to numerically investigate the soil resistance against the pile group supporting a large billboard sign in the Bangkok area, and 2) to study the p-multipliers for a laterally-loaded pile in a group subjected to wind load. The three-dimensional finite element analysis was performed and created graphically using a standard set of commands in the ABAQUS/CAE package. To simulate the behaviors of soil and pile foundations subjected to wind load acting on a large billboard sign, the virtual interface element technique was employed to relatively control and monitor the pile-soil-pile interaction when the lateral movement was induced. The effective interface element thickness was assigned to be 10% of the pile diameter. The research results revealed two findings. First, the lateral soil resistance against the piles was found to be at its ultimate value at the topmost layer near the existing ground, the so-called critical depth at about 2 times of the pile diameter at its widest part, when considering the maximum wind loads applied to the billboard sign according to Building Control Acts. It was found that piles installed in the leading row resisted larger lateral stress distribution than those in the trailing row. Second, the  p-multipliers of piles in the leading and trailing row were equal to 0.884 and 0.772, respectively. This is due to the fact that the pile-soil-pile interaction induced among piles within a group and surrounding soil, are dependent on the position of each pile in a group and also the direction of the lateral load applied to the pile foundation.