DANG HOANG SON 

Study on contact pressure and ultimate bearing capacity of rigid footing under eccentric vertical load

Ohtsuka Satoru

In geotechnical engineering, the ultimate bearing capacity (UBC) of the rigid footing is an important issue in term of complexity of applied load as well as type of load bearing soil underneath. The superposition formula proposed by Terzaghi (1943) has been widely employed to calculate the ultimate bearing capacity of the footing under the vertical load. However, the ultimate bearing capacity of the foundation regarding horizontal loads and moments has not been sufficiently scrutinized. The scope of previous research is mainly limited to pure sandy and clayey soils or central vertical load only, only few researches have been conducted to study the wide range of soils and loading condition. In this study, rigid plastic finite element method (RPFEM) is employed to calculate the ultimate bearing capacity of the rigid footings under the eccentric vertical load on the intermediate soils by using an interface element to simulate perfectly frictional and smooth condition between footing and soil. The results 
illustrate that UBC is least dependent upon the roughness condition, but significantly alters with the cohesive shear strength.
The contact pressure being an important contributing factor towards bearing capacity is also investigated in this study and compared with current design codes. The comparison projects the similitude between magnitude of contact pressure, though contact pressure distribution is significantly different in both methods. Finally to summarize, RPFEM rationally evaluates the bearing capacity and contact pressure distribution under eccentric vertical load in contrast with existing theories.