Transient dynamic analysis of underground structures

Abstract

A nonlinear, plane-strain, dynaaic finite element method of analysis computer program is developed to study the interactive behaviour of underground structures. Static problems can also be solved without loss of efficiency. An extensive description of the analytical models used in the code is given. A planned scheme of analyses was performed to study the dynamic response of soil without buried structure and the interactive response of a buried structure subjected to impulsive loading on the surface. Base conditions of rigid and semi infinite cases were investigated to study their influence on the response of the system. A parallel series of nonlinear static analyses was performed for the maximum magnitude of the shock loading. An optimum position of the structure in the soil was found giving minimum moments in the structure. For rigid base case, proximity of the structure to the base severely affected the system response. Elimination of the reflected wave actions by use of viscous base yielded that no specific advantage in load sharing of the structure can be gained for high depth of burial. Inadequacy of the presently available recommendations for a unique dynamic magnification factor was proved by comparing the,results of parallel dynamic and static analyses.