The application of stone column technique for improvement of soft soils has attracted a considerable attention during the last decade. However, in a very soft soil, the stone columns undergo excessive bulging, because of very low lateral confi nement pressure provided by the surrounding soil. The performance of stone column can be improved by the encapsulation of stone column by geosynthetic, which acts to provide additional confi nement to columns, preventing excessive bulging and column failure. In the present study, a detailed experimental study on behavior of single column is carried out by varying parameters like diameter of the stone column, length of stone column, length of geosynthetic encapsulation and stiffness of encapsulation material. In addition, fi nite-element analyses have been performed to access the radial deformation of stone column. The results indicate a remarkable increase in load carrying capacity due to encapsulation. The load carrying capacity of column depends very much upon the diameter of the stone column and stiffness of encapsulation material. The results show that partial encapsulation over top half of the column and fully encapsulated fl oating column of half the length of clay bed thickness give lower load carrying capacity than fully encapsulated end bearing column. In addition, radial deformation of stone column decreases with increasing stiffness of encapsulation material.
The integrity of a reinforced concrete structure should be safe and stable under lateral loads, especially those structures that depend on the behaviour of the beam-column joint. The ductility capacity of structural elements has a key role to play in seismic design. The ability of the structure to sustain levels of inelastic deformation under lateral loads, implicit in ductility values, is dependent on the material and detailing used. For the ductile behaviour of beam-column joints, a considerable amount of lateral reinforcement is necessary. An experimental investigation is presented on the use of steel fibre reinforced concrete (SFRC) to provide ductility in a beam-column joint even after the increase in hoop spacing of lateral ties. Six one-third scale exterior beam-column joints were tested under reverse cyclic loading. The SFRC beam-column joint contained volume fraction of 1 . 5% steel fibre for all variable hoop spacing. The results were compared and evaluated with respect to strength, displacement ductility, energy dissipation, specific damping capacity and stiffness. Experimental results reveal that a SFRC beam-column joint performs satisfactorily and improved joint behaviour is indicated. The results also indicate that a reduction in the number of lateral ties in the beam-column joint by the appropriate use of SFRC can be an alternative solution for avoiding conjunction of reinforcement.
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