Comparative Analysis Between Internal Forces of Fixed and Flexible Foundation under Earthquake Load
Abstract
Pile foundations can be designed as fixed or flexible according to the soil parameters, the
seismic condition of the area, and the characteristics of the building. This research compares the
effect of internal forces working on fixed and flexible foundations with the structure of a
symmetrical 15-story building of reinforced concrete without a structural shear wall located in
Yogyakarta, Indonesia with medium soil according to SNI 1726:2019.
This study analyzes the effect of the flexibility of pile foundations on the natural period of
vibration of a building, compares the internal forces acting upon fixed and flexible pile foundations
in medium soil, and reveals the effects of soil shear modulus distribution. The outcomes can be
obtained after an extensive design that is generally divided into two stages of planning according to
FEMA P-750 and P-751. After the structural planning, the analysis of the spring stiffness parameters
of the flexible foundation is carried out, which is used to compare the internal forces results with the
fixed foundation.
The result of the comparison analysis shows that the building with a flexible foundation has
a longer fundamental period. The internal forces including base shear and column bending moment
of the flexible foundation are relatively smaller than the fixed foundation, while the beam bending
moment, column shear force, drift ratio, joint rotation, and horizontal joint displacement all show a
higher value. Meanwhile, the effects of soil shear modulus distribution with a homogeneous soil
profile show a higher value compared to the parabolic soil profile.
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- Civil Engineering [4205]