Soil-Pile-Structure Interaction Effects in Alluvium with Non-constant Shear Modulus in Depth
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Soil-Pile-Structure Interaction Effects in Alluvium with Non-constant Shear Modulus in Depth Vahid Shirgir 1 & Ali Ghanbari 1 & Ali Massumi 1 Accepted: 16 August 2020/ # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract This study developed a simple analytical model to evaluate soil-pile-structure interaction effects on the alluvium with non-constant shear modulus in depth. Numerical analysis was performed to verify the accuracy of the proposed analytical model. A good agreement between analytical and the numerical results evidenced the accuracy of the proposed analytical model. Two systems were compared analytically: case A—single degree-of-freedom (SDOF) system located on a pile in a soil layer with constant shear modulus in depth; case B—SDOF system located on a pile in a soil layer with a nonconstant shear modulus in depth. The results showed that for case B, soil-structure interaction effects on structures located on soil alluvium with a non-constant shear modulus in depth were more significant, similar to those of the SDOF system located on softer soil. In case B, the shear modulus of soil near the surface of the layer was lower than the depth soil, and the degree of freedom at the pile head was more flexible (rocking DOF), which increased the vibration period of the system at least 8%. Hence, dynamic behaviors of tall and heavy structures significantly affected the alluvium with non-constant shear modulus in depth. The assessment of soil-structure interaction is a local issue and for dynamic analysis one should use the shear modulus around the foundation, not the mean value of 30-m depth of soil alluvium. Keywords Soil-pile-structure interaction . Alluvium with non-constant shear modulus in
depth . Analytical model
* Vahid Shirgir [email protected]; [email protected] Ali Ghanbari [email protected] Ali Massumi [email protected]
1
Faculty of Engineering, Kharazmi University, 49 Mofatteh Ave., Tehran 14911-15719, Iran
Transportation Infrastructure Geotechnology
1 Introduction Soil-structure interaction can be divided into two phenomena: the inability of the foundation to match the free-field deformation (kinematic interaction) and the effect of the dynamic response of the structure-foundation system on the movement of the supporting soil (inertial interaction). Kinematic interaction can induce the rocking and torsional modes that are not present in a free-field motion. Inertial interaction occurs when the forces transmitted to the soil by the dynamic response of the structure produce foundation movements that would not occur in a fixed-base structure. The effects of inertial interaction are usually more pronounced than those of kinematic interaction (Kramer 1996). Adopting the most accurate and realistic modeling technique and computation method for treatment of dynamic soil-structure interaction (SSI) effects in seismic analysis and design of structures resting on soft soil deposits is one of the most discussed and challenging issues in the field of seismic design and r
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