1 / 15

Soil-Pile Interaction

Soil-Pile Interaction. Melissa Novak ECI 281A December 3, 2003. Introduction. Seismic waves traveling through the ground create loads on the soil and piles within that ground Structures under dynamic loading can be more effectively analyzed when studying the soil-pile-structure interaction.

abra-weaver
Download Presentation

Soil-Pile Interaction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Soil-Pile Interaction Melissa Novak ECI 281A December 3, 2003

  2. Introduction • Seismic waves traveling through the ground create loads on the soil and piles within that ground • Structures under dynamic loading can be more effectively analyzed when studying the soil-pile-structure interaction

  3. Substructuring • Substructuring is an effective technique used to evaluate this interaction, which consists of two steps • The first step is the kinematic interaction analysis, which incorporates the effects of seismic waves due to free field ground motion on the piles without the superstructure • The second step is the inertial interaction analysis, which deals with the earthquake forces generated by the motion of the building

  4. Complete Seismic Response Analysis

  5. Kinematic Interaction • The stiffness and mass of the piles create an interaction with the soil where the piles interfere with the path of the seismic waves • Kinematic interaction can be expressed as dimensionless ratios, relating the absolute values of pile head amplitudes to the free field horizontal amplitudes at ground surface (Ug) • These ratios mainly depend on the soil profile, the number of piles and their spacing (only relevant for multiple piles), the stiffness ratio (Ep/Es), the type of seismic wave, and the dimensionless frequency (a0 = wd/Vs)

  6. Inertial Interaction • Closely spaced piles interact with eachother because the displacement of one pile affects the displacement of the next pile • The principle of superposition is an alternative method for performing direct group analysis as opposed to Finite Element Analysis (FEM) • This method is implemented through the flexibility approach along with dynamic interaction factors (α): α = dynamic displacement of pile 2/ dynamic displacement of pile 1

  7. Inertial Interaction • General definition of horizontal or vertical dynamic group impedance: K^G = K Σ Σ εir K = the single pile complex impedance εir = elements of the inverted matrix [α]^-1 = [ε] [α] = all the complex dynamic interaction factors αir between any 2 piles in the group

  8. Dynamic Loading on an RC Group-Pile Foundation • The proper evaluation of the individual nonlinear behavior of soils and piles is very important in a dynamic analysis • Zhang & Kimura proposed a new beam theory to evaluate reinforced concrete material • The theory is based on a weak form in which the axial-force dependency in the nonlinear moment-curvature relation is considered • The new theory is validated using experimental results of an RC cantilever beam

  9. Dynamic Loading on an RC Group-Pile Foundation • A three-dimensional elastoplastic finite element analysis is used to evaluate an elevated bridge with a twelve pile foundation made of cast-in-place reinforced concrete • The ground soil is simulated with a tij subloading model which incorporates concepts of kinematic hardening and subloading

  10. Dynamic Loading on an RC Group-Pile Foundation

  11. Dynamic Loading on an RC Group-Pile Foundation • The bridge is supported by a group-pile foundation made of 3 x 4 reinforced concrete piles, 30 meters in length and 1.2 meters in diameter. The piles are spaced 2.5 meters apart from center to center The ground is made up of five layers. • The surface layer consists of sandy reclaimed soil, followed by a 10 meter thick soft alluvial clayed layer. The third layer is alluvial clayed soil followed by alluvial sandy soil, and the bottom layer is diluvial gravel

  12. Dynamic Loading on an RC Group-Pile Foundation • The results demonstrate the largest shear strains to occur at the interface between the soil and outside piles of a pile group. • The hysteresis of the shear stress-strain relations at different soil layers demonstrates the same phenomenon, showing much larger loops at the interface between the soil and outside piles • The larger the axial force is, the larger the shear force and bending moment will be for that particular pile

  13. Conclusions • The new beam theory can well simulate the axial-force dependency of RC materials under monotonic and cyclic loadings • The numerical analysis predicting the dynamic behaviors of a group-pile foundation should still be validated with centrifuge testing or model tests in future research

  14. References • Clough, R. W. and Gulkan, P. (eds.) (1993): Pile-Soil-Pile Interaction Under Small and Large Displacements by Novak, M., Developments in Dynamic Soil-Structure Interaction, 361-379. • Kimura, M. and Zhang, F. (2002): Numerical Prediction of the Dynamic Behaviors of an RC Group-Pile Foundation, Soils and Foundations Vol. 42, No. 3, 77-90.

  15. The End

More Related