Location

San Diego, California

Session Start Date

5-24-2010

Session End Date

5-29-2010

Abstract

For the design of the Golden Ears approach bridge in Vancouver (Canada) a disconnected spread footing (DSF) was considered as alternative to a conventional pile foundation. In a DSF, a spread footing rests on natural ground improved by piles. Footing and piles are separated by a layer of coarse grained material. The mechanisms governing the behavior of the DSF during strong earthquake events have been investigated in a numerical finite element (FE) analysis using a (visco-)hypoplastic constitutive relationship. The FE model consists of a soil column (height 45 m) which includes the concrete piles. The superstructure is represented by a point mass attached to the end of a vertical beam. Material parameters for the constitutive law were derived from available field and laboratory tests. The numerical model was validated using results of large-scale in-situ tests, where a single-pile DSF was subjected to alternating vertical and horizontal loading. The goal of the numerical study was the investigation of the influence of pile spacing and gravel layer thickness on the dynamic foundation response and internal pile forces during a strong earthquake. Comparative calculations were carried out for a conventional pile foundation. A significant kinematic decoupling between footing and improved soft soil through the gravel layer did not occur in the simulations. Analysis results show that the internal forces in the piles of a DSF are significantly smaller compared with those in a conventional pile foundation, particularly in the upper part of the pile. However, in the investigated range, a dependence of bending moments and shear forces in the piles on the thickness of the gravel layer was not observed. On the other hand, the pile spacing in a DSF has a more pronounced influence on the internal pile forces.

Department(s)

Civil, Architectural and Environmental Engineering

Appears In

International Conferences on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics

Meeting Name

Fifth Conference

Publisher

Missouri University of Science and Technology

Publication Date

5-24-2010

Document Version

Final Version

Rights

© 2010 Missouri University of Science and Technology, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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May 24th, 12:00 AM May 29th, 12:00 AM

Numerical Analysis of Disconnected Spread Footing on Soft Soil During Strong Earthquake

San Diego, California

For the design of the Golden Ears approach bridge in Vancouver (Canada) a disconnected spread footing (DSF) was considered as alternative to a conventional pile foundation. In a DSF, a spread footing rests on natural ground improved by piles. Footing and piles are separated by a layer of coarse grained material. The mechanisms governing the behavior of the DSF during strong earthquake events have been investigated in a numerical finite element (FE) analysis using a (visco-)hypoplastic constitutive relationship. The FE model consists of a soil column (height 45 m) which includes the concrete piles. The superstructure is represented by a point mass attached to the end of a vertical beam. Material parameters for the constitutive law were derived from available field and laboratory tests. The numerical model was validated using results of large-scale in-situ tests, where a single-pile DSF was subjected to alternating vertical and horizontal loading. The goal of the numerical study was the investigation of the influence of pile spacing and gravel layer thickness on the dynamic foundation response and internal pile forces during a strong earthquake. Comparative calculations were carried out for a conventional pile foundation. A significant kinematic decoupling between footing and improved soft soil through the gravel layer did not occur in the simulations. Analysis results show that the internal forces in the piles of a DSF are significantly smaller compared with those in a conventional pile foundation, particularly in the upper part of the pile. However, in the investigated range, a dependence of bending moments and shear forces in the piles on the thickness of the gravel layer was not observed. On the other hand, the pile spacing in a DSF has a more pronounced influence on the internal pile forces.