Short Course on LRFD for Deep Foundations

By: 

Dr. Muhannad T. Suleiman – Lehigh University, USA

Dr. Sherif S. AbdelSalam – the British University in Egypt

INTRODUCTION

Deep foundations, such as bored and driven piles,are more frequently used to support bridges and buildings with large structural loads. Typically, the capacity of deep foundations is initially estimated using static analysis methods, while construction control aspects are addressed via field load tests and pile integrity tests. For a selected static method, the deep foundation design may be achieved using the working (or allowable) stress design (WSD) or the limit state designthat is commonly referred to as the load and resistance factor design (LRFD). At present, the regional practice for the design of deep foundations still rely on the WSD using a global factor of safety (FOS), which is subjective and cannot ensure consistent, reliable, and sustainable performance of deep foundations. This drawback of the WSD stems from ignoring various sources of uncertainties associated with loads and capacities (or resistances), causing highly conservative FOS to be used in some cases.

Over the past few years, there was a progressive international trend towards transitioning to reliability-based pile design approaches. Consequently, LRFD guidelines were included in established geotechnical design standards such as the Eurocode 7 (2004) and the AASHTO (2007) and their updates. Currently, the regional codes are being updated to include the LRFD approach for deep foundations. The primary reason for this update is twofold; first to follow the international trend of adapting more consistent and cost effective designs; and second to integrate the construction control techniques in the reliability-based framework.

Objective

To provide the participants with adequate knowledge on the general principles andapplications of the LRFD approach for design and construction of different types of deep foundations.

Participants

Design engineers of international and local consulting firms; contractors and sub-contractors specialised in foundation works, bridges and highways; and geotechnical engineers who are interested in the design and construction of deep foundations.

Credit

8.0 Professional Development Hours (PDH)

Outline

1. LRFD philosophy
2. Background and advantages
3. Calibration requirements and technique
4. Subsurface investigation
5. Pile load test data
6. LRFD resistance factors calculation
7. Design example for bored and driven piles
8. Regional pile database overview