Tall Building Foundation Design

Tall Building Foundation Design by Harry G. Poulos

Tall Building Foundation Design by Harry G. Poulos

I have been involved in the design of tall building foundations for almost three decades,
during which time building height records have been broken several times. The demands
on foundation design for these buildings have increased accordingly, and have resulted in
significant changes in design practice. State-of-the-art techniques are now becoming routine
and the amount and quality of geotechnical data being acquired for the design process has
also improved substantially. As I advance well into my eighth decade, I felt that it might be
useful to set out an approach to tall building foundation design that I and my consulting
and academic colleagues have developed and employed on a significant number of projects.
The approach that is described in this book employs a three-stage process, starting with
a preliminary or concept design phase, followed by a detailed phase and then a final phase
in which all aspects are checked, the construction drawings are finalised and the design is

ready for implementation. The level of computational sophistication and the amount of geo-
technical data available will generally increase as each phase proceeds, often starting with

a relatively sparse amount of data, and then increasing in detail and quantity as the design
process proceeds. This second phase would normally consist of detailed drilling, geophysics
and in situ and laboratory testing. The final phase would incorporate filed element testing,
usually on piles and perhaps shallow foundations, to enable optimisation and final “tuning”
of the design.
The objectives of this book are as follows:

1. To clarify the issues that need to be considered in design, not only from the structural loadings, but also from loadings that arise from the ground inwhich the foundationsare located.

2. To summarise some of the available information on geotechnical design techniques, for each of the three phases of design. These techniques range from empirical approaches
that can be used as a first rough estimate of design requirement, through simplified but sound methods that may be employed for the detailed design, to detailed numerical analyses suitable for the final stages of the design process.

3. To set out methods by which the relevant foundation design parameters can beassessed.

4. To discuss procedures for pile testing and then for monitoring the performance of the foundation during and after construction.

5. To present some details of a limited number of case histories in which the various analysis and design techniques described in this book have been applied. These case histories are limited to ones in which I have been involved, but there are other pub-lications which discuss many more case histories, for example, Hemsley (2000) and

Katzenbach et al. (2016).

While this book focusses on the geotechnical design of foundations, there are brief sec-tions on other aspects of tall building design which the geotechnical designer should be
familiar with. These include the various structural forms of tall buildings, the options avail-able for the foundation system, the various sources of load on the foundations and some very basic aspects of the structural design of the foundation system.

Because of the diverse sources of information contained in this book, no attempt has been
made to unify the notation. Rather, the notation of the original source has generally beenretained, with some minor departures. As a consequence, there are many over-worked sym-bols whose meaning is very much dictated by the context in which they appear. Accordingly,

the definition of such symbols as α, β, a, b, c, d, D, e, L, k, K, P, p, R, u and V, among many
others, must be examined carefully before use.
The field of geotechnical engineering and its sub-field, foundation design, continues todevelop and progress and so some of the material in this book may become dated in time.

However, the general principles set out in this book are philosophically rather basic, and itis hoped that they will stand the test of time more durably than some of the empirical and simplified calculation methods.

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