Geoscience Reference
In-Depth Information
CHAPTER 10
SEISMIC DESIGN AND PERFORMANCE OF SURFACE FOUNDATIONS
Michael Pender
Department of Civil & Environmental Engineering, University of Auckland,
New Zealand
m.pender@auckland.ac.nz
Abstract.
Within the context of shallow foundation design this paper considers the need for more
effective interaction between geotechnical and structural design teams so that progress towards
the integrated design of structure-foundation systems can be achieved. The paper considers four
aspects: (i) the role of the shallow foundation bearing strength surface, (ii) the variability in soil
propertiesrelativetovariationsinstructuralproperties,(iii)theobservationthatbed-of-springmod-
els cannot represent correctly vertical and rotational stiffness of shallow foundation, and (iv) an
exampleofthenumericalpredictionofseismicresponseofalow-risestructurefoundedonshallow
foundations is presented which indicates that moment free connections between the foundations
and building columns leads to a more economical design.
1. Introduction
Given the very powerful computer resources that are now available for civil engineering
and infrastructure design, a pressing need is to improve interaction and communication
between the structural and geotechnical communities. An obvious priority is for the two
communitiestoworktogetherinamoreintegratedfashion.Themostdirectwayinwhich
this can be achieved is by the two groups developing integrated numerical models of
complete structure-foundation systems. Too often in the past the practice has been for
consideration of the foundation and superstructure to be considered almost in isolation.
Lapsing into anthropomorphism, we can say, that from the perspective of an incoming
earthquake,thestructureandthefoundationsystemsupportingitisseenasasingleentity.
Ifthisisacceptedthenthedesignapproachneedstobebasedonasingleintegratedmodel
of the building-foundation system. Nowadays exceedingly capable software is used for
analysis and design of structures. The full potential of this software will not be realised
until a complete model of the structure-foundation system isused.
Thispointofviewiscertainlynotbasedontheassumptionthatthefutureofengineering
designliesinevermore sophisticatedsoftwareinamanner thatreduces human inputand
minimises opportunities for engineering judgement - certainly not. But what is intended
is that the exercise of engineering design judgement will be enhanced, so enabling the
designertoobtainamorerealisticunderstandingofthehowthedesignwillperform,and
yetthisisnotabigstepforwardforthecapabilitiesofavailablesoftware.Whatisneeded
