underlying TLA in the context of an arch or cupola dam, i.e. arch–cantilever
load distribution and node deflection matching, are essentially as outlined in
Section 3.2.8, in relation to the gravity dam in a steeply sided valley.
Finite element analysis, FEA, also identified in Section 3.2.8, is
extensively applied in arch dam design. Considerable effort has gone into
the development of suitable software, and in its most refined three-
dimensional form FEA is now the most powerful, reliable and well-proven
approach to design. In this application it is, however, a highly specialist
analytical method demanding experience in its application. It is also highly
sensitive to the quality of the input information, notably as regards proper
characterization of the load response of both concrete and rock founda-
tion. The solutions it provides, while mathematically correct, must there-
fore be interpreted with some caution. Reference should be made to
Clough and Zienkiewicz (1978) or USCOLD (1985) for a comprehensive
introduction to FEA and other numerical/computational methods in the
specific context of dam analysis and design.
3.5 Design features and construction
3.5.1 Introduction
All analyses are founded to a greater or lesser degree on assumptions with
respect to load régime, material response, structural mechanisms, etc.
Application of the analytical methods introduced in preceding sections
represents only the initial phase of the design process. The second phase is
to ensure that by good detail design the assumptions made in analysis are
fulfilled to the greatest extent commensurate with rapid and economic
construction.
Certain key design features reflect the engineer’s approach to prob-
lems of loading, e.g. uplift relief drain systems. Other features are dictated
by the characteristics of mass concrete, discussed in Section 3.6, or by pres-
sure to rationalize and simplify in the interests of cost containment. Good
detailing is not necessarily a matter of rational and formalized design. In
many instances it is the application of empirical principles based on prece-
dent and satisfactory experience. Thomas (1976) addresses design features
and detailing in considerable depth, aided by an extensive selection of
illustrative examples taken from international practice.
Design features divide into three major categories: those which
relate to the control of external or internal seepage; those which accom-
modate deformation or relative movement; features which contribute to
structural continuity, i.e. load transfer devices. A possible fourth category
could be formed from those which simplify or facilitate construction. The
most important features are introduced in succeeding sections.
164 CONCRETE DAM ENGINEERING
