Two of the lectures are technical in nature, the other
one of more general interest.
The lecture on non-elastic features of concrete considers
the fundamental issues of elastic and non-elastic design
of structures, gives the reasons for the use of elastic
methods but points out that local non-elasticity is a
condition which must be satisfied. A brief mention of
non-elastic methods is made but the topic of design for
creep forms the subject matter of the second technical
The lecture on non-elasticity further considers the
stress-strain relation in concrete and reviews the
various definitions of the modulus of elasticity and the
methods of its determination. The influence of the rate
of application of load is mentioned. Data on the
variation in the modulus within structures are presented.
Behaviour of concrete under cyclic loading is considered
with especial reference to deformation: the changes in
the shape of the stress-strain curve on loading and
unloading and the resultant variation in the area of the
hysteresis loop of the stress-strain relation are
described. The elastic and non-elastic strain at failure
are considered as an evaluation of fatigue life.
Creep under static and cyclic loading is compared, and
data on the influence of the amplitude and mean value of
a cyclic stress on creep are presented.
The lecture on creep design first justifies the need for
consideration of creep in design of reinforced and
prestressed concrete structures of various types.
Shrinkage and creep, including its basic and drying
components, are defined.
Creep buckling is defined, and the time-dependent
variation in the moment-deflection relation in reinforced
concrete columns is considered. Hence, a method of
prediction of life under a sustained load is described.
The fundamental equation for the rate of creep approach
to the solution of deformation problems involving load
increments applied at various ages is presented. The
relaxation coefficient is then introduced to account for
the effect of ageing on the ultimate value of creep for
stress increments applied at various ages; thus the
change in stress due to creep and the associated
relaxation of stress by creep are allowed for.
The influence of reinforcement is taken into account by a
stiffness coefficient which reflects both the amount and
position of the steel.
Using this approach, the strain in a member under various
conditions of shrinkage and load can be expressed, and
the method is extended to cracked beams. Prestressed
concrete, both pretensioned and post-tensioned, is also
considered. The application of the method to continuous
beams with sinking supports is also mentioned.
The third and last lecture is concerned with education
and training of civil engineers, mainly in England, but
brief comments on other Commonwealth countries and on the
U.S. are made. The essential features of the British
system are emphasized and the way in which slow changes
are made is mentioned.
The lecture also raises the more fundamental question of
purposes of university education, and reviews the
relevance of a university course to future employment.
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||67|
|Publication status||Published - 1972|
|MoE publication type||D4 Published development or research report or study|
|Series||Valtion teknillinen tutkimuslaitos: Betoniteknillinen laboratorio. Tiedonanto|