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 lecture. 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|
Neville, A. M. (1972). Paper 1. Concrete - a non-elastic material in the laboratory and in structures. Paper 2. Design of concrete structures for creep. Paper 3. Comments on the education and training of civil engineers in English-speaking countries. VTT Technical Research Centre of Finland. Valtion teknillinen tutkimuslaitos: Betoniteknillinen laboratorio. Tiedonanto, No. 17