ABSTRACT
A more precise method of calculation is often used, for example in Germany, which allows for the fact that a simply-supported beam becomes statically indeterminate when it is prestressed, the initial effect of the prestressing force and the effect of changes occurring with the passage of time being therefore considered independently of each other. Although this may be theoretically correct, its application to practical design produces complications. The designer should know in advance the conditions under which the concrete will be cast and cured, and should also allow for the effect of weather conditions on creep. It is rarely possible to anticipate these conditions accurately, and it is essential that the most unfavourable assumptions be made in order to allow for the maximum possible losses of the initial prestress. The accuracy of the method is therefore unlikely to exceed that of the simpler method.
