Structural Design of Roofs over the Sports Arenas for the 1972 Olympic Games: Some Problems of Prest

In this paper is presented a study on dynamic stability of thin-walled bars with open cross-section, subjected to compression by an axial force, composed from a static component and a variable one. The case of non-symmetric profiles is analysed in the first instance, to obtain general equations of vibratory motions; these are then particularized for profiles with an axis of symmetry, currently used in construction.

In the behaviour of structures under earthquake, the most effective role is played by the fundamental period of vibration of structures because it is one of the main parameters to determine the earthquake forces applied to the structure and it specifies the dynamic stability of the structure. In this paper'a simple approximate formula is proposed to calculate the fundamental period of vibration. The calculation with this formula is very short and easy. No mathematical background is necessary to apply the formula. In addition to the derivation and discussion of the formula, several examples showing its application are given.

A computerized finite difference method is presented for the analysis of slender reinforced concrete columns. The method is developed in detail for the particular case of columns fixed at the base and prevented from deflecting laterally at the top as compressive loading is applied. Symmetric bending is assumed. The columns may have a cross-section varying along the length. The effects of cracking of the concrete, initial lack of straightness, and of initial deflexion of the top of the column by cantilever action are allowed for. Reduction in the capacity of the column arising from creep of the concrete is examined. The method presented may be adapted to suit end conditions other than fixed base pinned top. Flow diagrams for the computer analysis are given.