THE ASTRONOMICAL ORIENTATION OF THE URBAN PLAN OF ALEXANDRIA

Alexander the Great founded Alexandria in 331 BC. An examination of the topography of the city today allows the identification of the essential elements of the original urban system, and shows that the site was chosen mainly for religious and symbolic reasons. In fact, Alexandria was the prototype of a series of Hellenistic towns designed as ‘king's towns’ that aimed to make explicit the divine power of their founder. We examine the orientation of the orthogonal grid, which was based on a main longitudinal axis, and show that this axis is orientated to the rising sun on the day of Alexander the Great's birth. At the time of foundation, ‘King's Star’ Regulus was also rising along the same direction.     

ON THE ORIENTATION OF ROMAN TOWNS IN ITALY

Summary.   Several Roman writers report on the existence of a town foundation ritual, inherited from the Etruscans, which allegedly included astronomical references. However, the possible existence of astronomical orientations in the layout of Roman towns has never been considered in a systematic way. As a first step in this direction, the orientation of 38 Roman towns in Italy is studied here. Non-random orientation patterns emerge from these data, calling for further research in this field.     

A FIBRE FINITE BEAM ELEMENT WITH SECTION SHEAR MODELLING FOR SEISMIC ANALYSIS OF RC STRUCTURES

The paper describes the formulation of a non-linear, two-dimensional beam finite element with bending, shear and axial force interaction for the static and dynamic analysis of reinforced concrete structures. The hysteretic behaviour of “squat” reinforced concrete members, in which the interaction between shear and flexural deformation and capacity is relevant for the overall structural performance, is emphasised. The element is of the distributed inelasticity type; section axial-flexural and shear behaviours are integrated numerically along the element length using a new equilibrium-based approach. At section level a “hybrid” formulation is proposed: the axial-flexural behaviour is obtained using the classic fibre discretisation and the plane sections remaining plane hypothesis, the shear response instead is identified with a non-linear truss model and described with a hysteretic stress-strain relationship. The latter contains a damage parameter, dependent on flexural ductility, that provides interaction between the two deformation mechanisms. The element has been implemented into a general-purpose finite element code, and is particularly suitable for seismic time history analyses of frame structures. Analytical results obtained with the model are compared with recent experimental data.