**3. Technological Innovations in High-Rise Buildings**

### *3.1. New Design Trends in Geometrical Forms*

High-rise buildings were often designed in the form of rectangular blocks with glass façades. Such buildings, although practical and aesthetic, are somewhat monotonous. Contemporary architecture is trying to face this monotony. Apart from the mass execution of rational high-rise buildings, the appearance of another trend has been noted. This is the phenomenon of erecting "iconic" buildings, which are distinguished by their shape and scale. Based on the information gathered in the CTBUH database and also looking at new created high-rise buildings, it is reasonable to believe that the next generation of tall buildings will be more towards aerodynamic and curvilinear shapes and forms. Analysis of wind action on tall buildings shows the importance of the effect of form and geometry of

high-rise buildings. For instance, in Taipei 101, corner modifications provide 25% reduction in the base moment when compared to the original square section.

Geometric solids (such as polyhedra, cones, cylinders, spheres, ellipsoids and toruses) and curved surfaces appear as the components of each modern skyscraper [13].

Analyzing the form of a building can identify the specific types of basic solids or surfaces used in all or part of the building. In addition to creating the composition of a building, different kinds of distortion of the solids or surfaces are used. Generally, spatial forms can be geometrically divided into polyhedra, solids of revolution and surfaces [14]. Polyhedra are solids limited by a closed surface and constructed with a finite number of flat polygons. They are divided into: Prismatoids (pyramids, prisms, anti-prisms and octahedrons), polyhedra (platonic solids), semiregular polyhedra (the Archimedean solids) and other polyhedra compounds (Catalan, Johnson and toroidal).

The second group of geometric forms is the solids of revolution, which are limited by a closed surface of revolution or toroidal based on a circle, ellipse or other closed figure. In them are a sphere, ellipsoid or torusoid of revolution with a normal section in the shape of a circle or ellipse.

The last group of spatial forms is surfaces, which include: Ruled surfaces (Catalana, conical and cylindrical), curved surfaces of a constant generatix (rotary, torusoidal and translational) and curved surfaces of a varying generatix (wedge, parabolic-elliptic and minimum). From an architectural point of view, modern skyscrapers can be categorized into the following groups: Extruder, rotor, twister, tordos and also free form.
