Introduction to the design of multi-storey buildings: part 2

1. INTRODUCTION

The use of structural steels in the last century permitted a great increase in the height of building constructions leading to modern high-rise buildings.

For low-rise buildings, the most common structural solution is obtained by integrating two different load resisting systems in the same structure:

• semi-rigid or pinned frames, which resist vertical actions only
• steel bracings or concrete walls and cores, which resist horizontal actions

By means of the so-called 'fourth dimension of steel construction' (which introduces, besides the three geometrical dimensions, the range of available material strength), it is possible to unify the cross-sections of members and, therefore, to obtain optimum and economic solutions for a range of building forms.

For high-rise buildings (up to 120 storeys), different structural systems are used according to the height range:

• up to 30 storeys: concrete wall or core systems
• from 30 to 60 storeys: frame systems
• above 60 storeys: tube systems

For 'braced' steel frames, different types of bracing can be used according to the structural and functional requirements.

Appropriate calculation models for multi-storey buildings can be used for pin-ended structures and truss bracings.

For seismic-resistant steel structures, an excellent performance in terms of strength and ductility can be obtained. The design requirements in such cases correspond to three given limit states: serviceability, resistance to damage, and prevention of collapse.