Dr. Nasrellah H A

• DEFINITION OF TALL BUILDINGS

• “tall building or high-rise building” is a local concept and “skyscraper or super tall building” is a global concept. To be able to define a tall building as a skyscraper or super tall building, it is not sufficient for it only to be tall in its own region; it is necessary for it to be recognized around the world as a skyscraper or supertall building

• From the structural design point of view, it is simpler to consider a building as tall when its structural analyses and design are in some way affected by the lateral loads

Introduction

• For the structural engineer the major difference between low and tall buildings is the influence of the lateral forces on the behaviour of the structural elements. Generally, it can be stated that a tall building structure is one in which the horizontal loads are an important factor in the structural design

PLANAR LATERAL LOAD RESISTING ELEMENTS

1. Rigid-jointed Frames

• A rigid frame, also called a moment frame is a vertical support system that also serves as a lateral load-resisting system. It is constructed with beam and column elements either rigidly

or semi rigidly joined together with moment-resisting connections.

• The rigid frame derives its unique strength to resist lateral loads from the moment interaction between beams and columns.

• Rigid frame systems efficiently and economically provide sufficient stiffness to

• resist wind and earthquake induced lateral loads in buildings of up to about 25

storeys

Flat plate/slab systems:

Flat plate/slab systems are used in reinforced concrete buildings. This system consists of beamless floor slabs of constant thickness and columns. Shear walls also can be placed in addition to or instead of the columns

• Flat plate/slab systems efficiently and conomically provide sufficient stiffness to resist wind and earthquake induced lateral loads in buildings of up to about 25 storeys.

2. Braced Frames:

• The lateral stiffness of a rigid frame can be improved significantly by providing diagonal

members.

• Bracing can be either in storey height-bay width module or they could extend over many bays and stories.

• shear wall systems :

Shear wall systems are used in reinforced concrete buildings. This system consists of

reinforced concrete shear walls, which can be perforated (with openings) or solid.

• Shear wall systems efficiently and economically provide sufficient stiffness to resist wind and earthquake induced lateral loads in buildings of up to about 35 storeys.

• shear-frame systems

• Rigid frame systems economically do not have sufficient resistance against lateral loads in buildings over 25 storeys because of bending on columns that causes large deformations. In this case, the total stiffness and so the economical height of the building can be increased by adding vertical shear trusses (braces) and/or shear walls

FRAME TUBE SYSTEMS

• The idea here is to develop a fully three-dimensional structural system that engages the entire building inertia to resist lateral loads. The goal is to achieve a higher degree of efficiency toward lateral load resistance for taller buildings. The resulting organization for a framed tube system is generally one of closely spaced exterior columns and deep spandrel beams rigidly connected together

• Examples of Tall Buildings and Their structural systems: