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Wednesday, September 28, 2016

Lateral Deflection of Multi-storey Rigid Frame Buildings under the Action of Wind Load: A Comparative Analysis

Rigid frames, rigid planar shear walls, coupled shear walls, and cores are usually employed when forming the bracing system of a multi-storey building. These different units contribute to the overall resistance of the system, but their contributions can be very different both in weight and in nature, so it is essential for the designer to know their behaviour in order that optimum bracing system can be produced (Zalka, 2013). The effect of wind becomes very influential as a building gets taller. Under the action of wind, vertical
structures are subjected to load regimes which are often modelled as lateral (horizontal) loads, and as a result, lateral deflections are induced in the building (sway). It is very important to consider this behaviour in a tall building from both statics and dynamics perspective, in order to guarantee the performance of the structure while in use.

Rigid frames are very significant in the structural behaviour of buildings. They possess all the three basic stiffness characteristics, i.e., they have local bending stiffness, global bending stiffness and shear stiffness. Under lateral loads, the behaviour of frames can be complex, because they undergo both bending and shear deformations. Hence, the behaviour of frames in resisting lateral loads may be characterised by three types of stiffnesses and corresponding deflection types which are;

(a) Shear deformation
(b) Global bending
(c) Local bending

In the paper downloadable from this post, a twenty storey multi-storey rigid frame was subjected to a uniformly distributed wind load of 5.05 KN/m calculated by using the Eurocodes. The deflection behaviour of the rigid frame was investigated using manual method proposed by Zalka (2013), and computer based method (finite element analysis). From the results of the two methods employed, it is observed that the value obtained from manual method gave a lower value for the top deflection of the building. The maximum deflection from finite element was 60.441mm, while the result from manual calculation was 55.524mm. This shows that the result from finite element analysis to manual method was about 8.135% greater than that of the manual method. However, this offers a great insight for the speedy check of computer based processes and results.

An excerpt picture from the manual analysis is shown below;

An excerpt picture from finite element analysis is shown below;

To download the paper in PDF format, click HERE

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