Wind Performance of a Steel Timber Composite Tower
Ze Wen Chuan
This report examines the tower designed in the joint project last year (2012). It contains a brief explanation of the structural system of the tower, technical data and dimensions of its elements and analysis of their performance during wind loading, which will be discussed afterwards. The analysis will be on 3 separate cases to examine their individual effects upon the structure. Axial, normal loads and moment forces along elements, along with stresses on panels will be analysed to view how the tower behaves under the loadings. All analysis is done using Robot Structural Analysis Software 2013.
Materials and Properties
Checking Sums of Forces
The structure that is analysed is a 24m height tower with 11m deep piles as foundations. It is clad with closely-packed shingles. There are 3 main platforms at the heights 8m, 16m and 24m with breaks at mid-intervals (4m, 12m, 20m) and stairs connecting them. The structural system is a basic beam and column system with symmetrical cross bracing at the corners.
The main analysis of this report is the effect of wind loading on the tower. This is because wind has a major effect on tall structures due to their likeliness with vertical cantilevers. Wind values are obtained from Part 2 of BS 6399.
It is also anticipated that the unsymmetrical stairway and flooring structure will influence the structural behaviour of the tower, which will also be further explored and discussed.
Based on prior desk study, dominant wind direction is from the West to East side of the tower, reaching up to 21m/s at the top of the tower (24m). The tower performance will be analysed under 3 load cases:
Serviceability Limit State (SLS):
1. Pure wind loading on external structure (without stairs and platforms) 2. pure wind loading on whole structure
to observe the effects of wind loading on the tower and the influence of the internal structure on the overall behaviour of the building.
Ultimate Limit State (ULS):
3. Combined loading (self-weight and wind) on whole structure to analyse building performance for design scenarios.
1. The stairs are modelled as inclined platforms.
2. Piled foundation and floor slab is infinitely stiff and rigid to simplify model.
3. Wind loading is represented by equivalent point loads to simplify load distribution calculations.
4. All connections between members are rigid.
5. Cladding is assumed to form a smooth surface envelope around the tower.
Figure 9: Dimensions of tower plan
Figure 10: Dimensions of height
Materials and Properties
|Element |Material |Section (mm) | |Beams |Glulam GL36h |250x500, solid | |Columns |S275 Steel |350x500, hollow, t = 50 | |Cross bracing |Glulam GL24h |150x300, solid | |Stairs |Glulam GL24h |t = 300 | |Platforms |Glulam...
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