Tall columns wind loads

Wind loading will only be important on tall columns installed in the open. Columns and chimney-stacks are usually free standing, mounted on skirt supports, and not attached to structural steel work. Under these conditions the vessel under wind loading acts as a cantilever beam, Figure 13.19. For a uniformly loaded cantilever the bending moment at any plane is given by ... 

An allowance of 0.4 m should be added for a caged ladder. The calculation of the wind load on a tall column, and the induced bending stresses, is illustrated in Example 13.3. Further examples of the design of tall columns are given by Brownell (1963), Henry (1973), Bednar (1990), Escoe (1994) and Jawad and Farr (1989). 

Skirt supports are recommended for vertical vessels as they do not impose concentrated loads on the vessel shell they are particularly suitable for use with tall columns subject to wind loading. 

When an estimator costs pressure vessels such as reactors and distillation columns, care must be taken to ensure that the wall thickness is adequate. The default method in IPE calculates the wall thickness required based on the ASME Boiler and Pressure Vessel Code Section VIII Division 1 method for the case where the wall thickness is governed by containment of internal pressure (see Chapter 13 for details of this method). If other loads govern the design, then the IPE software can significantly underestimate the vessel cost. This is particularly important for vessels that operate at pressures below 5 bara, where the required wall thickness is likely to be influenced by dead weight loads and bending moments from the vessel supports, and for tall vessels such as distillation columns and large packed-bed reactors, where wind loads may... 

The walls of pressure vessels are usually relatively thin compared with the other dimensions and can fail by buckling under compressive loads. This is particularly important for tall, wide vessels such as distillation columns that can experience compressive loads from wind loads. 

For a column under live load, maximum deformation and internal force of nodal sections are closely related to natural vibration period and vibration mode. Therefore, natural vibration period of a column must be determined for calculating wind load and seismic load of the column (Wei, 1985). Columns used in chemical plants or refinery plants typically have one end fixed and the other free, which may be considered as cantilever beam structures. Tall columns are high-rise flexible buildings with less damping resulting in simplified free vibration (Jeary, 1997). 

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