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G.16.3 Wind Load Generator

The Wind Load Generator is a utility which takes as input wind pressure and height ranges over which these pressures act and generates nodal point and member loads.

This facility is available for two types of structures.
  • Panel type or Closed structures
  • Open structures

Closed Structures

Closed structures are ones like office buildings where non-structural entities like a glass facade, aluminum sheets, timber panels or non-load bearing walls act as an obstruction to the wind. If these entities are not included in the structural model, the load generated as a result of wind blowing against them needs to be computed. So, the steps involved in load generation for such structures are:
  1. Identify the panels – regions circumscribed by members so that a polygonal closed area is formed. The area may also be formed between the ground level along one edge and members along the other.
  2. Calculate the center of gravity (CG) of each of the panels.
  3. For each panel, draw straight lines from the center of gravity to the midpoint of the members (or the ground) that form the panel boundary. The panel region will now contain several quadrilaterals whose two sides are made of portions of the respective members (or the ground) and the other two sides are lines going from the CG to the midpoint of the corresponding members.

    Influence area of Node i

  4. The area contained in any quadrilateral is allocated as the influence area for the node located at the meeting point of two members.
  5. Multiply the influence area by the average wind pressure contained inside the influence area and by the exposure factor for the node. The resulting value is the concentrated wind force for the joint.

Plates and solids are not considered in the calculation of the panel area. Openings within the panels may be modeled with the help of exposure factors. An exposure factor is associated with each joint of the panel and is a fractional number by which the area affecting a joint of the panel can be reduced or increased.

The automated load generator should only be used for vertical panels. Panels not parallel to the global Y axis (for Y UP) should be loaded separately.

Open Structures

Open structures are those like transmission towers, in which the region between members is "open" allowing the wind to blow through. The procedure for load generation for open structures is

  1. Calculate the exposed area of the individual members of the model.
  2. Multiply that exposed area by the wind pressure to arrive at the force and apply the force on individual members as a uniformly distributed load.

It is assumed that all members of the structure within the specified ranges are subjected to the pressure and hence, they will all receive the load. The concept of members on the windward side shielding the members in the inside regions of the structure does not exist for open structures. Members loaded as an open structure need not be vertical.

Parent topic: G.16 Load Generator
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