Wind Tunnel Test Wind Load

Forces from a wind tunnel test can be easily entered into RAM Frame for the lateral analysis by the help of creating wind tunnel load cases. The values provided by the wind tunnel tests are F_x, F_y, M_z, X, and Y for each story, plus several "combinations" that indicate the % of each of F_x, F_y, and M_z. A wind load generator takes the values in this form directly and then, it creates the various load cases.

A wind tunnel load case dialog is composed of two sections (or grids): the top grid is for the input of the basic story forces. When wind tunnel tests are performed these basic values are provided. Then, each load case is some combination of a portion of these basic forces. The lower grid is for the designation of the percent of each basic story force to include in the given load case.

For each load case generated, applied wind loads for a given diaphragm are determined as follows:

A p p l i e d F_{x} = % F_{x} * F x

A p p l i e d F_{y} = % F_{y} * F y

A p p l i e d M_{z} = % M_{z} * M_{z}

in which percentage values (i.e., %F_x, %F_y and %M_z) are taken from the lower grid, whereas those F_x, F_y, and M_z are from the top grid. Note that these calculated loads are applied to diaphragms at (X, Y) coordinates.

It should be noted that the current implementation is only for rigid diaphragms. In other words, those calculated for semirigid or pseudo/flexible diaphragms are skipped.