A simple 2-Dimensional braced-frame structure is used here to demonstrate the use of the Drift Control module in generating useful information in controlling drift with minimum weight/volume considerations. The following figure shows problem definitions and loadings on the frame. The frame is subjected to lateral loads of 100 Kips, 75 Kips and 50 Kips at the roof, the second and the first floors, respectively. A virtual load of 100 Kips is applied at the roof.

The member sizes are given in the following table. As shown in the table, columns and braces contribute most to the flexibility of the frame, particularly Columns 5 and 6 at first floor and braces 2 and 3 at second and first floor, respectively, which is an expected behavior. To decrease the roof drift, the column sizes at the first floor and the braces need to be increased. The breakdown into components suggests that columns of higher axial area are needed to reduce drift since it is the axial contribution that is very significant. A column with higher Ixx and Iyy will not necessarily reduce drift as much as expected.

The beams could be made much smaller because they account for less than 5% of the whole deformation. From a weight optimization point of view, an increase or decrease in brace sizes will produce the most change in drift. In other words, the braces have the highest sensitivity index. To reduce drift, increasing the brace sizes (i.e., area) produces an efficient system. This exercise results in maximum stiffness with a minimum volume of material.

On the other hand, if the need arises to allow more drift, then member sizes could be reduced. The tabulated results indicate that beam and column sizes could be safely reduced without introducing a significant increase in drift. The only practical limit on the sizes of the beams and columns will be gravity load designs. However, since the braces have the highest SI (Sensitivity Index), then reducing their sizes even slightly (particularly cross-sectional area) will result in large increase in drift. This reduction in brace sizes is therefore very much limited, compared to beams and columns.