The RAM Frame Drift Control module provides a great functionality to study and control the drift behavior of buildings. Drift, related to the axial, shear, flexural, torsional and beam-connection behavior of each member of a building structure, is an important design consideration. The total drift at a point can be considered as the sum of all governing displacement components from each member such as joint , axial, shear, flexure, torsion and beam-connections related displacements. To this end, RAM Frame Drift Control module helps users identify which member contributes the most to the drift at a point. The break-down of a member contribution to the drift constitutes displacement components such as joint, axial, shear, flexure, torsion and beam-connection and this information helps the user identify what sectional properties of a member to change to arrive at an optimized size. The joint displacement represents the deformation in the rigid-end zones (panel-zones).

The module is based on the well-known Castigliano’s Energy Theorem where a fictitious or "virtual" load is applied in the direction of the drift under investigation. A special acknowledgement is given here to Dr. Finley A. Charney, President, Advanced Structural Concepts Inc., for his prior work in this area, particularly the virtual work based concepts as implemented it in the computer programs DISPAR and PANELS, published by Advanced Structural Concepts, Inc., Golden, Colorado.

Energy methods, such as Castigliano’s, help determine the deflection of a structure at a given point due to an external load by "pairing" it with what is commonly called a "virtual load". The loads are referred to as "fictitious" or "virtual" interchangeably only because they do not represent any "real-world" load cases. The module helps users quantify the contribution of each frame member to the flexibility of the building under investigation. This information can then be used to modify the sizes and topology of the frames to arrive at a building design optimized for drift considerations.

The steps required in using the module are explained in detail in Chapter 2. The chapter describes how to set up nodal and story load cases that are required to calculate the so-called displacement participation factors that help quantify the contribution of a member to the building flexibility. The chapter also discusses the graphical and report outputs for the module. Chapter 3 covers the theoretical basis for the Drift Control module.