The design of composite columns is seamlessly integrated within the program. Initiation of the design process, along with control of various design parameters, is accomplished using the Design menu. Automated design at the object level is available for any one of a number of user-selected design codes, as long as the structures have first been modelled and analyzed by the program. Model and analysis data, such as material properties and member forces, are recovered directly from the model database and are used in the design process in accordance with the user-defined or default design settings. As with all design applications, the user should carefully review all of the user options and default settings to ensure that the design process is consistent with the user’s expectations. Composite column design options include the use of the Direct Analysis Method. The software is well suited to make use of the Direct Analysis Method because it can capture the second-order P-Δ and P-δ effects, provided the user specifies that a nonlinear P-Δ analysis is performed.
For each design combination, composite column members are checked at a number of locations (stations) along the length of the object. The stations are located at equally spaced segments along the clear length of the object. By default, at least three stations will be located in a column or brace member. The user can overwrite the number of stations in an object before the analysis is run and refine the design along the length of a member by requesting more stations. Refer to the program Help for more information about specifying the number of stations in an object.
The code requires that stability shall be provided for the structure as a whole and for each of the elements. Any method of analysis that considers the influence of second-order effects of P-Δ and P-δ, geometric imperfections, out-of plumbness, and member stiffness reduction due to residual stresses is permitted by the code. The effects of geometric imperfection and out-of-plumbness generally are captured by the use of notional loads. The effect of axial, shear and flexural deformations and the effects of residual stresses on the member stiffness reduction has been considered in a specialized method called “Direct Analysis Method.” This method can come in different incarnations (formats) according to the choice of the engineer as allowed in the code.
