AISC 360-16, AISC 360-10, and AISC 360-05 contain specific requirements regarding the analysis of the lateral frames. Three methods are listed: The Effective Length Method, the First-Order Analysis Method, and the Direct Analysis Method. Generally any of the three approaches is acceptable, but if the ratio of the 2nd -order drift to 1st -order drift is greater than 1.5 (based on a model with nominal member properties), the Direct Analysis Method is required. The Direct Analysis Method, found in Appendix 7 of the Specification of the AISC 360-05 specification, is implemented in the program. See Section C2-1b in Chapter 2 and Appendix 7 in AISC 360-05 for further information. In the AISC 360-10 and AISC 360-16 specifications, the method can be found in Chapter C.