21.3.9.3. SAO based Hybrid Method Process

When one uses SAO method for reliability analysis, select Reliability: SAO in AutoDesign menu. Then, you can see the design variable list. The current values are directly inputted in Mean values. Select the probability distribution type and define the standard deviation values. Then, check the performance index dialogue. In this window, you can define the limit state function and its’ limit value. Figure 21.121 shows these processes.

Figure 21.121 Define the reliability analysis problem

Figure 21.122 Define the Analysis Control

Figure 21.122 shows the analysis control dialogue. We provide three SAO methods such as AFORM, AFORM+DRM1 and AFORM+DRM2. Even though AFORM+DRM2 is more accurate than others, we use AFORM+DRM1 because the limit state equation is quite simple. Next, let’s see the convergence criteria. ‘Objective Change … is used to check the change of ‘reliability index’ between consecutive iterations. Its’ tolerance is recommended as 0.05 ~ 0.01. Limit State Value is used to check the satisfaction of limit state value. As dynamic analysis results are noisy numerically, its’ convergence tolerance is recommended as 0.01. Next, push Execution button. Then, SAO approach is performed.