Non-prismatic frame assignment

To model non-prismatic frame elements, elements should initially be drawn with a constant cross section, then assigned a tapered-section definition. To begin, select Define > Section Properties > Frame Sections to ensure that the start and end sections of the tapered element are available in the Frame Properties menu, shown in Figure 1:

To import sections, select Import New Property, then click the icon for section type. Scroll down to select the section database, labeled SECTIONS8.PRO, and add any sections desired for modeling.

To define a non-prismatic frame section, select Add New Property > Other on the scroll-down menu, then select the Non-prismatic icon, shown in Figure 2:

Next, name the section, specify the start and end sections associated with element taper, and specify segment Length as 1.0 and Length Type as Variable. This applies taper as a ratio of the length between each node. The Absolute option correlates with exact taper length. Finally, specify how moment of inertia varies. Wide-flange sections are parabolic in major and linear in minor directions. Select ADD to complete the definition, and OK to complete the process, as shown in Figure 3:

To model a series of tapered segments within an element, follow the same process while adjusting the Length definition in proportion to each tapered segment.

Now that the tapered section is defined, select the elements to be tapered, then assign the tapered section by selecting it from the options under Assign > Frame > Frame Sections.

The Set Display Options command (indicated by the check-box icon) gives users control over model views. Users may enable Local Axes to ensure that start and end nodes are as desired for tapered elements. Users may also enable the Extrude View feature to review the profile of section depth.

SAP2000 Tutorial 06 Nonprismatic Sections of the CSI

video series presents a useful demonstration on this topic.