Overview

Section Designer is a powerful utility that allows design of simple and complex cross sections. Section properties, interaction surface and moment-curvature relationships can be displayed. The following sections provide some useful insights into using Section Designer.

Local Axes Definition and Orientation

Take special care to draw pier sections using the correct orientation. Before you begin to draw a wall section in Section Designer, it is crucial that you understand the local axes definition for the pier. Section Designer always displays a plan view section of a pier. The positive local 2-axis is horizontal pointing to the right, always. The positive local 3 axis is vertical pointing up, always (unless, of course, the computer monitor is upside down). Consider carefully the local axes orientation before beginning to draw a pier section to avoid having a pier section with the wrong orientation.

Material Properties

To review or change the material property associated with a pier, right click on the polygon area object that defines the pier to access the Section Information form. Use the form to change the material property.

Modify the Geometry of the Concrete Section

Revise the geometry of a polygon by changing the coordinates of the corner points. Click on the Reshaper button, . Clicking the Reshaper button causes handles to appear on each corner of the polygon. Use either of the following methods to change the geometry of the concrete section:

• Left click on one of the handles and while holding the left mouse button down, drag the handle to a new location. Release the left mouse button.

• Right click on one of the handles to access the Change Coordinates form; type in new coordinates for the corner point of the polygon.

Revise Rebar Size, Cover and Spacing

By default, for a polygon section, single rebar elements are provided at each corner of the polygon and rebar line patterns are provided along each face of the polygon. Note the following about these rebar elements:

• Rebar line patterns are defined by a rebar size, maximum center-to-center spacing and clear cover.

• The bars are spaced equally in a rebar line pattern. The equal spacing is measured from the center of the corner bar at one end of the rebar line pattern to the center of the corner bar at the other end of the rebar line pattern.

• Single rebar elements at the corners of a polygon are defined simply by a bar size. The clear cover for these corner bars is determined from the clear cover of the line rebar on either side of the corner bar.

To further illustrate the reinforcing, refer to the figure above. The figure shows a typical wall pier. The four edges of the pier are arbitrarily labeled Edge A, B, C and D for the purposes of this explanation. Note the following about the reinforcing steel illustrated in the figure:

There are corner bars located at each of the four corners. Consider the corner bar in the upper left-hand corner at the intersection of edge C and edge D. This corner bar is located such that the clear distance from edge D to the bar is equal to the cover distance specified for the rebar line pattern along edge D. This is true even though the rebar size for the rebar line pattern has been set to "None" as would usually be done for the reinforcing along the edges that define the ends of the wall. Similarly, the clear distance from edge C to the corner bar is equal to the cover distance specified for the rebar line pattern along edge C.

The corner rebar size may be different at each corner of the pier.

As mentioned in the first bullet item of this list, the rebar size associated with the rebar line pattern along edges B and D is specified as "None." Note that the cover associated with these rebar line patterns is still valid, even though the rebar size is "None." The cover is still used to locate the corner bars.

The rebar line pattern along an edge of the pier is parallel to the edge of the pier and extends from the center of the corner bar (or its projection perpendicular to the pier edge) at one end of the considered edge to the center of the corner bar (or its projection perpendicular to the pier edge) at the other end of the considered edge. The rebar line pattern is then divided into equal spaces whose length does not exceed the specified spacing for the rebar line pattern.

The rebar line pattern size, spacing and cover may be different along each edge of the pier.

Methodology

To edit rebar line patterns along an edge of the member, right click on the rebar line pattern to access the Edge Reinforcing form; use the form to modify the edge rebar size, maximum spacing and clear cover.

In the Edge Reinforcing form, there is also a check box that when checked, applies the specified reinforcing to all edges of the polygon. Note that if you have already specified the rebar size along an edge of the polygon to be "None,"  the Apply to All Edges command does not apply the specified reinforcing size and spacing to that edge. It will, however, apply the specified cover to that edge.

To edit corner rebar, right click on the rebar element to access the Corner Point Reinforcing form. Use the form to specify the size of the corner bar. There is also a check box that allows you to say that this size applies to all corner bars. Note that if you have already specified the corner rebar size to be "None," the Apply to All Corners command does not apply the specified reinforcing size at that location.

Section Data Form

The following bullet items describe each of the areas in the SD Section Data form:

• Section name: Specify or modify the name of the frame section.

• Base Material: Specify or modify a defined material property. The options available in the Section Type area depend on the design type of the material property selected:

• If the design type of the specified material property is Steel, the General Steel Section and Other (not designed) options are available.

• If the design type of the specified material property is Concrete, the Concrete Column and Other (not designed) options are available.

• If the design type of the specified material property is None, only the Other (not designed) option is available.

The base material serves two purposes. First, it determines what design postprocessing options are available for the section. Second, the section properties are calculated by converting the area of each shape that makes up the section into an equivalent area of the base material. Thus, while a section can be made up of various shapes with different material properties, the reported section properties are based on an equivalent area of the base material.

See also: Show Section Properties

• Design Type: Specify the section type. If the section type is General Steel Section, any frame section assigned this property is designed by the Steel Frame Design postprocessor as a general section. If the section type is Concrete Column, any frame section assigned this property is designed by the Concrete Frame Design postprocessor. If the section type is No Check/Design (not designed), any frame section assigned this property is not designed by any postprocessor.

• Concrete Column Check/Design: This area is only active if the Concrete Column option is selected in the Design Type area. Specify whether the concrete column is to have its specified reinforcing checked or new longitudinal reinforcing designed when it is run through the Concrete Frame Design postprocessor.

• Define/Edit/Show Section: After you have appropriately specified items in the rest of the form, click the Section Designer button in this area to go to the Section Designer utility and draw the section. When you exit the Section Designer utility you return to the SD Section Data form.

Viewing Interaction Diagrams and Moment-Curvature Plots

• View an interaction diagram by clicking the Show Interaction Surface button, , or click the Display menu > Show Interaction Surface command.

• View a moment-curvature plot by clicking the Show Moment-Curvature Curve button, , or click the Display menu > Show Moment-Curvature Curve command.