Design Optimization

RISAFoundation will optimize Concrete beams and slab reinforcement. The criteria used for this optimization are the selected design code and the Design Rules assigned to the beam or slab design strip/cut.

The Design Rules Spreadsheet records the parameters for the optimization. Optimization is performed for minimum weight, taking into consideration any depth, width, rebar limitations, etc. Note that the design rules input is one large spreadsheet, thus all of your design rules will be in the same place. Note that the dimensional rules and the reinforcement rules are all a separate entity; they have no interaction with each other in the program, they are simply all input into the same location. For example, your minimum member width rules will not be influenced by concrete beam reinforcement rules. On each tab of the Design Rules Spreadsheet, you have the option to enter the maximum bending and shear unity checks in the Max Bending Chk and Max Shear Chk columns of the spreadsheet. This should usually be specified as '1', however, if you desire a larger factor of safety, provide a lower factor (i.e. 0.95).

You can assign the design rules graphically as you draw elements, or later as a modification. Design rules for slab design cuts may only be applied via the Design Cuts Spreadsheet. For more information, see Modifying Beam Properties, Slabs - Design Strips and Slabs - Design Cuts.

For additional advice on this topic, please see the RISA Tips & Tricks webpage at risa.com/post/support. Type in Search keywords: Redesign.

Design Rules - Beam Rebar

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Note: If you would like to define specific flexural and shear rebar layouts for beams and columns, either use the Explicit option discussed below or see Custom Rebar Layout Database for Custom Rebar layouts.

The entries for the Beam Rebar tab are explained in the following table.

Column Header	Description
Optimize Rebar	The options in this column are Optimize and Explicit. Optimize tells the program to find the most optimal size and spacing of the reinforcement. The Explicit option indicates the exact number and size of reinforcement bars. When Explicit is selected, additional columns are editable and allow you to enter the quantity for Top/Bottom Bars and Shear Bar Spacing. These columns are grayed out when Optimize is selected.
Flexural Bars	Use the Min Flex Bar and Max Flex Bar columns to restrict bar sizes for your beam flexural reinforcing. Currently, we support the ASTM A615 (imperial) and ASTM A615M ("hard" metric, i.e. #8M is an 8mm bar) reinforcement standards. You may specify your rebar set on the Rebar tab of the Model Settings . You can force the program to analyze one bar size by setting the Min and Max values to be the same bar size.
Shear Bars	Use the Shear Bar column to enter the size of your shear ties. Currently, we support the ASTM A615 (imperial) and ASTM A615M ("hard" metric, i.e. #8M is an 8mm bar) reinforcement standards. You may specify your rebar set on the Rebar tab of the Model Settings.
Legs per Stirrup	Use the Legs per Stirrup column to enter the specific information about how many legs (2 to 6) each of your shear ties is expected to have.
Concrete Cover	The Top Cover and Bottom Cover columns are used to specify the clear cover measured to the beam flexural reinforcing steel. The Side Cover column is used to specify the clear cover measured to the shear reinforcing. The units are listed in the column header.

Design Rules - Slab Rebar

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The entries for the Mat Slab Rebar tab are explained in the following table.

Column Header	Description
Rebar Sizes	The Top Bar and Bottom Bar columns register the flexural reinforcement bar sizes that are to be used in the footing design. Currently, we support the ASTM A615 (imperial), ASTM A615M ("hard" metric, i.e. #8M is an 8mm bar) and CSA G30.18 (Canadian) reinforcement standards. You may specify your rebar set in the Model Settings.
Rebar Spacing	The Max Top Bar Spacing, Min Top Bar Spacing, Max Bot Bar Spacing and Min Bot Bar Spacing columns are used to set the maximum and minimum bar spacing for the top and bottom slab flexural reinforcement. The units are listed in the column headers. The Spacing Increment column sets the rebar spacing increment that will be used by RISAFoundation when analyzing various rebar layouts between the maximum and minimum bar spacing set in the previous columns. The units are listed in the column header.
Side Cover	The Side Cover column is used to specify the clear cover from the edge of a design strip or cut measured to the nearest slab flexural bar. The units are listed in the column header. Note that this entry should probably be '0' for design strips or cuts that do not extend to the edges of a slab, provided that they are not directly adjacent to another design strip or cut with a side cover greater than '0'.
Rebar Options	The last column allows the user to place their slab reinforcement at the mid-depth of the slab, force it to be placed at the top and bottom, one single layer at any depth or to be optimized by the program solution.

Note:

For mid-depth rebar, the program will use the bottom bar size and spacing options.
For single layer rebar, the design uses the top bar size and spacing options. The top cover under the General tab is used to define the rebar placement from the top of the slab.

Design Rules - Footing/Pile Cap Rebar

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The entries for the Footing/Pile Cap tabs are explained in the following table.

Column Header	Description
Rebar Sizes	The Top Bar and Bottom Bar columns register the flexural reinforcement bar sizes that are to be used in the design. Currently, we support the ASTM A615 (imperial), ASTM A615M ("hard" metric, i.e. #8M is an 8mm bar) and CSA G30.18 (canadian) reinforcement standards. You may specify your rebar set in the Model Settings.
Concrete Cover	The Top Cover and Bottom Cover columns are used to specify the clear cover measured to the beam flexural reinforcing steel. The units are listed in the column header.

Design Rules - Pile/Pedestal Rebar

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The entries for the Pile/Pedestal tabs are explained in the following table.

Column Header	Description
Rebar Sizes	The Top Bar and Bottom Bar columns register the flexural reinforcement bar sizes that are to be used in the footing design. Currently, we support the ASTM A615 (imperial), ASTM A615M ("hard" metric, i.e. #8M is an 8mm bar) and CSA G30.18 (canadian) reinforcement standards. You may specify your rebar set in the Model Settings .
Pedestal Bar Cover	The last column, Pedestal Bar Cover, is used to specify the clear cover measured to the shear reinforcing. The units are listed in the column header.