Multi-Cell CIP Box Section Dialog Box

The Multi-Cell CIP Box Section dialog box allows you to define a typical box-girder cross section. To open this dialog box, open the Cross Section Layout dialog box by clicking the Cross Section button on the Geometry tab. Select the section you want to modify, and then click the Section button located in the grid.

Defining Exterior Girders

One of five available shapes defines each exterior girder and its dimensions, including thickness, slope factor, and radius of the corner. If any of the three dimensions (thickness, factor, and radius) is not applicable to a shape, then the field will be disabled.

Perform the following steps to define the exterior girders for the current section. These steps must be repeated for both the left and right girders.

Select the exterior girder type from the drop-down list.

Setting	Description
Vertical	The girder edge will be defined vertical.
Slope	The girder will edge will be sloped by defining the factor "f".
Chamfer	The girder will edge will vertical and the bottom corner will be chamfered by defining the distance "F".
Vert Round	The girder edge will be defined vertical and a rounded bottom corner of radius "r" will be defined.
Slope Round	The girder will edge will be sloped by defining the factor "f".and a rounded bottom corner of radius "r" will be defined. The distance "f" measures from the overhang length "l" to the PI of the rounded corner.
None	No exterior girder is present.

Enter the web thickness for the exterior girder in the Thickness (t) field.
Enter the factor for the exterior girder in the Factor (f) field.
Enter the radius for the exterior girder in the Radius (r) field.

Defining Section Properties

You can choose to specify the cross section properties instead of the calculated values. These properties include centriodal location, area, moment of inertia, and volume-to-surface ratio. To calculate the section properties, select Auto Calculate. To enable the manual input of section properties, select User Input and then complete the following fields:

Setting	Description
CGz	Enter the center of gravity location along the z-axis.
Cgy	Enter the center of gravity location along the y-axis.
Area	Enter the area of the section.
Izz	Enter the moment of inertia of the section.
Vol/Area	Enter the volume-to-area ratio of the section.

Defining Material Properties

You can define the basic material properties that are used in analysis, calculation of loss of prestress, and capacity of the section. Click the Material button to define the material properties of the section using the Concrete Material dialog box.

Defining Cross Section Parts

Parts of the basic geometric shapes can be added or removed from the section. This capability can be used to add to the thickness of a specific interior girder, to remove the concrete at the location of utilities, or for other similar applications. Click the Parts button to add additional cross section parts using the Multi-Cell CIP Box Parts dialog box. By selecting the Parts Only option, the cross section properties will be based on the parts only and will not include the properties of the box girder section.

Defining Superstructure Width and Depth

Complete the following fields to define both the width and the depth of the superstructure, including the overhangs:

Setting	Description
Width (w )	Enter the overall width of the structure from Edge-of-Deck (EOD) to EOD. In addition to defining the size of the cross section, these fields are also used in the calculation of the Live Load Distribution Factors.
Depth (d)	Enter the overall depth of the structure from the top of the deck slab to the bottom of the soffit slab.

Defining Slab Thickness

Complete the following fields to define the thickness of both the top and bottom slabs:

Setting	Description
Top Thick (tt)	Enter the thickness of the deck (top) slab.
Bottom Thick (bt)	Enter the thickness of the soffit (bottom) slab.

Defining Interior Girders

Complete the following fields to define the number of interior girders and the web thickness to be used for all interior girders:

Setting	Description
Number	Enter the number of interior guides.
Web Thick (tw)	Enter the web thickness to be used for all interior girders.

Fillet

You can define the fillets with equal width and height to be added to the top or bottom of the girders. The size of the fillet is measured from the intersection of the face of the girder and the face of a slab as a vertical or horizontal dimension.

Complete the following fields located to define top and bottom fillet size:

Setting	Description
Top Fillet (tf):	Enter the horizontal/vertical delta for all top slab fillets.
Bottom Fillet (bf)	Enter the horizontal/vertical delta for all bottom slab fillets.

Exterior Overhangs

Perform the following steps to define the exterior overhangs for the current section. These steps must be repeated for both the left and right overhangs.

Enter the horizontal length of the overhang in the length (Len (l)) field.
Enter the interior thickness of the overhang in the interior thickness (ti) field.
Enter the exterior thickness of the overhang in the exterior thickness (te) field.

Technical Discussion

Cross section dimensions are used to calculate the properties that are used in analysis. These include location of center of gravity (CG), area, bending moment of inertia about the horizontal axis, torsional moment of inertia, and volume-to-surface ratio. Shear deformation is ignored; therefore, shear area is not calculated. The volume-to-surface ratio is calculated based on the entire section, as the ratio of the area of the cross section to the outer perimeter of the section, and affects the creep and shrinkage deformations when ACI, LRFD, or FIB model codes are selected.