Rectangular Box
 @RECTANGULAR_BOX_DEFINITION {
 @RECTANGULAR_BOX_NAME {RboxName} {
 @OPTION_DEFINITION {o_{1}, o_{2}, o_{3}}
 @DIMENSIONS {
 @DIMENSION_01 {w}
 @DIMENSION_02 {h_{L}}
 @DIMENSION_03 {t_{L}}
 @DIMENSION_04 {α_{L}}
 @DIMENSION_05 {h_{R}}
 @DIMENSION_06 {t_{R}}
 @DIMENSION_07 {α_{R}}
 @DIMENSION_08 {t_{tf}}
 @DIMENSION_09 {t_{bf}}
 @DIMENSION_10 {t_{trf}}
 @DIMENSION_11 {t_{brf}}
 @DIMENSION_12 {α}
 @DIMENSION_13 {β}
 }
 @MATERIALS {
 @MATERIAL_01 {Mat_{1}}
 }
 @IS_DEFINED_IN_FRAME {FrameName}
 @MESH_DENSITY {m_{d}}
 @COMMENTS {CommentText}
 }
 }
Notes
 ShapeBuilder can generate beam crosssections in the shape of a “rectangular box.” The base section is a closed section consisting of top and bottom flanges connected by left and right webs to form a closed rectangular box, as illustrated in fig. 1. Three options are available for this shape.
 Option 1, activated by setting o_{1} = 1, adds core material in the area defined by vertices NI–FI–EI–PI.
 Option 2, activated by setting o_{2} = 1, consists of a reinforcement located on top of the top flange.
 Option 3, activated by setting o_{3} = 1, consists of a reinforcement located the the bottom of the bottom flange.
 Optional dimensions @DIMENSION_12 and @DIMENSION_13 define two shaping parameters, denoted α and β, respectively, which are used to round the corners of the section. (Default value: α = β = 0.5).
 Sectional shapes are defined in their own local coordinate system, which is assumed to coincide with the global coordinate system. If a fixed frame, FrameName, is specified, the local coordinate system coincides with this fixed frame.
 The mesh density parameter, m_{d}, determines the level of mesh refinement. (Default: m_{d} = 4)
 It is possible to attach comments to the definition of the object; these comments have no effect on its definition.
The rectangular box: base configuration
Figure 1. Configuration of the rectangular box
 Fig.1 illustrates the base configuration of the rectangular box, which is composed of the top and bottom flanges, and the left and right webs.
 The geometric configuration of the rectangular box if defined by the dimensions listed in table 1, which are also indicated in figs. 1, 2, and 3. Dimensions labeled in red are required. Dimensions labeled in blue are optional and are assigned the default value indicated in table 1.
Component  Dimension  Symbol  Default  Nb. 
Rectangular box  width  w  required  01 
LeftWeb  height  h_{L}  required  02 
LeftWeb  thickness  t_{L}  required  03 
LeftWeb  skew angle  α_{L}  90°  04 
RightWeb  height  h_{R}  h_{L}  05 
RightWeb  thickness  t_{R}  t_{L}  06 
RightWeb  skew angle  α_{R}  90°  07 
FlangeTop  thickness  t_{tf}  t_{L}  08 
FlangeBot  thickness  t_{bf}  t_{L}  09 
FlangeTopReinf  thickness reinforcement  t_{trf}  t_{L}  10 
FlangeBotReinf  thickness reinforcement  t_{brf}  t_{L}  11 
Table 1. Dimensions defining the geometry of the rectangular box

Zone 1 of the rectangular box is defined as follows.
 It comprises the following faces: TopFlangeLeft, TopFlange, TopFlangeRight, RightWebTop, RightWeb, RightWebBot, BotFlangeRight, BotFlange, BotFlangeLeft, LeftWebBot, LeftWeb, and LeftWebTop.
 It is associated with material Mat_{1} , which can refer to material properties or solid properties.
Figure 2. Configuration of the left portion rectangular box Figure 3. Configuration of the right portion rectangular box
The rectangular box: external edges
For the rectangular box, the following external edges are defined.
 TopFlangeOuter. This external edge comprises the outer side of the top flange along the line joining vertices MO–NO–PO–AO, see fig. 1.
 BotFlangeOuter. This external edge comprises the outer side of the bottom flange along the line joining vertices GO–FO–EO–DO, see fig. 1.