Pipe diameters, invert elevations, node structures, and inlets can be all designed with the same set of design constraints. You also have the option to adjust these values individually for each pipe or structure.

The Default Design Constraints dialog is divided into the three following tabs:

• Gravity Pipe
• Node
• Inlet

Gravity Pipe Tab

The Gravity Pipe tab allows you to enter default constraints to be used for the design of pipes when performing a calculation run in design mode. The dialog is divided into the following sections:

• Default Constraints
• Extended Design

Default Constraints Section

In this section, there is a Velocity tab, a Cover tab, a Slope tab, and a Tractive Stress tab. You can specify the following default constraints to be used for the design of gravity pipes:

• Velocity Tab: The Velocity tab consists of the following controls:
  • Velocity Constraints Type–When Simple is chosen, a single minimum and maximum Velocity value is selected. When Table is chosen, you can specify multiple Rise vs Velocity (Minimum) vs Velocity (Maximum) points in tabular format.
  • Velocity (Minimum)–Specify the minimum allowable velocity value. This control is only available when the Velocity Constraint Type is set to Simple.
  • Velocity (Maximum)–Specify the maximum allowable velocity value. This control is only available when the Velocity Constraint Type is set to Simple.
• Cover Tab: The Cover tab consists of the following controls:
  • Consider Cover Along Pipe Length?: When this box is checked, cover along the pipe length is considered, by checking against the active terrain model. This ensures that any undulations in the surface between the ends of the pipe are taken into account when the elevations of the pipe are calculated. If this box is unchecked, then the cover is only considered at the start and end of the pipe, using the ground elevations of the start and end nodes.
  • Active Terrain Model: Read-only field telling you what the active terrain model is, which has been specified in View > Terrain Models.
  • Measure Cover To: Choose whether cover is measured to the pipe soffit or crown.
  • Cover Constraints Type–When Simple is chosen, a single minimum and maximum Cover value is selected. When Table is chosen, you can specify multiple Rise vs Cover (Minimum) vs Cover (Maximum) points in tabular format.
  • Cover (Minimum)–Specify the minimum allowable cover value. This control is only available when the Cover Constraint Type is set to Simple.
  • Cover (Maximum)–Specify the maximum allowable cover value. This control is only available when the Cover Constraint Type is set to Simple.
• Slope Tab: The Slope tab consists of the following controls:
  • Slope Constraints Type–When Simple is chosen, a single minimum and maximum Slope value is selected. When Table is chosen, you can specify multiple Rise vs Slope (Minimum) vs Slope (Maximum) points in tabular format.
  • Slope (Minimum)–Specify the minimum allowable slope value. This control is only available when the Slope Constraint Type is set to Simple.
  • Slope (Maximum)–Specify the maximum allowable slope value. This control is only available when the Slope Constraint Type is set to Simple.
• Tractive Stress Tab: The Tractive stress tab consists of the following controls:
  • Include tractive stress design – this check box specifies if the design includes tractive stress or not.
  • • Tractive Stress (Design Minimum) -- the minimum tractive stress in the conduit for the flow that the designer tries to achieve during the design process (note: the maximum cover and maximum velocity are of more priority than tractive stress if there are conflicts).

Extended Design Section

This section lets you specify if the following design parameters are to be used. If they are to be used, you can also specify the associated default value. The Extended Design section is split into three tabs:

• Part Full Design Tab: The Part Full Design tab consists of the following controls:
  • Is Part Full Design?–When checked, allows you to specify the Percent Full target to be used by the design algorithm.
  • Percent Full Constraint Type–Allows you to specify how the Percent Full constraints are defined. When Simple is chosen, a single Percentage Full value is selected. When Table is chosen, you can specify multiple Rise vs Percent Full points in tabular format.
  • Percentage Full–Specify the Percent Full value to be used when the Is Part Full Design? box is checked. This control is only availble when the Percent Full Constraint Type is set to Simple.
• Number of Barrels Tab: The Number of Barrels tab consists of the following controls:
  • Allow Multiple Barrels?–When checked, allows the design algorithm to use more than one identical section in parallel, up to the specified Maximum Number of Barrels.
  • Maximum Number of Barrels–The maximum number of identical sections allowed to be used in parallel when the Allow Multiple Barrels? box is checked.
• Section Size Tab: The Section Size tab consists of the following controls:
  • Limit Section Size?–When checked, limits the pipe section height to the specified Maximum Rise value during the design process. There may be situations in design where it is desired to limit the size of the designed pipe. This may be done to avoid conflicts with obstructions or other utilities, for example. For these situations, The program enables you to limit the maximum section rise that will be selected. A smaller size will be used if possible. If none of the available design sections have a small enough rise, the smallest one will be used.
  • Maximum Rise–The maximum rise a section height is allowed to be used in the design when the Limit Section Size? box is checked.

Node Tab

This tab lets you specify the design constraints to be used by default for all gravity structures when performing calculations in design mode. During a constraint based design, the program will adjust the elevations of the pipes adjacent to the structure according to the structure's matching constraints. The two choices for matching are Inverts and Crowns. Additionally, the downstream pipe can be offset from the upstream pipe(s) by a specified amount. This value is called the Matchline Offset. Optionally, the program supports the design of drop structures. In some situations, drop structures can minimize pipe cover depths while maintaining adequate hydraulic performance.

Inlet Tab

This tab lets you specify the design constraints to be used for all inlets when performing a calculation run in design mode. During a constraint based design, the program will adjust the length of the inlet in order to meet the design constraints.

• For an inlet in sag, the Default In Sag Design Constraints consist of maintaining the gutter spread and water depth under a given value.
• For an inlet on a grade, the Default on Grade Design Constraints consist of ensuring that at least a given percentage of the gutter flow is intercepted.

Default In Sag Design Constraints Section

This section lets you specify the design constraints to be used for all inlets located in sag when performing calculations in design mode. During a constraint based design, the program will adjust the length of the inlet in order to meet both design constraints:

• Maximum Spread in Sag–The maximum allowed spread of water at the inlet, measured from the curb.
• Maximum Gutter Depth in Sag–The maximum depth of water allowed at the inlet.

Default On Grade Design Constraints

This section lets you specify the design constraints to be used for all inlets located on a grade when performing a calculation run in design mode. During a constraint based design, the program will adjust the length of the inlet in order to meet a minimum inlet efficiency, or percentage of gutter flow intercepted by the inlet, that you specify in the minimum Efficiency on Grade field.