Requires: Advanced Level

Introduction

VisualAnalysis can design generic members (composed of any shape and any material) according to user specified stress and deflection limits. Generic members are designed for axial load, bending (strong axis and week axis), combined axial and bending, and torsion. The maximum unity value (demand to capacity ratio) for the member is shown in both the Design View and in the Report View, allowing the user to quickly identify if the member is passing (unity ≤ Unity Success Limit) or failing (unity > Unity Success Limit). In addition to checking the stress levels for generic members, VisualAnalysis can check the deflection limits for the members based on the deflection limits set by the user and the Deflection Check load combinations. The shapes for generic members can be manually adjusted in the Project Manager | Modify tab until a satisfactory design is reached or VisualAnalysis can automatically optimize the shape for the Design Group using the Design the Group button in the Design Ribbon. The Generic member design feature is intended to perform preliminary design checks for members that fall outside of the other design types (Concrete, Steel, Wood, etc.) and is not intended to be a comprehensive design tool.

Auto-Stress Groups

VisualAnalysis can automatically create stress-check Design Groups for ungrouped members such as members with custom shapes, tapered members, or members with materials that are not supported by the other design checks. Enable the Auto-Stress Checks feature in the Project Manager | Modify tab when modify is set to Project Settings.

Generic Design Parameters

Several parameters must be defined to design generic members in VisualAnalysis. The design parameters are set in the Project Manager | Modify tab when the Design View is selected. After creating a Design Group, choose one of the members that belongs to the group in the Design View to set up the Design Group's Parameters. Since the design parameters apply to all members in the Design Group, it is often best to choose the most conservative condition that applies to any member in the group.

Generic	Specification Level - The type of load combinations to be used for design checks, service (ASD) or strength (LRFD). Overstrength? - Causes the Design Group to be designed using overstrength load combinations. Live Load Reduction - If specified, design checks will only consider result cases with the matching live load reduction. Combinations with live load reduction can be created in the Load Case Manger. Disable Checks? - Causes selected Design Group to be omitted from design checks. This feature can be used to speed up design checks and focus on targeted areas of larger models. Check Level - Determines the level of detail reported from design checks. Options are: To Failure (Fastest), Each Limit State, and All (Slowest, but provides the most information).
Axial Strong Bending Weak Bending Axial + Bending	Perform Check - Should checks be performed for this limit state? Tension Limit - The tension stress limit to use for the design checks. Compression Limit - The compression stress limit to use for the design checks.
Torsion	Perform Check - Should checks be performed for this limit state? Limit - The torsion limit to use for the design checks.
Deflections	Strong (dy) - Specify the type of limit for beam deflections in the y-direction. Use Total to include the displacements of the nodes at each end of the element. Weak (dz) - Specify the type of limit for beam deflections in the z-direction. Use Total to include the displacements of the nodes at each end of the element.
Size Constraints	Limit Depth/Width? - Allows the design search to 'Fail' if the shape is outside the Min/Max range.

Generic Member Design Process

To achieve an adequate design, the section for the members in a Design Group can be manually adjusted until all the design checks pass. Alternatively, the built in optimization feature in VisualAnalysis can be used to find an adequate shape for the members in a Design Group. The optimization feature can be used to search for adequate Database Shapes or to iterate through the parameters of a Standard Parametric shape until an acceptable shape is found.

1. Create the Members

In the Model View draw or create the members.

2. Support and Load the Members

Define support conditions for the model and apply the service level loads to the members. Set the load combinations in the Load Case Manager.

3. Specify the Parameters

Select a preliminary Database Shape or Standard Parametric Shape and set the material properties.

4. Analysis and Preliminary Design

VisualAnalysis will automatically analyze the model and perform the appropriate design checks. Simply click on the Results View tab to view the analysis results for the model or the Design View tab to see the design results.

5. Create/Modify Design Groups

VisualAnalysis will automatically create groups for generic members if the Auto-Stress Checks feature is enabled in the Project Manager | Modify tab. Alternatively, Design Groups can be created or modified manually as explained in the Groups Category.

6. Define the Parameters

For each Design Group, set the generic parameters (design specification, overstrength, etc.) in the in the Project Manager | Modify tab in the Design View. Also, adjust the stress limits, deflections, size constraints, for the Design Group as needed.

8. Design the Group

After selecting a Generic Design Group, click the Design the Group button in the Design ribbon. In the Design Selection dialog box, choose the search type (Database or Parametric) and set the number of shapes to be returned from the optimization. For a database search, choose which database is to be searched and the category of shapes that are to be searched within the database. Also, set the size constraints if needed. For a Parametric search, select the parametric type (I-shape, Angle, Channel, etc.) and specify the search range (Start and End) and the Increment for each parameter of the shape or choose to hold the parameter constant. Once the search parameters are set, click the Optimize Now button to search for various sections and display the unit value for each shape. If a warning stating "demands could not be satisfied" appears, then all the shapes within the search parameters have a unity value larger than the Unity Success Limit defined in the Preferences. Enabling the Return all Shapes feature will provide information on every considered section which may be useful for determining why a section failed or was not optimal.

9. Select a Section

Once the optimization is complete, select a section from the list and click the Accept Design button. Now the unity value for all members in the Design Group are displayed using the selected section. The tilde symbol (~) in front of the unity value indicates that the unity checks must be validated with another analysis since the member stiffness and resulting load distribution may have changed.

10. Synchronize Design Changes

Click the Synchronize Design button in the Design ribbon to automatically update the model with the new cross-section, re-analysis the model with the new member stiffness, and rerun the design checks with the updated analysis results.

11. Verify Unity Ratios

The final step in the design process is to verify that Unity Ratios in the Design View are less than the Unity Success Limit defined in the Preferences. If member sizes were drastically changed during the design process, final unity ratios can differ from predicted unity ratios because the analysis results may vary significantly.

Generic Design Reports

The generic design reports in VisualAnalysis are highly customizable. To control what is included in a report, simply click on a table in the report and adjust the settings in the Project Manager | Selected Table tab. The Extreme Rows feature is particularly useful to produce concise reports of only the controlling cases or to produce detailed reports that display every design check that is made. When this feature is set to Show All, the reports may become excessively large which can be controlled by adjusting the Conciseness feature. The reports for general design include both a summary of the parameters input for the Design Group and tables that included the various design checks. These tables have the following columns:

Column Name	Description
Member	The member's name.
Section	The member's cross-section (e.g. Angle 6x4x0.25).
Offset	This is the distance from the 'start' end of the member. The number and locations of offsets are as defined in the performance settings in VisualAnalysis.
Result Case	The result case that is used for the design check.
Demand/Capacity	These columns varies depending on the type of design check (axial, flexure, combined, etc.).
Code Reference	Since Generic Design do not reference an actual design specification, this column displays the limit that is checked (e.g. axial compression, axial tension, bending compression, etc.)
Unity Check	The unity check value for this particular member, load case, and offset. Unity checks are calculated as the absolute value of an actual stress divided by an allowable stress [ASD] or as the ultimate stress (factored) divided by the design stress (factored) [LRFD].
Details	Intermediate values and other information which can be helpful for validating results.

Generic Assumptions and Limitations

• Sign Convention - Tensile stress is positive (+) while compressive stress is negative (-).
• Axial Stress - The axial force (P) is applied at the centroid of the cross section. Therefore, the axial stress (fa) is the axial force (P) divided by the area (A).
• Bending Stress - The bending stresses (fbz and fby) are calculated and reported with respect to the local z-axis and y-axis, which are the principal axes for the cross-section. The bending stress (fb) is calculated as the moment (M) divided by the section modulus to the extreme fiber (S) .
• Combined Axial and Bending Stress - Axial and bending stresses at the extreme fibers are combined with a simple algebraic sum.
• Shear Stress-  Shear stress limits are not considered for the members in Generic Design Groups.
• Torsion Forces - The maximum torsion in each member is checked against the specified torsion limit. Torsion stresses are not calculated for members in the Generic Design Group.