Model Settings

Number of Reported Sections controls how many places along each member you receive reportedmember force, stress, torsion, and deflection results. This only affects the amount of data displayed in the results spreadsheets, and has no effect on the solution of the model or the code checks. See Printing and Member Results for more information.

Number of Internal Sections controls how many places along each member the software calculates and stores results such as deflections and code checks. The member force diagrams displayed in the model view and the detail plot are also drawn from these results. Increasing this value means that the program will make more "cuts" along the beam's length, which means it is more likely to hit the theoretical maximum and minimum values for code checks.

The Member Area Load Mesh Size is used to determine the maximum size when meshing an area load and attributing the load to members. See Area Loads to learn more about this.

Check the Consider Shear Deformation check box if shear deformation considerations are to be included in the model solution. See Member Shear Deformations for more information.

Approximate Mesh Size is the base mesh size that is used when wall panels solved. If there is a constraint smaller than this mesh size, the mesh will be refined to accommodate this constraint.

You can see the mesh size graphically on the wall panels when you solve your model.

Transfer Forces Between Intersecting Wood Walls lets you decide whether wall panels framing into each other will transfer loads. Wall panels that are parallel to and touching each other will always transfer loads.

This setting was added for times when intersecting perpendicular walls are not actually attached to each other, thus they may separate if loading conditions cause this.

Increase Wood Wall Nailing Capacity for Wind Loads automatically increases the shear capacity of wood wall and diaphragm panels by 1.4, for all load combinations that contain wind loads. Load combinations that have both wind and seismic loads acting simultaneously will not receive this increase.

Run a P-Delta Analysis for Wall Panels is used to enable P-Delta analysis for wall panels. Even if this box is checked, the P-Delta analysis will only be performed on load combinations that have P-Delta enabled.

Optimize Masonry and Wood Walls defines whether you want to automatically iterate the solution for masonry and wood walls.

Single lets you use a single core to run the model solution.

This option is useful when you have several other computer programs that are CPU intensive running in conjunction with RISA-3D.

Multiple (Optimum) lets you use half of the available cores on your computer to run the solution.

This option provides a faster solution time compared to using a single core but still allows half of your computer’s available cores to be used for other programs and computer processes.

P-Delta Convergence Tolerance is used to adjust the tolerance used to determine convergence of the P-Delta analysis. Be sure to enter this value as a percentage! The default for this is ½ of 1 percent (.5%). See P-Delta Analysis to learn more about this.

Eigensolution Convergence Tolerance is used to set how close a subsequent solution must be to the previous solution for a mode to be considered converged. See Dynamic Analysis for more information.

Gravity Acceleration is used to convert loads into masses for the purpose of a dynamic analysis.

In previous versions, the default Subgrade Modulus and Allowable Bearing were entered in the Model Settings. In version 10.0 and higher, the default subgrade modulus and allowable bearing pressure are entered in the Soil Definitions spreadsheet. There is a check box in the Soil Definitions spreadsheet to determine which soil definition will be used as the default. The default soil definition properties will be applied to the entire model except where another soil region is drawn in the model. It is not necessary to draw a soil region for the default soil definition.

Merge Tolerance is used as the maximum distance 2 nodes can be apart and still be merged together. It is also used when scanning for crossing members and for unattached joints along the spans of members.

Static Solver lets you define the solver to be used during the solution.

This setting can be selected by clicking on the Static option and then choosing Standard Skyline or Sparse Accelerated from the drop down arrow.

See Solution for more information on these two options.

Dynamics Solver lets you to choose between the Standard Solver, Accelerated Solver and Ritz Vector Solver solutions. Refer to the Solution topic for a more details.

• Standard Solver uses a simple sub-space iteration to solve for the natural frequencies.  This solver has been used for years and the accuracy of the results is very well established. It has been included only for comparative / verification purposes.
• Accelerated Solver uses an accelerated sub-space iteration with a Lanzcos starting vector. The accelerated solver is the default and should produce solution in a fraction of the time that the standard solver would take to produce them.
• Ritz Vector Solver does not solve for true mode shapes and natural frequencies. However, it is generally the best choice when running a response spectra analysis. The use of Load Dependent Ritz vectors provides a more accurate response spectra analysis for the same number of modes.

Time-History lets you choose between the Modal Superposition and Direct Integration solution methods. It also allows the user to set the damping preferences for each of these solution methods. Refer to the Solution and the Dynamic Analysis - Time History topics for more details on these settings.

The P-Delta Analysis options allow the user to choose between the Standard Nodal Shear method and Geometric Nonlinear Stiffness method. Refer to P-Delta Analysis for more details on these two methods.

Vertical Axis can be set here as well. Setting the vertical axis may require you to set the Default Member Orientation also shown. As you specify new members RISA-3D will try to orient them correctly.

The member local z-axis is typically the strong axis for a member and RISA-3D will orient members such that when you draw non-vertical members (beams) they will automatically be oriented such that loads in the vertical direction are resisted by the strong axis bending of the member. See Member Local Axes and Defining Member Orientation for more information.

Check the Convert Existing Data check box to convert the existing orientation data to the newly selected vertical global axis.

HR Steel indicates which code is to be used for the design of hot rolled steel. For more information see Hot Rolled Steel Design.

Connection indicates which code is to be used for connection design. This entry is only considered if you are also using RISAConnection. See the RISAConnection Integration topic for more information.

CF Steel indicates which steel code is to be used for the design of cold formed steel. For more information see Cold Formed Steel Design.

Wood indicates which wood code is to be used for the design of wood, including wood walls and structural composite lumber. For more information see Wood Design.

Concrete indicates which concrete code is to be used in the design of concrete members and walls. For more information see Concrete Design.

Masonry indicates which masonry code is to be used for the design of masonry walls. For more information see Masonry Design.

The Aluminumentry indicates which aluminum code is to be used in the design of aluminum. For more information see Aluminum Design.

Analysis Methodology controls which method is used to determine the biaxial column capacity. The options are the PCA Load Contour Method and the Exact Integration Method.

Parme Beta Factor is used to approximate the column’s 3D interaction surface when using the PCA Load Contour Method. See Biaxial Bending of Columns  for more information.

Compression Stress Block lets you choose what type of stress block to consider in your analysis. The options are the constant Rectangular Stress Block and the Parabolic Stress Block. See Parabolic vs. Rectangular Stress Blocks for more information.

Check the ‘Analyze using Cracked Sections’ box if you want to modify the member and wall stiffnesses by the Icr Factor as described in both the Concrete - Design and Wall Panels topics.

Check the ‘Leave room for horizontal rebar splices (2*d bar spacing)’ box, if you want to default to a two bar diameter or one inch clear spacing, whichever is greater, to allow for lap splices and continue to maintain adequate spacing between parallel bars. Otherwise a minimum spacing of one bar diameter between parallel bars will be allowed. 

Minimum % Steel for Columns lets you choose the minimum percentage of reinforcement steel to be used in a concrete column section. The percentage entered is multiplied times the gross area of the column section to determine the minimum amount of reinforcement required in each column. 

It should be noted that the minimum percentage allowed by ACI 318-14 Section 10.6.1.1 (ACI 318-11 Section 10.9.1) is 1%.

Maximum % Steel for Columns lets you choose the maximum percentage of reinforcement steel to be used in a concrete column section. The percentage entered is multiplied times the gross area of the column section to determine the maximum amount of reinforcement allowed in each column. It should be noted that the maximum percentage allowed by ACI 318-14 Section 10.6.1.1 (ACI 318-11 Section 10.9.1)1 is 8%.

Rebar Material Spec lets you choose from the standard ASTM A615 (imperial), ASTM A615M ("hard" metric, i.e. #8M is an 8mm bar), BS 4449 (British), prENV 10080 (Euro), CSA G30.18 (Canadian), IS 1786 (Indian), and AS/NZS 4671:2001 (Australian/New Zealand) reinforcement standards.

Check the ‘Warn if beam-column framing arrangement is not understood’ box to see bad framing warnings in the Warning Log.

Story No. Above Critical Section establishes the critical section location for shear force amplification consideration in special concrete walls as per ACI 318-19. More information regarding shear force amplification can be found in the Concrete Wall - Seismic Design.

(Ω) is the “Overstrength Factor”. This can be included in the seismic load combinations generated by the LC Generator.