The Global Parameters Dialog, accessed through the Options Menu, is used to define information that
influences the model and its solution in an overall (global) manner. You may save any of the information as the default setting so that when you start a new model that information is already there. To do this, simply enter the information that you want to save and click the Save as Defaults button.
Description
The entries under the Description tab are used to enter descriptive information such as a title for the particular model being defined, the name of the designer and a job number. The title may then be printed at the top of each sheet of the output, and on the graphic plot of the model. Note that for any of these tabs, you can click on Save as Defaults and then your settings will be saved the next time you open the program.
Global Parameters
Solution
The entries under the Solution tab are used to control settings that affect the general solution of the model.
Number of Sections controls how many places you receive reported beam force, stress, 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. SeePrintingandMember Resultsfor more information.
Number of Internal Sections controls how many places along each beam the software calculates and stores results such as deflections and code checks. The beam 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.
Note:
l Number of Sections cannot exceed 20. Also, Number of Internal Sections cannot be less than twice the Number of Sections. If unacceptable values are entered for either of these fields the program will auto-matically reset them to acceptable values.
The Subgrade Modulus is used to set the default Subgrade Modulus to be used wherever soil regions are not defined. If the soil on your site is uniform then you only need to set the subgrade modulus here. However, if you have regions of varying soils you can manually draw soil regions with theDraw Soil Regionstool. For additional advice on this topic, please see the RISA News website: www.risanews.com. Type in Search keywords: Varying Soil.
The Allowable Bearing is used to set the default Allowable Bearing Pressure to be used wherever soil regions are not defined. If the soil on your site is uniform then you only need to set the allowable bearing pressure here.
However, if you have regions of varying soils you can manually draw soil regions with theDraw Soil Regions tool. For additional advice on this topic, please see the RISA News website:www.risanews.com. Type in Search keywords: Varying Soil.
Note:
l This is taken as a Gross Allowable value
The Mesh Size is used to control the coarseness or fineness of the slab mesh when RISA auto-meshes slabs dur-ing solution.
The Maximum Iterations defines the maximum number of iterations the program will undergo for tension and compression springs in a model. Soil regions are always modeled as compression springs, but piles may be ten-sion springs, compresten-sion springs or both. In the first iteration the program assumes a compresten-sion spring for every support node in the model. The program then checks the forces (tension or compression) in these springs against the soil moduli or pile stiffness. Soil springs have no tension stiffness, and piles may or may not have ten-sion stiffness. If a support location sees tenten-sion, then the springs in this location are switched to tenten-sion springs of the appropriate capacity. Soil springs will have a tension stiffness of zero and piles will have a stiffness defined in the Pile Definitions spreadsheet. At this point the model is re-run for its second iteration. The model is then checked again to make sure that tension springs are in tension and compression springs are in com-pression. If so, the solution is stopped. If not, the springs are updated to the proper tension or compression des-ignation and the model is re-run again. At least 3 iterations are required to get acceptable behavior, though more may be needed in complicated loading scenarios.
The Coefficient of Friction is used in theslab slidingcheck to calculate the resisting force against sliding.
The Merge Tolerance is used as the maximum distance 2 points 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 beams.
The Solver to be used during solution may be selected by clicking the radial button next to Standard Skyline or Sparse Accelerated. SeeSolutionfor more information on these two options.
Design
The entries under the Design tab contain options related to the analysis and design of concrete beams.
The Shear Tie Options allow you to control the Number of Shear Regions that will be used when detailing a beam span. It also allows you to specify the increment that you'd like the program to use when increasing or reducing the spacing of the shear ties.
The Parme Beta Factor is used to approximate the column’s 3D interaction surface when using the PCA Load Con-tour Method.
Global Parameters
The Concrete Stress Options allow you to 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. Rec-tangular Stress Blocksfor more information.
Check the Optimize Footings for OTM/Sliding to get simple spread footings to be sized for overturning and slid-ing forces.
Checking the Minimum 1 Bar Dia Spacing box will allow a minimum spacing of one bar diameter between par-allel bars. Otherwise, RISA will 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. This option applies to beams only.
The Concrete Rebar Set allows you to choose from the standard ASTM A615 (imperial), ASTM A615M (metric), BS 4449 (British), prENV 10080 (Euro), CSA G30.18 (Canadian), and IS 1786 (Indian) reinforcement standards.
The Code drop down list allows you to choose the concrete design code that you would like to use.
l The 2011, 2008, 2005, 2002 and 1999 Editions of ACI 318
l The 2004 Edition of the Canadian code (CSA-A23.3)
l The 2004 Edition of the Mexican code (NTC-DF)
l The 2007 Edition of the Saudi Building Code (SBC 304)