Requires: Design Level
VisualAnalysis designs aluminum members according to the Aluminum Design Manual (ADM) produced by the Aluminum Association. Design checks per chapters A, B, D, E, F, G & H are provided for standard sections (found in Part V of the ADM 2010) and Parametric shapes (rectangular, solid round, plates, etc.) are supported. Checks are performed according to either of the following specifications:
- ADM ASD 2010
- ADM LRFD 2010
Please note that you must use appropriate load combinations (Strength for LRFD, Allowable for ASD) to obtain design checks.
Aluminum Design Quick Links
- Aluminum Assumptions and Limitations
- Aluminum Capabilities
- Aluminum Parameters
- Aluminum Report Options
- Aluminum Report Organization
- Aluminum Report Notation
- Aluminum Report Notes and Warnings
- Aluminum References
Aluminum Assumptions and Limitations
All forces and moments are assumed to act about the principal axes of a member's cross-section. Similarly, shear loads are assumed to pass through the shear center so that no torsional moments will be present in the results. Axial loads are assumed to pass through the centroid of a member so that no moments are present in a first order analysis of an axially loaded member. Because of these assumptions that are made in the software, it is up to you to watch for and check any second-order effects or other conditions that violate assumptions made in the analysis or design.
Span Length Assumptions
VisualAnalysis looks at member-elements to determine the span length which in turn affects unbraced length. For members designed according to the ADM specifications, this might also effect the determination of Cb. If your member span is longer than the element span, you may want to use the Combined Member feature in VisualAnalysis to help make the design software smarter. Alternately, you can specify an unbraced length directly and also override the calculated values for Cb.
There is no support for tapered members. All members will be checked and designed as prismatic.
VisualAnalysis will not design or check built-up shapes (channels on wide flanges) or shapes that do not fall into the normal ADM profile categories (I, C, Z, L, etc.). Custom extrusions or other complex shapes are not supported. There are also limits on member dimensions: deep beams (plate girders) are not checked for example.
Deflection checks are made using the gross-section of the shape, no reduction is taken for effective widths according to ADM L.3.
ADM 2010 Code Notes/Limitations
- Stability requirements of Chapter C are not implemented.
- The entire cross section of members specified as "Heat Affected" (welded) is assumed to be affected. Reduced stress values are used for all limit states.
- G.2 is assumed to provide Fs for one edge supported shear (weak axis in most cases) as well as both edges supported. B is assumed to be clear distance from face of web to tip of flange.
- Solid shapes are assumed to have Fs = Fsy. Mechanics equations 3V/2A, 4V/3A are used for stress calculations.
- Pipe Shape shear strength is based on Equation G.3-2 with the Lv parameter taken as the entire member length. This is conservative.
- B.5.4.1 Local Buckling strength for singly symmetric sections is based on elastic buckling strength. The allowed increase for Post buckling of singly symmetric sections buckling globally about the strong axis is not utilized.
- Code provisions for Torsional and Flexural-Torsional Buckling (E.3.2) are applied to all shapes because no exceptions are made. This leads to smaller capacities than if this provision is omitted such as in ADM2010 Part VII-18 Example 9 ( I-Beam in Axial Compression ).
- The provisions of ADM2010 F.8 are implemented using the weighted average flexural strength per section F.8.3.
- F.2.1 For doubly symmetric sections, rye = ry as allowed in section F.2.1. Per ADM 2010, page II-25: “Section F.2.1 gives very conservative results for certain conditions, namely for values of Lb/ry exceeding about 50, and for beams with transverse loads applied in a direction away from the beam’s shear center.”
- Single angles are always assumed to be bent about principal axes. Local buckling checks are made per F.5. a) (1). Local buckling checks per F.5.a) (2) (the case of an angle leg in uniform compression bent about the geometric axes) is not covered.
- A conservative view of chapter H section 3 is taken: we assume that the maximum flexural shear stress, normal bending stress, and torsional shear stress all occur at the same point on the cross section and that these can all be superimposed with the axial stress. They are combined per interaction equations H.3-1 thru H.3-4.
- Torsion is checked per chapter H.2 and H.3. These checks are limited to closed shapes and solid rods (round sections). These shapes are not subject to warping stresses. Open shapes are not checked for torsional capacity as no code provisions exist. Open shapes are subject to warping stresses due to torsion. Open shapes must be checked independently for torsional capacity and potential warping stresses.
VisualAnalysis was created to check and design ADM standard shapes in the IES Shape Database. Any shape (or shape category) in the shape database that supports one of the 'property sets' required by Aluminum design can be checked by this software as well. In addition to the database shapes, VisualAnalysis will design the Standard parametric shapes created directly in VisualAnalysis . These include: rectangles, squares, rectangular tubes, I-beams, channels, tees, single angles, zees, round, pipe sections. Spandrels are not supported, but the equivalent section can be created with a single angle.
VisualAnalysis looks at axial force, shear, flexure and deflections. Checks are automatically made whenever a force is present in the results. Where appropriate, both the strong and weak axes of the member are checked in addition to any interaction requirements. A St. Venant torsional shear stress is calculated from the torsional moment and added to the shear stress calculated in VisualAnalysis. No provision is made for warping stresses of any kind, which means that cross sections that are not "closed shapes" are not fully checked if torsion is present. The maximum torsional moment is reported at the bottom of the design report to help you remember this and to check for other torsional stresses that may be present.
Note: All of the parameters described below are edited/selected on the Modify Tab of the Project Manager while in the Design View.
Specification: Choose between ASD and LRFD code provisions.
Structure Type: Choose between Building and Bridge type structures (affects resistance and safety factors (Φ and Ω).
Member Type: Selects general member type, changing the selection of user input parameters. By default, these are set based on member orientation in the model (i.e. Beam-horizontal, Column-Vertical)
Overstrength: Designs member for higher seismic forces based on user specified Overstrength factors and IBC Seismic Design Category.
Shape Category: Chooses shape category from which the VisualAnalysis "Design" feature selects shapes to optimize design.
Disable Checks: Prevents design checks from being performed on the selected design group. Allows you to speed up design checks and focus on targeted areas of larger models.
Heat Affected: Specifies that a member is Heat or Weld affected. Entire member is assumed to be affected. Design checks are performed with Ftyw, Ftuw, Fcyw, Fsuw stress values. You can avoid being overly conservative for member design by splitting members and specifying "Heat Affected" only where appropriate.
Member Bracing - By default, member unbraced length is the equal to the member length between nodes. See Bracing in VisualAnalysis for a complete description of bracing member elements for design checks.
Deflection criteria are only available when a Member Type is specified as "Beam" or "Other". Deflections maybe specified in a variety of ways. Specified Deflections criteria does affect unity checks. You must also include "deflection" load combinations in the Load Case Manager to obtain deflection checks. More information is available on the Design Concepts..
Axial / Column
Specify parameters for effective lengths. See the common Design Parameters.
Specify size limits on member shapes. See the common Design Parameters.
Overrides Require: Advanced Level
Fty, Ftu, Fcy, Fsu: This option allows you to ADM stress parameters used for unity checks and design. The value of Fsy will be affected by Fty. These overrides only affect design if the 'Heat Affected? check box is not selected (i.e. no part of the member is Welded).
Ftyw, Ftuw, Fcyw, Fsuw: This option allows you to ADM stress parameters for weld affected sections used for unity checks and design. The value of Fsyw will be affected by Ftyw. These overrides only affect design if the 'Heat Affected? check box is selected.
Cb: This option allows you to override the ADM bending coefficient.
Aluminum Report Options
The Aluminum design report includes a number of optional components. You may control what information is included by double-clicking on the report after it is generated. By default the report echoes the design parameters and shows only the controlling checks for each member and load case.
Aluminum Report Organization
Reports have two primary parts: Input Parameters and Checks. The parameter section presents the information you entered in the parameters dialog. It is grouped and formatted for easy reading. If the group has a valid design shape, there will be some additional information about that shape attached to the end of the parameter section. (If the group does not have a valid design each member might be a different shape, so details about the shape are not reported.)
Checks are organized in the form of tables. The layout of columns in a typical report table is as follows:
|Member Name||The member's name as in VisualAnalysis.|
|Member Section||Only in member reports, the cross section (e.g. W8x10).|
|Load Case #||Load cases are listed by number in design reports. The numbers are keyed to the table included at the top of the design report. Refer to the table under "Design Group Results" or "Design Member Results". Forces and stresses are obtained from strength load cases while deflection checks utilize the service case numbers. A load case may have both a strength number AND a serviceability number, that may differ.|
|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|
|Actual Forces, Stresses, Intermediate Calculations||These values can be traced back directly to analysis results.|
|Allowable Stresses, Nominal Forces||These columns vary depending on the type of check, but they represent code stipulated values. In most cases these are used directly in the unity check, but there are some special cases where the unity checks also include intermediate values, or values not reported.|
|Code Reference||The controlling equations or provisions from the specification. For example, "F1-8" refers to this equation number in the ASD or LRFD manual. A code reference like "AE3-3" refers to equation (A-E3-3) in Appendix E of the manual. Sometimes there are additional references given, like ", AB5-6" to indicate a reduction for slender compression elements (Q < 1).|
|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 force (factored) divided by [F x (the nominal force)] [LRFD].|
Aluminum Report Notation
The Aluminum reports attempt to use a notation similar to that used in the ASD and LRFD specifications. We have not used subscripts however, so a parameter that appears as Lr in the specification will appear as simply Lr in a VisualAnalysis report. The other major difference in notation is the use of section axes coordinates z and y in place of the ADM coordinates x and y.
Accordingly: fa, fb, fv are actual axial, bending and shear stresses, respectively. Similarly, Fa, Fb, Fv represent allowable axial, bending and shear stresses, respectively. P is an axial force, M is a moment and V is a shear.
Greek characters are used in the LRFD reports, using the Symbol font installed on most Windows systems. Where this is not possible (dialog boxes and other on-screen controls), the Greek characters are spelled out: phi, lambda, etc.
Aluminum Report Notes and Warnings
By default, a given check table will only display the worst-case unity check for a given member and load case. You may view the complete set of checks by clicking on the table and choosing Table Properties from the context menu. Then make adjustments in the dialog.
In some cases there will be notes and or warnings displayed either in a check table or at the bottom of the report. These are designed to be self-explanatory.
VisualAnalysis was written to conform to the following specifications:
Specification for Aluminum Structures, 2010 Aluminum Design Manual (ADM). The Aluminum Association, ISBN 978-0-9826308-0-8
Aluminum Structures, Second Edition, J.R. Kissel & R.L.Ferry, John Wiley & Sons, Inc.2002