ADA Booklet2.pdf

Advance Design America (VisualDesign) TUTORIAL 2

3D-Building Modeling & Static Analysis

May 2008

© CivilDesign Inc 1995-2008

M O D E L I N G O F A 3 D B U I L D I N G

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A two-storied steel building will be modeled with the Building Generator tool. The lateral resisting system is composed of X-bracings and rigid frames. Next, a linear and non-linear static analysis (P-delta effects) will be performed and results will be compared.

• Click the New Project icon on the Standard toolbar.

Project Configuration • Select the Project Configuration dialog box in the File menu. Enter

general information about the project on the General tab. Select the Analysis tab and select the "Linear" option in the "Type of static analysis" section. Click OK.

Building Generator

• Click the Building Generator icon on the Tools toolbar or select Structure /Tools/ Building Generator. The following dialog box appears on the screen. Enter the following parameters on the Geometry tab:

As indicated in the dialog box, members are generated above support level and two-way floors are modeled as horizontal surfaces. Supports are fixed. No exterior sheathing is selected because wind loads are directly applied to columns instead of using vertical surfaces with pressure loads.

Modeling a 3D-Building

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• Select the X-Axis tab. The building has two bays of 6 meters each in the x direction.

• Select the row 1 header and insert two rows with the [Insert] key. Click the "Delta" column title and right click to open the context menu. Select the Replace function and enter "6".

• Select the Y-Axis tab. The building has two stories of 4 meters high centre-

to-centre of beams.

• Select the row 1 header and insert two rows. Use the Replace function and enter "4".

• Select the Z-Axis tab. The building has two bays of 7 meters each in the z direction. Do as explained above.

• Select the Mat / Sec tab. Select preliminary steel shapes and grades for columns and beams.

• Click the "Preview" button to view the structure. Click the OK button to

generate the structure.

• Press the [Pg Up] key to get an isometric view of the structure or select the Camera function in the View menu. Select the 45 degrees view option. Click OK.


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Translucent Surfaces Select the Graphic tab of the View Options dialog box (View menu) and select the "Translucent surfaces" option for all elements.

• Save the project: Select the Save as function in the File menu. Select a directory and give a name to the .vd1 file.

Member End Conditions

• Select the Member icon on the Elements toolbar.

Columns

• Select Edit/ Select /Columns. Click the Properties icon to open the Member Characteristics dialog box:

• Specify column end conditions as "Fixed-Fixed" for Mx and My bending. • Click OK.


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Beams

• Select Edit /Select / Beams. Click the Properties icon.

• Specify the beam Hinged-Hinged (o-------o) end conditions for Mx and My bending.

• Click OK. Displaying Member End Conditions • Select the Attributes tab of the View Options dialog box and select the

End Conditions option.


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Adding Bracings • Display the node numbers through the Elements tab of View Options

dialog box . Check the "Number" option in the "Node" section.

• Select the Project Configuration dialog box in the File menu. On the Preferences tab, disable the display of dialog box when adding elements for a faster editing at section Dialog Box Display. Bracing properties will be defined at the end of modeling.

• Select the Member icon on the Elements toolbar and click the Add

mode icon.

• Click the node cA2 and then, node cB1. Do the same for nodes cB2 and cA1, cA1 and cB0, cB1 and cA0. To exit the Add mode, click the

Restricted window or Extended window .

Bracing Properties • While pressing the [Ctrl] key, select the bracings and click the Properties

icon to open the Member Characteristics dialog box:


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• Click the I-Beam icon to open the Shape selection tree. Expand the Steel root, the L branch and select the L102x102x13 shape.

• Select the 350G/W/WT/AT steel grade and select Hinged-Hinged end conditions for Mx and My bending.

Pin Connections Note The bracing end conditions must be defined BEFORE creating the pin connection. Otherwise, a hinge will be generated at the centre of the X-bracings, creating instability in the structural model. A warning message is displayed at the beginning of he analysis, telling that a null pivot has been found in the stiffness matrix (Null pivot in the stiffness matrix = mechanism).

• Select two crossing members and click the Pin Connection icon on the Split toolbar.

• The following dialog box appears on screen. Loads are not applied to bracings so click the OK button.


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• Do the same for other bracing.

Bracings are now created in the z direction.

• Repeat the procedure to model bracings in the z direction, on axis 1, between axes A and B.

Translation nodes (Pin Connection) When a pin connection is modeled, Advance Design America adds a translation node to the split node located at the junction of crossing members. The translation node is linked to the central node through a rigid link. To view the master nodes and slave nodes, select the Nodes spreadsheet in the Structure menu.

Modeling Rigid Frames Rigid frames are modeled on axes A, B, 2 and 3.

• Select the beams located on axes A, B, 2, and 3 and click the Properties icon. Modify the Mx and My bending end conditions to fixed-fixed on the Member tab of the Member Characteristics dialog box. Press OK.

The model is now completed.


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Loads Load Cases Load case titles and types must be defined in the Loads Definition spreadsheet. An additional dead load case and a live load case are applied to floors and beams, and a wind load case is applied to columns.

• Select Loads/ Load Cases /Definition and insert three rows in the Loads Definition spreadsheet. (The first row, the structure dead load, is automatically created and correspond to the element self-weight (based on the selected materials) and is not editable).

• Give a name to load cases and double click the "Type" column to select the load case types, in accordance with the building code you want to use.


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• Select the Dead tab. By default, the "Dead" load case is used for

calculating the element self weight. This tab allows differentiating dead load cases when a project includes construction stages.

• Select the Live tab. A live load reduction is applied to floors: Double

click the Tributary Area Reduction column and select the appropriate formula (See CNB – 1995 or 2005) in the drop-down list. Enter 2.4kPa as floor overload, in the Tributary Area Overload column.

Note The value entered in the "Overload" column is used to calculate the live load reduction on columns. (Reduction is also applied to beams) This overload input DOES NOT replace the step that consists in applying loads graphically on the structure as you will see further on.

• Click OK to save data.


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Applying Loads Additional Dead Load on Floors • Select the Load Case mode on the Activate toolbar. Click the arrow to

open the Title Selection drop-down list and select the "Add dead" load case title.

• Select the floor icon on the Elements toolbar.

• With the cursor, draw a window around the whole structure to select all the

floors. Click the Properties icon to open the Load on Floors dialog box.

• Insert a row on the Distributed tab.. The floor dead weight is a distributed load of 1.5 kPa. Double click in the Wi cell and enter -1.5 as global projection. You will notice that the same load is automatically entered in other cells.

Note: Wi, Wj, Wk and Wl represent the pressure load applied at each corner of the floor, according to the floor local axis, as shown on the figure:


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• Click OK to save data. Loads are displayed on the screen if the floor

"Outline" option is selected on the Elements tab of the View Options dialog box.

Live Loads on Floors • Select the "Live" load case on the Activate toolbar drop-down list. (The

floor icon is still active on the Elements toolbar).

• With the cursor, draw a window around the whole structure to select all the

floors. Click the Properties icon to open the Load on Floor dialog box.

• On the Distributed tab, select row 1 header and insert a row. The floor live load is 2.4 kPa. Double click in the Wi cell and enter –2.4 for a global projection. Click in the Wj cell.

• Click OK.

Renumbering Nodes The building generator puts prefixes and suffixes to generated element numbers. To simplify the model, members are renumbered. To do so, select the Structure mode and open the Members spreadsheet (Structure / Members).

• Select the Number column header and right click to open the context menu. Select the Auto numbering function. Keep the default setting. Click OK.



Wind Loads on Columns Distributed loads on vertical members are applied on the strong or weak axis. Before applying wind loads to columns, make sure that columns are well oriented in space (beta angle):

• Select the Attributes tab of the View Options dialog box and select the "Local Axis System" option in the "Members" section. Then, select the Elements tab and select the "Numbers" option in the "Members" section.

• Select the Member icon of the Elements toolbar. If required, adjust

the font size by clicking the icon on the View toolbar.

Trapezoidal wind loads are applied to columns #36, 39, 42, 27, 30 & 33 in the negative direction of the global x-axis.

• Select the 3D Display option in the "Members" section on the Attributes tab of the View Options dialog box.



Columns are not well oriented. Beta angles must be modified to 90 degrees.

• Select Edit / Select / Columns and click the Properties icon. Enter 90 in the "Beta angle" field and click OK.

The following wind loads are acting on columns:

Member Local Axis and Incidence Nodes



The member local z-axis is always pointing towards node j. Therefore, we can see the member incidence (position of nodes i and j). It is useful when applying loads on columns.

We can see that wind loads must be applied in the positive direction of the member local y-axis and projected at 90 degrees on the local x-axis:

• Select the Load Case mode and select the "Wind" load case on Activate toolbar.

• Select the Member icon on the Elements toolbar.

• Press the [Ctrl] key while selecting members #36 and #42 and click the

Properties icon.

• Insert a row on the Distributed tab of the Loads on Member dialog box and enter the magnitude of trapezoidal load Wa (node i) and Wb (node j). Wind load is projected on the member strong axis, at an angle of 90 degrees.

• Click OK.

• Do the same for members #27 and #33. Enter a trapezoidal load of 0 kN/m at node i (Wa) and 9 kN/m at node j (Wb).

• Select members #39 and #30 and use the shortcut key [Ctrl] + H to open the default spreadsheet. Enter the following loads on the continuous column. Click OK.

All loads are defined and applied to the structure.



At least one load combination is required to perform an analysis. Load combinations are generated with the Load Combination Generator.

Generating Load Combinations • Select Loads / Load Combinations / Generator. The General Options

page is displayed on the screen. Select the NBC-05 building code in the "Code" drop-down list and select the generation of envelopes option.

• Click the "Next" button to access the Specific Options page. Select

ultimate and deflection load combinations. Select the "Live (L)" and "Wind (W)" load cases for deflection load combinations.



• Click the "Next" button to access the Selections page. This page supplies

the load combinations that Advance Design America is planning to generate.



You can remove load combinations by deselecting them before the generation.

• Click the "Finish" button to generate load combinations.

The Load Combinations spreadsheet appears on the screen.

To temporarily disable a load combination for a particular analysis, double click in the "Required" cell. To reactivate it, double click again.

Generated Envelopes Envelopes have been generated and can be viewed in the Envelopes dialog box (Loads / Envelopes.

• Click OK.

You are now ready to perform a linear static analysis.



Static Analysis

• Click the Analysis icon on the Tools toolbar or select the Static Analysis command in the Analysis menu.

The Linear Static Analysis dialog box appears on the screen.

• Click the "Analyze" button in the Static Analysis dialog box. When analysis is completed, close the dialog box.

The "Load Combination" mode is automatically active when the analysis is done and the Title Selection drop-down list box is open. You can select a load combination title on Activate toolbar, or press the [Esc] key to open the result Summary in the Results / Load Combinations menu.

Summary for Analyzed Load Combinations We recommend consulting this spreadsheet when the analysis is completed. The spreadsheets include information about the maximum node displacements and rotations, for each load combination. The obtained precision and number of iterations are supplied for a non-linear static analysis and design.

Results are not valid if a load combination has not converged. Check the maximum node displacements and rotations. It can be a hint when the model is unstable. Too many hinges could be present, so display the member end conditions and look carefully.

If the model seems to be adequate but convergence is still not reached, select the Analysis tab of the Project Configuration and increase the number of iterations. Be careful if you increase the convergence parameter, P axial. The more it is increased, the lesser accuracy you'll get.

• Select Results / Load Combinations / Summary.

Linear Static Analysis & Results



Node cB2 is the critical one for displacements when wind load is aplied. The critical load combination is ULS4_06.

Graphic Results Display the Structure Deflection Select load combination ULS4_06 on Activation toolbar.

• Click the View Options icon and select the Results tab. Select the Deflection option in the "Members" section and click OK.

• Use the Diagrams toolbar icons to adjust the diagram amplitude. To rotate the structure, use the keyboard arrows or the control keys [Home], [Pg Up], [End] or [Pg Dn].

The Mask Function

To help you visualizing diagrams, use the Mask function, which masks elements that are not selected.

• Select a ZY view: Select the Camera function or click the icon.

• Select the Restricted Window selection mode.

• Select members located on axis 2: Draw a window with the cursor, as shown on the figure.



• Select the Mask function by doing one of the following:

• Click the Mask icon • Select View / Mask • Press the shortcut key M.

• Select a XY view.

Deflections on strong axis, v, are as follows:

Bending moments on weak axis, My, are:



• Unmask the structure by clicking the Unmask icon.

Numerical Results Support Reactions There are many ways to consult support reactions:

1. Select a load combination on Activate toolbar and select Results / Load Combinations / Support Reactions.

2. Select the Support element on the Elements toolbar and double click any support to open the Results at node dialog box.



Envelope Results for Supports This spreadsheet supplies the maximum and minimum forces at each support with corresponding critical load combination.

• Select the Envelope mode and the ultimate limit state envelope on the Activate toolbar. Select Results / Envelope / Support Reactions + Concomitants.

Member Internal Forces and Deflections • Select the Member element on the Elements toolbar and double click any a

member to open the Member Internal Forces and Deflections spreadsheet.



The Find Function Find the location of node cB2 with the Find function of Edit menu.

• Select the Node icon on the Elements toolbar.

• Click the Find icon on the Edition toolbar. Enter the node number and click the "Next" button.

Advance Design America™ draws a fuchsia circle (default color) around the found element, as shown on the figure.

• To view the numerical value of node displacements, select the Node element on the Elements toolbar and double click the node.



• To view the numerical value of displacements for selected nodes, select

Results /Load Combinations / Node Displacements.



Non-linear Static Analysis A non-linear static analysis includes P-delta effects due to lateral loads such as wind loads.

• Rename the file.

• Select the Project Configuration dialog box in the File menu. Next, select the Analysis tab and select the "Non-linear" option at the "Type of Static Analysis" section. Click OK.

• Launch the non-linear static analysis.

Deflection on Axis 2 We are going to compare the deflection on the strong axis for columns located on axis 2, for load combination ULS4_06.

The next tutorial shows the steps to perform a steel design of this building with the Steel Design module.

Non-Linear Static Analysis & Results



Bending moment My:

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ADA Booklet2.pdf