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  • 207RAM Concept

    Chapter 40

    40 PT Flat Plate Tutorial: ACI 318-05

    This chapter describes the steps for modeling a post-tensioned two-way flat plate with uniform loads.

    The objective of this tutorial is to build on the skills learned in the Chapter 39 RC tutorial and introduce new steps, such as using a CAD drawing and post-tensioning.

    Some tools and methods described in the RC tutorial are not used here. As such, it is highly recommended that you first do the RC tutorial.

    This is not a particularly aggressive design. After you have completed the tutorial, you may wish to make the slab thinner to investigate the ramifications.

    You could also use this as a reinforced concrete tutorial by making a few adjustments (for example, a thicker slab).

    For information on creating a new file, see Creating and opening files on page 5.

    40.1 Import the CAD drawing

    The CAD file you import is located in your RAM Concept program directory

    Import the CAD file:

    1 Choose File > Import Drawing.

    2 Select the CAD drawing file flat_plate.dwg.

    The File Units dialog box appears.

    3 Select Inches (the units used in the CAD file) and click OK.

    40.2 Define the structure

    To use the CAD file you need to make it visible on the Mesh Input layer.

    Show the drawing on the mesh input layer:

    1 Choose Layers > Mesh Input > Standard Plan.2 Choose View > Visible Objects ( ).

    Note: You can also right click to see a popup menu that includes the Visible Objects command.

    3 Click the Drawing Import tab.4 Click Show All, and then click OK.

    Draw the slab area:

    1 Turn on Snap to Intersection ( ) and Snap to Point ( ).2 Double click the Slab Area tool ( ) to edit the default properties.3 In the Default Slab Area Properties dialog box:

    Choose a Concrete Strength of 5000 psi.

    Set Thickness to 10 inches.

    Leave Surface Elevation as 0 and Priority as 1.

    Click OK.

    4 With the Slab Area tool ( ) selected, define the 10 vertices of the slab outline by snapping to the imported drawings slab corners.

    Note: There are two vertices near each other near B-5 at 86, 27 ft and 86, 29 ft. Cursor plan coordinates display next to the command prompt.

    5 Complete the polygon by clicking at your starting point (or type c in the command line and press Enter).

    Figure 40-1 The slab outline on the Mesh Input: Standard Plan.

    Draw the balcony slab area:

    1 Double click the Slab Area tool ( ) to edit the default properties.2 In the Default Slab Area Properties dialog box:

    Change Thickness to 8 inches.

    Change Surface Elevation to -2 inches.

    Change the Priority to 2, and click OK.

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    RAM Concept

    3 With the Slab Area tool ( ) selected, define the six vertices of the balcony outline by clicking at each vertex, and then click at your starting point (or type c in the command line and press Enter).

    Figure 40-2 The balcony slab on the Mesh Input: Standard Plan.

    Draw the drop caps:

    1 Double click the Slab Area tool ( ) to edit the default properties.2 In the Default Slab Area Properties dialog box:

    Change Thickness to 20 inches.

    Change Surface Elevation to 0, and leave the Priority as 2.

    Click OK.

    3 With the Slab Area tool ( ) selected, define the four drop caps with four or five vertices as appropriate.4 Go to Draw the opening:, or try the next method5 With the Selection tool ( ), select (by double-clicking) and delete the drop cap at B-2.

    6 Click Redraw ( ).

    Some tool button icons have a small triangle in the lower right corner ( ). This indicates that there are other similar tools available for this button.

    7 Place the mouse over the Slab Area tool ( ) and press down on the left mouse button for one second.

    A pop-up menu appears.

    8 Select the Drop Cap tool from the menu.

    The selected tool becomes current for that button.

    9 Click at the column at B-2.

    A Drop Cap Tool dialog box appears.

    10Enter an angle of zero degrees.11Enter a side dimension of 3.75 feet and click OK.

    Draw the opening:

    1 Select the Slab Opening tool ( ).2 Define the four corners of the opening by clicking at each location, and then click at your starting point.

    Figure 40-3 The opening on the Mesh Input: Standard Plan.

    Hatch the slab areas:

    1 Choose View > Visible Objects ( ).

    The Visible Objects dialog box will appear.

    2 Check Hatching under Slab Areas.3 Check Hatching under Slab Openings, and click OK.

    Note: You can also right click to see a popup menu that includes the Visible Objects command.

    Define the column locations and properties:

    1 Double click on the Column tool ( ).2 In the Default Column Properties dialog box:

    Choose a Concrete Strength of 5000 psi.

    Set Width to 24 inches.

    Set Depth/Diameter to 24 inches.

    3 Click OK.

    4 Click at the center of all 13 column locations shown on the imported drawing.

    Define the wall location and properties:

    1 Turn on Snap Orthogonal ( ).2 Double click on the Wall tool ( ).

    3 In the Default Wall Properties dialog box: Choose a Concrete Strength of 3000 psi.

    4 Click OK.

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    Chapter 40

    5 Define the wall by clicking at the start and end points, on the centerline.

    Place the cursor near 29.5, 87 ft and it will snap to where the center of the wall intersects the edge of the slab, and click.

    Place the cursor at the center of the column at C-2 (it will snap orthogonally) and click.

    You have now defined the structure but the element mesh does not yet exist.

    6 Go to Generate the mesh:, or try the next method.7 The wall should be highlighted as it is the current selection. If not, select it by double-clicking and press Delete.8 Click Redraw ( ).9 Place the mouse over the Wall tool ( ) and press down on the left mouse button for one second.

    A pop-up menu appears.

    10Select the Left Wall tool from the menu.11Click at the extreme corner of the slab near D-2.12Click at Grid C, near C-2.

    Figure 40-4 After defining the slab, the Mesh Input: Standard Plan shows the slab areas and opening (hatched), the columns and the wall.

    Generate the mesh:

    1 Click Generate Mesh ( ).2 In the Generate Mesh dialog box set the Element Size to 3 feet.

    3 Click Generate.

    View the mesh:

    1 Choose Layers > Element > Standard Plan.

    You will now see a somewhat random mesh. This will still produce reasonable results, but will significantly improve when you regenerate it later on.

    Figure 40-5 Element: Standard Plan.

    View the structure:

    1 Choose Layers > Element > Structure Summary Perspective.

    2 Use the Rotate about x- and y-axes tool ( ) to rotate the floor.3 Click the Set Print Viewpoint tool ( ).

    Upon returning to this perspective, you can look at the

    saved view by clicking Show Set Viewpoint ( ).

    Figure 40-6 Element: Structure Summary Perspective.

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    40.3 Define the loads

    RAM Concept calculates the concrete self-weight automatically.

    Concept uses superposition of loads. The easiest way to define areas with increased area loads is to draw a blanket area load over the entire floor, and then draw the additional loads.

    There is no limit to the number of loadings than can be specified.

    Define the typical live load:

    1 Choose Layers > Loadings > Live (Reducible) Loading > All Loads Plan.2 Double click the Area Load tool ( ).3 In the Default Area Load Properties dialog box:

    Change Fz to 40 psf and click OK.

    This tool will now draw area loads of 40 psf.

    4 Define an area load over the entire slab by clicking four corners of a quadrilateral and then typing c. This shape need not match the slabs exact dimensions, but should cover the slab.

    Define the balcony live load:

    1 Turn on Snap to Intersection ( ).2 Define an area load by snapping to the six vertices of the balcony (and then type c). In this situation, it is best for the load to match the balconys dimensions.

    You have drawn another 40 psf load. This load should be highlighted as it is the current selection. If not, select it before proceeding by double-clicking with the selection tool.

    3 Choose Edit > Selection Properties, or right-click and choose Selection Properties.4 In the dialog box, change Fz to 60 psf and click OK.

    There is now a total live load on the balcony of 100 psf.

    Note: You could have drawn the 60 psf load by first changing the area load default properties and then using the tool.

    Figure 40-7 Live (Reducible) Loading: All Loads Plan (showing the bal-cony area load).

    Figure 40-8 Live (Reducible) Loading: All Loads Plan (with area loads hatching turned on).

    Define the other dead loading:

    1 Choose Layers > Loadings > Live (Reducible) Loading > All Loads Plan.2 With the Selection tool ( ), select both area loads (fencing the balcony load selects both loads).

    3 Choose Edit > Copy.4 Choose Layers > Loadings > Other Dead Loading > All Loads Plan.

    5 Choose Edit > Paste.

    This pastes the live loads onto the Other Dead Loading: All Loads Plan, ready for editing.

    6 With the Selection tool ( ), select the blanket load by double clicking in the center of the floor.7 Right click on the plan and choose Selection Properties from the popup menu.8 In the Properties dialog box, change Fz to 20 psf, and click OK.

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