Ram Concep Ram Concept.pdft

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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 drawing�s 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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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.


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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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 slab�s 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 balcony�s 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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9 Double-click the balcony load.

The balcony load should be the only selected load.

10Right click on the plan and choose Selection Properties from the popup menu.11 In the Properties dialog box, change Fz to -20 psf, and click OK.

The balcony other dead load is now effectively zero.

Figure 40-9 Other Dead Loading: All Loads Plan (with area loads hatch-ing turned on).

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40.4 Define the post-tensioning

Post-tensioning methodology varies from country to country. In the USA it is common to use the �banding� technique for detailing tendons in two-way slabs. Banding means concentrating the tendons over support points in one direction, and distributing them uniformly in the orthogonal direction. This method is generally used in conjunction with full-panel design strips. That is, column and middle strips are not used.

Note: RAM Concept has two layers for tendons called latitude and longitude. Refer to �Using the latitude and longitude tendon layers� on page 117 for more information.

Note: The tutorial in Chapter 45 explains the use of Strip Wizard to establish an estimate of the number of strands required for the critical band.

Define the latitude tendons:

1 Choose Layers > Latitude Tendon > Standard Plan.2 Choose View > Visible Objects ( ).3 Click the Drawing Import tab.4 Click Show All, and click OK.

Showing the CAD file makes the following instructions easier to follow.

5 Double click the Tendon Polyline tool ( ) to edit its default properties.6 In the Default Tendon Properties dialog box:

� Set Strands per Tendon to 9.

� Set Profile at end 1 to 8.75 inches.

� Set Profile at end 2 to 1.25 inches, and click OK.

Note: The one-inch cover to the half-inch diameter strand determines these profiles.

7 Turn on Snap to Intersection ( ).8 With the Tendon Polyline tool ( ) selected, draw a tendon along grid A:

� Click at the center of the column at grid inter-section A-1.

� Click at the center of the column at A-2.


� Right click, and then click Enter.

9 Turn on Snap Orthogonal ( ).

10With the Tendon Polyline tool ( ) selected, draw a tendon along grid D:

� Click at the center of the column at grid inter-section D-4.

� Click at the center of the column at D-3.

� Click at the corner of the slab near D-2.


11Turn off Snap Orthogonal ( ).12Double click the Tendon Polyline tool ( ) to edit its default properties.13In the Default Tendon Properties dialog box:

� Set Strands per Tendon to 20, and click OK.

14With the Tendon Polyline tool ( ) selected, draw a tendon along grid B:

� Click at the center of the column at grid inter-section B-1.

� Click at the center of the column at B-2.




15With the Tendon Polyline tool ( ) selected, draw a tendon along grid C:

� Click at the center of the column at grid inter-section B.8-1.

� Click at the center of the column at C-2.




The latitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 10-inch slab.

16With the Selection tool ( ), select all of the terminated tendon segments, other than those over a drop cap, by:

� Double clicking at grid intersection B-1.

� Hold the Shift key down and double click at B.8-1.

� Hold the Shift key down and double click at C-4.

� Hold the Shift key down and double click at D-2.

� Hold the Shift key down and double click at D-4.

17Right click on the plan and choose Selection Properties from the popup menu.

18In the Properties dialog box, set Profile at end 1 to 5 inches and click OK.19With the Selection tool ( ), select all of the terminated tendon segments over a drop cap, by:

� Double clicking at grid intersection A-1.

� Hold the Shift key down and double click at A-3.

� Hold the Shift key down and double click at B-5.




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21In the Properties dialog box, set Profile at end 1 to 15 inches and click OK.

Note: This sets the tendon anchorage profile to the centroid of the 10-inch slab, rather than the centroid of the drop cap.

22With the Selection tool ( ), double click the tendon segment at B-2.23Right click on the plan and choose Selection Properties from the popup menu.24In the Properties dialog box, set Profile at end 1 to 18.75 inches and click OK.25With the Selection tool ( ), double click the tendon segment at C-2.26Right click on the plan and choose Selection Properties from the popup menu.27In the Properties dialog box, set Profile at end 1 to 6.75 inches, and click OK.

Note: This accounts for the step near this location.

28With the Selection tool ( ), select the tendon segments between C-2 and C-3.29Click the Calc Profile tool ( ).

The Calc Tendon Profile dialog box appears and reports the current balance load is -2.58 kips/ft. If this is not the number then you probably selected only one tendon segment.

30Click Cancel.31With the Selection tool ( ), select the tendon between C-3 and C-4.32Click the Calc Profile tool ( ).33Input the desired balance load as -2.6 kips/ft in the Calc Tendon Profile dialog box and click Calc.

The low point (end 2) adjusts to 5.01 inches.

34With the Selection tool ( ), select all the end span tendons between grids 3 and 5.

35Right click on the plan and choose Selection Properties from the popup menu.36In the Properties dialog box, set Profile at end 2 to 5 inches, and click OK.

Note: These steps first used the Calc Profile tool to determine a low point that produces a similar average uplift in an end span as the adjacent span, and then manually changed the low points for practical reasons.

Figure 40-10 Latitude Tendon: Standard Plan

Define the longitude tendons:

1 Choose Layers > Longitude Tendon > Standard Plan.2 Turn on Snap to Intersection ( ).

3 Double click the Full-Span Tendon Panel tool ( ) to edit its default properties.4 In the Default Tendon Properties dialog box:

� Set Strands per Tendon to 4.

� Set Profile at end 1 to 8.75 inches.

� Set Profile at end 2 to 1.25 inches, and click OK.

Note: The one-inch cover to the half-inch diameter strand determines these profiles. Strictly speaking, you should adjust Profile at end 1 at columns (to avoid a clash with latitude tendons) but you can ignore for this tutorial.

5 With the Full-Span Tendon Panel tool ( ) selected, draw tendons in the bottom left panel:





6 In the Tendon Panel dialog box:� Set Tendon Spacing to Equal.

� Set Spacing to 6 feet, and click OK.

Note: This spacing exceeds some code maxima, but the tendon layout is for design purposes and not necessarily for detailing.

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7 With the Full-Span Tendon Panel tool ( ) selected, draw tendons in the next panel:


� Click at the center of the column at B.8-1.



8 In the Tendon Panel dialog box:� Set Auto Connect, and click OK.

9 Turn on Snap Nearest Snapable Point ( ) and Snap

Orthogonal ( ).

10With the Half Span Tendon Panel tool ( ) selected, draw tendons in the balcony:

� Click at the center of the column at grid inter-section B.8-1.

� Click at the edge of the slab at 0, 59 ft.

� Click at the tendon profile point at 24, 56.6 ft.

Note: The snap orthogonal snaps the cursor to 24, 59 ft.

� Click at the tendon profile point at 24, 56.6 ft.

11 In the Tendon Panel dialog box:� Set Auto Connect, and click OK.

12Right click on the plan and choose Selection Properties from the popup menu.13In the Properties dialog box, set Profile at end 1 to 6 inches and Profile at end 2 to 4 inches, and click OK.14With the Selection tool ( ), select the two shortest of the half-span (cantilever) tendon segments.15Right click on the plan and choose Selection Properties from the popup menu.16In the Properties dialog box, set Profile at end 1 to 4 inches, and click OK.

Note: This makes the short tendon segments flat.

17With the Full-Span Tendon Panel tool ( ) selected, draw tendons in the next panel:





18In the Tendon Panel dialog box:� Set Tendon Spacing to Equal.

� Set Spacing to 6 feet.

� Check Skip start tendon, and click OK.






20In the Tendon Panel dialog box, click OK to accept the last choices. Alternatively, you could select Auto Connect, but you would have to uncheck Skip Start Tendon. 21With the Full-Span Tendon Panel tool ( ) selected, draw tendons in the next panel:

Note: This sequence is counterclockwise.

� Click at the center of the column at grid inter-section C-3.


� Enter 31, 86 (feet).

� Turn off Snap Orthogonal ( ).


22In the Tendon Panel dialog box:� Set Auto Connect.

� Uncheck Skip start tendon, and click OK.






24In the Tendon Panel dialog box:� Set Layout to Splayed.

� Set Tendon Spacing to Equal.

� Set Spacing to 6 feet.

� Check Skip start tendon, and click OK.


� Click at the center of the column at grid inter-section C-3.




26In the Tendon Panel dialog box:� Set Auto Connect.



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� Uncheck Skip start tendon, and click OK.

Note: Auto-connect will ignore the tendons at the first click because there are already two tendon segments connected at that point.

The panel in the top right has too many tendons and some should be deleted.

27Select the second tendon in this panel.28Hold down shift and select the fifth tendon in this panel, and press Delete.29With the Half Span Tendon Panel tool ( ) selected, draw tendons that terminate in this panel:

� Turn on Snap Orthogonal ( ).

� Click at the profile point at 63.2, 58 ft.

� Type r0,7.

� Click at the last tendon profile point at 72.8, 58 ft.

Note: The snap orthogonal snaps the cursor to 72.8, 65 ft.

� Click at the last tendon profile point at 72.8, 58 ft.

30In the Tendon Panel dialog box:� Set Auto Connect, and click OK.

31Right click on the plan and choose Selection Properties from the popup menu.32In the Properties dialog box, set Profile at end 2 to 5 inches, and click OK.

The longitude tendons are drawn but you need to adjust a number of profile points. Any profile point at the end of a tendon should be at the mid-depth of the 10-inch slab.

33With the Selection tool ( ), select all of the terminated tendon segments, other than those over a drop cap or within the balcony slab:

� Fence the tendon segments that end on grid A.

� Hold the Shift key down and repeat the procedure until you have selected all applicable end tendon segments (tendon segments terminating at grids B and D).

34Right click on the plan and choose Selection Properties from the popup menu.35In the Properties dialog box, set Profile at end 1 to 5 inches and click OK.36With the Selection tool ( ), select all of the terminated tendon segments over a drop cap, by:

� Double clicking at grid intersection A-1.

� Hold the Shift key down and double click at A-3.

� Hold the Shift key down and double click at B-5.


38In the Properties dialog box, set Profile at end 1 to 15 inches, and click OK.

Note: This sets the tendon anchorage profile to the centroid of the 10-inch slab, rather than the centroid of the drop cap.

39With the Selection tool ( ), double click the tendon segment at B-2.40Right click on the plan and choose Selection Properties from the popup menu.41In the Properties dialog box, set Profile at end 1 to 18.75 inches and click OK.

Finally, you need to move the tendon that goes through the opening.

42With the Selection tool ( ), select the tendon segment that passes through the opening.43Choose the Move tool ( ).44Click anywhere on the plan, and type r-1.5,0. 45With the Selection tool ( ), select the tendon segment above the moved tendon.46Choose the Stretch tool ( ).47Stretch the end of the tendon segment to meet the end of the moved tendon.

48Repeat for the tendon segment below the moved tendon.

Note: You could cut down the number of steps in moving the tendon from the opening by using the Utility tool. This combines the selection tool with move and stretch. Refer to �Expanding tool buttons� on page 6 and �Using the Utility tool to move and stretch� on page 17 for further infor-mation.

Figure 40-11 Longitude Tendon: Standard Plan.

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40.5 Create the design strips

Design strips are an essential part of RAM Concept because they link finite element analysis with concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. There are two directions called Latitude and Longitude.

Generate the latitude spans:

1 Choose Layers > Design Strips > Latitude Design Spans Plan.2 Double click the Span Segment tool ( ).

The Default Span Properties dialog box opens to the Strip Generation properties.

3 Click the General tab.4 Change Environment to Class U (corrosive).

Note: This actually has no effect because ACI 318 requires two-way post-tensioned slabs to be designed as class U.

Note: The Consider as Post-Tensioned box is already checked in the ACI 318 template.

5 Click the Column Strip tab.6 Set Cross Section Trimming to Max Rectangle.7 Change CS Top Cover to 1 inch.

8 Change CS Code Min. Reinforcement Location to Elevated Slab.9 Click OK.10Click the Generate Spans tool ( ), or choose Process > Generate Spans.

The Generate Spans dialog box opens with Spans to Generate set to Latitude.

11Set Minimum Span Length to 2 feet and click OK.

The span segments appear in the latitude direction.

Figure 40-12 Design Strip: Latitude Design Spans Plan.

Two span segments are skewed. How you treat skewed strips is often a subjective matter, but in this tutorial we suggest one strip is straightened and the other edited in a different manner.

Generate the latitude strips:

1 Click the Generate Strips tool ( ), or choose Process > Generate Strips.

The design strips appear in the latitude direction.

Figure 40-13 Latitude design strips (with hatching turned on). Some edit-ing is now required.

Concept uses imperfect algorithms that do not always produce acceptable span segments and span segment strips,



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as shown in Figures 40-14 through 40-16. You can make corrections with a number of tools

You can see this more easily if the strip hatching is turned on.

Hatch the strips:

1 Choose View > Visible Objects ( ).

The Visible Objects dialog box will appear.

2 Check Hatching under Latitude Span Segment Strips, and click OK.


Figure 40-14 Skewed span segment that snapped to end of wall

Straighten a span segment:

1 Select span segment 4-2 (between the wall and grid D3), as shown in Figure 40-14.2 Turn on Snap to Intersection ( ).3 Select the Rotate tool ( ).4 Click at the end of the span segment at grid D3.5 Click at the end of the span segment at the wall.

The command line prompts Enter rotation end angle.

6 Enter 180 and press Enter.

The selected span segment is now horizontal.

Figure 40-15 Diagonal strip that warrants manual improvement.

Edit the span cross section orientation:

1 Select span segment 3-1 as shown in Figure 40-15.2 Select the Orient Span Cross Section tool ( ).3 Turn on Snap Orthogonal ( ).

4 Click near the diagonal span strip and then again above or below the first click.

The orientation line half way along the span strip is now �vertical�.

Figure 40-16 Design strip with excessive width.

Draw a Span Boundary Polyline:

1 Select the Span Boundary Polyline tool ( ).2 Click at the intersection of Grid B and Grid C design strips near Grid 3 (point A in Figure 40-16).3 Click to the right of the slab edge (point B).

4 Right-click, and click enter.

Regenerate the latitude span strips:

1 Click the Generate Strips tool ( ).

The two edited spans produce improved span strips, as shown in Figure 40-17.

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Figure 40-17 Design Strip: Latitude Design Strips Plan after strip regen-eration.

Generate the longitude spans:

1 Choose Layers > Design Strips > Longitude Design Spans Plan.

2 Double click the Span Segment tool ( ).3 Click the Column Strip tab.

The defaults set up in the Latitude Design Spans Plan will have remained the same. Since the cover cannot be the same for both directions, change it for the longitudinal direction.

� Change CS Top Cover to 1.63 inches.

� Change CS Bottom Cover to 1.25.

� Click OK.

4 Click the Generate Spans tool ( ), or choose Process > Generate Spans.5 In the Generate Spans dialog box:

� Set Spans to Generate to Longitude.

� Click the �up-down� orientation button tool ( ).

� Click OK.

The spans appear in the longitude direction, as shown in Figure 40-18.

One span segment on grid 2 is slightly skewed due to the column wall detail at C2. Another span segment overlays a wall and is unnecessary since the slab is continuously supported (see �Drawing design strips near walls� on page 98 for discussion).

Figure 40-18 Design Strip: Longitude Design Spans Plan.

Straighten a span segment:

1 Select the span segment between grid B2 and C2 (the highlighted span segment in Figure 40-18).2 Turn on Snap to Intersection ( ).3 Select the Rotate tool ( ).4 Click at the end of the span segment at grid B2.

5 Click at the end of the span segment at the wall.

The command line prompts Enter rotation end angle.

6 Enter 90 and press Enter.

The selected span segment is now vertical.

Delete the span segment over the wall:

1 Select the span segment that overlays the wall, and press Delete.

Edit the span cross section orientation:

1 Select the diagonal span segment between B-5 and C-4.2 Select the Orient Span Cross Section tool ( ).

3 Turn on Snap Orthogonal ( ).4 Click near the diagonal span strip and then again to the left or right of the first click.

The orientation line half way along the span strip is now �horizontal�.

Generate the longitude strips:

1 Click the Generate Strips tool ( ), or choose Process > Generate Strips.

The design strips appear in the longitude direction.



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Figure 40-19 Design Strip: Longitude Design Spans Plan after strip gen-eration.

Check for punching shear:

1 Choose Layers > Design Strip > Punching Checks Plan.

2 Double click the Punching Shear Check tool ( ).3 In the Default Punching Shear Check Properties dialog box:

� Change Cover to CGS to 1.63 inches (cover to centroid of top reinforcement).

� Click OK.

4 Fence the slab with the Punching Shear Check tool.

Figure 40-20 Design Strip: Punching Checks Plan.

40.6 Regenerate the mesh

The presence of design strips can significantly improve the regularity of the finite element mesh. We recommend that once you have completed the design strips, you regenerate the mesh.

Regenerate the mesh:

1 Click Generate Mesh ( ).

2 Enter Element Size of 2.5 feet and click Generate.

There is now a better mesh. View the mesh on the Element: Standard Plan.

Figure 40-21 Element: Standard Plan after regeneration.

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40.7 Calculate and view the results

After you run the model, you can view the results of the analysis and design calculations.

Review Calc Options:

1 Choose > Criteria > Calc Options2 Review the options, and click OK.

Note: See �Calculating the results� on page 125 of Chapter 27 for more information.

Calculate:

1 Click Calc All ( ), or choose Process > Calc All.

An error message appears concerning a problem with a tendon out of the slab in strip 6C-2.

2 Click Continue three times to clear the error message.

The source of the error messages must be investigated.

View the design strips with tendons:

1 Choose Layers > Design Strips > Longitude Cross Sections Perspective.2 Choose View > Visible Objects ( ).3 Click the Tendons tab.4 Select the Longitude Tendons layer, check Tendons, and click OK.5 Use the Rotate about X and Y axes tool ( ) and the Zoom Rectangle ( ) tool to view the problem location shown in Figure 40-22 and Figure 40-23.

Figure 40-22 Longitude Cross Sections Perspective with longitude ten-dons visible.

Figure 40-23 Rotation and zoom-in of the problem location in Figure 40-22.

The problem is that the cross sections are trimmed with the Max Rectangle setting. For span segment 6-2, that setting is causing a problem because of the combination of the drop cap and thinner balcony slab.

Edit span segment 6-2:

1 Choose Layers > Design Strips > Longitude Design Spans Plan.2 Choose View > Visible Objects ( ).3 Check the Numbers box under Longitude Span Segments, and click OK.4 Select span segment 6-2.5 Right click on the plan and choose Selection Properties from the popup menu.6 Click the Column Strip tab.7 Change CS Cross Section Trimming to Inverted T or L, and click OK.

Recalculate:

1 Click Calc All ( ), or choose Process > Calc All.

Concept completes the calculations without errors.

See �Cross Section Trimming� on page 91 for a thorough explanation of Cross Section trimming.

40.7.1 Design status

Look at design status:

1 Choose Layers > Design Status > Status Plan.

Figure 40-24 Design Status: Status Plan.

This shows OK for all design strips. This means that there are no violations of code limits for ductility, flexural stress and one-way shear. Note that status does not flag excessive deflections.



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There are punching shear status results at each column. You can see these more easily on the dedicated punching plan.

2 Choose Layers > Design Status > Punching Shear Status Plan.

Concept has noted �Non-standard section� at six column locations and �OK with SSR� at one column.

�Non-standard Section� is a warning, not an error. What it means is that at least one of the critical sections that Concept is investigating for that column does not perfectly fit one of the three ACI 318-05 cases: interior, edge and corner. Concept still calculates a stress ratio for non-standard sections. Refer to �Non-Standard Sections: ACI 318� on page 135 of Chapter 28 for more information.

Where the unreinforced stress ratio (USR) is less than 1.0, the column�s punching shear is satisfactory without any reinforcement (subject to the comments above concerning �Non-standard section)).

Stud shear reinforcement is required where Concept reports �OK with SSR�.

If Concept reports �Failed� then SSR does not solve the problem and a thickening is required.

Note: Choose > Layers > Design Status > SSR Plan to view the stud shear reinforcement.

Figure 40-25 Design Status: Punching Shear Status Plan.

40.7.2 Design reinforcement

Look at design reinforcement:

1 Choose Layers > Design Status > Reinforcement Plan.

Figure 40-26 Design Status: Reinforcement Plan.

This shows all the code-determined reinforcement for each of the design strips. Since the slab is post-tensioned, there is not much reinforcement. You might choose to view all design reinforcement on the one plan, or you can access plans in the Design Status layer that separate reinforcement according to: face (top or bottom) and direction (latitude or longitude).

2 Choose the plans that best convey the results without too much clutter.

Figure 40-27 Design Status: Latitude Bottom Reinforcement Plan.

The Reinforcement layer plans show detailed reinforcement. In particular, the top bars are rationalized so that the number is consistent each side of columns.

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Look at detailed top reinforcement:

Choose Layers > Reinforcement > Top Bars Plan.

Figure 40-28 Reinforcement: Top Bars Plan

40.7.3 Concrete stresses

ACI 318-05 has limits for the hypothetical stresses due to flexure and axial loads. The code bases the rules upon �averaging� rather than peak values.

Stress contour plots of the net flexural stresses are available in Concept. Most designers will not be interested in these plots because, in following the code, Concept does not use the contours directly in design.

What will likely be of interest are the plans that show the concrete stresses plotted along the design strips. These are the average stresses based upon the design strip widths.

View top stress plan:

1 Choose Layers > Rule Set Designs > Service Design > Top Stress Plan.2 Right click over the plan and choose Plot ( ).

3 In the Plot Settings dialog box:� Change Max Frame # to 4.

� Click OK

Figure 40-29 Service Design: Top Stress Plan.

To view the Max Demand more easily you can uncheck Max Capacity in the plot options.

Similarly, you can view the bottom stress plan at Layers > Rule Set Designs > Service Design > Bottom Stress Plan.

40.7.4 Deflection

Usually you are interested in short-term and long-term deflections. The Service LC (dead and live load plus post-tensioning if applicable) and LT Uncracked Deflection LC (load factors used to simulate creep and shrinkage) provide contour plans for deflection.

RAM Concept uses gross section inertia for these deflection contours.

You can investigate the effects of creep, shrinkage and cracking with �ECR� and long-term deflection strip-based plots. See Chapter 56, �Estimating deflections� for more information.

Note: The strip based long-term deflection plots are not overly useful for two-way post-tensioned flat plates designed to ACI318. This is because the design method assumes uncracked sections.



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View service deflection:

1 Choose Layers > Load Combinations > Service LC > Max Deflection Plan.

Figure 40-30 Service LC: Max Deflection Plan.

2 Right click over the plan and choose Plot ( ) to change Plot Type from Color Contour to Contour.

View long-term uncracked deflection:

1 Choose Layers > Load Combinations > LT Uncracked Deflection LC > Max Deflection Plan.

Figure 40-31 LT Uncracked Deflection LC: Max Deflection Plan

40.7.5 Bending Moments

While it is not necessary to view bending moments, it can be useful, especially for irregular structures. Even though principal moments are important, the default moment contours plans are for Mx (moment about the x-axis) and My. This is because most designers detail reinforcement orthogonally, and the directions are usually the x- and y-axes. You can view moments about any axes, including the principal axes.

It is not particularly easy to assess the moment contours. This is why Plot Distribution Tools are so useful.

View Factored LC Moments:

1 Choose Layers > Load Combinations > Factored LC: 1.2D + 1.6L + 0.5Lr > Mx Plan.

The Mx contours should be visible.

2 Turn on Snap Orthogonal ( )3 Click the Selected Plot Distribution tool ( ).4 Click first at grid intersection B-3, and then click at grid intersection D-3.

This shows the bending moment shape along the line you have drawn.

5 While pressing the Shift key, click at grid intersection B-1, and then click at grid intersection B-3.

This shows how Mx varies across the panel, and highlights the approximate nature of the ACI318-05 post-tension design method.

See �Section distribution plots� on page 132 for more information.

Figure 40-32 Factored LC: 1.2D + 1.6L + 0.5Lr: Mx Plan showing use of Plot Distribution tool.

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View the balanced load percentages:

1 Choose Layers > Design Strips > Latitude Design Strips Plan2 Choose View > Visible Objects ( ).

3 Choose �Balanced Load Percentages� in the Visible Objects dialog box and click OK.

See �Calculating the balanced load percentages� on page 315 for more information.



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