Chapter 44
Chapter 44
44 Mat Foundation Tutorial This This chapter will walk you you throug rough the stepsformodelinga matfoundation, also known as araft. Al ternative metric values andunits areidentif are identified ied in squarebrackets [] next to the US units. Themetric T hemetric values val ues are not exact conversions. Thecod code used is ACI 318-05 8-05.
3 Click Cl ick the Drawing Import tab.
5 Define Defi ne each wall by snapping to the start and end points of the wall centerli centerlines nes shown on the CAD CA D drawing.
) andSnap to Point Point
2 Doublecli ck theSlab Areatool (
).
Define the area spring location and properties:
) to edit the default
properties. 3 In the Default Slab AreaProperties A reaProperties dialog box:
Set Thi ckness to 30 inches [750 mm].
LeaveSurfaceEl Leave SurfaceEleva evation as 0 and Priori ty as 1.
Click OK.
Note: You can type c to close the polygon instead o f
Note: You need horizon rizontal tal spring prings (r and s) withvery small stiffnesses since there are lateral loads. l oads. 3 Define Defi ne an areaspring over the entire slab sl ab by cli cking cki ng four corners of a quadril ateral. This T his shape need not match the
slabs exact dimensions, but should cover the entire s lab.
Youhavenow defined the structure but the elem lement mesh does not yet exist.
). ).
Choose a Concrete Strength of 5000 psi [32 M Pa for A S3600; C32/40 C 32/40 for BS8110].
Set Height to 10 feet [3 m].
2 Select the CAD drawing fi le mat_tutorial.dwg [mat_tutorial_metric.dwg].
Set Support Set to Above.
Figure 44-1 Mesh Input: StandardPl an
Generate the mesh:
dial og box: 3 In the Default Col umnProperties dialog
1 ChooseFil e> Import Drawing.
the CAD 3 Select Inches [Mi lli meters] (the units used in theCAD file) and click OK .
Set a z-force constant of 250 pci [0.07 N/mm N/ mm3], andclick OK .
) selected, define the four
corners of the slab by snapping to the imported drawings slab corners.
1 Turn Turn on Snap to Cent Center (
Set ans-force s-for ceconstan constant of 0.1 pci [0.00001 N/mm3].
2 Doubleclick on theColum Column tool (
TheFileUnits FileUnits dialogbox appears.
4 With theSlab Areatool (
).
Set an r-force constant of 0.1 pci [0.00001 N/mm3].
Choose a Concrete Strength of 4000 psi [25 M Pa for A S3600; C25/30 C 25/30 for BS8110].
Define the column locations and properties:
Import the CAD file:
1 Doublecli ck on theQuad-AreaSpring tool (
2 In the Default Area Spring Properties dialog box:
entering thelast the last point.
TheCAD fileyou you imp import ort islocated in your RAM Conc Concept programdirectory. programdi rectory.
Uncheck Fixed Near and Fixed Far.
Draw the slab area:
1 Turn Turn on Snap to Intersection(
(
44.1 Import the CAD drawing
Uncheck Shear Wall.
4 Click OK.
opening files on page 5. You should ensure that you select mat foundation in the new file dialog box.
A mat need not have columns andwall s modeled above. Thereasonsto model colu columnsandwalls aboveinclu veinclude improving improvi ng theappearance of the model, and providi ng snap points for point and line li ne loads. Additionally, Additionall y, awall a wall above will wil l stiffen stif fen themat in a beneficial way.
Set Thi ckness to 12 inches [300 mm].
4 Cli ck ShowAl l, and thenclick OK .
For i nformation on creating a new file, see Creating and
Most mats support columns and walls. wall s. You Y ou may chooseto model the columns and walls but you should be aware that this could affect the mat behavior. In particular, particul ar, if there are lateral loads l oads then you should be very careful in defining defi ning the supports above as having vi ng no horizontal restraint. Otherwise, the supportsaboverather abover ather than thesoil (springs) below coul d resist some lateral moment andshear.
1 Click GenerateMesh (
).
2 In the GenerateM esh dialog box set theElement Size to to
2 feet [0.7 m]. 3 Click Generate.
Set Width to 30 i nches [750 mm].
Set Diame Di ameter to 30 inches i nches [750 mm].
Check Roller at Far End.
Uncheck Fixed Near and Fixed Far.
View the mesh:
1 Choose Layers >El ement >Standard Plan.
Youwill now seeasomewhat randommesh. Thiswill still producereasonable results, butwil l signifi signi ficantly cantly improve when you regenerate it later on.
4 Click OK. 5 Click Cl ick at thecente the center of all 11 columnlocations locati ons shownon
44.2 Define the structure
the imported drawing.
To usethe CAD fileyou need to makeit visibleonthe Mesh Input layer.
).
2 Doubleclick on the Wall tool ( Show the drawing on the mesh input layer:
1 Choose Layers >M esh Input >Standard Plan. 2 Choos Choose View >VisibleObjects (
).
Note: You Youcan also right rightclick to see a popupmenuthat includes incl udestheVisibl the Visibl e Objects command.
RAM Concept
L ayers >Eleme >El ement >Structure Summary 1 Choose Layers Perspective. 2 Use the Rotate about x- andy-axestool ( floor.
Define the wall location and properties:
1 Turn Turn on Snap Orthogonal (
View the structure:
) to rotatethe
).
3 In the Default Wall Properties Properti es dialog ial og box:
Choose a Concrete Strength of 3000 psi [20 M Pa for A S3600; C20/25 C 20/25 for BS8110].
Set Height to 10 feet [3 m].
Set Support Set to Above.
Figure 44-2 Element: StandardPl an
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44.3 Define the loads
4 Choose Edit >Paste.
Mat loads could consist of point, li neand arealoads for a number of l oadings (such as live, other dead, north seismic, eastseismic, north wind and east wind). For simplici ty, this tutorial will not use area loads(except for the automatic calculation of self-weight) and will adopt loads belonging only to other dead, live, and ultimateseismic east loadi ngs.
Thispastesthe other dead loads ontothe Live (Reducible) Loading: All L oads Plan.
Chapter 44 Define the ultimate seismic east loading:
8 Doubleclick theLi neLoad tool (
1 Choose Layers >L oadings >UltimateSeismic East
Li neL oadProperties dialog box:
Loading >All Loads Plan. 2 Choose View >VisibleObjects(
).
3 Cli ck the Drawing Import tab.
Set theelevation above the slab surfaceto 360 inches [9000 mm].
Loads Plan. 2 Choose View >VisibleObjects (
).
3 Click the Drawing I mport tab. 4 Click Show All, and then click OK .
Showing theCAD f ile makes thefoll owing instructions easier to follow. 5 Turn onSnapto Intersection(
Click OK.
10Doubleclick theLi neLoad tool (
) and in theDefault
Li ne Load Properties dialog box:
1 Choose Layers >L oadings >Other Dead Loading >All
Set Fy to -12.8 kip/ft [-174 kN/m].
points, as shown in Figure 44-7 and Figure 44-8.
).
6 Double click the LineLoad tool ( Define the other dead loading:
9 Draw a line load by snapping to the wall i ntersection
4 Cli ck ShowAl l, and then click OK. 5 Turn onSnap to Intersection (
) andin theDefault
Set Fx to 4.1 kip/ft [60 kN/m].
Set all other itemsin the dialog box to 0.
Click OK.
) andin theDefault
Li neL oadProperties dialog box:
Set Fy to (+)12.8 kip/ft [(+)174 kN/m].
Click OK.
11Draw a line load by snapping to the wall i ntersection
points, as shown in Figure 44-7 and Figure 44-8.
7 Draw a line load by snapping to the wall i ntersection
points, as shown in Figure 44-5 and Figure 44-6.
).
6 Doubleclick thePoint Load tool (
).
7 In theDefault Poi nt Load Properties dialog box:
ChangeF z to 40Ki ps [180 kN], and click OK.
8 Defi ne 40 Ki p [180 kN] point loadsby snapping to
column centers at thefollowi ng locations:
A-1
A-3
D-1
D-3
Figure 44-3 Other DeadL oading: All Loads Plan
Figure 44-7 EastSeismic: All Loads Plan ( second set)
9 Defi nethe rest of thepoint loads asshown in Figures 44-
3 and 44-4. 10Doubleclick the Line Loadtool (
). Figure 44-5 EastSeismic: All Loads Plan
11In theDefault L ine Load Properties dialog box:
Set Fz to 8 kip/ft [120 kN/m], andclick OK.
12With theLine Loadtool (
) selected, draw a LineLoad along thecenterline of the wall on grid 2. 13Repeat for the wall at grid 2.5 with a load of 5.5 kip/ft
[80 kN/m].
Note: Draw these loads to the outside face of the intersecting walls. Copy to the live (reducible) loading layer:
Figure 44-8 EastSeismic: All L oads Plan (second set) [ME TRIC]
For simplicity, usethe samel oads for other dead and live (reducible) loads
Note: Theseismic loadsare approximations for a fivestorey building. T heload elevation is the average floor height (third storey).
1 With theSelection tool (
), selectall of theotherdead loads by fencing the entire slab. 2 Choose Edit >Copy.
Figure 44-6 East Seismic: All Loads Plan [M ETRIC]
Figure 44-4 Other DeadLoading: All LoadsPlan [MET RIC]
3 Choose Layers >Loadings >Live(Reducible) Loading >
Note: Theloadsin they-directioncancel the coupleabout the mat centroid.
All Loads Plan. RAM Concept
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44.4 Create the design strips
Chapter 44 Generate the latitude strips:
Regenerate the latitude span strips:
1 Click the Generate Strips tool (
), or chooseProcess >
Generate Strips.
Design strips are anessential part of RAM Concept becausethey link finite element analysis wi th concrete design. Their properties include reinforcement bar sizes, cover, and parameters that Concept uses to determine which code rules are applicable for section design. T here are two directions called Latitudeand Longitude.
1 Click the Generate Strips tool (
), or choose Process >
Generate Strips.
The design stripsappear inthe latitude direction. Hatch the strips:
1 Choose View >VisibleObjects(
).
The VisibleObjects dialogbox will appear. Draw latitude design strips:
2 Check Hatching underLati tudeSpanSegmentStrips,and
1 Choose Layers >Design Strip >Latitude Design Spans
click OK.
Plan. 2 Doubleclick theSpanSegment tool (
Note: Youcan also right click to see a popup menuthat
).
includestheVisible Objects command.
3 TheDefault Span Properties dialogbox openstotheStrip
Generation properties.
Set Column Strip Width Calc to Code Slab (this is thedefault for the AS3600 template).
Figure 44-9 Generate spans dialog box
Thespan segments appearin the latitudedirection.
Click the General tab.
Uncheck the Consider as Post-Tensioned box.
Click the Column Strip tab.
ChangeCS Top Bar and CS BottomBar to #8 [N25 for A S3600; T25 for B S8110].
ChangeCS Top Cover and CS BottomCover to 2 inches [50 mm].
Fi gure 44-12 Lati tudedesign strips after editing and regeneration.
Set theMin. Reinforcement Locati on to Tension Face.
Draw longitude design strips:
1 Choose Layers >Design Strips >L ongitudeDesign
Click the Middle Strip tab.
Spans Plan.
Check the Middle Strip uses Column Strip Properties box.
2 Choose View >VisibleObjects (
4 Click theGenerateSpans tool (
).
3 Click the Drawing Import tab.
Click OK.
4 Cli ck ShowAl l, and thenclick OK.
), or chooseProcess>
Generate Spans.
5 Doubleclick theSpanSegment tool ( Fi gure 44-11 Latitudedesign strips(with hatchingturnedon). Someediting is nowrequired.
5 TheGenerateSpansdialogbox openswith Spans to
Generate set toLatitude(as shownin Fi gure 44-9).
).
6 Click the Column Strip tab. 7 ChangeCS Top Cover and CS BottomCover to 3 inches
6 Click OK.
Two spansegmentsareslightly skewed. How you treat skewed strips is also a subjective matter, but in this tutorial we suggest the span segment strips cr oss sections are
manually reoriented.
Fi gure 44-10 Design Strip: LatitudeDesign Spans Plan.
Choosing span segments in a mat is a subjective matter. Concept uses imperfect algorithms that do not always produce acceptablespan segments and span segment strips. It is recommended that some span segments in thi s tutorial are deleted. 7 With theSelection tool (
), select the sevenspan segments highli ghted in red in Figure 44-10 and press Delete.
[75 mm], and click OK . 8 Cli ck theGenerateSpans tool (
), or chooseProcess >
Generate Spans. 9 In the GenerateSpans dialog box:
Edit the cross section orientation:
), select span segments 5-2 and 6-2 as shown in Figure 44-11.
Set Spans to Generate to Longitude.
Click the up-down orientation button tool ( ).
Click OK.
1 With theSelection tool (
2 Click theOrient SpanCross Section tool ( 3 Turn onSnap Orthogonal (
).
).
4 Click near oneof the span segments, and then again
aboveor below the first click. The orientationlinehalf way along the spanstrip is now
10 The spansappear inthelongitude direction, as shown in
Figure 44-13. Similar to thelatitude direction, some editing of thespan segmentsis required.
vertical.
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18Choose Edit >Selection Properties, or right-cli ck and
choose Selection Properties. 19In the dialog box:
Uncheck Detect Supports Automatically.
Uncheck Consider End 2 as Support.
ChangeSupport Width at End 1 to 12 inches [300 mm], andclick OK .
Fi gure 44-13 Design Strip: Longitude Design SpansPlan. Fi gure44-15 Longitudedesignstrips (withhatchingturnedon). Someeditingi snowrequired.
11With theSelection tool (
), select the span segments over the walls (highlighted in red in Figure 44-13) and press Delete. 12 Turn onSnapto Intersection(
Fi gure 44-16 Longitude design strips after editi ng and regeneration Edit the cross section orientation:
).
1 With theSelection tool (
), select span segments 9-3 and 12-1 as shown in Figure 44-15.
13With theSpan Segment tool (
), drawa spansegment by clicking at the wall intersections at point A and B in Figure 44-14.
2 Click theOrient SpanCross Section tool (
3 Cl ick near one of the span segments, and then again to the
14Choose Edit >Selection Properties, or ri ght-click and
choose Selection Properties.
left or right of first click. Fi gure 44-14 Manually drawnspansegments
The orientationlinehalf way along the spanstrip is now
15In the dialog box, change:
horizontal.
Min Number of Divisions to 0.
Generate the longitude strips:
Max Division Spacing to 30 feet [10 m], and click OK.
1 Click the Generate Strips tool (
Thisspan segmenthas beendrawnto assist with Concepts span segment strip wi dth calculation. 16 Turn onSnap Orthogonal (
SnapablePoint (
) andSnap Nearest
).
17With theSpan Segment tool (
), drawa spansegment by clicking at the wall intersection at point B and then at point C in Figure 44-14 (it should snapto thevisible grid line).
RAM Concept
).
), or choose Process >
Generate Strips.
Generate Strips.
Thedesign strips appear in the longitudedirection.
(span segment strips) have different widths either side of a column. You could rati onalize these strips such that they have similar widths at the column, especiall y the cantilevers. Seethediscussion in Defining strip boundaries manually on page 88 of Chapter 21, Defining Design Strips. In particular, Example 21-2 onpage88 and Example 21-4 on page 90. Check for punching shear:
Regenerate the longitude span strips:
1 Click the Generate Strips tool (
Note: Many of the latitude andlongitude design strips
), or chooseProcess >
1 Choose Layers >Design Strip >P unching Checks Plan. 2 Doublecli ck the Punching Shear Check tool (
).
3 In the Default Punching Shear Check Properties dialog
Two span segments areslightly skewed. Wesuggestthe
box:
span segment strips cross sections are m anually
ChangeCover to CGS to 3 i nches [60 mm] (cover to centroid of top reinforcement).
reoriented.
Click OK.
4 Fence the slab with the Punching Shear Check tool.
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1 Click GenerateMesh (
Chapter 44
44.6 Calculate and view the results
Regenerate the mesh:
2 Choose Layers >Design Status >Punching Shear Status
Plan.
).
2 Enter Element Size of 2 feet [0.7m] and click Generate.
Thereis nowabetter mesh. View themesh onthe Element: Standard Plan.
After you run the model, you can view the results of the analysis and design calculations.
Concept has noted Non-standard section at the corner column locations.
Review Calc Options:
Non-standard Section is a warning, not an error. What it
1 Choose>Cri teria> Calc Options 2 Review the options. 3 Uncheck Auto-stabilize structure in x- and y-directions, and click OK.
Note: See General options on page 126 of Chapter 27
means is that at least one of the criti cal sections that Concept is investigating for that column does not perfectly fit one of thethree ACI 318-02 cases: interior, edgeand corner. Concept still calcul atesa stress ratio for nonstandard sections. Refer to Non-Standard Sections: ACI 318 on page 135 of Chapter 28 for more information.
for moreinformation. Calculate:
Click Calc All (
), or choose Process >Calc All.
Look at reinforcement and design status:
1 Choose Layers >Design Status >Total Status Plan.
This shows OK for all designstrips and punchingchecks. This meansthattherearenoviolationsof codelimits for ductility, one-way shear, and punching shear. Note that status does not flag excessive deflections.
Fi gure 44-17 Design Strip: PunchingChecks Plan.
44.5 Regenerate the mesh Thepresence 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.
Fi gure 44-18 El ement: Standard Pl an after regenerati on. Fi gure 44-20 Design Status: Punching Shear Status Plan.
3 Choose Layers >Design Status >Total R einforcement
Plan. This shows all thecode-determined reinforcementfor each of thedesign strips. The results are, however, too congested to be useful. You can access plans in the Design Status layer that separatereinforcement according to: face (top or bottom),direction(latitudeorl ongitude),andtype(fl exural or shear). You should decide which plans best convey the results without too much clutter. View Specific Reinforcement: Fi gure 44-19 Design Status: Status Plan.
Thereare punchingshear status resultsat eachcolumn. Youcan see thesemoreeasily onthe dedicated punching plan.
1 Choose Layers >Design Status >L atitude Bottom
Reinforcement Plan. 2 Choose View >VisibleObjects (
).
The VisibleObjects dialogbox will appear. 3 Check Bar Spacings under Latitude Span Designs, and
click OK.
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Fi gure 44-21 Design Status: Latit udeBottomRei nforcement Pl an.
Fi gure 44-22 ServiceL C: Soil Bearing Pressure Plan.
2 Choose Layers>RuleSetDesigns >Soil Bearing Design
44.6.1 Bearing stres ses
>M ax Soil Bearing PressurePlan.
Maxi mumbearing stressis a critical consideration when designing a mat. Contour pl ots of the bearing stresses are available in RAM Concept. These will vary according to the load combination. Note that the minimum and maximumbearing values often occur for different load combinations. TheSoil Bearing Design rule set envelopes the maximum and minimumbearing pressures for all load combinations. Themaximumbearing pressureplan is probably themost useful for your design. View bearing stress plans:
1 Choose Layers >Load Combinations >Service LC >
Soil Bearing Pressure Plan.
Fi gure 44-23 Soil Bearing Design: Max Soil Bearing PressurePl an
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