STUDY ON DRAFTING SOFTWARE – AUTOCAD AND EXERCISES

 

EXERCISE 1: STUDY ON DRAFTING SOFTWARE – AUTOCAD

INTRODUCTION

AutoCAD is a commercial computer-aided design and drafting software application. Developed and marketed by Autodesk, AutoCAD was first released in December 1982 as a desktop app running on microcomputers with internal graphics controllers.

 

FILE FORMATS

AutoCAD's  file formats are denoted either by a .dwg, .dwt, .dws, or .dxf filename extension. The primary file format for 2D and 3D drawing files created with AutoCAD is .dwg. While other third-party CAD software applications can create .dwg files, AutoCAD uniquely creates RealDWG files. Using AutoCAD, any .dwg file may be saved to a derivative format. These derivative formats include:

·        Drawing Template Files .dwt: New .dwg are created from a .dwt file. Although the default template file is acad.dwt for AutoCAD and acadlt.dwt for AutoCAD LT, custom .dwt files may be created to include foundational configurations such as drawing units and layers.

·        Drawing Standards File .dws: Using the CAD Standards feature of AutoCAD, a Drawing Standards File may be associated to any .dwg or .dwt file to enforce graphical standards.

·        Drawing Interchange Format .dxf: The .dxf format is an ASCII representation of a .dwg file, and is used to transfer data between various applications.

AUTOCAD TOOLS

1. Line - Invoke the LINE command by choosing the LINE tool from the Draw panel, or by entering LINE or L at the Command Prompt. Specify the starting point of the line by clicking the mouse then you will be prompted to specify the second point. Terminate the LINE command by pressing ENTER, ESC or SPACEBAR.

2. Circle - A circle is drawn by using the CIRCLE command. Circle can be drawn by using six different tools, i.e., by specifying center and radius, by specifying center and diameter, by specifying two diametrical ends, by specifying three points on a circle, tangent to two objects, tangent to three objects.

3. Rectangle – Rectangle can be drawn by specifying two opposite corners of the rectangle, specifying the area and the size of one of the sides, or specifying the rectangle’s dimensions.

4. Polyline - Polylines means many lines. To draw a polyline, invoke the PLINE command. After invoking the PLINE command and specifying the start point, the following prompt is displayed:

·       Specify start point: specify the starting point or enter its coordinates.

·       Specify next point or [Arc/Halfwidth/Length/Undo/Width]: specify the endpoint of the first polyline segment.

·       Specify next point or [Arc/Close/Halfwidth/Length/Undo/Width]: specify the endpoint of the second polyline segment or press ENTER to exit the command.

5. Trim - Trim tool is used to remove the unwanted and extending edges. On invoking the Trim tool, you will be prompted to select the cutting edges. These edges can be lines, polylines, circles, arcs, ellipses, rays, splines, text, blocks, xlines or even viewports. After the cutting edge/edges are selected, you must select each object to be trimmed.

6. Extend - The Extend tool can be considered as the opposite of the Trim tool. The purpose of this tool is to extend lines, polylines, rays, and arcs to meet the other objects. Use this option whenever there is a need to extend the objects that do not actually intersect the boundary edge but would intersect its edge if the boundary edges were extended.

7. Copy - This tool is used to make the copies of the selected objects and place them at the specified location. On invoking this tool, select the objects and then specify the base point. Next, specify the second point where the copied objects have to be placed. Continue specifying the second point for creating multiple copies of the selected entities.

8. Mirror - This tool is used to create a mirror copy of the selected objects. The objects can be mirrored at any angle. This tool is helpful in drawing symmetrical figures. On invoking this tool, first there is a prompt to select objects. On selecting objects to be mirrored, again it is prompted to enter the first point of the mirror line and the second point of the mirror line. A mirror line is an imaginary line about which the objects are mirrored.

9. Rotate - On invoking this tool, first there is a prompt to select the objects and the base point about which the selected objects will be rotated. By default, a positive angle results in counter clockwise rotation, whereas a negative angle results in a clockwise rotation. The Rotate tool can also be invoked from the shortcut menu by selecting an object and right-clicking in the drawing area, and choosing Rotate from the shortcut menu.

10. Erase – This tool is used when there is a need to erase unwanted objects from the objects drawn. To erase an object, choose Erase tool from the Modify panel. To invoke the Modify toolbar, choose View>Windows>Toolbars>AutoCAD>Modify from the ribbon. A small box, known as a pick box, replaces the screen cursor on invoking the Erase tool. To erase the object, select it by using the pick box; the selected object will be displayed in dashed lines, and the Select objects prompt will be displayed again. You can either continue selecting the objects or press ENTER to terminate the object selection process and erase the selected objects.

11. Offset - Offset tool is used to draw parallel lines, polylines, concentric circles, arcs, curves, etc. While offsetting an object, specify the offset distance and the side to offset.

12. Move - The Move Tool is used to move one or more objects from their current location to a new location without changing their size or orientation.

13. Array- There will be a need to create an object multiple times in a rectangular or circular arrangement in some cases. This type of arrangement can be obtained by creating an array of objects. In Rectangular Array, you need to mention the number of rows and columns along with the Row offset distance and Column offset distance. Whereas in Polar Array, you need to specify the centre point around which you need the number of objects.

14. Scale – This tool is used to change the size of objects in a drawing.

15. Fillet - The edges in a model are generally filleted to reduce the area of stress concentration. The fillet tool helps form round corners between any two entities that form a sharp vertex.

16. Explode - This tool is useful when an entire drawing is inserted, and there is a need to alter a small detail. After invoking the Explode tool, there is a prompt to select the objects to explode. After selecting the objects, press ENTER or right-click to explode the selected objects and then end the command.

AUTOCAD COMMANDS

• L Command- This is the most common command used in this software. To use this command user has to type L on the taskbar provided at the bottom of the screen and then press enter. User has to define the starting point and endpoint. It will allow him to draw a simple line. The line can also be defined in the polar firm by providing angle and radius.
• C command- To use this user has to type C in the taskbar. It will allow the user to draw a circle by providing a point and radius.
• PL command- This will make Poly Line in your drawing. The endpoint of a first line will act as a starting of the second line and so on.
• REC command- This command is used to draw a rectangle in Auto CAD. To specify the length, breadth of a rectangle user has to specify a starting point and a point diagonally opposite to the first point.
• POL command- This will allow the user to construct a polygon. To use this command user has to specify the number of edges, the center of the polygon and also tell that the circle will be inscribed inside or circumscribed outside the polygon.
• ARC command- This will allow the user to create an arc. The software will ask the user about the starting point/center of the arc with 2 endpoints.
• CO command- This is used to copy on the object. To use this user has to select an object and paste it at its desired location.
• AL command- This command allows the user to align an object with another object. To use this one has to specify the source and destination point of the object. The source point is the location of the object which is to align and the destination point is the desired location. Users can also scale the source objects with respect to the destination object.
• AR command- This command allows us to create an array of objects. Users can create an array according to the desired profile.
• CHA command- This will create a chamfer between 2 non-parallel lines.
• E command- This will erase the selected object from the Auto CAD window.
• EX command- This will extend the object about the profile. To use this one has to select the object to be extended and then after pressing enter one has to select object up to which it has to be extended.
• TR command- This will trim the object. To use this one has to select the object to be trimmed and then press enter. After that one has to select the object about which the object has to trim.
• RO command- This command will rotate the object about the specified point. To use this one has to select the object to be rotated and then select a base point about which object is to be rotated.
• O command- This command will offset the object up to the desired distance. To use this user has to select the object to offset and then specify the distance up to which is to be offset.
• J command- This command will allow objects to join together.
• M command- This command will allow moving the object. To use this one has to select the object to be moved and then specify the point about which it has to move.
• JPGOUT command- This command will save your Auto CAD drawing in .jpeg format.
• ME command- This command will measure your concern object dimensions.
• COL command- This command will open a dialogue box for choosing the desired colour.
• DIV command- This command will divide your object into different segments. For example, a line is to be divided into parts
• F command- This command will provide a fillet/arc between 2 intersecting lines. To use this one has to select 2 intersecting lines and then press enter.
• H command- This command will provide a hatch to some specific area of your drawing. While using this command one has to take into mind that the area should be fully closed up otherwise this command will not work.
• G command- This command will group your objects together into one single object.
• I command- This command will insert a block inside your drawing. After pressing this command user has to browse the location of the block to be inserted inside the drawing.
• LA command- This command will allow the user to open a dialogue box in which a user can manage the layers inside the drawing.
• PE command- This command will edit the polyline. After pressing the command software will ask to select all the polylines to be close, join, adjust the width, edit vertex, fit lines, change it into spline, de curve lines.

·        SP command- This command will check the spelling of all the words inside the drawing.

·        TB command- This command will allow inserting a table with the desired number of rows and columns inside the drawing.

·        PO command- This command will allow the user to insert points inside the object as per user requirements.

·        PU command- This command will open a dialogue box that will allow the user to remove unused/ unwanted elements inside the drawing.

·        RE command- This command will regenerate your drawing with the updates you had done in your drawing.

·        REN command- This will allow the user to rename your layers, blocks inside the drawing in case you want to change their names.

·        T command- This will allow the user to insert multi-line text inside your drawing.

·        UN command- This command will allow selecting the measuring units of drawing. For example, units in inches, millimetres

·        U command- This command will allow the user to undo all previous commands.

 

 

 

 

 

 

 

 

EXERCISE 2: DETAILED STRUCTURAL DRAWING OF FOUNDATION UNITS – ISOLATED FOOTING

 

AIM: - draw a detailed structural drawing of an isolated footing of dimension 1600mm x 1600mm for a column of 300mm c/c

Software used: - Auto Cad

CALCULATIONS: -

Data

P_u     = 1600 mm

b       = 300 mm

D      = 300 mm

p       = 185 kNm²

f_ck     = 20 N/mm²

f_y      = 415 N/mm²

Size of footing

Load of column          = 1500 kN

Self-weight of footing = 150 kN

Total factored load w_u = 1650 kN

Footing area = 1650/(1.6x185) = 5.96 m²

Short side of footing  = 3x0.63 = 1.89 m

Long of footing          = 5x0.63 = 3.15 m

Depth of footing         = √((195x10⁶)/(0.138x20x10³))  

                                  = 266mm

EXERCISE 3: DETAILED STRUCTURAL DRAWING OF ONE WAY CONTINUOUS SLAB

AIM: - Draw a detailed structural drawing of one-way continuous slab of span 5m

Software used: - Auto Cad

Calculations: -

 

Clear Span	= 3.5m
Width of support	= 200mm
Live load	= 4kN/m2
Floor finish	= 1kN/m2
Fck	= 20N/mm2
Fy	= 415N/mm2 CALCULATION OF DEPTH OF SLAB
Assumed depth,d	= span/25
	= 3500/25
	= 140
Clear cover	= 25mm
Diameter of bar	= 10mm
Overall depth	= 165mm

CALCULATION OF EFFECTIVE SPAN

Least value of  :- 

                                                      

(a)   Centre to centre of supports 

                                             = 3.5+0.20

                                             =3.7m

Therefore, Effective span, L = 3.64m

CALCULATION OF LOADS

Floor finish	= 1kN/m2
Live load	= 4kN/m2
Total sevice load , W	= 9.125kN/m
Ultimate load , Wu	= 1.5 x 9.125
	= 13.69 kN/m

 

 

EXERCISE 4: DETAILED STRUCTURAL DRAWING OF DOUBLE REINFORCED BEAMS

 

AIM: - Draw a detailed structural drawing of double reinforced beams of span 6.4m with a width and depth of 300x500mm .Use 12 mm ∅ bars as reinforcement

Software used: - Auto Cad

Calculations: -

Dead load	= 10kN/m
Service load	= 15kN/m
Span	= 8m
Grade of concrete	= M20
fck	= 20N/mm2
Steel	= Fe 415 HYSD bars
fy	= 415N/mm2

CALCULATION OF CROSS SECTIONAL DIMENTION

Depth	= span/12
	= 8000/12
	= 666mm
So, adopt d	= 650mm
D	= 650 + 50
	= 700mm
b	= 300mm

CALCULATION OF LOADS

Self weight of the beam       = 0.3 x 0.7 x 25

	= 5.25kN/m
Dead load	= 10kN/m
Finishes	= 0.75kN/m
Total dead load , g	= 16kN/m
Live load, q	= 15kN/m

 

 

 

BENDING MOMENTS AND SHEAR FORCES CALCULATIONS

Negative moment at interior support

                          M_u                   = 1.5[(SL²/10) + (SL²/9)]

                                                    = 1.5[(16x8²/10) + (15x8²/9)]

                                                    = 314kNm

Positive bending moment  = 1.5[SL²/12 +SL²/10]

                                                    = 1.5[16x8²/12 + 15x8²/10]

                                                    = 182 kNm

Maximum shear force at the support section 

                           V_u                    = 1.5x0.6(g+q)

                                                    = 1.5x0.6x8(16+15)

                                                    = 223.2 kN

Limiting moment of resistance 

                           M_ulim             = 0.138 fck bd²

                                                    = 0.138 x 20 x 300 x 650² x 10^-6

                                                    = 350kNm

Since M_u < M_ulim , section is under reinforced

CALCULATION OF MAIN REINFORCEMENTS

                           M_u                               = 0.87 fy Ast d [1-Ast fy / bd fck]

                                 (314 x 10⁶) = (0.87 x 415 Ast x 650) x [1-415Ast/300 x 650 x 20]

                             Ast                  = 980mm²

                             ( for -ve BM)

*  Provide 4 bars of 25mm dia at the top tension force near the supports .

*  Provide 2 bars of 25mm dia at the bottom tension force at the centre of span sections .

 

 

 

CALCULATIONS OF SHEAR REINFORCEMENTS

Tr		=  Vu/bd
		= 223.2 x 103/300 x 650
		= 1.14N/mm2
Pt		= 100 Ast/bd
		= 100 x 1964/300 x 650
		= 1.007
Tc		= 0.62N/mm2 < Tr

So shear reinforcement are required .

Balance shear                                = [223.2 – (0.62 x 300 x 650) x 10^-3]

                                                             = 102.3kN

Using 8mm dia two – lessed stirrups , the spacing

                             S_v                            = (0.87 fy Asv d)/V_us

                                                         = (0.87 x 415 x 2 x 50 x 650)/102.3 x 10³

                                                             = 229mm

* Adopt 8 mm dia two lessed stirrups at 200mm centres near supports gradually increasing to 300mm towards the centre of span .

CHECK FOR DEFLECTION

At centre of span :

	Pt			= (100 Ast)/bd
				= (100 x 982)/(300 x 650)
Kt = 1.2 Kc = 1 Kf = 1				= 0.50%
	So (L/d)max			= [(L/d)basic x Kt x Kc x Kf ]
				= 26 x 1.2 x 1 x 1
				= 31.2
(L/d)actual				= 8000/650
				= 12.3 < 31.2

Hence defection is satisfied . 

 

EXERCISE 5: STUDY ON ANALYSIS AND DESIGN SOFTWARE – STAADPRO V8i

INTRODUCTION

STAAD.Pro is a general purpose structural analysis and design program with applications primarily in the building industry - commercial buildings, bridges and highway structures, industrial structures, chemical plant structures, dams, retaining walls, turbine foundations, culverts and other embedded structures. The software has now its latest version, STAAD.Pro V8i with new and improved features. STAAD Pro was developed by Research Engineering International since 1997. But this company was bought by Bentley Systems in 2005.

STARTING STAAD.PRO

·       Select the STAAD.Pro icon from the STAAD.Pro V8i program group found in the Windows Start menu. The STAAD.Pro window opens to the start screen.

·       There are two base unit systems in the program which control the units (length, force, temperature, etc.) in which, values, specifically results and other information presented in the tables and reports, are displayed in. The base unit system also dictates what type of default values the program will use when attributes such as Modulus of Elasticity, Density, etc., are assigned based on material types – Steel, Concrete, Aluminium – selected from the program’s library. These two unit systems are English (Foot, Pound, etc.) and Metric (KN, Meter, etc.)

We can change this setting either by going to the File > Configure

menu or by selecting Configuration under Project Tasks. In the dialog that comes up, choose the appropriate unit system.

·     Click Accept to close the dialogue.

CREATING A NEW STRUCTURE

 

In the new dialog, we provide some crucial initial data necessary for building the model .

1. Select file >New

Or

Select New project under project tasks

The structure type is defined as either Space, Plane, Floor or truss.

SPACE

The structure, the loading or both cause the structure to deform in all 3 global axis (x,y,z)

PLANE

the geometry, loading and deformation are restricted to the global X-Y plane only 

 

Floor 

a structure whose geometry is confined to the X-Z plane.

Truss

the structure carries loading by pure axial action. Truss members are deemed inca-pable of carrying shear, bending and torsion.2. Select

 Plane

the geometry, loading and deformation are restricted to the global X-Y plane only

 Foot

 as the length unit and

 Kilo Pound

 as the force unit.

Hint:

 The units can be changed later if necessary, at any stage of the model creation.4. Specify the File Name as

 PORTAL

 and specify a Location where the STAAD input file will belocated on your computer or network. You can directly type a file path or click

 […]

 to open the Browse by Folder dialog, which isused to select a location using a Windows file tree. After specifying the above input, click

 Next

.The next page of the wizard, Where do you want to go?, opens.