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1. LAYOUT DRAWING(For classes held on 26 and 27th Feb 07)

By Dr. G.S.Suresh, Professor, Civil Engineering Department, NIE, Mysore(Ph:9342188467, email: gss_nie@ yahoo.com)

1.1 Introduction to Structural drawing:

Drawing is the language of engineers, which conveys the idea of the engineer aboutthe shape, structural arrangement to builder. Structural drawings guide builders in theconstruction of apartment blocks, industrial buildings, highways, irrigation structures,bridges and other important structures.

The guidelines given in IS 962 (“Code of practice for architectural and buildings”)and SP 34 (“Handbook on Concrete Reinforcement and Detailing”) may be adoptedwhile preparing structural drawings for Reinforced Concrete Structures and itselements.

Structural drawings are prepared in different sizes and depend on the number ofdetailed drawings to be presented. In large projects, the structural drawings are ofsame size. The preferred size of drawing sheets are given in table 1.1

Table 1.1 Drawing Sheet Size

Sl. No. Designation Trimmed Sizein mm

Un Trimmed Size(Min) in mm

1 A0 841 x 1189 880 x 1230

2 A1 594 x 841 625 x 880

3 A2 420 x 594 450 x 625

4 A3 297 x 420 330 x 450

5 A4 210 x 297 240 x 330

6 A5 148 x 210 165 x 240

Margins and the divisions of drawings sheets into zones are given in Fig 1.1 a to f.The title block is an important feature in a drawing and should be placed at thebottom right-hand corner of the sheet, where it is readily seen when the prints arefolded in the prescribed manner. The size of the title block recommended by SP 34 is185 x 65 mm.

Layout of drawings is not standardized in detailing of reinforced concrete structures.However in practice, the key plan is placed in the upper left hand corner of the sheet,with the elevations and details below and on to the right side of the plan. Schedulesand bending details are place in the upper right corner of the drawing. Fig. 1.2 gives abroad outline of layout recommended. In large projects, the bending schedule can begiven separately and omitted in the structural drawing. Scale for drawings is selectedbased on the convenience to include all the details within workable size. Somecommonly used scales are :

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Plan:- 1:100, 1:50

Elevation:- 1:5, 1:30

Sections:- 1:50, 1:30, 1:25, 1:20,1:15,1:10

Fig.1.1a A0 Size Sheet

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Fig.1.1b A1 Size Sheet

Fig.1.1c A2 Size Sheet

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Fig.1.1d A3 Size Sheet Fig.1.1e A4 Size Sheet

Fig.1.1f A5 Size Sheet and Division of sheets

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Notes containing specifications of the concrete and steel to be used, size of chamfers andfillets, concrete cover, live load, SBC of soil, lap lengths for different diameter of barsetc,. Symbols and abbreviations to be adopted in the drawings are given below:

Symbols Relating to Cross-Sectional Shape and Size of Reinforcementa) plain round bar or diameter of plain round bar;b)plain, square bar or side of plain square bar; andc) # deformed bar (including square twisted bar) or nominal size (equivalent diameter orside) of the deformed bar .Symbols Relating to Shape of the Bar along its LengthsAlt Alternate barBt Bent barB Bottom barmin Minimummax MaximumSt Straight barStp StirrupSp SpiralCt Column tieT Top barSymbols Relating to Position and DirectionEW Each way@ Spacing centre-to-centre

Limit of area covered by barsDirection ‘in which bars extend

Symbols Relating to Various Structural MembersBm or B BeamsCol Column(s)Fg Footing(s)GR GirdersJT Joints(s)LL Lintel(s)LB Lintel beam(s)Sb or S Slab(s)WL Longitudinal wallWx Cross wallC Centre line

Graphical symbols given in Fig. 1.3 are recommended by SP34. Additional drawingconventions for use on drawings for reinforcement as suggested in ISO 3766-1977 isreproduced in Fig 1.4

Fig.1.2 Typical Layout of a Drawing

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Fig. 1.3 Graphical symbols

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Fig. 1.4 Drawing conventions

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Fig. 1.4 Drawing conventions (Contd.)

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1.2 General Layout of Building:

After the preparation of architectural plan of the buildings, the structural planning ofthe building frame is done. This involves determination of i) Positioning andorientation of columns, ii) Positioning of beams, iii) Spanning of slabs, iv) Layout ofstairs, v) Selecting proper type of footing.

Different structural members of a structure shall be marked using symbols,abbreviations and notations. A key framing plan shall be prepared to a convenientscale and the two axes marked one side with alphabets A, B, C etc, and the other withnumbers. If the structural arrangement in all the floors is same then only one key planis prepared titling it as typical plan. If the arrangement varies for different floors aseparate key framing plan with grid arrangement and areas may be used for each ofthe floor. The floors shall be specified in accordance with the requirements of IS2332-1973 (“Specifications for nomenclature of floors and storeys”). According tothis code BT symbol is used for Basement, MZ for Mezzanine, Floor 1, Floor 2 etcfor first, second etc floors respectively.

Columns and foundations shall be specified by grid arrangements giving reference tothe floor. For example FG Col C2 with reference to Fig 1.5 indicates Footing forcolumn C2, Col 2C2 indicates column C2 at floor 2.

Beams, slabs and lintels and tie beams shall be consecutively numbered from left-hand top corner as shown in Fig. 1.5. Lay out building are generally drawn i)Drawing showing position of columns along with excavation plan for footing and ii)Key plan showing arrangements of beams and plans and called as form workdrawing. Fig 1.6 and 1.7 shows a typical lay out drawing developed for a building.

Fig. 1.5 Typical Arrangement for the Key Framing Plan and marking DifferentStructural Members

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Fig. 1.6 Typical Drawing for a Multi-Storied Building showing columnposition and excavation plan.

Fig. 1.7 Typical Drawing for a Multi-Storied Building showing Slab and Beamalignment

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Problem1:

Prepare a general layout showing the positions and sizes of columns and footing to asuitable scale for an industrial building:

A clear dimension of factory floor is 11.75 m x 19.75 mSpacing of columns 4m c/cSize of columns 250 mm x 450 mmSpan of steel truss is 12.25 m c/cAt the ends to support the gable wall additional two RCC columns of size250 mm x 450 mm are to be provided at 4m c/c measured from end columnsAll the walls all-round are 250 mm thickHeight of columns = 3mSize of footing 1.4m x 1.8mThickness of footing 300 mm uniformDepth of foundation 1.2m below ground level

Also show the line of steel truss on the drawing

Solution:

External dimensions of the building:

Along X-direction = 11.75 + 2 x 0.25 = 12.25 mAlong Z-direction = 19.75 + 2 x 0.25 = 20.25 m

Centre line dimensions of the building:

Along X-direction = 12.25 – 0.45 = 11.80 mAlong Z-direction = 20.25 -0.25 = 20.00 m

Procedure for drawing the lay out plan

Note: Use Millimeter units for linear dimensions

1. Draw the centerline of the building having 11,800mm along X-direction and20,000 mm along Z-directions

2. Mark these centre lines as grid lines A and D for lines parallel to Z-directions& grid lines 1 and 6 for lines parallel to X-axis

3. Measure 4000mm from grid lines A and D to get grid line B and C

4. Measure 4000mm c/c along Z-axis starting from grid line 1 to get grid lines 2,3, 4 and 5

5. Draw rectangular filled box of size 250mm x 450mm at the intersection ofgird lines along A and D to indicate the position of column along these gridlines as shown in Fig. 1.8

6. Draw rectangular filled box of size 250mm x 450mm at the intersection ofgrid lines 1,6 with B and C respectively as shown in Fig. 1.8

7. Draw rectangles each of size 1400 mm x 1800mm symmetrically with respectto centre of column to indicate excavation marking for all columns. Here the

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shorter side of this rectangle box is parallel to the shorter side of column asshown in Fig. 1.8

8. Sectional elevation and plan of the footing of column is drawn just to the rightof the key plan drawn as shown in Fig. 1.8

Fig. 1.8a Layout Drawing

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Fig. 1.8b Footing Details

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