Introduction
The structure drawing must include reinforcement details as well as any other information required for detailing the reinforcement. The drawings must also include separate notes indicating live loads, concrete strength, steel quality and grade, the number of bars to be lapped and the lengths of the laps, and any special instructions for formwork erection, fabrication, and steel placement.
Paper Size for Structure Drawing
For preparing the structure drawing recommended paper sizes shall be used. This is because it is convenient for preparing the drawing at the office and enables easy of reading the drawings at the site. The recommended paper size are as follows:
| Sl.No. | Designation | Trimmed Size (mm X mm) | Untrimmed Size (Min) (mm X 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 |
The dimensions recommended for all margins and the divisions of drawing sheets into zones are given in the figure below.
The title block is an important feature of a drawing and should be placed in the bottom right-hand corner of the sheet, where it will be easily visible when the prints are folded in the prescribed manner. The recommended title block size is 185 X 65 mm.
Separate sheets should be used for each type of structural member or unit, such as a floor slab on one sheet, beams on another, columns on yet another, and so on. For small jobs, each standard-size sheet could be used to detail one floor of the structure, such as the ground floor slab, beams, and columns on one sheet and the first-floor members on another.
Layout -A single standard layout for detailing reinforced concrete drawings cannot exist. Practice drawing the usual (key) plan in the upper left sheet, with elevations and details below and on the right side of the plan. Schedules and bending details are shown in the drawing’s upper right corner. Figure 3.2 depicts the recommended layout in broad strokes. In larger projects, the bending schedule can be removed from individual drawings and replaced with a separate bending schedule drawing.
Dimensions of Drawings
Scale for Structure Drawing
The scales must be selected in a way that makes the details stand out clearly and keeps the drawings at a manageable size. No general advice can be given in this regard; the choice of scale will depend on the detailer’s or designer’s preferences. Below are some examples of commonly used scales:
| Drawings | Scale |
|---|---|
| Plans | 1 : 100, 1 : 50 |
| Elevations | 1 : 5, 1 : 30 |
| Sections | 1 : 50, 1 : 30, 1 : 25, 1 : 20, 1 : 15, 1 : 10 |
Information Shown on Structural Drawings
The sizes of any necessary chamfers and fillets at corners must be included in the overall dimensions of the concrete members. Additionally, the required dimensions of the concrete cover to the reinforcement, as well as the precise position, shape, size, and spacing of the reinforcement within concrete members, must be provided.
The location of any holes needed for service pipes in the members, the specifics of any pipes or other fixings that must be cast into the concrete, the location and specifics of construction joints and special recesses, etc., must all be indicated.
On detailed drawings, notes can be freely used. The most significant is the “bar marks,” which provide details about each or a group of related reinforcing bars. The notes must not be ambiguous and must be brief and precise. The notes that apply to the entire drawing, like the requirements for the concrete to be used, the dimensions of the chamfers and fillets, and the concrete cover, etc., can be grouped under a general heading at the bottom or side of the drawing.
The main dimensions of the structure, such as beams, wall panels, floor panels and columns are: Also, the thickness of the bottom and walls calculated by the designer must be indicated on the drawing.
The main dimensions of the structure, such as the distances between columns, heights between floors, beam and column sizes, floor and wall thicknesses, etc., as calculated by the design engineer, shall also be shown on the drawings.
Sections should be drawn at least twice the scale of the plan or elevation they reference. Complex connections such as the intersection of columns and beams can be detailed at larger scales such as 1:4.
The structure drawing should be complete and clear, leaving no doubt about any aspect of the construction. Complete and accurate dimensions must be displayed. To ensure proper rebar placement, clear and adequate details regarding special and unusual conditions should be provided. Detail of coping and wall intersection. Structural joints, window and door openings, and similar special features should be indicated on the corresponding drawings using sketches where appropriate.
Lengths of laps, points of the bend. cut-off bars should be specified by the designer. The dimensions are L/7, L/5 and L/4. etc. shown on typical drawings shall not be used unless justified by structural analysis.
Wherever possible. all control and construction joints should be indicated on structural d.rawings and construction details provided for such joints.
Symbols and Abbreviations
Symbols and abbreviations to be used on drawings of reinforced concrete structures. All reinforcing bars used in the structure must be properly labelled and numbered on both the drawing and floor plan.
- Symbols for reinforcement bar: –
| ø | plain round bar or diameter of plain round bar |
| ☐ | plain square bar or side of plain square bar |
| # | deformed bar |
- Symbols related to the shape of the bar along its length
| Alt | Alternate bar |
| Bt | Bent bar |
| B | Bottom bar |
| max | Maximum |
| min | Minimum |
| St | Straight bar |
| Stp | Stirrup |
| Sp | Spiral |
| Ct | Column tie |
| T | Top bar |
Representation of Symbols, Abbreviations and Notes
Some of the representations of symbols, abbreviations and notes shall be used in the following manner in order to avoid ambiguity.
a) # 20@ 200 means 20 mm diameter deformed bars spaced at 200 mm centre-to-centre.
b) 20-#12 means 20 numbers of 12 diameter deformed bars
c) ø32-St-12 EW means 12 numbers of 32 mm diameter plain round straight bars in each direction
Schedules
The reinforcement details of slabs, beams, columns and many other structural components can be effectively shown on working drawings in a tabular format known as a schedule.
Marks for the Part of Buildings
Marks are used to designating the different structural members of a structure. Different structural members of a structure shall be marked using symbols, abbreviations and notations. A keyframe plan should be prepared with a convenient scale. The frame prepared is in two axes indicated with alphabets and the other axes with numbers. These keyframe shows the floor plan and may be used for all floor or different key frame may be used for a different layout.
Column: – Columns and foundations shall be specified by grid arrangement giving reference to the floor.
Beam, lintel, tie beam and slab: – These members may be consecutively numbered from left-hand to corner. The longitudinal section of the beam is shown by the grid of the column or number of the column supporting the beam.
Wall: – Marking of walls shall be made in the serial order starting from the top left corner of the plan and proceeding towards the right.
Plotting Out of Structure drawing from CAD Program
Drawing and drafting of the structure are prepared in the computer program or application. These days computer applications are abundantly used for preparing drawings. AutoCAD is the most popular application for preparing structure drawings, in fact, all kinds of drawings. Revit structure is another dynamic BIM software from AutoDesk for the purpose of analysing and printing out the drawing.
The printed drawing shall be clean and neat. There should not be overlapping of annotation, dimension and text. The scale of the drawing shall be specified. Plotting or publishing the CAD drawing shall be done on the recommended sheet size.
References :
- SP 34-1987: Handbook on concrete reinforcement and detailing, BIS, New Delhi, 1987.
- IS 456-2000: IS code for practice for plain and reinforced concrete, BIS, New Delhi, 2000.
