Differences between drawings used in structural engineering works

The following types of drawings are commonly found in the office of a structural engineer.

Structural Drawings

The main purpose of preparing structural drawings is to explain the shape and position of all the parts of the structure. Such drawings are used to progress the Architect’s concept and then to enable construction of the structure on site. Structural drawings are also necessary for the preparation of the reinforcement drawings. Drawings for concrete structures consist of dimensional data necessary for the setting out and construction of the concrete formwork, e.g.:

• Setting out of the concrete structure on site.
• Plans, sections and elevations where appropriate showing layout, dimensions and levels of all concrete members within the structure.
• Location of all holes, chases, pockets, fixings and items affecting the concrete work.
• North point.
• Notes on specifications, finishes and cross references of the construction.

They also provide the detailer with the layout and sectional information required to specify the length, shape and number of each type of reinforcing bar [the Bar Bending Schedule (BBS)]. All these matters should be considered at the outset of every drawing programme.

Reinforcement Drawings

Reinforcement drawings describe and locate the reinforcement in relation to the outline of the concrete work and to relevant holes and fixings. Generally, circular holes up to 150 mm diameter and rectangular holes up to 150 × 150 mm in slabs or walls need not be indicated on the reinforcement drawings. All other holes should be indicated on the reinforcement drawing and should be trimmed, where necessary, by suitable reinforcing bars. Separate drawings or plans for top and bottom layers of reinforcement should be used only for fabric and in exceptional cases, e.g. voided bridge decks and box girders with four layers of reinforcement.

Reinforcement drawings are primarily for the use of the steel fixers. It is preferable that general arrangement and reinforcement drawings be kept separate, but for simple structures a combined drawing may be appropriate.

Standard Details

Standard details are those details that are used on a repetitive basis. Details used in this way must be carefully worked out, fully detailed and totally applicable to each location where they are to be specified. Standard details may apply to concrete profiles or reinforcement arrangements, and they should be drawn to a large scale.

Diagrams

Diagrams may be used as a means of communicating design ideas during both pre-contract work and the post-contract period. Diagrams may be formally presented or sketched freehand provided they convey information clearly, neatly and in detail. The information contained in diagrams should be drawn to scale.

Record Drawings

When the reinforced concrete structure has been constructed, the original drawings used for the construction process should be amended to indicate any changes in detail that were made during the construction process. A suffix reference should be added to the drawing number to indicate the drawing is a ‘record’ drawing. The amendments should be described in writing against the appropriate suffix reference. A register of drawings should be kept listing reference numbers, titles and recipients of drawings. The record drawings should be submitted to the client for safekeeping at handover of the project.

For further reading, consult,

Standard Methods of Detailing Structural Concrete; a manual of best practice (third edition). The Institution of Structural Engineers, London, United Kingdom.