Detailed Guide to Symbols in Structural Steel Drawings

Many professionals involved in construction projects may find it challenging to understand the symbols used in structural steel drawings. This lack of familiarity can significantly hinder the workflow, and sometimes, misinterpretation of these symbols can lead to material wastage, reduced project quality, and even structural risks.

The following article provides a detailed guide on how to read and interpret these symbols for better comprehension and application in structural steel drawings.

What Are Structural Steel Drawings?

Structural steel drawings are technical documents specific to the construction industry. They detail the dimensions, shapes, and assembly processes of steel components, including structural members and their connections. These drawings use standardized symbols to guide engineers in executing the design as specified by the designer or client.

Without proper instruction, understanding these symbols can be challenging. Consequently, you may find it difficult to ensure that your project is being executed as planned. This can directly impact the quality of your construction oversight.

(Illustration of a structural steel drawing)

How to Read Symbols in Structural Steel Drawings

Typically, structural steel drawings contain numerous symbols such as circles, squares, and triangles. Before diving into the more complex symbols, it is essential to understand the basic types of structural steel and their associated symbols.

There are three common types of steel structures: Steel frame system (used for constructing columns, beams, and some projects requiring firmness and good load-bearing); Shell steel system (capable of withstanding good deformation, often applied to large projects requiring flexibility in shape and aesthetics); Mixed shell and frame system (a complex structure combining shell and frame systems, meeting high requirements for loads, large volume, durability, flexibility, and aesthetics).

Symbols for Common Types of Steel

• Angle Steel Symbols: “L b1 x b2 x s” indicates the type of unequal leg steel. In contrast, “L b x s” indicates equal leg angle steel (where b is the width and s is the length of the leg)
• U/C-shaped Curve Steel Symbol (trough): Cn. Where n is the steel code corresponding to the height of the steel (h). The basic dimensions still include width b, thickness s, and average thickness t.
• I-shaped Steel Symbol: In. Where n is the steel code corresponding to the height of the steel (h). The basic dimensions still include width b, thickness s, and average thickness t.

Symbols for Some Other Types of Steel:

– Diameter: ø

– Solid Round Steel: ●. Example: ●ø15 (solid round steel with a diameter of 15)

– Round Pipe Steel: ○. Example: ○ø15 (round pipe steel with a diameter of 15)

– Solid square steel: ◾. Example: ◾30 (solid square steel with a side length of 30)

– Regular Box Steel: ☐. Example: ☐30 (square box steel with a side length of 30); ☐30×20 (rectangular box steel with a length of 30 and a width of 20)

– Plate Steel: ➖. Example: ➖ 30x15x10 (plate steel length 30, width 15 and thickness 10). In case the steel plate is used as a pad or web plate, you can write the dimensions and thickness right after the steel plate symbol.

– A few other types of steel are symbolized in letters according to their cross-sectional shapes. For example: T, Z or H…

Note:

The symbols in steel structure drawings usually indicate the cross-section code after the quantity of steel (for example: 3T30x3). Additionally, using symbols to describe the type of steel structure is also viable, such as ⌊30×3 or ⌉⌈40×3⌉.

Connection Types in Structural Steel Drawings

In addition to understanding the basic information about the types of steel structures, you should also pay attention to their connection forms. Typically, there are two types of connections used: detachable connections (nails, screws, bolts, …) and non-detachable connections (rivets, welding, …).

Symbols for Bolted Connections

For each steel structure drawing, connections made by nails or bolts are presented according to a previously agreed-upon symbol. Based on TCVN number 2234-77 section “Establishing steel structure drawings”. To clarify information, please refer to the table below.

Symbols for Welded Connections

For welded connections, they are typically divided into four types: butt welds (D), T-joint welds (T), fillet welds (G), and spot welds (C). Similar to detachable connections, welded connections also have standardized symbols as defined by TCVN 3746-83 as follows:

This article has introduced some basic information about symbols in structural steel drawings. However, due to the specialized nature of the topic, it is challenging to condense everything into a single article. We hope this guide has provided valuable insights for your needs. Stay tuned for more in-depth articles on this subject!

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