Symbols and Notations Used in Reinforcement Plans in BBS

Reinforcement plans, commonly referred to as reinforcement drawings, are vital documents in construction that detail the placement, size, and type of reinforcement bars used in concrete structures. These plans include various symbols and notations to clearly represent the reinforcement requirements. Understanding these symbols is essential for preparing an accurate Bar Bending Schedule (BBS) and for efficient execution in the field.

Common Symbols and Notations

The following are some of the most commonly used symbols and notations in reinforcement plans:

• Reinforcement Bar (Rebar): A line with a specific diameter and length marked, often with a bar mark to indicate the type or size of the bar. For example, 16Ø indicates a 16 mm diameter rebar.
• Bar Mark: A label assigned to each type of bar for identification in the drawing and BBS. For instance, T1 may represent the top reinforcement bar in a beam, while B1 represents the bottom reinforcement.
• Hooks: Symbols like 90° Hook and 135° Hook indicate the bends in the bars. The angles are specified to help interpret how the bars are shaped for anchorage.
• Stirrups: Symbols for stirrups, or ties, are typically represented by a closed-loop or square shape with a bar diameter and spacing indicated. For example, a symbol for stirrups might be marked as 8Ø@150, meaning 8 mm diameter bars placed 150 mm apart.
• Length of Bar: Bars are usually marked with a line indicating the total length, including the development length, lap length, or anchorage length, as required by the design.
• Spacing: The spacing between bars is denoted by @, which means "at" in reinforcement notations. For instance, 200@250 indicates bars placed 250 mm apart, with 200 bars in the total span.
• Lap Length: A notation for lapped reinforcement bars shows the overlapping portion of bars. This is typically specified with a length dimension, such as Lap Length = 40d, where d is the diameter of the bar.

Example of Reinforcement Plan Symbols

Consider a simple reinforcement plan for a beam:

• Top Bars: 2T1 16Ø (Two 16 mm diameter bars placed at the top of the beam)
• Bottom Bars: 3B1 20Ø (Three 20 mm diameter bars placed at the bottom of the beam)
• Stirrups: S1 8Ø@150 (Stirrups made of 8 mm diameter bars placed 150 mm apart)

Bar Bending Schedule Example for the Beam

The corresponding BBS might be prepared as follows:

Conclusion

The symbols and notations used in reinforcement plans are essential for accurately interpreting reinforcement details. By understanding these symbols, a Bar Bending Schedule (BBS) can be prepared efficiently, ensuring the correct material estimation and smooth construction process. Proper use of these notations helps in avoiding errors during reinforcement installation and enhances the quality and durability of the structure.