23/11/2025
Saya guna panduan kedalaman rasuk
Beam Depth = Span/12
[atau Span/14 utk beberapa keadaan]
sudah selama 30 tahun dan dapati saiz rasuk ini untuk rekabentuk awalan arkitektur selaras atau bersesuaian dengan rekabentuk jurutera struktur.
Mungkin panduan ini akan bermanfaat untuk para arkitek.
https://www.facebook.com/share/p/1WSxWiqM7X/
Beam Design
A reinforced concrete beam must be proportioned according to its span (L) so that it safely carries loads without excessive bending or shear.
The image shows general guidelines, not exact code rules — final sizes must be based on structural design.
1. Beam Depth (H)
H = L / 12
The depth (height) of the beam should be about 1/12 of the span length.
Example: If span L = 6 m,
→ H ≈ 6000 / 12 = 500 mm
This ensures the beam can resist bending moments.
2. Beam Width (B)
B = L / 24
The width of the beam is generally half of its depth.
Example: If L = 6 m,
→ B = 6000 / 24 = 250 mm
This proportion keeps the beam stable and avoids cracking.
3. Longitudinal Reinforcement (Main Bars)
The top image shows red lines representing the tension reinforcement.
For long spans, beams tend to lift upward near supports due to negative moments.
Additional bars called “swings” or extra top bars are placed over supports.
Purpose:
✔ Controls cracking
✔ Handles negative bending moment
✔ Strengthens beam over supports
4. L/4 Reinforcement Zones
The bottom image shows L/4 zones at both ends.
Why L/4?
Negative bending moments occur near supports.
So extra top bars must extend:
L/4 from the support into the span.
Example: If L = 6 m,
L/4 = 1.5 m
→ Extra top bars must extend 1.5 m from each support.
5. Main Idea
A beam must be:
Deep enough to resist bending
Wide enough to ensure stability
Properly reinforced at mid-span and supports
Extra top bars are required at ends (L/4 region)
6. Important Note
The images provide general proportions only.
Actual design depends on:
Load
Span
Material strength
Building code (ACI / IS / BNBC etc.)
Structural calculations are always required.
Related Hashtag: