1. Cellular Beam (CB) — โครงสร้างและพารามิเตอร์
GEOMETRY
H_cb Overall depth of CB
a₀ Opening diameter
S C/C spacing of openings
TEE SECTION
hs Tee stub height = (H_cb − a₀)/2
hw Web stem = hs − tf
e Web post width = S − a₀
NOTE
CB = H-beam cut in half along the web, re-welded with halves offset upward to form circular openings.
✦ Material exists only in 2 Tees (top + bottom)
✦ No steel in opening zone
2. Calculation Steps (ขั้นตอนคำนวณ)
1hs = (H_cb − a₀) / 2 Tee stub height (mm)
2hw = hs − tf Web stem height, excluding flange (mm)
3A_f = B × tf · A_w = tw × hw Flange and web stub areas (mm²)
4A_tee = A_f + A_w Area of one Tee section (mm²)
5ȳ = (A_f·tf/2 + A_w·(tf+hw/2)) / A_tee Tee centroid from flange tip (mm)
6d = H_cb/2 − ȳ Distance from Neutral Axis to tee centroid (mm)
3. Section Properties Formulas
I_x — Second Moment of Area about X-axis (cm⁴)
I_f= B·tf³/12 + A_f·(ȳ − tf/2)²mm⁴
I_w= tw·hw³/12 + A_w·(ȳ − tf − hw/2)²mm⁴
I_tee= I_f + I_w (Parallel Axis Theorem)mm⁴
I_x
= 2·(I_tee + A_tee·d²) / 10⁴
cm⁴
📌 Calculated values are 3–5% lower than TCS/Stream Rice catalog
because fillet radius (r₁) is not included → conservative for design use
Z_x — Plastic Section Modulus (cm³)
PNA (Plastic Neutral Axis) is at H_cb/2 (symmetric section).
Each Tee contributes: A_tee × d
Z_x
= 2 · A_tee · d / 10³
cm³
✦ Only actual material (2 Tees) is counted
✦ Web at opening zone excluded → correct net section ✓
S_x · I_y · S_y
S_x
= I_x · 10⁴ / (H_cb/2) / 10³
cm³
I_y
= (2·tf·B³/12 + 2·tw³·hw/12) / 10⁴
cm⁴
← 2 flanges (B³ about Y-axis) ← 2 web stubs (tw³ about Y-axis, not hs³)
S_y
= I_y · 10⁴ / (B/2) / 10³
cm³
4. Preset Geometry — F1 Floor / F2 Roof
F1 — Floor Beam
a₀= 1.0 × Hmm
S= 1.5 × a₀mm
H_cb≈ 1.3–1.4 × H (from catalog)mm
Applications: Floors, Carparks, Offshore structures
Objective: Optimise load/weight ratio
Code range: a₀=0.8–1.1h · S=1.2–1.7a₀ · H₂=1.3–1.4h
F2 — Roof Beam
a₀= 1.2 × Hmm
S= 1.2 × a₀mm
H_cb≈ 1.4–1.6 × H (from catalog)mm
Applications: Roofing, Gangways, Wide-span purlins
Objective: Optimise height/weight ratio
Code range: a₀=1.0–1.3h · S=1.1–1.3a₀ · H₁=1.4–1.6h
📌 H_cb (Preset ●) — ค่า H_cb ใช้จาก TCS / Stream Rice catalog โดยตรง · ไม่ได้คำนวณจากสูตร
📌 H_cb (Formula ○) — คำนวณจาก H_cb ≈ a₀ × 1.4 (F1) หรือ a₀ × 1.32 (F2) แล้ว clamp ใน Code range
📌 Custom mode — เมื่อ a₀ ตรงกับ preset → ใช้ H_cb จาก catalog · ไม่ตรง → คำนวณจากสูตรข้างต้น
📌 I_x — ต่ำกว่าตาราง ~3–5% เนื่องจากไม่รวม fillet radius (r₁) → conservative, suitable for design
