---
title: "Ductile design per IS 13920, beam and column"
subject: "Design of RCC Structure"
chapter: 12
key: "semester_7/design_of_rcc_structure:ductile-design-per-is-13920-beam"
source: https://www.bctengineer.com/q/semester_7/design_of_rcc_structure/ductile-design-per-is-13920-beam
site: BCT Engineering
---

# Ductile design per IS 13920, beam and column

Design of RCC Structure · Chapter 12: Introduction to Earthquake Resistant Design and Provisions for Ductile Detailing

- Asked in: 2082 Bhadra, 2+2+2 marks
- Video: [Ductile detailing of Beams as per IS-13920-2016 | detailing of beams |Beam detailing as per IS-13920](https://www.youtube.com/watch?v=OtGZM99vFLg) — Civil Engineering Mastery
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/design_of_rcc_structure/ductile-design-per-is-13920-beam
- Whole chapter: https://www.bctengineer.com/md/semester_7/design_of_rcc_structure/chapter-12

## Question

Perform the ductile design and detailing requirements of flexural reinforcement in beam and for axial load as well as biaxial bending moments in columns as per IS 13920. Explain with neat drawings.

## Short answer

For beams: design under seismic combos, ensure b≥200mm, b/D≥0.3, D≤L/4; limit ρ, provide two continuous bars top and bottom, bottom steel ≥50% top steel; shear designed for hinge capacity. For columns: size limits, biaxial bending check, strong-column weak-beam (ΣMc≥1.4ΣMb), confining hoops over lo with Ash=0.18 s h (fck/fy)(Ag/Ak−1), and mid‑height splices.

## Answer

#### Ductile design of beam flexural reinforcement
1. Analyse the frame for the gravity and seismic load combinations ($1.5(DL\pm EL)$, $1.2(DL+LL\pm EL)$, $0.9DL \pm 1.5EL$) and get the design hogging and sagging moments at the faces of the supports.
2. Check the geometry: $b \ge 200$ mm, $b/D \ge 0.3$, $D \le L/4$.
3. Design the steel for $M_u$ using IS 456 limit state design, keeping $x_u \le x_{u,max}$.
4. Detail it: $\rho_{min} = 0.24\sqrt{f_{ck}}/f_y \le \rho \le 2.5\%$; two bars continuous at the top and bottom; bottom steel at a joint face $\ge 50\%$ of the top steel; capacity at any section $\ge 25\%$ of the maximum end capacity.
5. Shear: design for the shear from the hinge capacities,

$$
V_{u} = V_{u,a}^{D+L} \pm 1.4\,\frac{M_{u,lim}^{As} + M_{u,lim}^{Bh}}{L_{AB}}
$$

where $M_{u,lim}$ are the moments of resistance of the sagging and hogging steel provided at the two ends A and B. Provide closed stirrups with $135^\circ$ hooks, at spacing $\le \min(d/4,\ 8\phi,\ 100)$ within $2d$ of the joint.

#### Ductile design of columns (axial load plus biaxial bending)
1. Size: $b \ge 200$ mm and $b/D \ge 0.4$.
2. Design for $P_u$ and the biaxial moments $M_{ux}$, $M_{uy}$ using IS 456 cl. 39.6:

$$
\left(\frac{M_{ux}}{M_{ux1}}\right)^{\alpha_n} + \left(\frac{M_{uy}}{M_{uy1}}\right)^{\alpha_n} \le 1
$$

with $\alpha_n$ from $P_u/P_{uz}$ (1.0 to 2.0). Longitudinal steel between 0.8% and 4% (IS 13920), including at laps.
3. Strong column-weak beam: $\sum M_{c} \ge 1.4\sum M_b$ at each joint (IS 13920:2016; ACI 318 uses 1.2).
4. Column shear: $V_u = 1.4\,\dfrac{M_{u,lim}^{bL} + M_{u,lim}^{bR}}{h_{st}}$; provide confining hoops over $l_o = \max(D,\ h/6,\ 450)$ at 75-100 mm, with $A_{sh} = 0.18\,s\,h\,(f_{ck}/f_y)(A_g/A_k-1)$.

```text
 BEAM: |hoops 2d @ <=100|   d/2    |hoops 2d @ <=100|
 COLUMN: hoops lo @ 75-100 | normal | hoops lo @ 75-100
```

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Design shear in ductile beams is based on:
   A. Gravity load shear only
   B. Shear from hinge (flexural) capacities at the ends plus gravity shear, with factor 1.4
   C. Half the elastic shear
   D. Minimum shear steel only
   Answer: B. Capacity design makes shear strength exceed flexural strength. (Key point: Beam design shear)

2. Columns under axial load and biaxial moments are checked using:
   A. (Mux/Mux1)^an + (Muy/Muy1)^an <= 1 with an from Pu/Puz (1.0 to 2.0)
   B. Mux + Muy <= Pu
   C. Only Mux
   D. Mux x Muy <= 1
   Answer: A. IS 456 cl. 39.6 interaction equation. (Key point: Biaxial bending check)

3. Column longitudinal steel limits are:
   A. 0.8% to 6% (4% at laps)
   B. 0.1% to 1%
   C. 2.5% fixed
   D. 6% to 10%
   Answer: A. Min 0.8%, max 6%, 4% at laps. (Key point: Column steel limits)

4. At each joint the column moment capacity should be:
   A. Equal to beam capacity
   B. Less than 0.5 times beam capacity
   C. About 1.1 to 1.4 times the sum of beam moments
   D. Zero
   Answer: C. Sum Mc >= 1.1 (to 1.4) sum Mb ensures beam hinging. (Key point: Strong column weak beam ratio)

## Related in Design of RCC Structure

- [Ductile detailing of beams and columns](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aductile-detailing-of-beams-and-columns) — Design of RCC Structure, chapter 12, asked 2×
- [Ductile detailing of columns, confining steel](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aductile-detailing-of-columns-confining-steel) — Design of RCC Structure, chapter 12, asked 4×
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- [Short column 300x450 with ductile detailing](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Ashort-column-300x450-with-ductile-detailing) — Design of RCC Structure, chapter 10
- [Beam-column joint with ductile details](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Abeam-column-joint-with-ductile-details) — Design of RCC Structure, chapter 12, asked 2×
- [Importance of ductile detailing, sketches](https://www.bctengineer.com/question.md?key=semester_7%2Fdesign_of_rcc_structure%3Aimportance-of-ductile-detailing-sketches) — Design of RCC Structure, chapter 12

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