---
title: "Base plate for ISHB 350, 1200 kN"
subject: "Design of Steel and Timber Structure"
chapter: 6
key: "semester_6/design_of_steel_and_timber_structure:base-plate-ishb350-1200kn"
source: https://www.bctengineer.com/q/semester_6/design_of_steel_and_timber_structure/base-plate-ishb350-1200kn
site: BCT Engineering
---

# Base plate for ISHB 350, 1200 kN

Design of Steel and Timber Structure · Chapter 6: Compression Members

- Asked in: 2069 Bhadra, 10 marks
- Video: [#SlabBase #Design Of Slab Base #Design of steel structures #Welding #BasePlate #IS 800:2007 #Bolting](https://www.youtube.com/watch?v=aM4Dbnylm8U) — CIVIL ENGINEERING COURSE Theory & Practical
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/design_of_steel_and_timber_structure/base-plate-ishb350-1200kn
- Whole chapter: https://www.bctengineer.com/md/semester_6/design_of_steel_and_timber_structure/chapter-6

## Question

Design the base plate for a ISHB 350 column to carry factored load of 1200KN. Take E250 grade of steel and M20 grade of concrete.

## Short answer

Bearing strength 9 N/mm2; required area 133333 mm2; use 450 x 350 mm plate, pressure 7.62 N/mm2. Thickness from cantilever projection is 12.11 mm, not less than flange 11.6 mm, so provide 14 mm plate with 4 M20 anchor bolts and 6 mm fillet weld.

## Answer

**Data:** ISHB 350 @ 72.4 kg/m: $h=350$, $b_f=250$, $t_f=11.6$, $t_w=10.1$ mm. Factored load $P=1200$ kN; steel E250; concrete M20.

#### 1. Bearing strength of concrete (IS 800:2007 cl. 7.4.1)
$0.45f_{ck}=0.45\times20=9.00$ N/mm²

#### 2. Plate size
$$
A_{req}=\frac{P}{0.45f_{ck}}=\frac{1200\times10^3}{9.00}=133333\ \text{mm}^2
$$
Projection of about 50 mm all round the column (not less than 50 mm): $L=350+2\times50=450$ mm, $B=250+2\times50=350$ mm. Area provided $=157500$ mm² $>A_{req}$ ✓
$$
w=\frac{P}{BL}=\frac{1200\times10^3}{450\times350}=7.62\ \text{N/mm}^2<9.00\ \text{N/mm}^2
$$

#### 3. Thickness (cl. 7.4.3.1)
Projections $a=50$ mm and $b=50$ mm (larger and smaller):
$$
t_s=\sqrt{\frac{2.5w(a^2-0.3b^2)\gamma_{m0}}{f_y}}=\sqrt{\frac{2.5\times7.62\times(50^2-0.3\times50^2)\times1.10}{250}}=12.11\ \text{mm}
$$
It must also be not less than the flange thickness $t_f=11.6$ mm. **Provide $t_s=14$ mm.**

#### 4. Connections
- The column end is machined to bear on the plate; connect with a nominal 6 mm fillet weld all round (load is transferred mainly by contact).
- Anchor bolts: 4 nos. M20, embedded about 450 mm with a washer plate (for erection and to resist any uplift).

**Answer: base plate 450 × 350 × 14 mm, 4 anchor bolts M20, 6 mm weld, pedestal of M20 concrete.**

## Check yourself

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

1. Which expression gives the minimum base plate area for the ISHB 350 column on M20 concrete?
   A. 1200x10^3 / 20
   B. 1200x10^3 / (0.45 x 20)
   C. 1200x10^3 / (0.67 x 20)
   D. 1200x10^3 x 9
   Answer: B. A_req = P/(0.45 f_ck) = 1200x10^3/9 = 133333 mm^2. (Key point: Required area)

2. For ISHB 350 (h = 350, b_f = 250) with 50 mm projection all round, what are L x B?
   A. 400 x 300 mm
   B. 450 x 350 mm
   C. 350 x 250 mm
   D. 500 x 400 mm
   Answer: B. L = 350 + 2x50 = 450 mm and B = 250 + 2x50 = 350 mm, giving 157500 mm^2 > 133333 mm^2. (Key point: Plate dimensions)

3. Which statement matches the design of the thickness and connections?
   A. The thickness formula gives 12.11 mm, which is rounded to 14 mm and is at least t_f = 11.6 mm
   B. The thickness is 12.11 mm exactly, which is less than t_f, so it fails
   C. The column is welded all round with 6 mm fillets because it must carry the full load by welds
   D. Four M20 anchor bolts carry the entire axial compression
   Answer: A. t_s = 12.11 mm > t_f = 11.6 mm, so it is rounded up to 14 mm. Since the column end is machined, load goes mainly by contact and the 6 mm weld is nominal. (Key point: Thickness and connections)

## Close variants set in other exams

- [Base plate for ISHB 450, 1400 kN](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Abase-plate-ishb450-1400kn) — Design of Steel and Timber Structure, chapter 6, asked 2×

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