---
title: "Slab base for ISHB 350@710.2, 1000 kN"
subject: "Design of Steel and Timber Structure"
chapter: 6
key: "semester_6/design_of_steel_and_timber_structure:slab-base-ishb350-1000kn"
source: https://www.bctengineer.com/q/semester_6/design_of_steel_and_timber_structure/slab-base-ishb350-1000kn
site: BCT Engineering
---

# Slab base for ISHB 350@710.2, 1000 kN

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

- Asked in: 2073 Magh, 6 marks; 2072 Asoj, 6 marks (asked 2 times)
- Video: [Design of slab base](https://www.youtube.com/watch?v=gInOIJdb3_0) — WIT Solapur - Professional Learning Community
- 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/slab-base-ishb350-1000kn
- Whole chapter: https://www.bctengineer.com/md/semester_6/design_of_steel_and_timber_structure/chapter-6

## Question

Design a slab base for a column ISHB 350@710.2 N/m subjected to a factored axial compressive load of 1000 kN. Concrete pedestal of grade M20.

## Short answer

Bearing strength of M20 concrete is 9 MPa. Base plate 450×350 mm; pressure 6.35 MPa. Thickness from bending and flange requirement is 12 mm. Use 4 M20 anchor bolts and6 mm fillet weld.

## Answer

**Data:** ISHB 350 @ 710.2 N/m (72.4 kg/m): $h=350$, $b_f=250$, $t_f=11.6$, $t_w=10.1$ mm. Factored load $P=1000$ kN; pedestal M20; steel E250 ($f_y=250$).

#### 1. Bearing strength of concrete (IS 800:2007 cl. 7.4.1)
$0.45f_{ck}=0.45\times20=9.0$ N/mm²

#### 2. Plate size
$$
A_{req}=\frac{1000\times10^3}{9.0}=111111\ \text{mm}^2
$$
Provide equal projections of 50 mm: $L=350+2\times50=450$ mm, $B=250+2\times50=350$ mm. Area $=157500$ mm² $>A_{req}$ ✓
$$
w=\frac{1000\times10^3}{450\times350}=6.35\ \text{N/mm}^2<9.0
$$

#### 3. Thickness (cl. 7.4.3.1)
Projections $a=b=50$ mm:
$$
t_s=\sqrt{\frac{2.5w(a^2-0.3b^2)\gamma_{m0}}{f_y}}=\sqrt{\frac{2.5\times6.35\times(50^2-0.3\times50^2)\times1.10}{250}}=11.06\ \text{mm}
$$
Also $t_s\ge t_f=11.6$ mm. **Provide $t_s=12$ mm.**

#### 4. Connections
- Column to plate: 6 mm fillet weld all round (nominal; column end machined for bearing).
- Anchor bolts: 4 nos. M20 (minimum), embedded 450 mm, with washer plate, placed outside the flanges.

**Answer: base plate 450 × 350 × 12 mm, 4 anchor bolts M20, 6 mm weld.**

## Check yourself

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

1. A_req for P = 1000 kN, M20 pedestal is
   A. 111111 mm2
   B. 50000 mm2
   C. 200000 mm2
   D. 157500 mm2
   Answer: A. A_req = 1000 x 10^3 / 9.0 = 111111 mm2. (Key point: Required area)

2. ISHB 350 (350 x 250) with 50 mm projections gives plate
   A. 450 x 350 mm
   B. 350 x 250 mm
   C. 400 x 300 mm
   D. 550 x 450 mm
   Answer: A. Add 2 x 50 mm to each dimension. (Key point: Plate size)

3. w = 1000 x 10^3 /(450 x 350) =
   A. 9.0 N/mm2
   B. 11 N/mm2
   C. 6.35 N/mm2, less than 9.0
   D. 2.2 N/mm2
   Answer: C. Pressure must not exceed 0.45 fck = 9.0 N/mm2. (Key point: Actual pressure)

4. Calculated ts = 11.06 mm but tf = 11.6 mm. What is provided?
   A. 11 mm
   B. 10 mm
   C. 16 mm
   D. 12 mm
   Answer: D. ts must be at least tf and calculated value; round up to 12 mm. (Key point: Thickness provided)

## Related in Design of Steel and Timber Structure

- [Gusseted base for ISHB 350, 2000 kN](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Agusseted-base-ishb350-2000kn) — Design of Steel and Timber Structure, chapter 6
- [Foundation base for ISHB 350 column](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Afoundation-base-ishb350-120kn) — Design of Steel and Timber Structure, chapter 6
- [Base plate for ISHB 350, 1200 kN](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Abase-plate-ishb350-1200kn) — Design of Steel and Timber Structure, chapter 6, asked 2×
- [Splice plate for ISHB 350 column](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Acolumn-splice-ishb350-1000kn) — Design of Steel and Timber Structure, chapter 6
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- [Slab base for ISMB 350, 850 kN service](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Aslab-base-ismb350-850kn) — Design of Steel and Timber Structure, chapter 6

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