---
title: "Design load P on SC 250, two brackets"
subject: "Design of Steel and Timber Structure"
chapter: 4
key: "semester_6/design_of_steel_and_timber_structure:bracket-sc250-two-plates-p"
source: https://www.bctengineer.com/q/semester_6/design_of_steel_and_timber_structure/bracket-sc250-two-plates-p
site: BCT Engineering
---

# Design load P on SC 250, two brackets

Design of Steel and Timber Structure · Chapter 4: Connections in Steel Structures

- Asked in: 2070 Magh, 12 marks
- Video: [eccentric bolted connection analysis problem](https://www.youtube.com/watch?v=-Eakmu0QC2M) — Simpleciviltamil
- 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/bracket-sc250-two-plates-p
- Whole chapter: https://www.bctengineer.com/md/semester_6/design_of_steel_and_timber_structure/chapter-4

## Question

If two bracket plates are connected to the flanges of the column SC 250 as shown in figure below find the design load 'P' that can be applied at an eccentricity of 300 mm.
[Figure: (a) bracket plate with bolts of M20 grade and property class 4.6, 3 bolt rows with vertical pitch 60 mm, 60 mm, 60 mm, end distances 40 mm and 40 mm, bolt gauge 120 mm, load P at 300 mm; (b) section showing column SC 250 with the load applied 30 mm off the column axis]

## Short answer

Each bracket uses 8 M20 4.6 bolts. The design load for two brackets is P = 156.2 kN.

## Answer

**Assumptions:** the two bracket plates share the load equally, $P/2$ each. Each bracket has 4 rows of 2 bolts (pitch 60, end distance 40, gauge 120 mm) = 8 bolts M20, grade 4.6, bracket thickness at least 10 mm. The load is in the plane of the bolts at $e=300$ mm from the bolt centroid. The 30 mm off-axis position of $P$ in the section view is assumed to be taken by the column (not by the bolts).

#### Bolt value (IS 800:2007 cl. 10.3)
- Shear: $V_{dsb}=\dfrac{400}{\sqrt3}\times\dfrac{245}{1.25}\times10^{-3}=45.26$ kN
- Bearing ($e=40$, $p=60$, $t=10$ mm): $k_b=0.606$, $V_{dpb}=99.4$ kN
- Bolt value $=45.26$ kN

#### Force in the critical bolt per unit load $P_b$ on one bracket
- $\Sigma(x^2+y^2)=8(60^2)+2\times2(30^2+90^2)=64800$ mm²
- Corner bolt ($x=60,\ y=90$): $F_x=\dfrac{P_b\times300\times90}{64800}=0.4167P_b$; $F_y=\dfrac{P_b}{8}+\dfrac{P_b\times300\times60}{64800}=0.4028P_b$
- $R=\sqrt{F_x^2+F_y^2}=0.5795P_b$

#### Safe load
$$
P_b=\frac{45.26}{0.5795}=78.1\ \text{kN per bracket}
$$
**Answer: $P=2P_b=156.2$ kN** (design/factored load for the two brackets together; working value = this / 1.5 if needed).

## Check yourself

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

1. With two identical bracket plates, how is the load treated?
   A. Each bracket carries the full P
   B. Only one bracket works
   C. Each bracket carries P/2, so P = 2 P_b
   D. The column carries all of it
   Answer: C. The load is shared equally, so the total design load is twice the load P_b for one bracket. (Key point: Sharing between brackets)

2. In the 8-bolt group (x = +/-60, y = 0 to +/-90), which bolt is critical?
   A. The corner bolt at x = 60, y = 90
   B. The bolt at x = 60, y = 30
   C. The bolt nearest the centroid
   D. Any bolt, they are equal
   Answer: A. The farthest corner bolt has the largest torsional force, giving R = 0.5795 P_b. (Key point: Critical bolt)

3. How is the load P_b on one bracket found?
   A. P_b = 0.5795 x 45.26
   B. P_b = 45.26/8
   C. P_b = 45.26 x 300
   D. P_b = 45.26/0.5795 = 78.1 kN
   Answer: D. Set the critical bolt force R = 0.5795 P_b equal to bolt value 45.26 kN. (Key point: Finding P_b)

4. What is the design load P for both brackets?
   A. 78.1 kN
   B. 156.2 kN
   C. 234.3 kN
   D. 39.05 kN
   Answer: B. P = 2 P_b = 2 x 78.1 = 156.2 kN. (Key point: Final design load)

## Related in Design of Steel and Timber Structure

- [Check bolted bracket on SC 250 (25 cm eccentricity)](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Abracket-sc250-100kn-25cm) — Design of Steel and Timber Structure, chapter 4
- [Bracket plate on column flange, 5 M20 bolts](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Abracket-bolted-5-m20) — Design of Steel and Timber Structure, chapter 4
- [Safe load P on bolted bracket, M20 4.6](https://www.bctengineer.com/question.md?key=semester_6%2Fdesign_of_steel_and_timber_structure%3Abracket-bolted-safe-load-p-m20-120) — Design of Steel and Timber Structure, chapter 4
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