Home Back

Length of Secondary Member using Collapse Prevention Level Calculator

Length of Secondary Member Formula:

\[ Ls = \frac{Cp \times 10^7 \times Ip}{32 \times Lp^4} \]

m⁴/m
m

1. What is Length of Secondary Member Calculator?

Definition: This calculator determines the appropriate length of secondary structural members based on the collapse prevention level, moment of inertia of primary members, and length of primary members.

Purpose: It helps structural engineers ensure proper member sizing to meet collapse prevention performance levels in building design.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ Ls = \frac{Cp \times 10^7 \times Ip}{32 \times Lp^4} \]

Where:

  • \( Ls \) — Length of Secondary Member (meters)
  • \( Cp \) — Collapse Prevention Level (±5%)
  • \( Ip \) — Moment of Inertia of Primary Member (m⁴/m)
  • \( Lp \) — Length of Primary Member (meters)

Explanation: The formula relates the secondary member length to the primary member properties and structural performance level.

3. Importance of Secondary Member Length Calculation

Details: Proper calculation ensures structural integrity, meets building code requirements, and prevents collapse under extreme loading conditions.

4. Using the Calculator

Tips: Enter the collapse prevention level (±5%), moment of inertia of primary member, and length of primary member. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is Collapse Prevention Level?
A: It's a building performance level that focuses on preventing structural collapse, with ±5% tolerance for safety factors.

Q2: How do I determine Moment of Inertia?
A: Moment of inertia depends on the cross-section shape and can be calculated using standard formulas or obtained from structural tables.

Q3: Why is primary member length raised to the 4th power?
A: The strong dependence on length reflects how member stiffness decreases rapidly with increasing span length.

Q4: What units should be used?
A: Use consistent SI units - meters for lengths and m⁴/m for moment of inertia.

Q5: How accurate is this calculation?
A: The calculation provides a theoretical value; always consult structural engineering standards and consider additional safety factors.

Length of Secondary Member Calculator© - All Rights Reserved 2025