Please note that this lesson has two parts. As such, there will be only one quiz and assignment which can be found at the end of the 3-term vs. 4-term Deflection Equation Example video.

Introduction

The video explains the difference between the non-linear 4-term deflection equation from SDPWS Figure C 4.3.2-1 and the  and the simplified 3-term linear approximation now available in Shearwalls Program.  The 3-term equation, adapted from the American SDPWS standard, combines the shear and nail slip components into a single shear term, making calculations linear.

While both equations yield the same deflection at 100% design capacity, the 3-term equation estimates higher deflections at lower loads and helps avoid convergence issues in the Shearwalls Program, particularly when distributing load between wood sheathing and gypsum wallboard. This simplification improves the accuracy and reliability of load sharing in shear wall design calculations.

Learning Outcomes

By the end of this lesson, you will be able to:

• Differentiate between the 3-term and 4-term deflection equations used in shearwall analysis, including their assumptions and applications.
• Explain the benefits of using the simplified 3-term deflection equation in structural design, particularly in program applications.
• Analyze how load distribution varies when using the 3-term versus the 4-term deflection equation, especially in walls with multiple sheathing materials.
• Evaluate the impact of equation selection on deflection accuracy and the ability to model real-world shearwall behavior in engineering design program.

Instructional Video

Video Run Time: 04:08 minutes