Critical Load for Portal Frame with Column Fixed at Base — Lesson 3

This lesson covers the concept of critical load for a portal frame with a column fixed at the base. It delves into the two modes of buckling - symmetric and anti-symmetric. The lesson explains how in symmetric buckling, the portal frame is not allowed to move sideways, while in anti-symmetric buckling, it is allowed to move sideways. The lesson also discusses the derivation of the critical load for a portal frame with a column fixed at the base, considering both buckling modes. It uses mathematical equations and graphical representations to explain the concept. For instance, the lesson illustrates how the characteristic equation can be solved graphically to find the intersection point, which represents the smallest root used to find the critical load.

Video Highlights

00:32 - Explanation of symmetric and anti-symmetric buckling modes
07:43 - Calculation of the critical load using the smallest root
13:56 - Graphical solution of the characteristic equation for anti-symmetric buckling

Key Takeaways

- The critical load for a portal frame with a column fixed at the base can be derived considering both symmetric and anti-symmetric buckling modes.
- In symmetric buckling, the portal frame is not allowed to move sideways, while in anti-symmetric buckling, it is allowed to move sideways.
- The characteristic equation can be solved graphically to find the intersection point, which represents the smallest root used to find the critical load.
- The critical load is equivalent to a column with end conditions hinged-hinged with an effective width length.