Design Envelopes and Finding the Worst-Case Demands - Intro to Structural Analysis

A design envelope provides the worst-case shear and moment demands along the length of a structure for a suite of load scenarios. In this video, we examine the combination of a static dead load, a patterned (distributed) live load, and a single movable point load.

We use the influence lines to find the critical load patterns and positions for the live load. The effect of a distributed load is equal to the magnitude of that distributed load multiplied by the area under the influence line, while the effect of a point load is simply the magnitude of the load multiplied by the value of the influence line at the location of the load.

These previous videos show how to compute the influence line (pre-requisite for this video):
Influence Lines (statics method) - https://youtu.be/cNdEgnCmNU0
Muller-Breslau Method (the easy method!) - https://youtu.be/1VcwsaQeUMY