Structural dynamics / tutorial
A pressure pulse on a wall panel
The duration relative to the period decides everything about a short load.
Teaching basis and review status
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Read the lesson register and outstanding review notesA wall panel is to be checked against a short pressure pulse from an accidental release in an adjacent plant room. The pulse can be idealised as rectangular. The panel's period is fixed by its span and construction; the pulse duration is not well known, so the answer must be given as a function of it.
- Panel treated as a single-degree-of-freedom system, undamped for this check
- Rectangular pressure pulse of duration td
- Three candidate durations: td/Tₙ = 0.2, 0.5 and 2.0
Practice
First, the reference case: what is the dynamic load factor for a load applied suddenly and held indefinitely, on an undamped system?
Practice
What is the peak dynamic load factor for a rectangular pulse with td/Tₙ = 0.2?
Practice
And what is the peak dynamic load factor for a pulse of duration td/Tₙ = 0.5?
Practice
And for a much longer pulse, td/Tₙ = 2.0 — what is the peak dynamic load factor?
The whole answer is decided by one ratio, and the panel's period is the engineer's lever on it. A stiffer panel has a shorter period, which RAISES td/Tₙ and moves it towards the plateau — so stiffening a panel against a short pulse can increase the demand on it. That is the opposite of the static intuition.