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Queensferry

Cumulative tutorial 04

A pressure pulse on a wall panel

The duration relative to the period decides everything about a short load.

A 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.

What you are given

  • 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
Draws on6. Impulse response, arbitrary loading and convolution7. Energy in vibrating structures

Tutorial 04

Work the problem

4 questions

  1. Question 1

    First, the reference case: what is the dynamic load factor for a load applied suddenly and held indefinitely, on an undamped system?

  2. Question 2

    What is the peak dynamic load factor for a rectangular pulse with td/Tₙ = 0.2?

  3. Question 3

    And what is the peak dynamic load factor for a pulse of duration td/Tₙ = 0.5?

  4. Question 4

    And for a much longer pulse, td/Tₙ = 2.0 — what is the peak dynamic load factor?

What this establishes

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.