Everything about Structural Dynamics totally explained
Structural dynamics is a subset of
structural analysis which covers the behaviour of
structures subjected to
dynamic loading. Dynamic loads include people, wind, waves, traffic,
earthquakes, and blasts. Any structure can be subject to dynamic loading. Dynamic analysis can be used to find dynamic
displacements, time history, and
modal analysis.
A
static load is one which doesn't vary. A dynamic load is one which changes with time. If it changes slowly, the structure's response may be determined with static analysis, but if it varies quickly (relative to the structure's ability to respond), the response must be determined with a dynamic analysis.
Dynamic analysis for simple structures can be carried out manually, but for complex structures
finite element analysis can be used to calculate the mode shapes and frequencies.
Displacements
A dynamic load can have a significantly larger effect than a static load of the same magnitude due to the structure's inability to respond quickly to the loading (by deflecting). The increase in the effect of a dynamic load is given by the
dynamic amplification factor (DAF):
»
where u is the deflection of the structure due to the load.
Graphs of dynamic amplification factors vs non-dimensional
rise time (t
r/T) exist for standard loading functions (for an explanation of rise time, see
time history analysis below). Hence the DAF for a given loading can be read from the graph, the static deflection can be easily calculated for simple structures and the dynamic deflection found.
Time history analysis
A full time history will give the response of a structure over time during and after the application of a load. To find the full time history of a structure's response you must solve the structure's
equation of motion.
Example
A simple single
degree of freedom system (a
mass, M, on a
spring of
stiffness, k for example) has the following equation of motion:
» Further Information
Get more info on 'Structural Dynamics'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://structural_dynamics.totallyexplained.com">Structural dynamics Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
