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During truss fabrication, the truss member are usually connected by welding does behave like fixed joints not pin joint so how will that behave like truss without pin connection?

Mahendra Gunawardena
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MK khatri
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  • The two parts connected together by welding behave as one part according to the dimensions in each direction... – Solar Mike Sep 05 '19 at 06:11
  • i mean, even if joints are made by welding , does it behave like a truss? – MK khatri Sep 05 '19 at 06:13
  • What do you think a truss behaves like? – Solar Mike Sep 05 '19 at 06:21
  • if joints were pinned, it would not restrain rotation so member wouldnot undergo bending but with welded joint rotation is restrained and thus mumber undergoes bending too;but in truss, member should be subjected to axial load only, isn't it? – MK khatri Sep 05 '19 at 06:29
  • Pins can restrain rotation... depends which axis they are in and the direction of rotational force. – Solar Mike Sep 05 '19 at 06:31
  • Provide a diagram showing exactly what you are considering and how the loads are applied. – Solar Mike Sep 05 '19 at 06:35
  • i think i didnot make my question clear so let me put it another way, in theoritical analysis of truss we assume only axial loading of its members but in practical fabrication of truss joints are welded so is that assumption of only axial loading still valid – MK khatri Sep 05 '19 at 06:37
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    Edit ansd improve your question, comments are not for improving questions. Also correct your typos and grammar. – Solar Mike Sep 05 '19 at 06:39
  • If it looks like a conventional truss, the loads carried in bending are small enough to be ignored. If the individual members are thick enough to carry bending loads, it's not a truss, it's a fabricated assembly of beams. – alephzero Sep 05 '19 at 09:07
  • i am analysis this structure in staad pro. Based on theoritical knowledge about truss, i tried releasing moments at end of truss member but it led to very high nodal displacement .But when i analyzed it without any release , just like simple structure , without doing anything to make it like truss; analysis worked out fine.why is that? plz dont mind my english, english is not my first language. – MK khatri Sep 05 '19 at 10:45

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The geometry of the trusses are usually long narrow members carrying axial loads,connected to each other in triangles. And the connections are designed to let the axis of truss members pass trough a common center on the connection plate or connection bolted bracket.

Because of this geometry there is no moment at the connections, even if they are rigidly connected. Therefore the connection can be assumed to be a pin connection.

There may be very small tertiary moments due to heat expansion or deflection but those are well within the tolerance range of the truss.

That doesn't mean if a truss will be designed for extreme temperatures or large deflections the effect can be ignored.

kamran
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