Absolute Maximum Allowable Deflection
Absolute Maximum Allowable Deflection
(OP)
First of All - I have been particiapating in this forum for 3 months and just want to tell all of you that the quality of both questions and answers is impressive - Thank You.
I'm familiar with use of typical deflection/span limits for a steel member (1/360, 1/240, 1/180, etc.) but have not come across an answer to the following:
If the amount of defection is not a concern, what is the deflection/span ratio that would, by itself, be a limiting factor; that is greater deflection would cause permanent beam deformation?
I hope that I have state this clearly.
I'm familiar with use of typical deflection/span limits for a steel member (1/360, 1/240, 1/180, etc.) but have not come across an answer to the following:
If the amount of defection is not a concern, what is the deflection/span ratio that would, by itself, be a limiting factor; that is greater deflection would cause permanent beam deformation?
I hope that I have state this clearly.






RE: Absolute Maximum Allowable Deflection
But the question is that going up to the limit elastic capacity of a structure has not been seen sound policy by most structural designers, that always preferred -and not just as s measure in order to safety, but also to serviceability- to use working stresses below the limit of proportionality or elasticity, this ensuring more reserve strength and longer life.
Hence, whichever your structure surely the serviceability of the same will suggest some practical limit to the deflection. Serviceability on the other hand is misunderstood if taken in general as to not be a life safety standard. There are plenty of examples that may prove the contrary, be it by the risks derived (remember for example how sagging of an electrical line is blamed for the last big blackout) or directly because the need of its intrinsical consideration to prevent failure, such when limits to the absolute lateral deflection in buildings is imposed.
RE: Absolute Maximum Allowable Deflection
RE: Absolute Maximum Allowable Deflection
so yes ishvaag concur totally on structure vs. member however do need to consider individual member and effects large deformations can have on its ends and even the member itself. Plates and large deformations being an example and a whole different thing in any case. It really goes back to the fundamental assumptions of Linear Elasticity as you state.
RE: Absolute Maximum Allowable Deflection
RE: Absolute Maximum Allowable Deflection
The answer, I think, is that you would calculate the load that results in the stress level equalling the maximum allowable stress, then calculate the deflection from that load, and ratio it to the span.
Note that for relatively large high deflections to occur, your structure has to mimic your calculation assumptions and boundary conditions, including secondary members picking up portions of the load.
In some of my structure designs, deflection is not an issue and the members are designed to allowable stress levels. We don't even calculate the deflection. These are very simple structures used in industrial applications where there is no human occupancy.
RE: Absolute Maximum Allowable Deflection
RE: Absolute Maximum Allowable Deflection
RE: Absolute Maximum Allowable Deflection