Shear and Moment Calculation

cmmcnamara

Hello,

I have been using MECWAY to extract the shear and moment diagrams for beams by using the post processing feature which does this. However I noticed that when compared to analytical results found in typical textbooks, the shear is in opposite sign of typical convention. I think this may be because typical positive internal shear definitions require that it causes the element to experience a clockwise rotation while the positive/negative conventions for moment are aligned with typical clockwise/anti-clockwise convention for positive and negative angle.

Is this a bug or just a different sign convention being used?

Thanks.

Victor

It's just a different sign convention. Mecway follows what seems to be common for FEA software. I'm not sure if there's an important reason for that difference (something to do with being 3D?) or just legacy. Consistency with bending moments like you say might be part of it - You can see in the diagram on p53 of the manual, also attached here, that the shear force arrows are aligned with the correspondingly indexed bending moment arrows. And Mecway's bending moments follow textbook sign convention, as does axial force so that leaves shear force to break convention in favor of internal consistency.

wolinski

@cmmcnamara What post processing has this option?

cmmcnamara

@wolinski This is only available when using 1-D beam elements and the internal solver rather than CCX. You can add this to the post processing by right clicking Solution then selecting "New force and moment" then "bending moment (beams)" or "shear force (beams)".

wolinski

@cmmcnamara Thank you for reply, I thought you mean some other post processing software, not Mecway.