All Activityhttp://www.sepakistan.com/discover/Structural Engineering Forum Of Pakistan - All ActivityenRotational spring constants in ETABSCould you help me understand how moment will be distributed in two ends of beams if one end of beam is fixed and other end is partially fixed? Say, previous 24ft beam with 15k/ft udl....FEM are -720 k-ft both sides.....now one of end has been partially released so that it can develop 360k-ft how will moment be distributed to other end...I am getting 900 k-ft at fully fixed end and shears at 2 ends became 157.5 and 202.5 kips..., I fail understand how to solve this indeterminate beam with one partial fixed end...
Thanks for your helpSun, 22 Apr 2018 22:22:31 +0000settlement of foundationSun, 22 Apr 2018 19:11:14 +0000Rotational spring constants in ETABSThanks for your reply. Actually your blog was one of the first I studied before doing it.
I understood it now. ETABS is using equation like M=(n/(n-1))*4EI/L*theta. so rotational stifness constant k=(n/(n-1))*2EI/L. If you are reducing stiffness on both sides consider using spring constant of (n/(n-1))*2EI/L
n=% of moment to be resisted.....for n=1 we will get fully fixed, for n=0 we will get fully hinged.
The graph can be considered to be n(Y-Axis) and (n/(1-n))*2 as X axis.
The data makes sense now. i am worried about 3D now, I have 55 story building in which i have to model connection loss in terms of decrease of stiffness. I don't know if I could useSun, 22 Apr 2018 18:43:48 +0000settlement of foundationWhat kind of foundation system is there.
you can consult a geotechnical engineer as well to get some option interms of soil improvement etc.
From a structural point of view, you can always introduce more columns and reduce load per existing column to reduce settlement.
Thanks.Sun, 22 Apr 2018 13:13:59 +0000settlement of foundationplz help me out of this problem.. the foundation is settling down week by week. it is a warehouse. a big Under ground water tank is adjacent to the failed column. we have only little space to work. this is in dubai. Suggestions please what so i can do. plz do replySun, 22 Apr 2018 12:35:18 +0000Rotational spring constants in ETABSFirst, the stiffness of this beam is 2EI/L. See here;
http://classes.mst.edu/civeng217/concept/12/03/index.html
Second, see the fixed end beam in this link, hope it clarifies. Do share the findings afterwards please.
https://waseemrana.com/2013/04/16/how-to-partial-fixity-in-etabs/Sun, 22 Apr 2018 09:19:29 +0000Rotational spring constants in ETABSI am trying to understand how rotational spring constants work in ETABS.
I have considered 24ft long beam with 15kips udl applied so that fixed end moment is 720k-ft
I assume that spring constant will be function of EI/L. I assumed that ETABS would have linear spring, so that if I find lowest spring constant to give me 720k-ft fixed end moment, I would half that spring constant to give me half restain so that moment will be 260k-ft.
In reality results are far from it. the graph attached shows factor which I multiplied to (EI/L) to get spring constant in kip-in/rad in X axis and Y axis shows corresponding end moment/720.
Can somebody explain how etabs spring constant work so I find factors representing fraction of total restrain.Sat, 21 Apr 2018 23:57:24 +0000Beam deflection in EtabsDid you got the answer of your question?Sat, 21 Apr 2018 10:53:26 +0000Design Guide - PEB StructuresSat, 21 Apr 2018 02:32:58 +0000Design Guide - PEB StructuresMBMA guidelines might be used in PEB structures. I know @BAZ used to have a MBMA design document.
http://www.mbma.com/Fri, 20 Apr 2018 22:31:09 +0000Steel Design by ASD or LRFD?JazakAllah khair!Fri, 20 Apr 2018 06:52:53 +0000Design Guide - PEB StructuresThanks!
I was hoping someone might be an expert at this in this forum, could give me a heads-up to the practically applicable design guides in the industry. Thanks, anyways!Fri, 20 Apr 2018 06:52:33 +0000Structural System with small and economical crossectionOne Can't control drifts without adding RCC walls. Another option, impractical may be, to have RCC frame structure with reinforced masonry.Thu, 19 Apr 2018 10:17:51 +0000Load Bearing StructureACI 332Thu, 19 Apr 2018 04:18:04 +0000Load Bearing StructureBeing a civil engineer, we learn how to design RC structures which consists of beams and columns. what about load bearing structure? Where can I get information regarding design of brick masonry structure that is common practice in most part of Punjab... And can we model it on Etabbs and check pier and spandrel forces, etc?Wed, 18 Apr 2018 16:46:24 +0000Structural System with small and economical crossectionDear Members,
I am designing 13 storey commercial building. Plot is trapezoidal having larger length in Y direction and shorter in X direction. Due to the shape of plot and building as well i have to introduce shear walls in X direction to control torsion and drift. But client is not happy with the dimensions of shear walls and colum. Can anyone suggest a structural system for designing in which i can economize the cross-sections and control the drifts as well?Wed, 18 Apr 2018 12:29:51 +0000Expansion joint in etabs model.Aoa members.
if there is an expansion joint in a building so should we model them all together by dividing the expansion joint portion or should we model them completly differently in etabs ?Wed, 18 Apr 2018 11:05:10 +0000Beam Fail In Torsion And Shear In Etabs Then Why Torsion Modifire Reduce To 0.001But, as my understanding stiffness modifiers has nothing to do with redistribution of moment for statically indeterminate structure. As stiffness modifiers are applied through out the length of the member (here in this case i am addressing a beam particularly) to account for cracks which might occur whether at mid-span or support, whereas redistribution of mement due to cracking too should be applied through the provision of beam-end releases only until the moment at support reaches the desired value; as per design codes the reduction is allowed up to 30% of the support moments. Thanks.Wed, 18 Apr 2018 09:20:15 +0000MS Distant learningI did mine from Heriot Watt, UK. Distance Learning. But I would not recommend it. Its a pain in the back. Plus the fee is almost the same.Wed, 18 Apr 2018 04:57:41 +0000Beam Fail In Torsion And Shear In Etabs Then Why Torsion Modifire Reduce To 0.001The analysis is Linear. Automatic redistribution would have been possible if analysis were Non-Linear. In order to approximate redistribution (during cracking), the USER has to put some kind of stiffness modification. This applies to shear, torsion, moments, axial...everything.Wed, 18 Apr 2018 04:56:55 +0000MS Distant learningAOA to all respectable seniors,
Please share your thoughts on whether Masters in Structural engineering ONLINE/distant learning is recognized?
If yes, which uni should be preferred? secondly any Scholarships?Mon, 16 Apr 2018 17:24:34 +0000Beam Fail In Torsion And Shear In Etabs Then Why Torsion Modifire Reduce To 0.001Thaks engineer. But do you mean that for flexural monents unlike for torsional moments, the program has a capability to redistribute the values automatically; witout providing release/stifness modifier?Mon, 16 Apr 2018 17:06:32 +0000checking the reasonability of my result; when running dynamic analysis Ax ratio turned up till ratio of (2) ;though there was no Ax in static analysisForget check Ax on dynamic. If you need to check, then check as on ETABS online wikki. If so, you have to combine all modes manually. That's time taking and complex.
Check Ax on all static load combinations and whatever is the value, apply this in response spectrum.Mon, 16 Apr 2018 12:03:45 +0000Beam Fail In Torsion And Shear In Etabs Then Why Torsion Modifire Reduce To 0.001The paper says that upon cracking the internal redistribution occurs. However like for moments, ETABS does not redistribute Torsion automatically. If you want it, then release (or apply modifiers) to redistribute forces. That is why I said, after this, you need to check for increased forces in slab. Its that simple.Mon, 16 Apr 2018 12:00:55 +0000Islamabad GatheringIt was short 2 day trip. Came back already. Next time.Mon, 16 Apr 2018 11:56:28 +0000