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hello, your vision is respected, but moving to uae is not as easy as it sounds since the government has started localization and that means that they prefer hiring their own local for the betterment of their economy ,rather than hiring expat. your best bet is to gain experience after your post grad for about 10 years in a specialized field in civil and then look into applying for job in a multi national company like AECOM, CCC,Atkins,FLOUR and etc , since these multi national companies also have their offices in the middle east and you could have a better chance of getting transferred. your second option is to apply for jobs in other gulf countries like Qatar and Oman since they are looking for professional expats as their own locals aren't that educated enough to proceed with higher positions. good luck! regards wessam shaukat

Please go through the following document. It may help in analyzing the two different approaches and then you can check your model accordingly. http://www.iitk.ac.in/nicee/wcee/article/14_05-01-0524.PDF

Thanks Imran Zafar, I will study this in detail and will update if I find something new. Sir Umar, unfortunately what we discussed (that shell and frame should give same base shear in those elements) is not matching with my models. I checked models again with Poisson's ratio = 0 so shell = frame stiffness. But still I am surprised to see that those few elements when modelled as lines carry only 329 kN shear and when modelled as shell carry 922 kN shear. What could be the reason? Line elements have one pin support at base. Shell elements have 3 pin supports at base. Now if I change shell pin supports from 3 to 1 (keeping the middle pin support) the shear on shells is almost the same as that of frames. It is now 342 kN (very near to 329 kN of frame elements) So the base fixity is doing something here? What you say?

Well basically code considers a member as compression member when primary stress is longitudinal compression. The differentiation between column and wall is based on the principal use However code permits walls to be designed using principles stated for column. With that just to differentiate arbitrarily code defines columns basing on aspect ratio. In combination these two aspects support the point of view that member under your consideration should be treated as column and may be modeled as frame. Moreover moment diagram may not be a decisive factor in your case because what i got from discussion your member is a compression member. So the question is how to model that compression member.

No, i don't agree with the explanation. You can mesh the wall finer and increase the number of supports from 3 to 6 and you should still the same base shear. Try it. Thanks.

Umar, there is a difference between stiffness of shell and a line element due to Poisson ratio although negligible. I am getting higher forces because the line element was pinned and when modelled as shell...it is also pinned but now has 3 pin supports instead of 1 in line...so these 3 pin supports making the shell more stiff at base. PS: This explanation is not mine..so I am not satisfied with this too.. because as I know the lateral force in rigid diaphragm should depend on stiffness of vertical elements and stiffness of line and shell dont differ much so the the base shear in these columns should not jump from 70% to 95%. Agreed. Btw does the above explanation about base fixity has any effect? I dont think so but just asking?

Uzair I know the clause you are talking about. But it is for special moment frames whereas I have ordinary. Umar, these large rectangular columns attract 70% of base shear when modelled as frames and 95% when shells. What would you do when you have 10mx20m large bulky column? Still model it as frame? Whereas in reality it has continuous support like compression tension couple making the base fixed? I know we can model 200x200mm column as frame and then longer things as shells and then a mass by 3d brick elements. So whats close to reality? 1200mmx600mm vertical element as shell?

Your warning messages are loss of accuracy. Nothing critical as you don't have any stability warnings. Normally, what you can do is that wherever you have a **Warning** message, you can go to the joint of interest; for information below, error is for UZ at Joint 3354, and zoom in to the Joint for visual inspection to see if everything looks good. * * * W A R N I N G * * * THE SOLUTION LOST 7.8 DIGITS OF ACCURACY FOR DOF UZ OF JOINT 3354 LOCATED AT X = 66.600000, Y = 30.650000, Z = 18.400000, STIFFNESS MATRIX DIAGONAL VALUE = 5.0055E+15 I haven't used ETABS in years, but, I remember that when I used to get such messages, I would check the joints, zoom in and would always find some kind of misalignment of slab with beam. The slab or beam would not align and there would be some gap or misalignment. You can spot it visually if you zoom there. You can then redraw the slab or refine your mesh there. Give it a try and post any pictures of mismatches that you find. Thanks.

Aoa. Keeping in view ACI 318-05 section 21.4.1.2 for special moment frames, a vertical member with 1200x600mm cross sectional dimension should be treated as a "column". Therefore, 1) a "frame' system should be adopted for analysis, 2) the 1200x600mm section should be modelled as a 'frame' or 'column'.