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Rana last won the day on April 15

Rana had the most liked content!

About Rana

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    FEA, Tall/long structures, Dynamic analysis, Seismic, Travelling, Writing

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  1. AQ, there is nothing wrong with the conversion. I stated "87.5mmx10=87.5cm" which is 87.5mm for each storey x 10 storeys = 875mm = 87.5cm. This is the total drift of top floor relative to base 0,0.
  2. I am such a big fan of Dr. Naveed, wish he delivers a lectures in Dubai.
  3. I am not sure how the slab is supported? Is it a flat slab? How many stories? Beam flexure also plays part in seismic resistance. You have to see what is your system and how much beams are resisting the lateral forces.
  4. Share the diagrams you calculated? What do you mean the shear force goes only upward? You mean like a cantilever in isolated footing? If yes, then strip footing is not a cantilever but like a continuous frame. And one way shear, yes one-way shear could also be a problem (bigger problem than the 2-way punching shear) even in isolated footings. Dont under estimate it. For example if the bearing reaction too huge.
  5. Could you please explain that logic? Furthermore; seismic inter-story drift is limited to 2.5% of story height. If story height is 3.5m, the allowable inter-story drift is 87.5mm. If all floors were to be within the drift (so code requirements are satisfied) then a 10 story free standing building would have total roof drift of 87.5mmx10=87.5cm. Thats a lot, yes. But I do not see any limits in code for the seismic total drift as long as you have satisfied the inter-story drifts. Ofcourse, more the building overall drift, more will be p-delta effects, (that could be huge for a massive tall building). In wind design, overall drift is limited due to problem of acceleration at top floors. But in a seismic event, obviously human criteria is not something you should aim for.
  6. Because there is none except that you have to provide sufficient seismic gap between two buildings. If its one free standing building then no limits except inter story drifts.
  7. I invite other members to also shed some light. For example it could be something like this; If a post is related to let's say wood design (and not to a specific software) we could ask the user to include tags such as "wood" in the question. I am opposed to making so many categories. That would create mess. We could control the sub categories by appropriate tags (strict policy to be imposed on users to input appropriate tags based on the materials /pre-defined sub-categories). All users to be requested politely to contribute in the proper section. For example some one asking how to calculate the time period should directly go to BASIC FAQs section and search the thread, if not found then post the question. Or we could enforce new users to post only in the #4 section, unless we see that the user is not a university student but a more experienced one. So we, as moderator team, could grant him permissions to post in all the forum anywhere he/she likes. This could be a bit more work for moderators but how many 'ACTIVE' users we have? Also this would keep the forum 'clean' and decluttered. Don't you think each and every group on Linkedin and other places are full of one famous question about ETABS i.e. stiffness modifiers? Every new comer post the same question. And also don't you think following two questions should be in two different categories; 1. What is the purpose of stiffness modifiers in ETABS. 2. Although not required by ACI codes, how do you guys model the shear stiffness of shear walls? To reduce f12 or not? etc. Most of the times a design issue is always related to a specific software issue, such as no.1 . So the categories I have recommended are not the final words. Just a direction to start the discussion on the topic.
  8. I think its time now to categorize questions based on the difficulty level. For example; A toddler asking very basic question like what is mass source or time period, should be classified under lets say Easy or 0 or Beginner or Simple etc category. And as such specific moderators should be assigned to take care of that forum. Then we can make other sections like moderate or difficult. Where one really need to relearn/review the question and think about the answer carefully. I think all the internet is full of the same basic questions like time period, base shear etc. Isnt it the time to take SEFP a step ahead and not just another forum full of the same basic questions? How can we re-categorize the SEFP sections to give it a new feel, not just like concrete, steel, software issues etc. What do you think?
  9. By consistent, it means that in order to draw the ‘design’ response spectrum you got to know the PGA, PGV and PGD. Usually when these are unknown, PGA is taken as 1g. PGD and PGV are estimated by the relationships given by Newmark and Hall (see Chopra book). However, in your case, you already got PGV and PGD for PGA=1.0g, right? Now you have to make the pseudo-accelration/velocity/deformation spectrums based on this. After that, you have to scale the calculated response spectrums for 0.25g simply by multiplying them by 0.25. For more on this refer to Chopra book (4th edition) section 6.9.
  10. That might have caused some inconsistencies in the calculations (very small/large values) and could have caused this error. There is not much diff in behaviour if you change from 0.01 to 0.0001 so keep the previous value. That would not solve the problem i reckon.
  11. The biggest problem would be to control the excessive sway. The question you need to ask is if there would be any human occupancy in there/visiting deck etc? 99% chances are NO. There will be no human occupancy so limiting the sway & acceleration is out of the equation now. That leaves you with a sway limit of as high as 1/100 instead of usual 1/400 for buildings under service winds. You might need to pay attention to non structural components design for the drifts they gonna accommodate.
  12. You question to me is unclear. Could you clarify what you wanna ask (may be in bullet points)?
  13. Ask your self, why you dont check punching for the wall? Think about the load it has, think about the area over which this load would be distributed (area bounded by the parameter equal to A+d). What value of shear stress you get? very low right?
  14. @Hira Malik Your signatures stand out quite big. Mind making it in line with font size of rest of the posts?