UmarMakhzumi

I was browsing through code and noticed something I thought would share as this question keeps coming in the forum. It is about when to consider torsional stiffness and when to ignore it. Thanks.

W/salaam, The answer is in the commentary. Please see the highlighted text in the quote. Keep it simple. Thanks.

The company I work for has license for SAP2000 and RISA3D only. They don't use ETABS and thats why I don't use ETABS either. I have found RISA3D more friendly for connection output. You should be able to do it. I haven't used RAM connection but you should be able to get output from SAP2000 and use that in RAM Connection. The softwares (SAP2000 and RAM Connection) I believe are not integrated and you would have to manually enter data in RAM Connection. I did some google and noticed that Ram Connection is integrated with Staad Pro. You can check the following website for more details: http://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/8354.tips-for-using-ram-connection-within-staad-pro-tn Pin or Fixed from a geotechnical perspective: http://www.sepakistan.com/topic/1578-pin-support-or-fixed-support/ Pin or Fixed from Column Base Plate Connection perspective: http://www.sepakistan.com/topic/1500-steel-column-base-plate-modelling-in-sap/ I am not very familiar with ETABS. I would let someone else answer this. A fix support assignment for connection between your column and baseplate would induce moment in your baseplate. You need to design your baseplate for the reaction moment along with other loads. You should export all load combinations for strength design of foundation. Please note that some load combinations might not be applicable for bearing pressure check depending upon the code you follow but they are applicable for foundation design (flexural and shear design of foundation). You should consider stiffness modifiers irrespective or p-detals. Thanks.

Juli, For steel, I do the software analysis and member sizing of the members using SAP2000 or RISA3D. For baseplate design, I either do manual calculations or use an in-house software. For connection design, I show the connection loads on the design drawings and provide them to a fabricator. The fabricator's engineer designs the connections, stamps his drawings and submits the shop drawings to me for review before they are issued for construction. This is the standard practice in North America. Thanks.

I do them manually. I take the reactions from SAP2000 or RISA 3D and rest all is manual. There are a number of 3rd party base plate design softwares available that you can also use. Thanks.

Yeah.. you are right.

More details here: http://www.bbc.com/news/world-asia-india-35933452 Thanks.

AQ, What is your truss resting on? Show what the members are from bottom of truss to foundation and then I can answer how truss connection would work. Thanks.

You need to go through the links Uzair gave you to design the dome for reinforcement. Thanks.

The link is working. Thanks.

Sohaib, Please go through the tutorials here: https://www.csiamerica.com/products/sap2000/watch-and-learn Thanks.

Your understanding is correct. The higher mass participation, the important the mode. Once you have figured out which modes have the greatest mass participation, take time to see the mode/ demformed shape and think about how can you improve your structural framing. Thanks.

I have worked with some engineers that like to assign high stiffness modifiers to rafts to get conservative flexural and shear design of foundation. Assigning modifiers would increase amount of rebar in your raft. I personally think that this is good practice as nothing is perfectly rigid and cracking in inevitable, which would result in loss of inertia and high flexural stresses. The general procedure is to create two models. One with no stiffness modifiers and one with modifiers for foundation/ raft. You should use the first model to calculate piles reactions and the second to do flexural and shear design. Thanks.

Ahmed, It is explained very clearly in UBC 97. You need to consider pertinent clauses together. See excerpts below. 1631.5.4 Reduction of Elastic Response Parameters for design. Elastic Response Parameters may be reduced for purposes of design in accordance with the following items, with the limitation that in no case shall the Elastic Response Parameters be reduced such that the corresponding design base shear is less than the Elastic Response Base Shear divided by the value of R. 1. For all regular structures where the ground motion representation complies with Section 1631.2, Item 1, Elastic Response Parameters may be reduced such that the corresponding design base shear is not less than 90 percent of the base shear determined in accordance with Section 1630.2. 2. For all regular structures where the ground motion representation complies with Section 1631.2, Item 2, Elastic Response Parameters may be reduced such that the corresponding design base shear is not less than 80 percent of the base shear determined in accordance with Section 1630.2. 3. For all irregular structures, regardless of the ground motion representation, Elastic Response Parameters may be reduced such that the corresponding design base shear is not less than 100 percent of the base shear determined in accordance with Section 1630.2. The corresponding reduced design seismic forces shall be used for design in accordance with Section 1612. Section 1631.5.4 refers to 1630.2, which is your Static Force Procedure. Please see the following topic to understand how to setup your model for Response Spectrum and do the scaling. Thanks.

Your base shear used for dynamic analysis can't be less than 85% of static. This would not affect your R. See responses above. Thanks.

Dear Uzair, The preview feature is unfortunately no longer available. However, you can still edit your comments after posting. These features are still available through keyboard shortcuts. You can use Ctrl+Z to Undo and Ctrl+Y to Redo. The Redo is a bit buggy and may not work at all times. Yeah I remember this. I was looking forward to get feedback from you on how the new auto save is working for you. So let me know. If you are not satisfied, I will talk to a developer to see if we can get that option. There are a number of ways you could do it. You can go to search and on the left side select members (see highlighted term in the photo) and hit search. It would return all the member listing. Feedback is always appreciated. Thanks.

Changes in ACI 318 Anchorage Concrete Seismic.pdf

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I have only done one Class 4/ Slender section (it was an angle) design. My line of work has more standard sections. Class 4/ Slender Sections fail locally before yield moment can be obtained thus greatly reducing section capacity. If your line of work has a lot of Slender Sections, I would advise you to get a book and use the examples in the book to understand the design of these sections. These sections are common in pre-engineered building industry and if you deal with them on daily basis, get a reference book. That would help you. Thanks.

Strength would't effect much as I explained above. Also your member web is Class 4 or Slender Sections (I believe thats what they call them in US). I would never do a non-compact section design on a software. Use software for analysis only and design it manually. Thanks.

SAP2000 is calculating the moment resistance of beam considering all design limit states like lateral torsional buckling, maximum unrestrained length etc. What you are referencing is Mr= Mf/Sx which is not the only governing parameter. Strength of beam depends upon its unbraced length. Thanks. SAP2K Output.pdf

How much do your results get affected by the two approaches? Have you done a sensitivity study on this? Thanks.

Welcome to the forums. Here are the answers: 1) To satisfy code requirement that dynamic analysis base shear can't be less than 85% of static analysis base shear. 2) Static load combinations for static loads like dead, wind, live and snow and dynamic load combos for earthquake. 3 and 4) Please see the following articles on this forum: 5 and 6) Please see the following articles on this forum: 7) Please see the following topic: 8) Because it would result in huge over-design. Its counter intuitive and defies statistical philosophy behind load combinations. 9) Inertia causes forces and mode shapes. 10) The difference is hard to summarize in a short answer. You can post a new topic and we can discuss it there. Time history is more accurate. 11) Effect is in the form of deformation. Slabs are considered rigid in plane and may deform in their plane. You need to design them such that they can transfer lateral loads to lateral load resisting system. Beams deform and bend under seismic loading. 12) Right. 13) Please see this article: 14) Don't put. 15) Energy dissipation, cracking, elasticity 16) Please see answers to 3) and 4) above. Hope that helps. Cheers!

The above image is not complete. It should look something like attached. Can you re-upload it? Thanks. .

Can you share a sketch of your problem. Post SFD too. Thanks