UmarMakhzumi

Leong, Here is the description of this error: Please check your model for instability although the above does say that it is a warning not an error but that is my suggestion. Negative force in column means that you column is in tension. This is common condition. For lateral loads, one side columns are normally in tension and other side in compression. Thanks.

MS Khan, I was not able to gather a complete picutre of the situation from your posted snapshots, but something that comes to mind is that for shells the moment is not about the axis but in the direction of the axis. This is typical nomenclature for all plate analysis softwares. Please also see this:

Hi Suarez Good question and thanks for posting the references. Can You please also post the reference Section 1634.2 as that is the one that allows the exception to IMF. Then we can discuss. Thank you.

W.Salaam, Well, Did you compare the individual reactions for each load case to see where the difference it. Normally, I would hand check all the basic load cases. There can be a lot of reasons why you are getting this error. Btw, sorry for the late reply. Were you able to figure out why this happened. Thanks.

Hi Saqib, Assuming model is all stable and there are no stability issues, you can try increasing the number of modes. Thanks.

No, there are no concerns. Generally speaking, with narrow edge distance and shallow embedment of anchor bolts, it is hard to develop them for tension. Your loads might not be big enough so you might be good, but the base fixity just caught my eye so I thought I will ask you. Thanks.

Abbas, Excellent question. I personally don’t have any experience designing stone masonry retaining walls but I can suggest one method to look at this, which I have used in the last to analyze situations that are unfamiliar. The method is to look at failure limit states. That would mean, thinking about how the wall can fail. I can think of the following methods the wall can fail apart from stability failures. 1) Shear failure of any section along the height of wall. 2) Flexural failure of wall. While shear strength of stone masonry can be checked similar to brick masonry (with some assumptions) the real question comes if the wall will be able to take any flexural bending. In real life scenarios, since the wall is stone masonry, therefore it cannot take any flexural stresses or bending. Speaking of theory (not real life) one way I can think of wall is able to resist any flexural loads is that if it is under very very significant axial compression or the width of wall being so big that it acts like one rigid mass and technically there is no flexural stresses. I think you are better of designing stone masonry walls that are very short in height that can have minimal stresses and if you have have something serious, go for rcc. Thanks

I don't personally think that there is any deflection requirement unless you are mounting cladding type advertising panels that have deflection requirement(higher deflection might break the panel) Also, I am noticing that you have used fixed base. What kind of details you have for the column base. If you change it to pin, (assuming columns are connected), the deflection will increase substantially. Kind Regards,

For directionality, perpendicular to surface would make sense. Some people might say that wind will simultaneously act on say both surfaces (say if it blows left to right) first it hits the first billboard and then the second one by entering inside the V, but I personally believe that would be unlikely since inside the V, there would be “dead air” that would let external wind slide by. I got this concept is one of AISC presentations. Let me find it if you are interested in it. Again this is just an opinion. It all depends what you think as engineer if you are the engineer of record. Also a lot of engineers that I have worked with will just make a very conservative first case, for example, for your situation like double the wind load and see if everything still passes and if it does, leave it there. Thanks.

Hi Khan, Good question. Please check the total dead weight reaction of the structure with load combination that includes all the dead weights (both self weight and superimposed dead weight). Thanks.

Hi Anwar, Before I answer the question, I would like to know If you modelling a slab with variable finished height? Is that why you would like to apply vertical offsets? Thanks.

Hi @sochtheking, What does the design report say to limit state of thermal cracking? The 0.0018 or 0.002*BH is termed as “Temperature and Shrinkage Reinforcement “. If this is governing, your slab is likely very thick relative to loads. But to answer your question, we need to first look at software design report to first establish what does it refer to when it states Thermal Cracking. Can you please share the detailed design output of slab? Thanks.

You can simplify this. Calculate the maximum wind load and apply it perpendicular to the surface. I would connect the member between the two billboards to make a “space truss”. I am not familiar with ASCE but in National Building Code of Canada we have different formulae to calculate wind load on signage and boards, walls etc so make sure you are using the correct formula in ASCE as I assume they would have something similar (assuming) .. take some time and research the document. Thanks.

I was thinking to reply to this but @Nustian371 might be more suitable because of his background on masonry! Let’s see what he has to say. Thanks

Wsalaam Hashmi, There are similar topics on the forum that can help. I can find one: Try the replies, it might help. Apart from that, you can also contact CSI. Thanks.

Wsalaam Hashmi, The way I read it is that if you have already included the effects in your analysis. I believe ETABS has an option to apply Seismic force at eccentricity. I am a bit rusty on this. Thanks.

W.salaam Hashmi, For the check 2, your base shear is different and so is deflection. What is the basis of this check? Thanks.

Dear Abbas, Probably because short side means less construction works especially for sawed-joints. I would suggest checking out ACI 224 as it is the go to document for constructions joints for more info. Hope that helps. https://www.concrete.org/store/productdetail.aspx?ItemID=224395&Format=DOWNLOAD&Language=English&Units=US_AND_METRIC Thanks.

Hamza, To size, find the moment and shear at the section where the two rafts meet and ensure you have 1) enough flexural rebar 2) enough ties or shear capacity (Chapter 17 ACI 318-14) for shear limit states. Thanks.

100 PSF is minimum .. if such case, what we normally do is submit a project decision to Client highlighting the risk associated with it, and ask client to accept the risk associated with it if the information later is different .. for example, you can ask Client that you will design the floor for 200 Psf and go from there.. other options include expediting information from Computer Hardware vendor so that they can provide you exact loads sooner. Thanks.

W.salaam, You should look for Client Specifications and if you can't find anything, scour ASCE 7. It has good recommendations on various occupancies. Thanks.

W/Salaam, Yes, I think so. Thanks.

Based on building code. Yes.

W/salaam, If you like IT, then why don't you do masters in Computer Engineering. That can be good option. If you still want to stay in Civil Engineering, for IT related stuff, you should search for master/ research Professors, that are working in AI, Machine Learning etc. It might have some scope. Afaq Ahmed, a professor in UET Taxila is doing something related. You can look him up on Linked him. Thanks.

For trusses, all members should be pinned but any cantilever members that go beyond the support should be modelled, designed and detailed as continuous/ moment connections or else the system would be unstable. What are your boundary condition for these truss members that cantilever? Thanks.