SMAQ

Walaicum Salaam, In General we design Structures for, Dead Loads, Live Loads, Super dead loads, Collateral loads. Wind Loads, Seismic Loads and, Snow loads (For Special Regions). There are some special cases for pump rooms or Parking areas or Storage tank etc. You have to consider those as well. Regarding Load combinations, You can go bothways. I suggest you define your own Combinations as to get aware of things. I Suggest you to read ASCE-10 before you go in to modelling process. Regards !!

Hello All, Modelling a G+3 Concrete framed Structure. The building has 100 mm thick precast panel Cladding on all the External faces. Wondering how to consider the load of these panel on the framing. Shall I consider it as a Line load on all the Exterior beams. Can anyone please suggest the exact method to consevatively consider the load of these panels on the structure.

@Nustian371Thanks for your interest and feedback. Yes, you are right, those foundations were failing in uplift. Those were as per my initial assumptions. I Finally opted for a Trapezoidal Raft of 8X3.2X0.6 meter ☺️.

Thanks Mr.Umar for, your response. I used fixed support as I am going to use a base plate mounted on a contineous concrete pad measuring around 5.8 meter in length 1.2 in width and depth. Is there any issue if I use it as fixed base.

Yes I did the same but Load, I kept it same as per calculation. According to my understanding The maximum load will from one direction, as the back side is open the wind load will be on bracings only and that too will be very less. Just a question out of context is, do you have idea of allowable deflection for the columns of such signs as I am getting maximum deflection under service loads as 13mm at the tip. I am also attaching staad files for your reference. PS-Sign board.std

Thanks for the reply Mr. Umar. Yes I already calculated the loads for the signs. I was enquiring about the direction of application only.

Hello all, I am designing a Billboard Structure in StaadPro the details are 12 meter High, 5 meter wide and it is in "V" shape, I need to now the number of directions I need to apply the wind loads. The claculated wind load as per ASCE is 1.3 kN/m on each column as columns are spaced at 1.25 meter Spacing along its width as shown with cross marks in pic below. Can anyone please elborate on number of load cases I need to consider for the design. A Hand Sketch for the same would be helpful. Thanks !!

@ayesha, Thanks for suggesting the Books. As I mentioned in my post, I have these books and this one is nice but sadly ☹️ they are in USC units. I was looking for some solved examples on Response Spectrum Calcs, in Metric units as I get confused with USC units. Any solved Examples will do also.

Hello Friends, I was wondering if I get suggested for good Text Book on Earthquake/Seismic based on ASCE/IBC but in "METRIC UNITS". I have many text books but all of them are in US customary units and I find it difficult to undestand as I follow Metric Units. Kindly, please Suggest me a text as such or if anyone of you have some notes/ course Material / solved examples on response spectrum Analysis ,in METRIC UNITS. Thanks !

Recently I designed a G+4 Building in Etabs, After Designing and getting all the results cross checked I had detailed the drawings accordingly.I had a 9"X12" columns at the upper floors i.e. From first to Roof floor. However as per my load coalculations, analysis and Design results I needed 697 Sqmm Steel area, I provided 4 dia 16 mm rebar i.e. 800 Sqmm Steel Area and released the drawings.Now another Engineer at site is in a technical Argument with me that, we cant provide 4 dia 16 bar in those columns and we need to Provide 2-12 dia Extra Rebars in them i.e 4-16+2-12.He is giving the IS456 code Ref. Clause# 26.5.3.1, point # g) "Spacing of longitudinal bars measured along periphery of the column shall not exceed 300 mm".However in my case it is not exceeding but he is telling since its at the boundary we shall opt for 2 dia 12 extra bar as "Code" Doesnt allow.My Question is, Why shall add Extra bars as my design and loads are cent percent correct and I met the minimum Reinforcement criteria.Coould someone help me in this regard. I know this topic is as per Indian Code but, it can be discussed in general.

Please Post your plan, that would help to Address the issue clearly.

@padika, if you want to follow the code, this is the criteria of minimum reinforcement for me. You are opting for the minimum reinforcement because as per your analysis, you are getting less reinforcement what it supposed be minimum as per code, Right? I suggest just draw a simple bending moment diagram of the bhaviour of the footing and study it upside down. Hope it will clarify your doubt.

Well, this is a bit complicated topic and also very simple, perhaps. I see many of us have a different approach to it, here is mine. Say, the two way rectangular footing is supported two columns which are located towards the ends of the long side. The usual loads, dead, live, seismic, wind, etc. are being transmitted through the columns. There is some shear at the column base, too.Now, which is the tension face of the rectangular footing?Is it just the bottom of the footing? With gravity and all the other loads acting downwards from the top of the footing, the top of the footing would be in compression and the bottom would be in tension. So we would need to reinforce the bottom of the footing.How about the soil pressure acting upwards on the footing? Visualize an upside down footing, with the columns as supports, and the soil pressure a uniformly distributed load on the footing. The bottom of this "visualization", i.e. corresponding to the top of the footing would be in tension.Would not the top of the footing be the tension face then, too, and needs to be reinforced, too?

Hi Sundass, it would be better if you upload your model. However, In addition to what @Ayesha had suggested, I can see from your attached pic that, some of your columns are fixed and some are hinged at the base. Is it done deliberately or overlooked? Please check, as this may affect the model too. Also try changing the orientation of the columns and study the behaviour.

Simple Structures explained the topic very nicely. But if we analyse the building with fully pinned supports, the reactions we are going to get for foundation design are without moments i.e Mx=My=0. If a structure involves large moments at base and we are not considering it in our design, because practically structure will not behave as 100% pinned or fixed but indeed there will be partial fixity, so we are making it fully pinned in analysis and finally we are neglecting those partial moments that are going to act on the foundations.

@Muhammad Umair Anwar , its very hard to predict whats wrong with your model without checking it. However you can check your model through Tools drop down list . For perfect modelling of plates please check the attached pics. If you still couldn't solve the issue please post your model.

Effective Length I took is 4.812, and I used un braced condition Sir.

@Saifuddin18, please dont be sorry. However what I did is I tried to design it in PROKON with the loads as under P=1215 kN, Mx ( Bottom) = 9.071 Knm, Mx (Top) = 25.3 kNm, My (Bottom) = 23.06 kNm, My (Top) = 7.3 kNm. I took the partially Fixed end conditions. When I design as per BS code its passing and ACI code it is failing in Buckling. Now I am thinking to connect it with plinth beam as the pattern in attached pic as I am not getting any Idea, and frankly I don't have idea to calculate the "k" value as per ACI-318. Also You mentioned the model is showing "k" calue > 3, But the model I see the "k" Value as "1" only. I dont know some thing is wrong.

Sure I will attach the model, The Columns @ Grid "K'-8" and Grid "b-7" are failing at Ground/Parking level. Please find the attached model below. MBP-Final.$ET

Thanks @ Saifuddin18 for your reply. Sure I will do that, but I am wondering why the column is failing in Etabs and how to overcome this error, because Etabs calculate the column forces using "k=1" on conservative side, so playing with "k" vlaue does solve this issue, but I don't know the exact procedure, I was wondering if I can get an idea of how to do that.

Can anyone please reply in this regard.

Hello Mates, I am struck in a small Issue, I am designing a G+4 building, subjected only to Gravity loads, The typical Floor Height is 3.2 meters and Height below the (up to Bottom Of Foundation) Plinth level is 2 meters. Ground floor has a Water tank hence, at that particular location I cant provide a Plinth/ Grade beam as it will crosses the tank so, I have to design that column for a height of 2+3.2-(depth of foundation-24" (Say))- (depth of Roof beam(15")) =4.21 meter (Effective). In my Etabs model when I am removing that Grade beam I am getting OS#5 Error ( Column load Exceeds Euler's Buckling Force), mean that Column is failing in Buckling. On the other hand when I put a grade beam there it is easily passing. But in practical/ at site, it is impossible to provide the beam. My query is shall I play with Effective length ratio "K" factor to pass that column without beam as I cant increase the size of Column as it is already 9"X24" column, and If I opt to change "K" factor how to calculate it as by default in Etabs "K" value fixed in "1". I am designing the Building for "Intermediate Brace". Kindly provide guidance in this regard.

Hello Fellow Engineers. Well I do Know that, Etabs Checks all the members for there minimum area of Reinforcement as per code. But I came across one design of mine where I see for a beam size of 228.6 mm wide and 304.8 mm deep. Etabs gives Bottom reinforcement less than what I calculated manually. I am attaching a few pics for the problem. I request to please put some light on this. The beam is designed for M20 and Fe 415 steel.

Wall Loads are calculated only for individual floors, Like for Ground beams you will consider walls of ground floors only. Please refer the attached pics for a clear understanding. Also for dead loads and density you can refer to the attached ASCE-10 pages. Where the densities are given including the plaster. ASCE 7-10desity.pdf

Hello, Can anyone please help me in this regard. Please !!!