Yasir Saleem

Yes sir, agree just forget to put that one in. Thanks,

As Uzair mentioned up there that is one way for the modelling of sag rods, but as per my experience it do not give satisfactory results. several reasons behind this one as it depends upon your building geometry like size of purlins or beams you want to bridge and there length as well. The sag rods behave as pin elements at the ends and they are most of the time lose tight with the main member which is a bit difficult to model, they come to action only in case of severe loading (Normally they are just holding the alignment of main beams). if you model them as per above method you have to break the main member at the connection point to send through the force to them so they act as tension member but as same time you have to make them pin assign due to which you will get very strange deflection shapes for the model, even the force distribution changes alot in some cases again depending upon geometry. Some time you hit the right nodes but most of the time results are a bit strange and some compromise is done in design of members, the best way i figured out is that you model line elements (with none material or frame property just null element) as sag rods and apply loading keep the main member as one piece without break and take out the member force generated in the null element. Design the tension rod or sag rod for that force manually as per required code. The above method is more suitable for building braces for lateral actions or tension rods for hanging cantilevers where high loads are expected. Thanks

Sir Umer sorry for replying so late as I just saw this today and didn't realize that it's a year old..

For the steel canopies with the glass on the top you have to consider few things for the design. As others mentioned you the strength of the glass can be and should be provided by the manufacturers according to your spans and wind load requirements. There is a small software for the glass thickness check saflex which is available for free on net check that to get approximate glass thickness you can put in your initial assumptions for the glass like tampered double glazed with air space with assumed size etc . This glass thickness can be used for the dead weight calculation to be used in calcs. Now for modelling you can model the frame and assign the area shell element with weightless properties. And put your dead loads for glass as well as the framing of the glass with will be provided on the steel to hold the glass panels as oneway loadings on the area elements. Put your live loads mainly for the cleaning purpose on the main steel members as point loads take impact load and apply as pressure load point load on the area element as the glass is tested against the impact of any thing falling on it from a height check the codes there is a value I don't remember now but you can check its steel ball impact test. Also apply the canopy wind loadings you can calculate that from ASCE-7-10 or the check internet for the Australian code it has a special clause for canopy wind laodings. Once these loadings are done make you appropriate load combinations and complete your analysis. No need to change any modifiers for steel structure. You can check your shear and axial values all along the beams to calculate the connections required for holding the glasses. There area special pressure plates and tobbler coneectors normally supplied by the glass suppler and they are enough for holding the things but still you can verify the small screws provided by the details. Please excuse as the dicription is soo long but I hope this will help you.

thanks sir g ... Eid MUbarik....

sir g i am attaching the architectural plan, sir have checked this for L/150 deflection considering it has a cantilever of 1925mm from column. And also checked for L/175 considering glass edge for the same cantilever side deflection . The only issue is now that which load criteria be used for live load. If i use 0.25Kpa load then deflection is different and if i use 0.58kpa load then different. Which is correct for this type of structure. Which one should govern for deflection. Thanks

Dear all , I am working on steel canopy structure , general layout is like, its a 12m long and 3.250m wide canopy. Supported by two circular columns. which are 6m apart from them leaving 3m cantilever on sides. Canopy frame is 1.925m cantilever on front side of columns and 1.25m on the back side of column. The canopy will be cladded with aluminum. I want to know that as per ASCE and IBC this will fall under which category for live load selection and deflection criteria check. I am attaching the code live load criteria with highlighted section and also the deflection criteria. one section of the structure is also attached for understanding. Other loads like wind seismic have been considered as per the code requirements. Actually the design and strength are no issues in this only the deflection under Dead +live load is the one worrying as there may be a glass walls under the canopy in future. So i am looking for correct deflection criteria and also the live load which needs to be considered. code 1.pdf code 2.pdf code 3.pdf code 4.pdf drwg.pdf

sir g thanks for guidance, Actually i am not sure for the dynamic loading but that was my question that if there is some force how we take it and what factor should be there but if there is no need for such loading i am ok with it, but that was my query i was just wandering... But ok i will do it accordingly as one of my course mate from Brasil also explained the same you are telling me so no big issues let me go with that.

Sorry for being late in reply, I am attaching the drawing which i got from the contractor till now. I hope they will give me something in good shape soon but at the moment to have an idea this is it. Sir umer my first suggestion was to provide the concrete column and beam but they say no to it. In this drawing you can see i have proposed some elements. I hope they will be more or less working. I will use bracing if i need from calculations. But i just want to confirm the checks which we apply to make sure that in any case of vibration of dynamic loading it is safe. So that is why i am looking for some example. Scanned copy.pdf

Hello Everyone, I am wandering if somebody guide me through the design of lift shaft for composite Structure. By composite i mean two existing walls are RCC one will be back wall and one side wall. Other two will be steel walls and opening is in steel wall. I have asked for the structural details of the existing RCC walls to check there steel and if they are designed as shear walls or not. I have to add the steel walls to make a shaft. I want help if i have to check the steel walls what should be my approach as it is not high rise its just a two storey building and lift will be GF plus FF only. the loading i have to consider is hoist load on the top of the walls which more or less behave like point load and i have to chk this for dynamic loading for vibrations that can cause or not later about the lateral loading. I think the connections will be simple as there will be no such great moments so i assume them pin connections. Loading for the diaphragm beam should be the slab load if there any and lateral loading. Bracing for the wall for lateral load. What about connections between RCC and steel should i keep them also pin or fixed with moments because what i am thinking that if the hoist is placed on RCC and steel wall then it will create the moments at the connection. So it has to be fixed. but then in that case the RCC wall should be able to resist the loading applied at that point. Please go through these points and suggest me what should i do. And yes if some one have any kind of design data or calculation example for lift shafts that will be great help. Regards. .

good work rana it reminded me my masters classes good refreshing one and with detail...

Welcome nadeem...

sir thanx for the detail comment i was going to write some of your concerns about the limits that sir umer shared above these are there when gravity load or point load is acting and drift the consultant concern for these posts is midspan deflection due to wind load how much they will deflect and what is limit. Sir Zeeshan the height of total frame system is 10 m but there are two floors each with height of 5235 and at mid the RCC element is slab with beam just like at top.

sir does that means that this we should not consider even if our deflection is like that much we just go with the delta if its oke then leave whatever the model show. and what about report when we print the report for certain load cases and the values are high does that will not annoy the checker ?

Sir g please have look at these what is wrong and where...all the deflection criteria which are available or i have seen give us or tell us about the end deflection only. Slenderness and buickling is only one thing which t=is there to chk the element but what about this what i as asking, and if i am wrong please do correct me.

Yes sir you are right that these are nonstructural members and and the limits you mentioned i have gone through these, but my element is attached at the top as well and consultant is asking question of inter story drift here and these deflections are again at the top end as you mentioned (not supporting the ceiling) what about the mid span if the element is fixed at both ends.

Sir g if you look at the drawing and first section at the top left side these columns the consultant has asked for inter story deflection for that section. so how will i chk that inter story deflection. i am attaching the commented copy as well from the consultant. The engineer who was working before me in this office calculated the deflection for that section busing L/200 and submitted that in the report which got rejected. So look at the drawing i think you will understand what i am saying. You will see the comment in the same first section top left side of drawing. NYU-ATA-DRG-C1-AR-00003-00.dwg NYU-ATA-DRG-C1-AR-00003-00 REV.02_STATUS_B_iss1_revA.pdf

sir agree with you about the first point and i have already gone through these pages but my concern is still about the deflection of a certian member in the mid span. I say it like this that you have a steel column which is fixed at both ends and its height is say 5 meters how much the allowed deflection for that at midspan. column is loaded by uniform lateral load. As if we go to that l/360 crityeria then the deflection is too much i have seen in BS that for curtian walls and mullions this is l/175 or l/250 my question is this deflection is at the end again what about the mid span. Oke one thing we chk the slenderness of the section and it should be less then 200. what if this ration is less like 60 or 160 and the deflectionn of our coulmn is like 100 mm to 300mm? What is the criteria for that. I chkd this by considering the coulmn as a simply supported beam and calculated the deflection manually at mid span . but again what are the upper limits to confine it. About wind what about the wind results from the analysis as in many cases no value any reason for it or i am doing something wrong.

Hello everyone, I am looking for some answers to simple questions like 1. What is the inter story drift limit for steel columns , and what is the maximum deflection allowed at the mid span of the column which has axial load and lateral loading as well ? 2. How we decide the end at which moment need to be released and which one like M22 or M33? Does this depends upon the support end and type of support? 3. What is the difference between the pin support and fix support in terms of its application to the model? As lateral meaning is not required its the sense that on which basis we decide that oke we donot model pin support and assign fix support to the model. and then when we are designing base connection like base plate and anchor bolt and position of anchors on the base plate. Does this all only gives us freedom in the fixity of structure at the base like we are free on locating the suitable position for anchors on the base plate or it has to do something else as well ? 4. What about the wind loading? if we calculate the wind load manually and then apply it as a lateral load to the whole structure is ok or we just go as making the areas around the nodes and apply the load only to the nodes and then chk the deformation. What about the wind analysis we do by the help of software how accurate are they as the deformation due to wind is nothing in many cases if you see the analysis report or table...

sir g go for The english Patient House of sand and fog Scent of a women Legends of the fall Assassination of Jassie james (My faviourite Classic old time)

correct rana but even in axial tension and compression both cases are very difficult to be applied to concrete so when they are applied separately the residual stresses and strains are there in the concrete they will have their effect on the concrete properties....

I agree with ayesha and Rana they are right,i was thinking same like rana still there is one thing that if we talk about a specific part of concrete section where force is applied so that section will have a compression and tension just simple case so the stress is proportional to strain at point so one modulus at that point but if you take tension is some other part of section and compression on other then you will have two curves so how can you compare them obviously they will have different moduli at that point but how can they be compared as mentioned by waqar as well concrete in not homogeneous so material properties at that point may differ..Rana and Ayesha please correct me if i am wrong ?

I am doubtful its not possible as far i think but i will check as well, If its same concrete with same material properties and strength then how its possible i am not sure but i would like some more explanation on this, stress strain are separate properties of a material...

Waqar your discussion seems very appealing but i have a query ,e.g what kind of loading will be in that case where horizontal splitting is occurring? Because that means you are pushing the bars from both sides is it like that?

I am too late to say eid mubarik to everyone but still i say that i hope you all had a wonderfull eid and ramadan...