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Showing content with the highest reputation since 01/22/2017 in all areas

  1. 4 points
    You can do like this; What you have to do is to note down the z coordinate of each shell element along the height (in Excel e.g.) and calculate the force at top and bottom node of each element, then apply the average pressure in local axis 3 (plus or minus). Tip: Always model retaining walls/swimming pool etc so that all the walls have local 3 axis either inside the pool/container or outside. So you can select all the walls once and apply the pressure in one go. And for that turn on 3d view in XZ or YZ in ETABS and select top most mesh, apply pressure and so on. Its not that difficult. To calculate average pressure you can either make your own excel sheet or use the following I once made. Water Pressure on Walls in ETABS.xlsx
  2. 2 points

    Vu* in concrete frame design

    It might be this; "For concrete frame design using the ACI 318-08 and ACI 318-11 codes, the design report for "Shear Details" has been enhanced for "Sway Special" frames by adding the field Design Shear (Vu) for clarity. Previously, only the factored Vu was reported, which may not be the governing force for capacity design." Incident Id: 64173 in ETABS 2013 13.1.4 enhancement user notes.
  3. 2 points
    (1). Structure Aspect Ratios The Horizontal/plan aspect ratio (Length to Width ratio) of the side block is 160/18=8.8 While its vertical/slenderness ratio (height to width ratio) is 60/18=3.33 I didn't come across any code limitations regarding these ratios But an indian research paper "Effect of Aspect Ratio & Plan Configurations on Seismic Performance of Multistoreyed Regular R.C.C. Buildings: An Evaluation by Static Analysis" concludes that, (a) The buildings with Horizontal Aspect Ratios 4 or less than 4, the seismic performance is reasonable. Above this, the worse effects of excessive forces, storey drift and displacement values may be obtained. Hence they should be discarded due to their unsatisfactory, weaker and unreasonable performances on the bases of above seismic parameters, which can cause detrimental and disastrous effects or otherwise be treated with the enough earthquake resistant elements. (b) The buildings with Vertical Aspect Ratios less than 4, the seismic performance is reasonable. Above this, the worse effects of excessive overturning, storey drift and displacement, period of vibration, etc. values may cause detrimental and disastrous effects to the buildings. Hence slender building configuration, as far as possible, should not be chosen, or otherwise be provided with the adequate earthquake resistant solutions. (2). Flexible Tower on Rigid podium UBC-97 Section 1629.8.3 item 4 says "Structures having a flexible upper portion supported on a rigid lower portion where both portions of the structure considered separately can be classified as being regular, the average story stiffness of the lower portion is at least 10 times the average story stiffness of the upper portion and the period of the entire structure is not greater than 1.1 times the period of the upper portion considered as a separate structure fixed at the base." And UBC-97 Section 1630.4.2 Item 2 says 2. The following two-stage static analysis procedures may be used for structures conforming to Section 1629.8.3, Item 4. 2.1 The flexible upper portion shall be designed as a separate structure, supported laterally by the rigid lower portion, using the appropriate values of R and ρ. 2.2 The rigid lower portion shall be designed as a separate structure using the appropriate values of R and rho. The reactions from the upper portion shall be those determined from the analysis of the upper portion amplified by the ratio of the (R/ρ ) of the upper portion over (R/ρ ) of the lower portion.
  4. 2 points

    Design life of RC structures

    Not sure about Pakistan building code, but this might be of your interest; http://www.concrete.org.uk/fingertips-nuggets.asp?cmd=display&id=750 Or in ACI 365.1R http://civilwares.free.fr/ACI/MCP04/3651r_00.pdf Or in terms of sustainability as per BRE (Building Research Establishment) or BREEAM program http://www.gov.scot/resource/doc/217736/0091011.pdf Also see this http://www.structuremag.org/?p=9459 http://citeseerx.ist.psu.edu/viewdoc/download?doi=
  5. 2 points

    Brick Mansonry design in ETABS

    Above referred site is related to Concrete Masonry. Following site may be helpful in connection with Clay Brick masonry:- http://www.gobrick.com/ Moreover, you may find several other sources through internet search. Regards.
  6. 2 points

    Modelling Two buildings near by

    You can use ETABS 2015 or higher and use 'Tower' option to separate both buildings in the same model.
  7. 2 points

    RCC Basement vs Pillar Foundation for Home

    Adding a basement for home construction is obviously the owner's choice. But as a structural engineer for home construction in Pakistan, I would highly recommend not to add basement. This is due to lot of additional expenses, like RCC retaining walls, waterproofing, flood control, toilet/bath expenses, ventilation etc. If designed and constructed properly you do not need to worry about earthquake. Again, I would have added one and half additional floors from the same money being spent on basement and also forget about the worries mentioned above. Or could have spent it elsewhere like finishes, elevations etc. And what do you mean by Pillar foundation?
  8. 2 points

    Purpose of design strips in safe

    Design strips are required to get total reinforcement area by integrating stresses of area objects.
  9. 2 points

    Brick Mansonry design in ETABS

    Thank you sir. This forum is by far one of the best forum I'm in.
  10. 2 points
    Waqas Haider

    Purpose of design strips in safe

    Hello Naqash, 1st of all welcome to this forum. And also try to spread this forum in your area/circle as much as possible, so that maximum people can take benefit of it. Naqash if you remember, in manual design of roof slab or footing slab, we use to consider a unit strip and design this unit strip for output results. Then we provide the steel and section calculated for this unit strip, to whole of footing or slab. Similarly, in Safe foundation, you are to define and assign design strip of unit width to let software show you output i.e. forces and steel etc for this unit design strip. you can also go for any width of design strip. Results will be accordingly but design will be same. Mostly a unit strip i.e. for MKS system 1 meter strip and for FPS 1 ft strip is defined and assigned. After running the model, you have two options to check your results of forces and reinforcement. 1) Based on Finite Elements In this method reinforcement and forces for each and every element, in which structure has been divided / meshed, will be reported. This is a bit different than our usual manual practice of designing. 2) Based on Design strips In this method reinforcement and forces are reported on strip based. This is quite easy to understand. You can check both methods for better idea. Another important thing is that we define 2 design strips "Strip A" and "Strip B" to read results in X and Y axis or in Shorter and Longer directions respectively. If you provide strip A in both X and Y directions, Then you will not be able to read results in X and Y axis, separately. display of results will be mixed. For this purpose we provide 2 different strips.
  11. 2 points

    Consequences of incorrect meshing in ETABS

    What meshing you are talking about? Slab meshing supported on these beams or beam meshing itself? What I could discern is you are using a shell element supported on beam. In this case, you should mesh the slab so that slab has nodes along the length of beam. Shell transfers loads to nodes and if not meshed, all the loads would go to beam ends at point loads.
  12. 2 points

    2nd order analysis

    First analysis tells you how much you structure would displace under gravity load. Second order analysis considers the displacement under gravity and its consequences. In simple words, you are checking a displaced structure under the effect of gravity load.
  13. 1 point

    Etabs 2013 installation issue

    Suarez, we do not handle pirated/cracked stuff. Please be aware in future.
  14. 1 point

    reinforced concrete longitudinal rebar placement

    Depends on design moment combination. Thats why i always recommend putting in the right reinforcement in columns in ETABS and put it on 'check' instead of design.
  15. 1 point

    Design life of RC structures

    I don't have a reference from Canadian Building Code, but I have seen a design life of 50 years in client specifications. Also, to me this is what is the basis is in design clauses (like Maximum Considered Earthquake is based on 2% probability of being exceeded in 50 years, or wind/ snow design loads are based on 50 year cycle). For Pakistan, it should be same as international code. In Canada, even though design life is specified in the documents, I have seen engineers continue to retrofit or modify existing structures which have passed the 50 years mark as long as field tests done to see the condition of concrete/ steel come acceptable. We have got a bridge in Edmonton that was built in 1915. It has been retrofitted and continues to serve the community. Thanks.
  16. 1 point
    ATIF NAZAR(PVT) LTD karachi based consulting firm LOOKING : 1- Structure design engineer having 3+ years experience in well reputed design firm. Applicant must have good command over design codes & structure engineering software (etab,safe,staad.pro etc) . Applicant should have skills in RCC design. Note: Engineer must having valid PEC registration. 2- Structure cad operator/structural draftsman having minimum of 5 years experience in reputed consulting firm/design firm. Applicant must have command on · Analyzing Architectural Drawings. · Analysis and Study of Structural Drawings · Checking of Structural Drawings. Interested people can send their CV at haseeb@atifnazar.com . Regards
  17. 1 point

    Modelling Two buildings near by

    Thanks. I forgot to state that I was using RISA3D but its good to know options available in ETABS. You can also use the formula for maximum inelastic response displacement to separate the buildings. Check this Thanks.
  18. 1 point

    Modelling Two buildings near by

    Hello everyone, I tried modelling two buildings which are close to each other in ETABS. When i tried to see time period at different modes. Etabs animated one building only for a particular mode. How does Etabs deal with such models? How can I see the animation of both building at once???
  19. 1 point

    Brick Mansonry design in ETABS

    The following site has good masonry design resources: http://ccmpa.ca/ Thanks.
  20. 1 point

    Modelling Two buildings near by

    It is a very good question. I was in a similar situation recently but I separated my models. Wonder how do softwares consider that..
  21. 1 point
    I remember Nowshera has some flood history too so you might want to reconsider the basement portion based on that. However, if you still wan to to have a basement, a semi-basement, just 4' below grade might be more in-expensive option. You can also ask your structural engineer to design a masonry retaining wall (if he can). That can save you some money. Also, things to watch out are water proofing details at the exterior face of the wall. Thanks.
  22. 1 point
    Only exterior walls need to be of RCC. For construction purpose, U can consult the following manual. and MUST follow its practices. But remember, it is not the design manual. So you need to have a good design of your house including footings, RCC walls, band beams, and corner columns etc.
  23. 1 point
    Naqash Ahmed Shah

    Purpose of design strips in safe

    Thanks Engr. Waqar haider for providing me such a usefull information regarding design strips.In shaa ALLAH I will recommend this site to my Engr. Friends
  24. 1 point
    hello friends, I am going to be a graduate engineer in BE civil engineering on July 2017 then will be looking for an internship in Pakistan in any field of civil engineering.i also have pursued one year of experience as the Associate engineer prior to my engineering degree for the execution of works on 9 story plaza.I 've 1 year of work experience abroad as a trainee engineer also but I want to learn the conservational way of designing of small residential homes in Pakistan, usage of software like ETAB, SAP. I am very good at QS also. I have good communication and presentational skills.. i am willing to go for master after next 3 years so i want to get more and more ground experience before it.please find my attached below software endorsements: Autodesk robot structural analysis( medium) AutoCAD 2d+3d(professional), Revit architecture advance, 3ds max advance, Microsoft word, Exel, ppts (professional), photoshop medium level, languages ( Urdu, English, Chinese) looking forward to join someone zubairbilal26@yahoo.com zubair...cv.pdf
  25. 1 point
    It can happen when lateral loads are included in combinations. Stresses of reversal due to lateral loads causes any side of joint in continuous beam to have tension on lower side causing positive moment at support on one side. So check if ur combination is including lateral loads.
  26. 1 point
    Also keep mesh size same i manual and automesh option. Automesh option, if not specified, does meshing at max size of 4ft x 4ft. If mesh size is same, Then do as sir Waseem said. i think results should not vary if slab is meshed manually or automatically.
  27. 1 point

    Design of L shaped 5 storey building

    Seismic performance or resistance of a structure having a 'torsional irregularity' will, in general, be less than a structure WITHOUT such irregularity. Therefore, the design codes have put limits and restrictions on the types of seismic-force-resistance-systems as well as the configurations that can be used for such structures. Actual performance level, however, will vary depending upon whether the torsional irregularity is less or more than the 'Extreme Torsional Irregularity' as given in applicable design or loading code. Torsional Irregularity may be reduced in certain cases, e.g., by changing the building configuration. Following links may help you understand torsional & extreme torsional irregularities as well as their effects on structures:- 1. Effects of torsional irregularity to structures during earthquakes 2. Extreme Torsional Irregularity Regards.
  28. 1 point

    Detailing Software

    CSI SAFE also has a Detailer. You may export ETABS results to SAFE and using the commands available under its 'Detailing' menu option, it will prepare structural drawings for you. You may give it a try to see whether it fulfills your requirements or not. Regards.
  29. 1 point
    Thank you very much sir. Thanks for your time and effort.
  30. 1 point
    You are welcome. Simplest way to learn something new to model is to take an example out of the book, do the model and compare the results. If your results are same as that of the book example, you have done a good job. Here are some tips: 1) Top and bottom members need to be modelled and designed as continuous members. 2) Make sure your unbraced lengths are correct. 3) Manually resolve wind and snow loads on trusses. In that way, you will minimize any chances of error in load application. 4) Manually check at least dead weight reactions and member forces. If they match, you can trust your model. Hope that helps. Thanks.
  31. 1 point
    Hi Rahul, There are a number of ways to do it. I have suggested one in the attached pdf. Thanks. Steel Truss Concrete Column Connection.pdf
  32. 1 point

    RCC Design Without Modifiers

    The factor of 0.35Ig is not applicable to beams with flanges. For the interior beam, the factor will be around 0.7Ig, and for the edge beam, it will be around 0.5Ig. Moreover, these factors are for un-braced frames; factors are different for braced frames. Please go through the commentary of the section 8.7.1 of ACI 318-08.
  33. 1 point

    2nd order analysis

    i think this kind of broad topic should be consulted to books better.
  34. 1 point
    Abid Qasmi

    Help required for analysis in etabs

    Dear all,i found out the reason why column reinforcement was 1℅ in all columns and it was that i had erroneously assigned oversized column dimensions in some columns. But my second querry yet remains unanswered that is whether the building be modelled as a whole or separated into two portions in order to avoid errors.thnx n regards
  35. 1 point
    Waqas Haider


    Why dont you simply assign insertion point to model this eccentricity? If you are having a frame, You can assign these insertion points to either the beam or the column a per situation? You can offset any end of member (Column or Beam) by this method to model eccentricity. If you are having a frame, and want to model the eccentricity at a specific joint, select the member at that joint (the member which is offest from center lines) and go to assign manu--> Assign insertion Point--> and assign desired offset nd desired axis. But dont forget to uncheck DON'T TRANSFORM STIFFNESS otherwise only geometry will be offset instead of stiffness i.e. required in calculations by the software. If you having only one column, You can also o the same, You want to provide eccentricity. You can either offset your load point as said by sir Rana, or you can offset your column centroidal axis by applying required offset in insertion points in desired axis. again dont forget to uncheck DON'T TRANSFORM STIFFNESS.
  36. 1 point
    waqar saleem

    Design of RCC basement walls

    Dear @muneeb1213 you have to consider loads on top of wall coming from the basement slab or any other wall directly on the wall. wall has basement slab attached on top so it will be like propped cantilever. there is an example 14.3 for basement wall(propped cantilever) in book "structural concrete by Nadim Hassoun" . you can design basement slab just like slab panel also if columns are closer and providing a beam at the top & bottom of wall and columns will act and must be designed as beams also but do check wall for shear against soil pressure at bottom half. Regards
  37. 1 point

    Foundation Design Floodlight Pole

    In calculating design forces, have you considered the application of point load on a panel, which will support lights, at the top of the pole, in addition to the UDL on the pole itself. Is it possible that only two bolts will be effective in resisting moment for a wind direction in which two bolts will lie on the neutral axis, and the moment arm will be sqrt(2) x 12.
  38. 1 point
    Yasir Saleem


    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.
  39. 1 point
    Turn off auto meshing if it's on and manually mesh the area in question. Avoid a very small element.
  40. 1 point
  41. 1 point

    Ubc Seismic Drift Limits

    *SEFP Consistent Design* *UBC Seismic Drift Limits* *Doc No: 10-00-CD-0003* *Date: June 04, 2013* The goal of this tutorial is to demonstrate how to evaluate building drifts and story drifts using UBC 97 guidelines. The philosophy behind Story Drift Limits is “Deflection Control”; In UBC 97, deflection control is specified in terms of the story drift as a limit on the lateral displacement of one level relative to the level below. The story drift is determined from the maximum inelastic response, ΔM. Let’s start by defining the design-level response displacements. The elastic deflections due to strength-level design seismic forces are called design-level response displacements. These are denoted by ΔS, where the subscript ‘s’ stands for strength design. Design level response displacements are what you get out of your software, when you run analysis. Please note that structural analysis softwares may provide these values in different formats; say a percentage of height or a direct output. Well, to calculate your story drifts, first you need to find maximum inelastic response displacements from your design-level response displacements. The maximum inelastic response displacement is defined as: ΔM = 0.7RΔS Where, R is the structural system coefficient, the subscript ‘m’ in ΔM signifies that we are calculating a maximum value for the deflection due to seismic response that includes inelastic behavior. Seismic drift values are much larger than wind values. UBC uses maximum inelastic response displacements rather than the design level displacements to verify the performance of the building. Seismic drift limits are 2% & 2.5% of the story height for long and short -period buildings. For a floor to floor height of 12 feet the max., allowable inelastic drift value would be 2% of 12 feet= 0.02*12*12 in=2.88 in. For wind for a 12 story height, drift would be L/400=12*12/400 =0.36 inches, A comparison of both wind and seismic drift limits shows that earthquake inelastic displacements are quiet large compared to wind displacements. That is why proper detailing is emphasized in seismic design. When calculating ΔS for seismic, make sure: You have included accidental torsion in your analysis.Use strength design load combinations: 1.2D + 1.0E + 0.5L & 0.9D + 1.0E.You are using cracked section properties for reinforced concrete buildings. Typical values are Icr walls= 0.5EcIg, Beams = 0.5EcI g & for Columns 0.5 - 0.7 EcIg.Use a reliability/ redundancy factor= 1 to calculate seismic forces.Whenever the dynamic analysis procedure of §1631 is used, story drift should be determined as the modal combination of the story drift for each mode. Determination of story drift from the difference of the combined mode displacements may produce erroneous results because maximum displacement at a given level may not occur simultaneously with those of the level above or below. Differences in the combined mode displacements can be less than the combined mode story drift. Example: A four-story special moment-resisting frame (SMRF) building has the following design level response displacements.(See attached Image) R= 7.0, I= 1 Time period= 0.6 sec (See the attached image for Story Information) Calculate: Maximum Inelastic response displacements.Story drift in story 3 due to ΔM.Check story 3 for story drift limit.Maximum Inelastic response displacementsΔM = 0.7RΔS ΔM = (0.7) (7) ΔS = (4.9) ΔS (See the attached image for Maximum Inelastic response displacements) Story drift in story 3 due to ΔMStory 3 is located between Levels 2 and 3. Thus ΔM drift = 5.39 - 3.43 = 1.96 in. Check story 3 for story drift limit.For structures with a fundamental period less than 0.7 seconds, §1630.10.2 requires that the ΔM story drift not exceed 0.025 times the story height. For story 3: Story drift using ΔM = 1.96 in. Story drift limit = 0.025 *(12*12) in = 3.6 in. > 1.96 in. Therefore, Okay.
  42. 1 point

    Free Concrete Design Publications From Pca

    Assalam-o-alaikum! A little addition. As far as I know, the passwords for the above mentioned two files are the same for all. These are given below: 1. PCA Notes on ACI 318-11 (Password: '2013PCAEB712') 2. 'Simplified Design of Reinforced Concrete Buildings', based on ACI 318-11 and IBC 2009 by Kamara & Novak 2013 (Password: '2011PCAEB204') Regards.
  43. 1 point
    The concept is that: "Shoot for the moon, even if you miss, you will land in stars". Just because you are trying to achieve something that is not possible from one perspective and even if you don't achieve it you will still become something not as great as your inspiration but better than what you used to be.