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  1. 4 points
    EngrUzair

    ETABS 9.7.4 Runtime Error Message

    AA. Here is the progress & update regarding the problem described in my original post, for the benefit of the interested SEFP users. 1. Automeshing was adopted in the original ETABS 9 model, with a maximum mesh size of 3 ft for the slabs & walls. The slabs included a raft slab as well, for tranferring the reactions to SAFE. 2. The model was being updated in steps, by refining the geometry along various edges of the slabs according to architectural plans at different floors. Model was running fine at all the steps. 3. The problem most probably occurred when the whole model (including the raft slab) was selected through 'Select all' command & automeshed again as stated in para-1 above. This action meshed the raft slab as well.The meshing of raft slab was haphazard in some regions, because of orientation of slab outer edges in different directions. 4. Following steps were taken in order to sort out the error:- a. Trials were made by automeshing the model at two different maximum mesh sizes of 4 ft & 2 ft (one at a time), but without any positive result. b. Third trial was made using 'default' meshing option ( meshing at grids & in Automesh options, by keeping the 'Further subdivide shell/wall in maximum element size of' option UNCHECKED. This trial helped in running the analysis completely, with 2 Warning Messages indicating presence of unconnected point & frame objects at the specified locations. Deletion of these extra objects removed the warning messages. c. Another trial indicated that thr problem is with the meshing of slabs, and not the walls. d. Trying to locate affected element # 22836 through the procedure advised by Rana, indicated that the relevant output table designates the slab & wall elements by the number types F### for slab elements & W### for wall elements. It followed that element numbers (like 22836 etc) are generated during analysis only. The same facts have been stated above by Saad Pervez. Thus, the affected element could not be traced once again. e. Keeping in view suggestion made by EngrJunaid, the affected model was opened in ETABS 2016. This time the affected element was located & found to be present in the automeshed Raft Slab, provided at the base level merely for exporting the Base Reactions to SAFE for further processing there. 5. Replacing the affected Automeshed Raft Slab, with a new unmeshed raft slab & remeshing the floor slabs & rc walls (after selecting the floor slabs & walls separately) at desired maximum mesh size finally solved the problem. In the end, thanks to all (especially @EngrJunaid) for contribution to reach the solution of subject problem, by suggesting various courses of action. Regards.
  2. 3 points
    Rana

    Flexural Analysis

    and for long term deflection and for increasing inertia and for moment reversal and in short spans.
  3. 3 points
    Rana

    Structural Engineering Books

    You guys scared the hell out of him. No one can read that many books. Dear Hassan, just pick one book and get the max out of it.
  4. 3 points
    EngrUzair

    Shear capacity of Column

    Following article (particularly its first paragraph) may help you understand the role of column ties in resisting shear during an earthquake:- EQ Tip 19.pdf Regards.
  5. 3 points
    Dear Fellow Researchers, Academicians, and research students, NED University of Engineering & Technology in collaboration with Institution of Engineers Pakistan (IEP) is organizing 9th International Civil Engineering Conference (ICEC 2017) on December 22-23, 2017 at Karachi, Pakistan. The congress details are available at its website www.neduet.edu.pk/icec Also attached is congress flyer for information and dissemination among your peers. Abstracts submission deadline has been extended till October 31, 2017. International Civil Engineering Conference (ICEC) is a regular feature in the calendar of events for Institution of engineering Pakistan and its Organizing partner NED University of Engineering and Technology Karachi. It is being organized frequently for almost two decades now. Eight international conferences have been organized in the past. Every year, the ICEC is held under an innovative theme related to contemporary issues that relate Civil Engineering and Socioeconomics of the society. The latest version of ICEC was held on December 23-24, 2016 at Karachi. The conference was organized in collaboration with Federation of Engineering Institutions of Islamic Countries (FEIIC), Federation of Engineering Institutions of South and Central Asia (FEISCA) and The Asian Civil Engineering Coordinating Council (ACECC). Theme of this congress was “Ensuring technological advancement through innovation based knowledge corridor” More than 40 international papers were presented at the 2016 conference including those from United States, United Kingdom, Malaysia, Srilanka, Bangladesh, Iran, and Nepal. The event was attended by a number of delegates both from academia and industry that provided a great opportunity for the stakeholders to meet and discuss various issues related to Civil Engineering education, profession and recent advancements. This year, the 9th International Civil Engineering Conference (ICEC 2017) will be organized on December 22-23, 2017, under the theme “Striving towards Resilient Built Environment?” The idea is to bring together latest civil engineering knowledge, research and development efforts from scientific community, engineers and practitioners that can help in contributing towards enhancing the resilience of the societies and thus establish a better built environment. The conference proceedings are published through blind peer-review procedure. The confetence will cover all areas of civil engineering, including, but not limited to, the following: · Structural Engineering · Construction Project Management · Earthquake Engineering & Design · Transportation Planning · Traffic Simulation and Modeling · Disaster Management · Geotechnical Engineering · Water Resources · Environmental Engineering For further details, contact the undersigned. Best Regards, ------------------------------------------- Dr. Farrukh Arif Co-Convener, ICEC 2017 Assistant Professor, Department of Civil Engineering, NED University of Engineering & Technology, Karachi, Pakistan farrukharif@gmail.com
  6. 3 points
    Rana

    My House Design Suggestions

    This is not the right place to discuss/seek consultancy advice/design of a complete structure, in fact it is dangerous. Please hire a professional structural engineer to properly check and design it.
  7. 2 points
    Rana

    Shear Wall vs Column

    what about 200x600 column? This is just the geometrical constraint as in UBC or other codes. Usually I do it as wall; 1. if it is more than 1500mm + the above geometrical constraint. 2. if analysis is for lateral loads. If you have huge number of such elements, it will make huge difference for lateral loads (just check the % of lateral resisting load). This is because for walls, there are multiple points of support (moment from couple). If you want to model it as wall and want to act like a column then just put one point support, then the only difference between shell and line will be 4% difference of stiffness due to poisson's ratio (negligible).
  8. 2 points
    UmarMakhzumi

    Android App for SEPAKISTAN

    Dear miqureshi77, Thank You for your feedback. Right now we do have a website skin that allows users on webpage to view a simpler version of the forum. The app is something that the team can look at. I can't promise it considering how busy we are right now but it is a good suggestion and we will look into it. Thank You and let us know if you have any additional comments.
  9. 2 points
    ILYAS

    Shear Wall vs Column

    length to thickness is greater then 3 so treat as wall
  10. 2 points
    BAZ

    Seismic Analysis

    The time history is the most accurate way to estimate the demand as well as detect the shortcoming in a structure. It is time-consuming and most design offices do not use it unless they have specifically charged from the client for such analysis. If your building is regular, response spectrum will suffice; you can check modal mass participation to verify that. If you are getting more than 60% mass in principle modes, then time history will not offer a significant advantage.
  11. 2 points
    BAZ

    Seismic Analysis

    You will use Time history analysis when you want the analysis done in highest possible detail. Yes, it will depend on the building height, as well as on the structural irregularities. For regular structures less than 20 stories, pushover analysis will do. But if you want to consider the effect of higher in modes even in buildings less than 20 stories, you should go for Time history analysis.
  12. 1 point
    BAZ

    Shear wall from 3rd storey

    The demand on the horizontal and vertical members that will transfer the forces of a wall to the foundation is a major concern. The demand will be calculated by considering the expected ductility and overstrength of the wall.
  13. 1 point
    Tufail Mabood

    Measuring The Bar Length!!!

    ACI 318-08 Code 7.1
  14. 1 point
    Alhamdu Abdella

    Flexural Analysis

    You should not use that.because your design become uneconomical.so,you have to use As' if the section is double renforced section, otherwise for single reinforced section provide As' equal to Asmin and also even for double reinforced section As' shall be less than As, because As' is required to avoid exceding of neutral axis from ductility failure limit.
  15. 1 point
    miqureshi77

    Flexural Analysis

    Top bar in slab at middle span is not required except for temp shrinkage only
  16. 1 point
    UmarMakhzumi

    Shear Wall vs Column

    You can model it both as a wall and column in two separate models and consider the most conservative results. Thanks.
  17. 1 point
    steel design - segui
  18. 1 point
    groszni awesome

    Flexural Analysis

    doesnt work like that, you gotta check the compression steels strain (ecs) , it usually dont yield so you couldnt use fy
  19. 1 point
    Alhamdu Abdella

    Flexural Analysis

    Why you put As equal to As'?
  20. 1 point
    EngrUzair

    Response spectrum

    Check the following link for the required information:- https://wiki.csiamerica.com/display/safe/Import+response-spectrum+load+case+from+ETABS+into+SAFE Regards.
  21. 1 point
    groszni awesome

    Seismic Analysis

    RSA would do it, there are so much parameters u gotta assumed/determine in time history analysis, plus you dont have that lot of seismic acceleration records in indonesia
  22. 1 point
    BAZ

    Shear capacity of Column

    Study section 11.2.1.2 of ACI 318-11. The relation you have mentioned above does not include the effect of axial forces.
  23. 1 point
    UmarMakhzumi

    Pile Cap Design

    The same way the you would design a slab.
  24. 1 point
    EngrUzair

    Pile Cap Design

    Following link that provides reference to several good documents related to pile cap design (including design examples), might be helpful in this regard:- Pile cap design
  25. 1 point
    miqureshi77

    R/f at top in isolated footing

    Sure for uplift , it requires, yes the foundation which is not backfilled for longer period shrinkage can be provided. But for shorter period no need to provide topr/f
  26. 1 point
    He must be kidding for one inch. In such cases you go with resins e.g. from hilti, and the drilling length is calculated from their manuals/softwares. It will be around 5 inches or more atleast, depending on conc strength, fy, thickness of materials etc.
  27. 1 point
    ILYAS

    PUNCHING SHEAR IN SAFE 16

    REPLY FROM CSI Ilyas, Regarding your questions: 1, 2 and 3- Results are not expected to be the same, in general, ETABS is based on 3D analysis of the building while SAFE is based on a single story. If you uncheck thick plate in SAFE slab property it is similar to shell thin in ETABS in which slab shear deformation is not accounted for in both programs. This is also depending on ETABS--->SAFE export option you are using, load cases involved, meshing, rigid zone over columns etc. 4- Please make sure to run latest version of SAFE 2016 v16.0.1 5- Concrete strength does not matter for stiff element property as program does not design stiff elements. Program magnify their bending stiffness by a factor of 100 to model the rigidity of the interface. Regards, Mohamad ____________________________ Mohamad Ali-Ahmad CSI Technical Support Computers & Structures, Inc. TECHNOLOGY FOR A BETTER WORLD 1646 N. California Blvd. Suite 600 Walnut Creek, CA 94596 – USA Main (510) 649-2200 Fax (510) 649-2299 support@csiamerica.com www.csiamerica.com
  28. 1 point
    EngrUzair

    PUNCHING SHEAR IN SAFE 16

    No. You must not refer to or send results obtained using 'cracked' software for advice. It is illegal. Your queries, and attached information or results MUST be those obtained using Licensed software only. You would need to include details of purchased License, while referring the case to CSI for clarification. Regards.
  29. 1 point
    EngrUzair

    PUNCHING SHEAR IN SAFE 16

    Since you are using Licenced software, the best option would be to refer the case to CSI directly with all relevant details. Regards.
  30. 1 point
    Slab element number during analysis and slab area labels are different. Slab number during analysis is the position of that element in the database, slab area labels have the notation F### and usually indicate when this particular element was drawn, slab area labels can also be repeated in different stories, slab element number is unique. Exporting to EXCEL will also not help because EXCEL will slab area labels, not slab element number. Exporting the model to .e2k and the importing it back might help, OR you can do a manual check of all your model by studying the mesh. In my experience, this error is caused by a shell element with 2 nodes only, which happens when you move one set of points to already existing points by move command, this will merge the points but the element defined between them stays in the database. Hope this helps.
  31. 1 point
    Ayesha

    Corbel action on Column analysis

    Make a free body diagram. Corbel transfers loads to column like any rigid attachment to column would. It would transfer a moment and axial load to column. The tough job is to design corbel itself. You should use Strut-and-Tie method for corbel design.
  32. 1 point
    Rana

    ETABS 9.7.4 Runtime Error Message

    Yes, but my post was, how to do this in ETABS 9.7 if some one doesnt have v13.
  33. 1 point
    Rana

    ground slab above mat foundation..

    If it is directly resting above mat foundation, then yes, all the loads (ground slab+backfill+dead+live) should be used to calculate bearing capacity.
  34. 1 point
    Sir the simplest & easiest way of finding the area by its unique name is ETABS v13. Open your model in ETABS v13, go to Select ----> Labels -----> Shell Unique Name ----> enter the name of the required area.
  35. 1 point
    You can also get help from: Reinforced concrete design, 6th Ed., by Mac Gregor and James K Wright and Seismic Design of Reinforced Concrete and Masonry buildings by Paulay & Priestely.
  36. 1 point
    Rana

    ETABS 9.7.4 Runtime Error Message

    The first step towards obtaining the stiffness matrix, is to obtain the Jacobian, using an equation which you can find in any finite element analysis book. This equation has a shape function matrix which depends on the nodal displacements. Once Jacobian obtained, the strain displacement matrix is obtained and transposed and then finally stiffness matrix is obtained. Jacobian will be negative if there are distorted elements, local axis of connected elements is different etc. Check element 22836. If you cannot find this in ETABS 9.7, then do this to find coordinates. Display > Show Tables > Model Definitions > Area Assignments > Area Assignment Summary Then export to EXCEL, find area 22836, and then within the same row, look for centroidx and centroidy coordinates.
  37. 1 point
    Strain compatibility means C=T equation for reinforced concrete design. The other end is in tension. Bending of wall will create compression at one face and tension on another. You can assign Tension forces at different bar levels as T1, T2, T3 and so on and use C=T to find the value of small 'c'. Hope that helps.
  38. 1 point
    Waqas Haider

    R/f at top in isolated footing

    Top reinforcement is needed in isolated footing majorly for two reasons. 1) Due to negative pressure under some or whole part of footing. In part of footing where there is positive pressure, the footing is in complete contact with soil and tension is in bottom side of footing. But in part of footing where there is negative pressure the footing is no more in contact with ground. Either it is designed as it is (and reduced contact area is used for calculations) or it is made to become in contact with ground by help of over burden loads. In either case, the bending of footing is in such a way which causes tension of footing at top of foundation demanding top reinforcement in footing. Mostly top reinforcement is less than bottom reinforcement but for simplicity, if it is not affecting economy much same reinforcement can also be used for top and bottom. 2) Due to temperature and shrinkage control. Code says we can provide temperature based minimum steel either in one layer at center or at any face or we can divide total steel in two layers i.e. half at top face and half at bottom. According to Zahid Ahmad Siddique (Professor at UET Lahore) in his book concrete structures mentions it is better to provide temperature steel in two layers if thickness of footing increases 18 inch.
  39. 1 point
    Here are my two cents:- 1. General guidance regarding placement of construction joints in RC work has been provided in Section 6.4 of ACI 318-08 and its commentary. Some clarity is given in section 6.4.3, where it is stated that "Construction joints shall be so made and located as not to impair the strength of the structure. Provision shall be made for transfer of shear and other forces through construction joints." For transfer of shear etc through construction joints, reference is made to the ACI Section 11.6.9 that deals with the calculation of shear-friction, at the interface between two concretes cast at different times (beside other situations described in section 11.6.1 of the code). Moreover, Section 6.4.4 suggests that "Construction joints in floors shall be located within the middle third of spans of slabs, beams, and girders. 2. Regarding construction joints in columns, however, Section 6.4 does not provide guidance clearer than that in Section 6.4.6 stating that the "Beams, girders, or slabs supported by columns or walls shall not be cast or erected until concrete in the vertical support members is no longer plastic." And, the commentary section R6.4.6 explains that "Delay in placing concrete in members supported by columns and walls is necessary to prevent cracking at the interface of the slab and supporting member caused by bleeding and settlement of plastic concrete in the supporting member." 3. The support member (referred in previous paragraph) will generally be a column or a wall. And, in a simplified form, Section 6.4.4 & its commentary are advising us NOT to cast beams & slab monolithically with the wall or column, BUT only after the supporting column (or wall) concrete has hardened, in order to avoid plastic cracking at the beam-column (or beam-wall) joint. 4. In our normal field practice (within Pakistan as well as abroad), beams & slabs are cast at least one day after casting of columns or supporting walls. This gap of one day (between casting of column & beam concretes) ensures that the column (or wall) concrete poured one day earlier has hardened (is no longer plastic), thereby avoiding any possibility of plastic cracking (discussed in paragraph 2 above). 5. Now coming to your queries; In general terms, it is preferable to cast the column in one pour.. However, in compelling circumstances it may be done in more than one pour too, subject to certain conditions. Already described in initial paragraphs. This is the normal & IMHO desirable practice, according to ACI code Section 6.4.6. IMO, leaving 9" or 12" column depth below the beam soffit is excessive & undesirable. It should not be more than 1" or 2" in any case. IMO, this practice is based on the requirements of ACI 318-08 (also ACI 318-11) Section 6.4.6. The same requirement is available in ACI 318-14 Section 26.5.7.2 (a) as well. HTH Regards.
  40. 1 point
    Rahulkld

    Beam/column Capacity

    Sir how to activate the feature for alert of exceedance of D/C ratio
  41. 1 point
    aslamwalekum to all, when we need semi rigid diaphragm , i normaly take rigid diaphram for beam slab system , i got a vetting project (model made on ETABS 2016) , in which flat slab are used and semi rigid diaphram is assign , A/c to IBC 2006 , concrete slab with thickness more than 1.5 in , not consider as flexible diaphram , here is the code refrence. ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' 1613.6.1 Assumption of flexible diaphragm. Add the following text at the end of Section 12.3.1.1 of ASCE 7: Diaphragms constructed of wood structural panels or untopped steel decking shall also be permitted to be idealized as flexible, provided all of the following conditions are met: 1. Toppings of concrete or similar materials are not placed over wood structural panel diaphragms except for nonstructural toppings no greater than 11/2 inches (38 mm) thick. 2. Each line of vertical elements of the lateral- force-resisting system complies with the allowable story drift of Table 12.12-1. 3. Vertical elements of the lateral-force-resisting system are light-framed walls sheathed with wood structural panels rated for shear resistance or steel sheets. 4. Portions of wood structural panel diaphragms that cantilever beyond the vertical elements of the lateral- force-resisting system are designed in accordance with Section 2305.2.5 of the International Building Code ''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' here in my case slab is 8 in thick , so can it be act as flexible diaphragm. i belive for metal decking , i can use semi rigid diaphram , but not for 8 in thick flat slab
  42. 1 point
    EngrUzair

    Mat Or Footing Option In Safe

    Wa-alaikum-assalam. IMO, 'footing' option should be used in case of isolated & combined column footings, as well as strip footings (supporting either wall loads, or a column line consisting of three or more columns). On the other hand, 'Mat' option should be adopted when a single footing is to be designed to carry the loads, supported by a numer of columns or walls, oriented in different directions. Regards.
  43. 1 point
    Rana

    Mat Or Footing Option In Safe

    I am not sure exactly but I have found that MAT options gives more bearing pressure and I always use MAT for strip and rafts. I consider FOOTING for modelling purposes in SAFE only for isolated or 2 combined column footing only.
  44. 1 point
    BAZ

    Diaphragm Flexibility

    *SEFP Consistent Design* *Diaphragm Flexibility* *Doc No: 10-00-CD-0004* *Date: August 07, 2014* I am writing this article about a very important, but mostly neglected topic of flexibility of diaphragm. I used to assume that all reinforced concrete slabs can be treated as rigid diaphragms. But as it turns out, only the slab with span-to-depth (depth is length of slab in direction of lateral loads) ratio of less than 3 and without horizontal irregularity can be treated as rigid diaphragm. The more important thing is that the span-to-depth ratio and horizontal irregularity is not the only criteria and one other factor also needs to be kept in mind before assigning rigid diaphragm to concrete slabs in numerical model of building. Another important concept that I learned, and it was a moment of epiphany for me, is about TRANSFER diaphragms. I had posted a topic “Amplification Of Forces In Etabs” earlier in this forum but we were not able to reach at a satisfactory conclusion. Now, I have the answer to that query: Back Stay effect. Another article is required to explain it , and this concept is not discussed in this article. This article is about flexibility of diaphragm. Diaphragms are horizontal members of the lateral-force resisting system of building structures. Their function is to distribute inertial forces, generated at its own level, as well as other levels, to vertical members of lateral-force resisting system. One kind of diaphragm only distributes inertial forces generated at its own level. This kind of behaviour is observed in buildings where there is a continuity of vertical members of lateral-force resisting system: building should not have a setback or podium at lower levels, or below grade levels. The other kind of diaphragm, known as “Transfer diaphragm”, not only distributes inertial forces generated at its own level, but also re-distributes forces coming from upper levels. This type of behaviour is typical of a building having setback or podium at lower levels, or below grade levels. Transfer slabs can attract huge forces due to a behaviour dubbed as BACKSTAY EFFECT. Now, coming to the issue of flexibility of diaphragm. According to ASCE 7-10, In addition to considering aspect ratio and horizontal irregularity as a basis for assuming concrete slab as a rigid diaphragm, the relative stiffness of adjoining vertical lateral load resisting system. Buildings with shear walls at ends and flexible frames in between are the ones where the assumption of rigid diaphragm leads to underestimation of drifts and erroneous distribution of base shear in vertical as well as horizontal direction (1)(2)(3); shear forces in middle frames can be reduced to 23% if rigid diaphragm is assigned in the model (1) for buildings with this type of structural configuration. M. Moeini et al. (2008) (3) conducted a parametric study using numerical analysis and proposed formulae that predicts the error associated with assuming concrete slab as rigid diaphragm. They also concluded that for buildings, without shear walls, rigid diaphragm assumption is suitable for irregular buildings as well. But, for long and narrow buildings with shear walls at ends, the assumption of rigid diaphragm is not suitable. The objective of writing this article was to warn engineers about the tendency of blindly assigning rigid diaphragm to concrete slab in any type of building configuration. The result could be underestimation of forces as well as drifts. Nakashima, M., Huang, T., Lu, L-W. “ Effect of Diaphragm Flexibility on Seismic Response of Building Structures”, In proceedings of 8th world conference on earthquake engineering.San Luis Obispo, MSc Thesis , “ An Investigation of influence of diaphragm flexibility on building design through comparison of forced vibration testing and computational analysis”, 2010.M. Moeini, B. Rafzey, W.P. Howsen, “Investigation into the floor diaphragm flexibility in rectangular reinforced concrete buildings and error formulae”, In proceedings of 14th world conference on earthquake engineering. The article is not finalized and would be completed in coming weeks.
  45. 1 point
    Zain Saeed

    Retaining Wall

    Basement wall design spread sheet BasementRetainingWall.xlsx
  46. 1 point
    Ayesha

    Structural Engineering Books

    Reinforced Concrete Mechanics and Design by James G. MacGregor.
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