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Showing most liked content since 02/20/2018 in all areas

  1. 2 points
    I will ask out to see if we can get someone experienced in Tunnels. The problem is not a lot of people are willing to dedicate time to this. But, will give it a shot. Thanks.
  2. 2 points

    Column to Beam Capacity Ratio

    Hinges at both levels only can lead to the loss of gravity-load-carrying capacity.
  3. 2 points

    Column to Beam Capacity Ratio

    Yes, it can be ignored at the top story if it is only at the top beam-column joint. The ratio should be satisfied at the bottom of the top story.
  4. 1 point

    Collector Elements

    In most cases, the force in the collector is not enough to enforce enlarged-section in the form of a beam. The reinforcement can be provided within the slab. There is no other way, One has to complete the load path.
  5. 1 point
    She is already in contact with me :). But unfortunately I had to get involved on another project, leaving the tunnel design as it was. Still I have shared all the stuff I had with her. I was hoping we have a tunnel design expert here in the group. Really needed.
  6. 1 point
    It is not only the difference of moments, the difference of axial load is also responsible for increased demand. The lower axial load, coupled with increased moments is the reason. In top story, the unbalanced moment is distributed among three members. In lower stories, four members share the unbalanced moment at the beam-column joint.
  7. 1 point
    Thank you Sir @BAZ I got the point, why Longitudinal reinforcement increasing, Due to M2-2 & M-33 is greater in Upper story than Lower. But another question arrived in my mind why upper story M2-2 @ M3-3 is larger than bottom? File Attached. though I assigned less load in Upper story than Bottom story beam and slab. No Wind & earthquake load applied. Please Explain me.
  8. 1 point
    If you will follow detailing of ACI then the foundation will provide rotational restraint. Modeling it with the pin is under-conservative. Column's longitudinal reinforcement is a function of the size of the cross-section, material strengths, axial force and bending moments. Compare them.
  9. 1 point
    Look at the design forces of members and compare, you will get the answer. Why are you modeling the foundation as the pin?
  10. 1 point


    You will assignment diaphragm property to your joints when you are not modeling area elements ( shells, plates or membrane) in the model, but the joints are connected by a horizontal area-member, or some combination of line-members, that will act as a diaphragm in the actual structure. ETABS will use it to distribute lateral forces to all joints based on that diaphragm property.
  11. 1 point

    Foundation Design

    Foundation should be designed for response spectrum cases too if they are used for super structure design also.
  12. 1 point

    Steps in slab

    Dear Irfan, see the attach photo, I hope this will be the best structure scheme for your plan.
  13. 1 point
    Dear Fawad, Dr Mona Liza of Quaid e Azam University Islamabad has done a lot of work on this. You can also consult Dr Qaiser of Uet Peshwar and Dr Shoaib Ahmad (Zeinth International). He is working on the same thing
  14. 1 point

    Column to Beam Capacity Ratio

    @BAZ, can you please also explain ‘why’ beam column capacity ratio of the top story can be ignored.
  15. 1 point
    Yes. Site experience is valuable where things are done 100% to the drawing. Where there is proper change management and all directions are taken from design office. I don't know about Jordan construction practises, but if what I described is you have there, you can opt for site for 6 - 8 months and then get back to design. If not, don't bother, start at a design office. Thanks.
  16. 1 point


    Salma, These bars are generally used in non-seismic area. Since after 2005 earthquake, seismic detailing has overtaken traditional detailing practice, that is why you don't see bent-up bars anymore. Thanks.
  17. 1 point

    Foundation Design

    You should design it for seismic case too. With response spectrum analysis, signs are lost and maybe that's why your office is not designing foundations for it but technically speaking, foundations need to be designed for all ULS Load Cases based on LRFD. Thanks.
  18. 1 point

    ACI detailing and design manual

    Firstly, conversion of reinforcement area for flexural (longitudial) beam reinforcement to 'number of bars' is similar to that for the vertical reinforcement of columns. However, for deciding the 'number of bars provided' in case of beams, we round the calculated value to next higher integer number only, whether it is even or odd. For example, if required steel area is 0.9 sq.in., and #5 bar is to be used, then required number of bars =0.9/0.307=2.93. In this case, we may use 3 #5 bars for the beam. (Whereas, in case of a square or rectangular column, we needed to use at least 4 bars.) Secondly, in case of a beam, required number of bars are to be provided along the relevant (top or bottom) face of the beam only, depending upon whether we are detailing the reinforcement for the negative or positive bending moment. In case, required number of bars (as calculated in previous paragraph) exceeds the maximum number of bars permissible in one layer, required number of bars will be provided in layers, separated vertically by spacers. Thirdly, total area of reinforcement provided, must be within the steel areas corresponding to Minimum & Maximum steel ratios prescribed by ACI 318 for the beams. Fourthly, detailing of all type of beam reinforcement needs be in accordance with relevant provisions of ACI 318 and ACI 315 (whether seismic or non-seismic, as applicable). Out of three reinforcement values shown along (the top or bottom side of) a beam, two outer values (0.9 & 0.9 at left & right sides of top face, and 0.6 & 0.4 at left & right sides of bottom face of the beam under discussion) indicate the amount of reinforcing steel required at the relevant (top & bottom) faces of the two supports. Whereas, the middle values (0.2 on the top, & the 0.6 on the bottom side) indicate the amount of reinforcing steel required at the mispan of the beam, on the top & bottom faces respectively. HTH Regards.
  19. 1 point

    Shear wall design

    The answer to your question is already in Waqas's posted reply above. However, I will elaborate it further. You can but there are benefits assigning different labels. For the above case, reinforcement would be reported separately for each wall segment which is extremely useful (and more practical) for detailing. Below is suggested Wall Pier and Spandrel Labelling scheme (Source: CSI Wiki). Wall Pier Labelling Scheme Wall Spandrel Labelling Scheme You can easily draw this in Section Designer. The only catch is that if you are using the "Wall Stack" feature in ETABS, it automatically assigns the same pier label to all walls. To simply things, you can reassign walls new pier labels in that case. Use a regular mesh and always use edge restraints. The role of edge restraints is that they provide continuity to adjacent edges which is extremely useful for the case where meshing doesn't line up (as it can cause instability issues). Thanks.
  20. 1 point

    Beam/column Capacity

    Finally I got it. It's only available for ACI codes.
  21. 1 point
    Could you please explain that logic? Furthermore; seismic inter-story drift is limited to 2.5% of story height. If story height is 3.5m, the allowable inter-story drift is 87.5mm. If all floors were to be within the drift (so code requirements are satisfied) then a 10 story free standing building would have total roof drift of 87.5mmx10=87.5cm. Thats a lot, yes. But I do not see any limits in code for the seismic total drift as long as you have satisfied the inter-story drifts. Ofcourse, more the building overall drift, more will be p-delta effects, (that could be huge for a massive tall building). In wind design, overall drift is limited due to problem of acceleration at top floors. But in a seismic event, obviously human criteria is not something you should aim for.
  22. 1 point

    Questions Need To Answers

    Welcome to the forums. Here are the answers: 1) To satisfy code requirement that dynamic analysis base shear can't be less than 85% of static analysis base shear. 2) Static load combinations for static loads like dead, wind, live and snow and dynamic load combos for earthquake. 3 and 4) Please see the following articles on this forum: 5 and 6) Please see the following articles on this forum: 7) Please see the following topic: 8) Because it would result in huge over-design. Its counter intuitive and defies statistical philosophy behind load combinations. 9) Inertia causes forces and mode shapes. 10) The difference is hard to summarize in a short answer. You can post a new topic and we can discuss it there. Time history is more accurate. 11) Effect is in the form of deformation. Slabs are considered rigid in plane and may deform in their plane. You need to design them such that they can transfer lateral loads to lateral load resisting system. Beams deform and bend under seismic loading. 12) Right. 13) Please see this article: 14) Don't put. 15) Energy dissipation, cracking, elasticity 16) Please see answers to 3) and 4) above. Hope that helps. Cheers!
  23. 1 point

    Beam/column Capacity

    It means you need to increase, or decrease, reinforcement in beam, or column. But, You have to have a reinforcement which satisfies your elastic elastic analysis. You can't reduce the reinforcement, below the level required for resisting factored combos, to satisfy this provision. You need to add more, or reduce. But reduced moment capacity of that member should satisfy the forces of design combos. If you have provided more reinforcement than the requirement of elastic analysis, you will need to check the shear corresponding to probable moment strengths. Increase in moment capacity of member will lead to an increase in seismic-shear. I hope, I have answered your query.
  24. 1 point

    Raft Modeling In Etabs

    For raft in ETABS or SAFE you will use area springs. You can assign springs by going to this menu Assign>Shell/Area>Area springs. You can also use point springs instead of area springs, but for that you have to multiply area spring stiffness value by the tributary area on that specific node that means if your mesh is not regular, you have to calculate point spring stiffness value for each spring
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