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  1. 3 points

    R/f at top in isolated footing

    Uplift will reverse moment diagram.
  2. 2 points
    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
  3. 2 points
    Dear colleagues! Assalamo-alaikum. Congratulations to all on 70th anniversary of independence of Pakistan. May Allah bless us & make it Pakistan (i.e., the land of pure people) in the real sense. Regards.
  4. 2 points
    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.
  5. 2 points
    Dear fawad najaum! The methodology for seismic design has been radically changed in ASCE7-05 from that used in earlier codes like UBC 1997,the governing parameter for development of response spectrum are now the ss (short period accelaeration) and s1(one second spectral acceleration) ss and s1 can be derived from the peak ground acceleration(PGA) using empirical relationshops based on performance level(EUROCODE 8).
  6. 2 points
    In general, this issue is controlled by relevant clause of contract agreement. Following are the possible options that may be or might have been specified in the contract:- a. Demolition & recasting, in case actual strength falls MORE than a certain percent below the required concrete strength b. Strength evaluation of actual structure, according to applicable design code & acceptability or rejection of structure accordingly. c. Rarely, there might also be an option to strengthen the structure (using conventional or advanced strengthening techniques & materials) to the required level (where possible). Regards.
  7. 2 points
    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 (a) as well. HTH Regards.
  8. 2 points
    Yes. ILYAS is right. Definitions of beam & column are also given in Section 2.3 of ACI 318-14. In earlier versions of the ACI 318 (2005, 2008, 2011 etc ) definition of column was also given in Chapter 2. However, definition of beam was not included till then. Rather it was referred as a flexural member. AFAIK definition of "beam" was most probably included for the first time in 2014 version of ACI 318, after it was included in ACI Concrete Terminology 2013. Regards.
  9. 2 points
  10. 2 points

    Screen Time

    I agree with waqar. IMO, childern must be motivated towards & provided opportunities to play different health improving outdoor games (football, cricket, badminton, etc) , instead of watching TV or playing games on computer. My chidren are school going, and whenever they have done their homework, and it is pleasant outside (especially after Asr prayer), I send them out in a nearby park area. There they can play football or cricket, and can do exercise as well. On weekends, during vacations and on other days when they are unable to go outside, they generally watch tv for 1-2 hours.
  11. 1 point
    Yes sir, agree just forget to put that one in. Thanks,
  12. 1 point

    Brick Mansonry design in ETABS

    1. AFAIK ETABS 2016 has the capabilty to design CMU (Concrete Masonry Units) Shear Walls only. The design is carried out in accordance with ACI 530-11 requirements. See the following link for the relevant Design Manual: https://www.google.com.pk/url?sa=t&source=web&rct=j&url=http://docs.csiamerica.com/manuals/etabs/Shear%20Wall%20Design/SWD-ACI-530-11.pdf&ved=0ahUKEwjfxIbNqcPVAhXGto8KHbPiAhgQFggtMAE&usg=AFQjCNHg0YZpIutlVDDoPos320qUvD_90g 2. Several masonry design software, other than Prokon ( https://www.prokon.com/design/masonry-design ) mentioned in previous post, are available on the internet. Here are the links of a few of thesr masonry design software:- a. MasterKey - BS & Eurocodes based ( http://www.masterseries.com/product-specific/masonry-design) b. NCMA Structural Masonry Design software; IBC, TMS402 & ASCE 7 based ( http://www.ncma-cpu.org/ProductSubCats.aspx?SubCatID=42) c. MASS - Canadian code based ( www.masonryanalysisstructuralsystems.com ) d. GEO5 Masonry Wall; Euro code & Australian code etc ( http://www.finesoftware.eu/geotechnical-software/masonry-wall/) e. DigitalCanal Masonry Wall - ACI 318-11 & IBC 2012 ( http://digitalcanalstructural.com/masonry-wall/ 3. A simple internet search will yield names & links for many more masonry design programs, if needed. Regards.
  13. 1 point
    Try to use Prokon to design brick/concrete masonry.. Its design is straightforward .. from load distribution of slab, corresponding slab load transferring into the supporting walls are calculated, the load keeps on adding down from each floor together with the wall line loads down the wall footings. Fk for characteristic compressive strength for the wall is calculated from the ultimate loads, the fk of the bricks or concrete blocks used taken from the manufacturer is checked then with the calculated one, if the brick/concrete blocks are adequate to bear the ultimate loads. Try to consult ACI 530-1999 or BS 5628-1985 for this type of design.
  14. 1 point
    Sag rod is basically a structural steel member, carrying tensile load only. For knowing detailed methodology for modelling a tension-only member in ETABS, see the following link:- https://wiki.csiamerica.com/m/view-rendered-page.action?spaceKey=etabs&title=Tension-only+elements+in+ETABS Regards.
  15. 1 point
    Fatima, In order for landings to be considered supported so you can consider a smaller length of stairs. stair length = 'total length - 2 x landing length' , you need to have both Beams C and D at 6'6" level and again have 2 Beams B and C in this case at 11'6" level. In that way both landings are 2 way supported and the stair flight between them can be considered as one way. You will have to design the landings as two way supported on two edges only. Thanks.
  16. 1 point

    Welcome Everyone! :)

    Aslamualikum: I am Volkan from Turkey. I wanna meet with my dear whole colleagues. M.Sc. has completed in 2013 May Almighty ALLAH bless you all. Best Regards.
  17. 1 point

    R/f at top in isolated footing

    Top reinforcement might be required in isolated column footings in following circumstances: a. When the foundation is in tension b. To counter shrinkage cracks Regards.
  18. 1 point
    The existing Building Code of Pakistan (BCP) enforces a typical short-period shaped, UBC 97-based response spectrum which is a function of seismic coefficients Ca and Cv. These coefficients are further dependent on seismic zone factor (Z) and soil profile type. The BCP provides a table for seismic zones derived from a relatively recent PSHA study for all tehsils in the country, however, it doesnt provide the Standard Soil Profile Type Map to be used in conjunction with seismic zones. Is there any standard soil profile type map (or Vs30 map) for Pakistan? There are few individual studies on this topic, however, I am interested in a widely-accepted definition/assumption of soil profile types down to tehsil level. Thanks Fawad
  19. 1 point
    Fatima, You can use a smaller slab thickness and do a deflection check to make sure stairs deflection it is below the maximum allowable. Service Live Load deflection based on Canadian Code should be less than L/360. I don't remember what ACI said, you can look it up. It should be similar. Other ways to reduce thickness would be to run a beam at the centre of stairs flight. For a stair run like shown above, such a beam would be hidden. Let us know how it goes. Thanks.
  20. 1 point

    ACI 440.1R-15

    hi, please help me to download this guide i try many sites but all i browsed is for sell... and i need free copy. ACI 440.1R-15 Guide for the Design and Construction of Structural Concrete Reinforced with Fiber-Reinforced Polymer (FRP) Bars
  21. 1 point
    Fawad, You can also find values of Ss and S1 for famous Pakistani cities in IBC Overseas Building Reference. See the discussion below: Thanks.
  22. 1 point
  23. 1 point
    Fatima Khalid

    Strap Footing

    Thank you for sharing the sheet and relevant material
  24. 1 point

    Solid slab

    Yes, why not, who is stopping you?
  25. 1 point

    Solid slab

    If you are asking about possibility of designing a single slab of given dimensions, theoretically it can be. Practically however such a large slab will have undesirably high self-weight and deflection, if designed without beams. Self-weight as well as deflection can be controlled by providing beams along outer edges & at suitable intervals parallel to short span of the slab for reducing required thickness of slab from deflection point of view. Regards.
  26. 1 point
    Salam Dear Junaid! Cold joints are common and practice is upto soffit, properly roughen the face and apply some chemical at the joint. Leaving column at mid height is not good. Regards
  27. 1 point
    According to ACI Concrete Terminology 2013, a "beam" is defined as " a structural member subjected primarily to flexure but may also be subjected to axial load." Whereas, a "column" is a "member with a ratio of height-to-least-lateral-dimension exceeding 3 used primarily to support axial compressive load." Design of a structural member (as a beam or column) in ACI 318 code is based on above-mentioned definitions. Regards.
  28. 1 point
    Dear Shafqat, AA. Field work of a civil engineer generally consists of following activities: a. Surveying / levelling of the project area b. Supervision of construction work for buildings, roads, culverts, bridges etc., in accordance with detailed working drawings, applicable material specifications and quality standards. c. Preparation of material estimates, by calculating quantities of different items of work (e.g., excavation, concrete, brickwork, plaster, reinforcing steel etc-in case of buildings, and subbase, base, wearing course etc, in case of roadwork) included in working drawings of the project. 2. To perform all these tasks in better & efficient way, you will need to review your class notes & text books of relevant subjects (Surveying, Civil Engineering Practice, Estimating & Costing, Highways & Roads, Engineering Materials) taught during your civil engineering studies, in order to understand theoretical & practical aspects of these subjects. 3. As regards, which subject you should review first, would depend upon the work you are asked /assigned to do by your senior engineer. As a Trainee Engineer, you will certainly be attached with a senior engineer, who will assign you different engineering tasks & check your work. You may & must obtain his advice in all the work matters, where you are in doubt, or unclear about how to perform a given task. 4. In case you have futher querries, please do ask, by narrating your problem in detail. I will be happy to help you, as far as I can. By the way, what kind of civil works are carried out by your company mostly? Building work, roadwork or both? Regards.
  29. 1 point
    , i just graduated as bachelor in civil engineering i got the job in chinese company due to my chinese language skill but i don"t know knowledge about civil engineering so i need some information to continue this job because i can speak chinese and don't know about my major , my duty is as trainee engineer mean and i want to get more knowledge about level ,instrument measure and theodolite it will really great help that what kind of knowledge i should learn mean while i will be waiting for reply
  30. 1 point
    Following are a few disadvantages of using higher strength rebars with a lower strength concrete: 1. Larger tension (as well as compression) development & lap-splice lengths will be required. 2. Overall load carrying capacity of a compression member will be lesser, compared with when higher strength concrete is used. 3. Maximum amount of steel reinforcement, that can be used in a flexural member, will also be lesser, thereby reducing its overall load carrying capacity. 4. Member size & self-weight will be somewhat larger, when steel yield strength is more than 60,000 psi. Regards.
  31. 1 point
    waqar saleem

    Screen Time

    My kid is 2 nd 3 months old, we normally try to keep screen time as low as 1 hour/ 2 hour, when he watches cartoon or use mobile for game more than 2 hours, he becomes too difficult to handle. So we bought books that we read with him like picture stories and take him outside where he can play, run and climb monkey bar etc, after playing he becomes satisfied and easy to handle. that's my personal experience :-). Regards
  32. 1 point
    *SEFP Consistent Design* *Torsion: Reinforced Concrete Members * *Doc No: 10-00-CD-0001* *Date: May 24, 2013* Torsional forces, generally speaking, occur in combination with flexural and transverse shear forces. From a design perspective, we need to understand difference between two torsion types: Compatibility Torsion Equilibrium TorsionCompatibility Torsion Compatibility Torsion is when a member twists to maintain deformation compatibility; its induced in structural members by rotations (twists) applied at one or more points along the length of member. The twisting moments induced are directly dependent on the torsional stiffness of the member. These moments are generally statically indeterminate and their analysis necessarily involves (rotational) compatibility conditions(click on the image to enlarge). For the floor beam system shown above, the flexure of the secondary beam BD results in a rotation ǾB at the end B. As the primary (spandrel) beam ABC is monolithically connected with the secondary beam BD at the joint B, deformation compatibility at B implies an angle of twist, equal to ǾB at spandrel beam ABC, and a bending moment will develop at the end B of beam BD. The bending moment will be equal to, and will act in a direction opposite to the twisting moment, in order to satisfy static equilibrium. The magnitude of ǾB and the twisting/ bending moment at B depends on the torsional stiffness of the beam ABC and the flexural stiffness of beam BD. Now here is the fun part, the torsional stiffness of a reinforced concrete member is significantly reduced by torsional cracking. So, if you don’t design your spandrels for compatibility torsion, they will crack, increasing ǾB and reducing the induced twisting moment. To paint the same picture while using ETABS, set your torsional stiffness of the main beam to zero. This will also increase the amount of flexural reinforcement in your secondary beams. Moreover, considering design practice in Pakistan (since we never design beams without shear reinforcement), compatibility torsion can be ignored for regular structures, as minimum shear reinforcement in most cases would stand up to cracking torque. From ACI 318 commentary R11.6.1, Do note that there are some situations (such as circular beams supported on multiple columns) where both equilibrium torsion and compatibility torsion coexist. Also, eccentrically loaded beams, member curved in plan, and member of space frames will be subjected to torsion. See the attached “Timesaving-TorsionDesign-IA.pdf” as a go-by. Timesaving-TorsionDesign-IA.pdf Equilibrium Torsion In simplest words, Torsion is a limit state in this condition; a structure is subjected to equilibrium torsion when it can maintain equilibrium only by resisting the torsion. In such a case, torsional moment cannot be reduced by redistribution of internal forces since the torsional moment is required for the structure to be in equilibrium. From ACI- 318 (click on the image to enlarge). Moreover, see the structures below that defy gravity when subjected to different kind of loads by standing up to equilibrium torsion. Overall Building Torsion For overall building torsion, the torsional effects can be minimized by reducing the distance between the center of mass and center of rigidity. Center of Mass is the point where the mass of an entire story is assumed to be concentrated. The center of mass is crucial as the location of seismic force at a particular level depends upon it. The distance between the Center of Mass and the Center of Rigidity should be minimized, but may not be possible due to building geometry. Invariably, effects of torsion are present in at all buildings although analysis may show that in some buildings torsional effects are negligible.
  33. 1 point
    Brick masonry can not be designed in these software because brick masonry is neither the frame elements which can be modelled in these software nor are the simple isotropic type materials which can be modelled easily like area elements. You will have to do design for brick masonry manually. But you can take help from these software to read results of different type of analysis u need while doing manual design. There might be other softwares which can do this perhaps. But regarding these two softwares, i hold this opinion.
  34. 1 point
    Many engineers are confused with stiffness modifiers stuff in ETABS including me. Let me add my cent here. 1. Any reasonable set of stiffness can be used as explained in ACI 318. 2. You have to determine what type of frame you are analyzing; braced or un-braced 3. Whats the analysis type? Strength, service? 4. Code allows use of 0.35,0.7 factors on inertia in chapter 10 of ACI 318 for slenderness effects. 5. Also according to code, you can use the above same model in step 4 for lateral deflections. 6. Now for lateral deflections, if the lateral load is service (like Wind load of ASCE 7-05 and previous) multiply above factors by 1.43 or 1.40 (see code). For strength lateral load like Earthquake, no need to multiply by this factor. 7. Some times you really dont need to apply modifiers at all. For example for strength design. 8. For a two-way frame with membrane slabs at top, you just need to apply 0.5 factor to beam elements. Code allows this which says for strength design you can either a. use the same modifiers as used for slenderness b. use 0.5 for beam stems only In simple words, modifiers are factors to reduce inertia for cracked sections. But if you are doing strength design, why you need the cracked inertia. And as far as serviceability is concerned, authors like Nilson even argue that a factor of 0.5 as we applied in step 8 can also be skipped because of the following reasons. a. For positive moment, beam is designed as T section but in ETABS we use rectangular section, Stiffness of T = approx 2 x stiffness of rect. So no need to apply 0.5 inertia factor to beams because T compensates for that. Just use the rectangular section in ETABS. b. For negative moments, beam is designed as rectangular, and we also model the rectangular section in ETABS. Now the cracking in this section is offset by the continuation of bottom bars into support which have stiffening effect. I hope that helps. Let me put it as a summary here; 1. Strength & service design with membranes (slab on rigid beams as compared to slabs). Beams = 0.5 or beams = 0.35 & columns = 0.7 (or whatever ratios just keep it constant). or no modifiers at all walls = 0.7 for un-cracked 0.35 for cracked 2. Strength & service design with shells (flat plates etc). beams and walls same as above slabs = 0.25 for out-of-plane m factors. just multiply above factors by 1.43 for service lateral deflections.
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