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footing slab on piles modelling using Ram Concept

Bill Zhao
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Hi there, I  modelled a square footing slab on 4 piles using Ram concept "mat foundation", and found the results for the reo are conservative compared with RAPT's. 

So should I try using suspended floor template in Ram Concept? 

Thanks 

Bill

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    Hi Andrej,
     
    Thanks a lot for your email. Actually I had modelled my footing slab that way similar to what you suggested.
     
    But I finally found the problem that lead to heavy reos: i.e., when I changed the design rule name “code minimum Design” from  “AS3600-2009 min. reinforcement” to “specified min. reo” . Then the reo amount has been reduced by over 40-50%.
     
    As3600-2009 Clause 16.3.1 for slab on ground or two way footing has specified a min. reo design formula, the reo per this formula (ranged from 0.0015 – 0.0020 approx. for N32/40 concrete for my case), is much lower than the result obtained from Ram. Perhaps Ram concept has used a min. reo rate of 1.4/fy  for one-way slab or beam for each direction?
     
    Can you please advise?
     
    Thanks.
     
     
     
    Kind regards

    Bill Zhao BEng PhD MIEAust  RPEQ
     
    2 / 631 Seventeen Mile Rocks Road Sinnamon Park
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  • 0 in reply to Bill Zhao

    According to the program manual, for one-way slabs, two-way slabs or beams, the program checks AS 3600-2009 section 8.1.6 and 9.4.3.2. If you turn on "Controlling Criteria" through visible objects in Ram Concept you should be able to see which is controlling in your case. 

    A few details for how each is implemented is posted below, but the formatting is not as clean as the RamConcept.pdf.

    62.6.5 8.1.6 Minimum Flexural Strength
    • Cross sections within 1/6 span from supports or 1/6 span from midspan are considered “at critical sections”.
    • If the design section is not declared as post-tensioned in the design section or design strip segment, then the Pe/Ag and Pee terms of 8.1.6.1 are assumed to be zero (even if the cross section includes tendons), where Pe is the total effective prestress force considered.
    • Cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section.
    • See ““Cracking Moment” Used in Design Calculations” for a theoretical discussion of the “cracking load”.

    62.6.15 Section 9.4.3.2 Shrinkage and Temperature
    • This criterion is applied as part of the minimum reinforcement designer as it is independent of the magnitude of forces upon a cross section.
    • This criterion is applied to both beams and slabs, although its application to beams is not required by AS 3600.
    • The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section.
    • Reinforcement may be applied to both faces if the cross section is subject to both positive and negative moments and the “tension face” reinforcement location is chosen.
    • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.
    • The amount of reinforcement provided is equal to 0.75 (per 9.4.3.2(b)) times the amount specified by either 9.4.3.4(a)(i), 9.4.3.4(b)(i), or 9.4.3.4(c).
    • For “protected” environments, the amount of reinforcement provided is: As = (0.75)(1.75 – 2.5 σ cp )(Ag)/1000
    • For “normal” environments, the amount of reinforcement provided is: As = (0.75)(3.5 – 2.5 σ cp )(Ag)/1000
    • For “corrosive” or “very corrosive” environments, the amount of reinforcement provided is: As = (0.75)(6.0 – 2.5 σ cp )(Ag)/1000
    • For non-PT design strips and design sections, σ cp is taken as zero.



Reply
  • 0 in reply to Bill Zhao

    According to the program manual, for one-way slabs, two-way slabs or beams, the program checks AS 3600-2009 section 8.1.6 and 9.4.3.2. If you turn on "Controlling Criteria" through visible objects in Ram Concept you should be able to see which is controlling in your case. 

    A few details for how each is implemented is posted below, but the formatting is not as clean as the RamConcept.pdf.

    62.6.5 8.1.6 Minimum Flexural Strength
    • Cross sections within 1/6 span from supports or 1/6 span from midspan are considered “at critical sections”.
    • If the design section is not declared as post-tensioned in the design section or design strip segment, then the Pe/Ag and Pee terms of 8.1.6.1 are assumed to be zero (even if the cross section includes tendons), where Pe is the total effective prestress force considered.
    • Cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section.
    • See ““Cracking Moment” Used in Design Calculations” for a theoretical discussion of the “cracking load”.

    62.6.15 Section 9.4.3.2 Shrinkage and Temperature
    • This criterion is applied as part of the minimum reinforcement designer as it is independent of the magnitude of forces upon a cross section.
    • This criterion is applied to both beams and slabs, although its application to beams is not required by AS 3600.
    • The cracking is assumed to be top (negative moment) or bottom (positive moment) based on the “Min. Reinforcement Pattern” selected in the design strip segment or design section.
    • Reinforcement may be applied to both faces if the cross section is subject to both positive and negative moments and the “tension face” reinforcement location is chosen.
    • User defined reinforcement that is at an angle to the cross section will only have the component perpendicular to the cross section considered.
    • The amount of reinforcement provided is equal to 0.75 (per 9.4.3.2(b)) times the amount specified by either 9.4.3.4(a)(i), 9.4.3.4(b)(i), or 9.4.3.4(c).
    • For “protected” environments, the amount of reinforcement provided is: As = (0.75)(1.75 – 2.5 σ cp )(Ag)/1000
    • For “normal” environments, the amount of reinforcement provided is: As = (0.75)(3.5 – 2.5 σ cp )(Ag)/1000
    • For “corrosive” or “very corrosive” environments, the amount of reinforcement provided is: As = (0.75)(6.0 – 2.5 σ cp )(Ag)/1000
    • For non-PT design strips and design sections, σ cp is taken as zero.



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