Modelling and Analysis of Runway Footing on Top of Suspended slab

Hi!

In STAAD Pro v8i, how are you going to model a runway footing on top of suspended slab(roof slab) and analyze & design the runway footing considering the strength of existing suspended slab? 

Thank you!

  • You can model the runway foundation slab as a mesh of plates. Since this would be supported on the suspended slab, you would need to simulate the stiffness due to this suspended slab using spring supports. You would need to define the stiffness of these springs as input. You can use FIXED BUT option where you input the spring stiffness directly or you can use the PLATE MAT option where you can define the subgrade modulus as input for calculation of the spring stiffness. Subsequently the footing can be analyzed and designed in STAAD.Pro.

    A better option is to model this footing as a mat foundation job in STAAD Foundation Advanced where you can similarly define the support stiffness using subgrade modulus as in case of STAAD.Pro. The advantage is, being a fully equipped foundation design software, STAAD Foundation Advanced would be able to carry out the shear checks for the footing too which STAAD.Pro will not do. You will need to have the license for STAAD Foundation Advanced though as it is a separately licensed software.



    Answer Verified By: Master Mac 

  • Hi Sye,

    Thank you for that very informative explanation/advice and also for spending time reading and answering my question. Appreciated much.

    Initially what i did is as per below:

    1) I modeled the suspended slab as mesh of plates supported by FIXED SUPPORTS at the perimeter only and defined the thickness  which is 3.0M THK concrete (Compressive Strength = 30Mpa).

    2) I then modeled the runway slab foundation as a BEAM at the middle of the mesh of plates (suspended slab) and make used of OFFSET to put it on top of the sus. slab. My runway slab now was a beam with defined properties of 1000m W x 400m THK sitting on middle top of the suspended slab.

    3) Finally, i applied my computed loads (Vertical, Longitudinal & Transverse Wheel Load) and PERFORM ANALYSIS. I take the MAX Values of Mz. My, Mx and Vy and execute manual calculation for the beam rebars assuming simply supported.

    Now, here is my follow up questions:

    1) Is my appproach correct or can be considered? 

    2) I will also do what you advised to me as above but how can i define the spring value of the suspended slab with Compression Strength of 30Mpa and Thickness of 3.0M? How to design footing of mesh plate model in STAAD?

    3) I want to use STAAD to design my beam and obtain the required steel area on top and bottom as well as the shear & torsion requirements. Is that ok?

    4) Since i will be putting my runway foundation on top of suspended slab, shear connectors between these two structure is required, How can i determine the required steel to resist shear force between runway foundation and suspended slab?

    5) Lastly, how am i going to check the deflection for both runway foundation and the existing suspended slab?

    Thank you in advance attached image below is my initial model as explain above.

    Regards,

    Master mac