Sathvika Meenakshisundaram's Activities

LEAP Superstructure - Nominal Capacity used to Calculate Shear Rating Factors

Sathvika Meenakshisundaram — Tue, 30 May 2023 17:54:14 GMT

Hello,

I am not matching LEAP's operating rating factors for shear (screenshots below) - 0.99 (HL93 Inventory), 1.46 (HL93 Operating), and 0.78 (FL120). I am using the appropriate live load factor for each case. The difference seems to be in the Shear Capacity value used by LEAP as the dead and live loads are consistent between Strength I and Strength II. Does LEAP print the values somewhere that are used in the rating equation? The capacity I use is calculated using the (phi*Vn)/Vu from Print --> Vertical/Horizontal Shear for the governing beam. I did independently verify the moment rating factors and they matched exactly; it is shear I am having trouble with.

Please let me know if you would like the models or the calculation files.

Thanks

LEAP Superstructure - Vertical Shear Capacity

Sathvika Meenakshisundaram — Sat, 22 Jan 2022 17:46:36 GMT

Hello,

I am doing an independent calculation to verify LEAP’s nominal moment and shear capacity at midspan. I was able to match the Moment Capacity at 0.5L pretty closely but I am having problems with Nominal Shear Capacity at this location. For shear, I am using Beta-Theta Equations method in the model.

In the picture above, all the highlighted values in yellow match the values I calculated. These are bv, a, de, dv, Aps, fpo, and Vp. However, when I use some of these variables in AASHTO 8^th edition Strain Equation 5.7.3.4.2-4, I am not getting the value shown in the LEAP output table. I have tried different values for Vu and Mu in this equation but no combination matches LEAP’s Strain value.

Could you please look into this? Please let me know if you would like to take any additional information. I can send LEAP model file or mathcad spreadsheets if it'll help find a solution.

Thank you

Vertical Shear - Factored Axial Nu

Sathvika Meenakshisundaram — Thu, 21 Feb 2019 16:14:02 GMT

How is the Axial Force, Nu calculated in LEAP per AASHTO LRFD 2018 Equation 5.7.3.4.2-4?

I'm load rating an exisitng AASHTO Type II beam per FDOT specifications. The shear inventory rating controls at 0.9L and the rating factor is less than 1.0. The vertical shear is being calculated by beta-theta equation method (AASHTO LRFD 2018 Section 5.7.3.4.2). In LEAP Analysis options, when the vertical shear method is toggled from beta-theta equations to beta-theta table (AASHTO LRFD Appendix B5), the rating went up to 1.2. Note that in the 2018 version of AASHTO, the Simplified Shear method has been removed and is no longer an option in LEAP.

LEAP's calculations for shear by beta-theta equations under Print ----> Vertical/Horizontal Shear does not mention any Axial Force (Nu).

At 0.9L, the ultimate shear and moment values that I independently calculated matches with LEAP's Vu = 119.5 kips and Mcor = 244.7 kip-ft. There's no external axial force applied. Is Nu being calculated for the applied pre-stress in LEAP? If so how exactly is it calculated and why is it not listed in the table above?

The strain value and the corresponding beta I calculated for Nu=0 kips is way different from LEAP. All my other values match, with Nu being the exception.

Also, using the beta and Epsilon(s) value given in LEAP shear results, I back-calculated factored Nu to be 93.625 kips. Not sure where this is coming from.

Here's the tendon info if requried -

7/16"-250ksi

12 total strands - 10 in the bottom flange and 2 at the top flange.

Please let me know if you need any additional information.

Thanks.

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Thu, 21 Feb 2019 02:55:40 GMT

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CONSPAN Custom Beam Design - Florida Slab Beams

Sathvika Meenakshisundaram — Wed, 24 Aug 2016 21:38:15 GMT

Hello,

The Florida Slab Beams (pre-stressed) were included in the FDOT design standards earlier this year. I am trying to model this in CONSPAN. There is a 4" thick bottom flange and a 14" web; there is no top flange. These dimensions are for FSB18. Please see figure below for a generic FSB layout.

To do this in CONSPAN, there isn't a pre-defined FSB beam type in LEAP, so the only other option is to modify one of the existing beam types. The closest the slab beam resembles to is an I-beam. I set the top flange dimensions to zero and entered dimensions for the bottom flange and the stem. I then went in to the "Edit..." tab at the bottom left corner of the window and re-drew the cross section of the slab beam and updated the strand template.

The problem here is that the program doesn't take zero for the top flange dimensions, neither does it accept a value lesser than the bottom flange width.

Is there a way around this? How else do I model an FSB?

Thank you,

Sathvika