MIDAS SET Column Concrete Shear Capacity Problem

MIDAS SET Column Concrete Shear Capacity Problem MIDAS SET 3.2.1 Column Concrete Shear Capacity Problem Link for CIVILEA topic MIDAS SET is a good tool to verify individual sections output. It incorporates a simple input data form on the left side and the detailed equations and output in the right pane. Despite of its good tools and features, I faced a problem while I was calculating the column shear capacity (concrete) manually and trying to verify it with MIDAS. To my astonishment it gave me almost double the value which I got using ACI-318 chapter 11 equation 11-4 for concrete shear capacity under axial loads. I will show you here the detailed steps to prove my point. If you find anything misleading or want to share your thoughts please respond. I have written an email to MIDAS and let’s see when can I get the response. Solve a simple column example B=500mm H=500mm Cover=50mm so d = 450mm Axial Factored Load is 700kN Compression f’c = 45 MPa Ag = 500x500 = 500 mm² From ACI-318(05M) chapter 11, equation 11-4 we get; Vc = 0.17 (1 + Nu/14Ag) (f’c^0.5) b.d Where Nu/Ag term should be in N/mm² Nu is –ve for TENSION and +ve for compression So putting all these values in this equation we get; Vc = [ 0.17 ( 1 + 700/14*500² ) (45^0.5) 500 x 450 ] / 1000 = 256.6 kN and Phi Vc = 0.75x256.6 = 192.45 kN whereas in MIDAS software, it gives Phi Vc in both the directions equal to 612.0 kN. This value is even more than 3 times the value we calculated from ACI equation. I am doubtful to use this software for verification because of this error.