bladeyus
Civil/Environmental
- May 10, 2013
- 6
I am trying to calculate the maximum design force for coupling beams in my building with ETABS. My question is even though it is stated in section 18.10.4.5 that the maximum allowable shear force is limited to 10.Acw.sqrt(fc'), the program calculates the maximum allowable shear force with equation 22.5.1.2 with multiplying the spandrel height with 0.8 (the ln/h ratio is 1 for this beam). Also when i check the results the concrete contribution is almost nonexistent. The results differ almost 1.5 times for those equations.
The software calculates the shear capacity this way for beams labeled as spandrel, however when i model those beams as frames and design those beams as "intermediate moment frames" the calculated shear capacities seem fine. I know that as the shear on the beams along with the aspect ratio does not allow me to design those beams as intermediate moment frames however i am trying to understand which equation should i use. Do you think it would be ok if i check the shear capacity of those beams with ETABS with using intermediate moment frames and than detail them as diagonally reinforced sections manually?
Another important issue is for the frame and shell models, the shear forces on the beams differ almost 2 times (coupling beams modeled as shell elements yields higher shear forces). For the frame and area models, i modified bending and shear modifiers (moment of inertia = 0.15, shear area= 025 for frame model, f11=f22=0.15, f12=0.25 for area model). I know bending modifiers are coupled for wall elements but why are those results differ that much?
Thanks in advance for your answers.
The software calculates the shear capacity this way for beams labeled as spandrel, however when i model those beams as frames and design those beams as "intermediate moment frames" the calculated shear capacities seem fine. I know that as the shear on the beams along with the aspect ratio does not allow me to design those beams as intermediate moment frames however i am trying to understand which equation should i use. Do you think it would be ok if i check the shear capacity of those beams with ETABS with using intermediate moment frames and than detail them as diagonally reinforced sections manually?
Another important issue is for the frame and shell models, the shear forces on the beams differ almost 2 times (coupling beams modeled as shell elements yields higher shear forces). For the frame and area models, i modified bending and shear modifiers (moment of inertia = 0.15, shear area= 025 for frame model, f11=f22=0.15, f12=0.25 for area model). I know bending modifiers are coupled for wall elements but why are those results differ that much?
Thanks in advance for your answers.
