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According to ACI 18.10.7.3, Coupling beams reinforced with two intersecting groups of diagonally placed bars symmetrical about the midspan should satisfy either of the two conditions given below;

1. Each diagonal bars group should be enclosed bu rectilinear transverse reinforcement having out-to-out dimensions of at least b_w/2 in the b_w direction and b_w/5 along the other sides. The transverse reinforcement should satisfy ACI 18.7.5.2, and minimum transverse reinforcement area A_sh is given below;

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   The transverse reinforcement spacing should be satisfy ACI Eq. (18.7.5.3) and not exceeding 6d_b of the smallest diagonal bars, and the maximum spacing of crossties or legs of hoops is 14 inches.

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   The transverse reinforcement should continue through the intersection of the diagonal bars. At the intersection, it is permitted to modify the arrangement of the transverse reinforcement provided the spacing and volume ratio requirements are satisfied. Additional longitudinal and transverse reinforcement should be distributed around the beam perimeter with total area in each direction of at least 0.002b_ws and spacing not exceeding 12 in.

2. The transverse reinforcement should satisfy ACI 18.7.5.2for the entire beam cross-section and minimum transverse reinforcement area A_sh is given below;

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   Maximum longitudinal spacing of transverse reinforcement is the lesser of 6 in. and 6d_b of the smallest diagonal bars. Maximum Spacing of crossties or legs of hoops both vertically and horizontally in the plane of the beam cross section should be 8 in. Each crosstie and each hoop leg shall engage a longitudinal bar of equal or greater diameter.

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