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 b.
Design of a Beam Subject to Torsion.
Problem:
Design the beam in Example Problem a. for a uniformly
distributed torsional load.
Given:
(1) Example Problem a, L, d, and vu.
(2)
Unbalanced support shears of roof slabs.
Solution:
(1) Determine torsional load d distance from the face of
support.
(2) Find torsional stresses using Equation (47a>.
(3) Determine shear and torsional capacity of unreinforced web
from Equations (48) and (49).
(4) Find required area of web reinforcing for shear stress
using Equation (45>.
(5) Find required area of web reinforcing for torsional stress
using Equation (51).
(6) Calculate total web reinforcing.
(7) Check minimum tie reinforcing area and maximum tie
spacing.
(8) Determine required area of longitudinal steel using
Equation (54a) or (54b).
(9) Determine distribution of bending and longitudinal steel
at beam section.
Calculation:
Given:
(1) Beam of Example Problem a., L = 240 in, d = 27.125 in, and
vu = 202.7 psi.
(2) Unbalanced support shear from two adjacent slabs
vs = 320 lb/in along the edge of the beam.
Solution:
(1) Design torsional load.
L
Tu = ( - d) x Vs x arm
2
2.08-115
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