Displacements of cracked members - Concrete Structures: Stresses and Deformations - page 296

reinforcement, assumed to be lumped at the four corners. Fig. 8.10(b) is a
free-body diagram showing the forces acting on a part of the wall of the box.
Fig. 8.11(a) is a truss idealization of a cracked box girder. The members in the
hidden faces of the box are not shown for clarity. The external applied twist-
ing moment is replaced by the forces

τ th and τ tb as shown, where τ t is the

shear fl ow (Equation (8.54) ):

τ t = T /2 hb (8.55)

where h and b are height and breadth of the truss model (see Fig. 8.11(a) ).

Figure 8.11 Truss idealization of a box girder cracked by twisting (see Fig. 8.10): (a) space
truss model; (b) a typical panel of truss model.