For inverted T beams the bearing stresses are reduced to an acceptable amount by the use of the ground strip forming the ﬂange of the inverted T.
The main rib of the T beam is then determined from the design requirements for longitudinal bending and shear forces keeping a reasonably standard proﬁle for shutter reuse to make the beam economic. The ﬂange thickness and reinforcement is determined from the bending moments and shear forces acting on the cantilever slab/ﬂange (see Fig. 11.35).
Casting of the beam is usually carried out in two lifts, the ground slab being cast up to the top of the ﬂange leaving a roughened surface with the cage reinforcement projecting.
The main beam is then cast on the cleaned surface of the slab up to its top level (see Fig. 11.36).
|Fig. 11.35 Inverted Tee beam – typical loads, moments and reinforcement.|
|Fig. 11.36 Typical casting stages for inverted |