TR-43 5.8.8 PT Minimum Reinforcement (UK National Annex Only)

Note: There are no minimum un-tensioned reinforcement requirements for post-tensioned beams or one-way slabs that are primarily bonded. Refer to "Determination of Bonded vs. Unbonded Cross Sections" for discussion.

For primarily unbonded post-tensioned beams and one-way slabs the requirements of 9.2.1.1 or 9.3.1.1 are applied as appropriate.

For post-tensioned two-way slabs in column strips, un-tensioned reinforcement is provided in support regions as follows:

A_s = 0.00075A_ct.
A_ct = sum of cross sectional area of column strip and adjacent middle strips(generated from the same span segment)

For span segment strips, this criteria is only applied to the first cross section at a support if the span ratio is less than 0.2.

For design sections, this criterion is applied when the span ratio is less than 0.2.

The 300mm spacing requirement is not checked. The requirement that this reinforcement be concentrated between lines that are 1.5 times the slab depth is not checked.

User defined reinforcement and bonded tendons that are at an angle to the cross section will only have the component perpendicular to the cross section considered.

For post-tensioned two-way slabs, minimum reinforcement consisting of un-tensioned reinforcement and bonded tendons is provided as follows:

A_s = 0.001 A_c
A_c = area of cross section

For span segment strips, this criteria is only applied to the first cross section at a support if the span ratio is less than 0.2.

For design sections, this criteria is applied when the span ratio is less than 0.2.

The spacing of this reinforcement is limited to 500 mm. Bonded (grouted) post-tensioning ducts that are on the tension side of the cross section centroid, or are within 10% of the cross section depth of the centroid elevation are considered as equivalent to an un-tensioned bar. These ducts are assumed to be optimally placed for spacing purposes – their plan locations are ignored.

User defined bars are counted toward satisfying the maximum spacing requirements. Bars at an angle to the cross section consider the sum of their vector components divided by the gross area of one bar as the total number of provided bars for spacing calculations.

The recommendations for slab edge reinforcement are not implemented.