Section 9.10 Tying Systems for Accidental Design Situations

Each cross section is considered to act as a portion of an internal tie. Reinforcement at each cross section is placed on the tension face in accordance with the force envelopes for the Accident Rule set. Peripheral ties are not explicitly calculated by RAM Concept .

UK National Annex

Tie force requirements are determined in accordance with the applied National Annex clause 9.10.2.3 (3).

The number of stories is input in the span segment or design section properties.

l_r is taken as the largest of the span being calculated or either adjacent span length. For design sections we use the span length and do not consider adjacent spans.

An equivalent uniform span load (force/length) is calculated representing (g_k + q_k) times the width of the span. This uniform span load is calculated as follows:

For span segments, the total span shear is calculated as the difference in shears at each end of the span. This value is calculated twice, once with the minimum V envelope at the span start and the maximum V envelope at the span end and once with the maximum V envelope at the span start and the minimum V envelope at the span end. The maximum of the differences in these values is used as the total span shear. The uniform span load is then calculated as the total span shear divided by the span length.
For design sections, the total span shear is calculated as the twice the maximum span shear, extrapolated from the cross section shear using the design section span ratio. The uniform span load is then calculated as the total span shear divided by the span length. For regions of low shear near mid-span where extrapolation may not be appropriate, we calculate the uniform span load from the moment at the cross section as M/al² where a = (1/24 – α/2) and α is the span ratio from this cross section to mid-span.

Generic National Annex

Tie force requirements are calculated at 20 kN/m.

Tie requirements are considered as minimum requirements, not in addition to other requirements. The design yield stress of bonded tendons located anywhere in the cross section are applied toward the tie requirements. Vector components are used for tendons that are not perpendicular to the cross section.