pystra.decision.targets.lqi_target_reliability

lqi_target_reliability(k1, variability='medium')

Return an LQI target reliability for a safety cost ratio.

Parameters:

• k1 (float) – Safety cost ratio. Medium-variability classes follow the ranges in Fischer, Barnardo, and Faber (2012), Table 3.

• variability (str) – Approximate consequence/resistance variability adjustment. The source table reports that high variability gives failure probabilities about five times larger and low variability about two times smaller than the medium case.

Returns:

The rounded table target for 1e-5 <= k1 <= 1e-2. Outside that range cost_class is "extrapolated" and the failure probability continues the table’s proportionality to k1 from the nearest edge: pf = k1 below 1e-5 and pf = k1 / 10 above 1e-2, with beta computed from pf rather than rounded. The failure probability is therefore continuous at both table edges; the index differs only by the table’s rounding (4.2 is tabulated for pf = 1e-5, whose exact index is 4.26). An extrapolated value is not a source-table value; use derive_lqi_target() to calculate a target for a stated resistance-demand model instead.

Return type:

TargetReliability