Reliability-based calibration of axial and shear strength models for composite walls in AS/NZS 2327

Composite walls are widely used in mid- and high-rise buildings for their structural efficiency and performance. To support reliable structural design, this study focuses on the accurate and cost-safety balanced estimation of axial and shear strength. It presents a structural reliability-based calibration of capacity factors for composite walls, contributing to the development of new design provisions in AS/NZS 2327. A total of 64 axial compression and 23 shear test results were collected from existing literature to evaluate and calibrate the design equations. Axial strength was predicted using a model based on effective length and concrete contribution factors, while in-plane shear strength was estimated using a simplified mechanics-based model. The reliability-based calibration procedure follows the methodology outlined in AS 5104, ISO 2394 and Eurocode 0 Annex D, aligning with recent practices in structural design standards calibrations. Capacity factors were determined using the first-order reliability method sensitivity factor concept, under consistent assumptions on uncertainty distributions and target reliability indices, as applied in similar practices, for example in the calibration of composite columns. Separate capacity factors for steel and concrete components were derived to account for material-specific behaviour, and also a unified factor format was adopted to minimise modelling uncertainty. The calibration shows that, for axial compression, a unified capacity factor of 0.64–0.89 meets the target reliability for varying concrete reduction factors, with a recommended value of 0.70 when a concrete strength reduction factor of 0.85 is applied; fixing the steel factor at 0.90 yields concrete factors of 0.50–0.83. For in-plane shear, a single unified factor of 0.77 is obtained. These findings provide a statistically consistent basis for the proposed AS/NZS 2327 design provisions for composite walls.