Web crippling performance of perforated Modular Construction Optimised beams under ITF loading.

The growing use of modular construction has increased demand for lightweight high-strength cold-formed steel (CFS) beams capable of carrying concentrated loads ef-ficiently. Modular Construction Optimised (MCO) beams have been developed to meet this need; however, in practice they often incorporate web openings to ac-commodate services. Such perforations reduce local strength and alter the web crip-pling response, while current design standards provide limited guidance for uncon-ventional CFS sections under Interior-Two-Flange (ITF) loading – a critical case in modular applications. This study presents a reduction-factor approach, derived from a numerical investigation, to predict the web crippling capacity of perforated MCO beams under ITF loading. Finite element (FE) models were developed, systemati-cally varying yield strength, opening ratio, section depth, thickness, and corner ra-dius. Circular openings ranging from 40% to 80% of the clear web height were considered. Results show capacity reductions of up to 26% at an 80% opening ratio, with reductions following a consistent trend that can be captured through reduction factors applied to baseline equations for plain webs. A new reduction-factor equation is proposed, achieving excellent predictive accuracy (Mean = 1.00, COV = 0.04) and validated against experimental data. The proposed method improves on current design provision while remaining simple for engineering practice.