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The development of new Cold-Formed Steel (CFS) channels with staggered slotted perforations has led to advances in improved thermal efficiency of buildings. These new generations of CFS channels reduce the thermal bridging effect interrupting the direct heat transfer across the web. However, the integration of these staggered perforations creates challenges in terms of reduced structural capacity. It is therefore vital to study the structural behaviour under various loading scenarios. Therefore, the web crippling performance of staggered slotted perforated channels under End-One-Flange (EOF) loading condition and flanges unfastened to bearing plate was investigated in the present paper. Finite Element (FE) models were developed to capture the web crippling strength and failure mechanism of these staggered slotted perforated channels. The validity of the FE modelling techniques was ensured by comparing the web crippling experimental results of CFS channels with solid and perforated webs under the EOF loading. Upon validation, an extensive parametric study comprising 360 FE models was then performed with the aim of (i) examining the effect of staggered slotted configurations and (ii) the corresponding degree of web crippling strength reduction. The results provided a direct mean of notable web crippling strength reduction up to 74%. The numerically derived data points were used to develop a reduction factor based new design equation, which can directly be applied to predictive equations of web crippling. The proposed approach yields more accurate and consistent strength predictions and improves the understanding of CFS channels with staggered slotted perforations.

A window wall is a lightweight external wall composed of glass and aluminium, which does not carry any gravity loads from the building except for its own weight. Wind load is transferred to the main structural system through the connections of sub-frames (consisting of sub-heads and sub-sills) with slabs. An aluminium sub-head with a removable bead (ASHWRB) is a common type of sub-head consisting of two parts: a base and a bead. Under wind load, the bead flange is directly loaded by the mullion and undergoes bearing failure due to its long length. This paper presents a detailed numerical study on the bearing capacities of the ASHWRB sections subject to wind loading. For this purpose, finite element models were simulated using ABAQUS/CAE and validated with our previously conducted experimental work in terms of ultimate loads, load-displacement curves, and failure modes. Validated finite element models of the ASHWRB sections were then used for an extensive parametric study covering a wide range of thicknesses, flange widths , bearing widths, and engagement lengths. Notably, the ultimate loads obtained from the parametric study are not product nor manufacturer specific, whereas, the data obtained from experimental study is specific to the manufacturer products. The acquired bearing database was used for a detailed assessment of the consistency and reliability of the previously proposed design rules by the authors (DRA) based on the experimental tests as well as currently available cold-formed steel design rules (DRSs). It was found that the bearing capacities determined by both DRA and DRSS are unreliable for predicting the bearing capacities of the ASHWRB sections in the window wall. Thus, modifications were made to DRA and DRSS. Consequently, new design rules were proposed in this paper (DRA P), which accurately predicted the bearing capacities and correlated very well with the numerical results.

The facade, as the exterior cladding of a building, is an essential element which provides waterproofing, thermal isolation and structural resistance against environmental actions. The vertical members in curtain wall facade systems, referred to as mullions, are the dominant load-bearing structural members. Despite aluminium being a durable material, conventional aluminium facade frames are weak in thermal performance, and hence thermal breaks are often used in the industry to provide the required insulation. In addition, timber frames may be preferred by building designers due to their aesthetic appearance and sustainability. Therefore, an innovative composite mullion was developed using aluminium and timber to combine the best features of both materials and is presented in this study. Experimental studies were also conducted to verify the structural performance of the composite mullion. The first series of tests was performed to investigate various aluminium-timber connections to ensure composite action. Four different connection types were considered in this study and the optimum connection was chosen and discussed. Four-point bending tests were performed next to investigate the bending behaviour and strength of the newly developed mullion as well as traditional aluminium mullions under positive and negative wind loading scenarios. It was found that the new composite mullions achieved higher section moment capacities than the traditional aluminium mullions, while being energy-efficient, aesthetically pleasing and more sustainable.