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To address the weight, cost, and sustainability associated with fibreglass application in structural composites, plant fibres serve as an alternative to reduce and replace the usage of glass fibres. However, there remains a gap in the comprehensive research on plant fibre composites, particularly in their durability for viable structural applications. This research investigates the fatigue and impact properties of pultruded kenaf/glass-reinforced hybrid polyester composites tailored for structural applications. Utilising kenaf fibres in mat form, unidirectional E-glass fibre direct roving yarns, and unsaturated polyester resin as key constituents, pultruded kenaf/glass hybrid profiles were fabricated. The study reveals that pultruded WK/UG alternate specimens exhibit commendable fatigue properties (18,630 cycles at 60% ultimate tensile strength, UTS) and fracture energy (261.3 kJ/m2), showcasing promise for moderate load structural applications. Notably, the pultruded 3 WK/UG/3WK variant emerges as a viable contender for low-load structural tasks recorded satisfactory fatigue properties (10,730 cycles at 60% UTS) and fracture energy (167.09 kJ/m2). Fatigue failure modes indicate that the stress applied is evenly distributed. Ductile failures and delaminations during impact test can be attributed to damping and energy absorbing properties of kenaf fibres. Moreover, incorporating kenaf as a hybrid alternative demonstrates substantial reductions in cost (35.7–50%) and weight (9.6–19.1%). This research establishes a foundation for advancing sustainable and efficient structural materials and highlights the significant role of materials design in shaping the future of engineering applications. [ABSTRACT FROM AUTHOR]

The subject of the study is a load bearing capacity of building structures from fiber reinforced polymer (FRP) shapes under the short term load, such as snow load and occupancy load, which significantly exceed values of dead load. Experimentally determined actual strength and stiffness under the short term load of following structural members and connections: of I-beams; bolted connections under the bearing load with different directions of material’s pultrusion relatively to applied force; connections transferring load via contact surfaces, at the ends of structural members, oriented normally to the direction of pultrusion; webs of the I-beams under locally applied load perpendicularly to the direction of pultrusion. Experimental studies deemed following results. Minimal flexural strength of beams obtained experimentally is on average 1.25 times higher than values of flexural strength determined theoretically. Strength of different types of connections obtained after testing procedures is on average 1.35–2.5 times higher of its theoretical values. Conducted studies allow widening of the field of an applicability of FRP profiles as structural members of small scale structures subjected to predominantly atmospheric or live loads, for instance, tiered and covered seating pavilion. Such types of structures subjected to short term load allow to utilize strength and stiffness of their structural members more deeply.

Abstract This paper presents an experimental study on a fiber reinforced polymers (FRP) truss-ultra-high performance concrete (UHPC) hybrid bridge. Firstly, push-out tests on bolted FRP-UHPC connections revealed steel bolts can supply strong FRP-UHPC composite action. Then, single- and double-lap shear tests on FRP joints showed bolted-bonded joints have smaller slip at the initial loading phase than bolted joints. Finally, a full-scale FRP truss-UHPC hybrid bridge model with one bolted side and the other bolted-bonded side in FRP joints, was tested under varies loading scenarios. The salient findings are: (i) the bridge model can withstand static road load in Chinese bridge specification; (ii) the responses of the FRP members and UHPC slab stayed at the elastic-linear stage under the load of 200 kN and only about 10% of the ultimate strain was reached; (iii) slips between concrete slab and upper FRP chords stayed below 0.36 mm, which shows the steel bolts transferred loads well; (iv) the bolted side had a 26.08% larger deflection than the bolted-bonded side, which validates the findings in shear tests; and (v) the deflection, instead of the stress of FRP members and UHPC slab, is the governing factor of the design of this hybrid systems. [ABSTRACT FROM AUTHOR]

A hybrid fiber-reinforced polymer (FRP) – aluminum modular space truss emergency bridge has been designed that consists of two triangular deck-truss beams incorporating a new structural form and advanced pultruded FRP profiles. As a fundamental investigation, this paper explores the detailed torsional behaviors of the new triangular deck-truss beam. A full-scale specimen was prepared and tested under pure torsion to evaluate the representative structural performances. A three-dimensional finite element model (FEM) was constructed and validated with experimental results showing good comparisons. Furthermore, the torsional behavior of the triangular deck-truss beam was numerically investigated by removing individual primary truss members to clearly understand the load transfer mechanism. It was found that the beam exhibited a specific and unfavorable mechanical behavior prohibiting full utilization of the FRP material' potential. The external torsional moment is confirmed to be primarily resisted by the torsion of the longitudinal profiles and the in-plane bending of the bilateral Vierendeel trusses rather than the out-of-plane bending of the web diagonals. Possible improvement and optimization procedures are further suggested for this beam when solely used as a structure subjected to off-axis load or pure torsion. [ABSTRACT FROM AUTHOR]

Hollow box pultruded fibre-reinforced polymers (PFRP) profiles are increasingly used as structural elements in many structural applications due to their cost-effective manufacturing process, excellent mechanical properties-to-weight ratios, and superior corrosion resistance. Despite the extensive usage of PFRP profiles, there is still a lack of knowledge in the design for manufacturing against local buckling on the structural level. In this review, the local buckling of open-section (I, C, Z, L, T shapes) and closed-section (box) FRP structural shapes was systematically compared. The local buckling is influenced by the unique stresses distribution of each section of the profile shapes. This article reviews the related design parameters to identify the research gaps in order to expand the current design standards and manuals of hollow box PFRP profiles and to broaden their applications in civil structures. Unlike open-section profiles, it was found that local buckling can be avoided for box profiles if the geometric parameters are optimised. The identified research gaps include the effect of the corner (flange-web junction) radius on the local buckling of hollow box PFRP profiles and the interactions between the layup properties, the flange-web slenderness, and the corner geometry (inner and outer corner radii). More research is still needed to address the critical design parameters of layup and geometry controlling the local buckling of pulwound box FRP profiles and quantify their relative contribution and interactions. Considering these interactions can facilitate economic structural designs and guidelines for these profiles, eliminate any conservative assumptions, and update the current design charts and standards. [ABSTRACT FROM AUTHOR]