Bending behavior of adhesively-bonded engineered wood-concrete composite decks

Four-point bending tests were conducted on five medium-sized (i.e., 2300 mm in length and 215 mm in width) engineered timber (laminated veneer lumber (LVL) and cross-laminated timber (CLT)) - concrete (wood chip concrete and plain concrete) composite decks. The concrete was glued to the wood substrate with epoxy and polyurethane adhesives. The observed failure modes of the composite decks were concrete crushing or wood failure in tension or shear. No failure of the adhesive interface was observed and the decks behaved linearly until failure. In the subsequent analysis, the authors quantified the shear flexibility of transverse layers (stressed perpendicular to the fiber direction) in CLT and LVL boards and its effect on the bending stiffness on the composite decks using γ-method described in EN 1995-1-1 (EC5). The analytical predictions of the effective bending stiffness were verified via experiments, showing consistently good agreement

Interfacial bond behavior of adhesively-bonded timber/cast in situ concrete (wet bond process)

The goal of this research was to study the strength of the interfacial bond between cast-in-situ concrete and engineered timber (cross-laminated timber (CLT)). Double lap specimens were manufactured using fresh concrete that was cast between two CLT blocks. Polyurethane and epoxy adhesives were used to bond the wet concrete with the CLT blocks. The shear strength of wet-bond specimens was compared with the specimens prepared under dry conditions (prefabricated concrete cube glued to CLT blocks). The statistical analysis (T-test) of bond strength showed that the shear strengths of wet- and dry-bond specimens using epoxy and polyutrthane adhesives were no significantly different for the tested C25 plain concrete and the CLT. The failure mode of dry-bond specimens were concrete failure near the interface, however, debonding at interface was the dominant failure for the wet-bondspecimens

Structural behaviour of composite floor systems under column removal scenario

In this study, four 3D composite floor specimens were quasi-statically tested to failure under an internal column removal scenario. Two principal objectives were achieved, viz. unveiling the load-resisting mechanisms (Alternate Load Paths) in 3D composite floor systems and reveal of effects from slab aspect ratio, degree of composite action and boundary condition. Besides, numerical models were employed to study inter-dependence among load-resisting mechanisms in 3D composite floor systems. It is found that dominant flexure would suppress the development of CA, since they are the two complimentary components in the double-span beams above the missing column. The slab contribution at the final stage involves TMA remains constant if steel reinforcement, profiled decking and dimensions of the slab are the same. Furthermore, the verified modelling method was applied to a full-scale 3D composite floor system subjected to sudden column loss, yielding the dynamic behaviour. Last but not least, a mechanical model was proposed to estimate the entire load-deflection response of 3D composite floor systems subjected to an internal column loss. Compared with actual test results and numerical simulations, the model shows reasonable accuracy. Besides, the model can capture the effects of key parameters, such as slab aspect ratio, joint type, number of joint bolts, slab thickness, reinforcement ratio in the slab and thickness of steel decking. Most importantly, the procedure of the model can be implemented by a spreadsheet method, which provides a simple and numerical robust tool for engineers to calculate progressive collapse resistance of structures for a missing column scenario.Doctor of Philosoph

Characterization of interfacial properties between fibre and polymer matrix in composite materials – A critical review

Synthetic fibre reinforced polymer (FRP) composite materials have been widely used in engineering fields, e.g., civil, automotive, and aerospace industry, due to their high specific modulus and strength, corrosion resistance, and relatively high durability. The interface between fibre and polymer matrix is critical for the short-term and long-term performance of the FRP composite materials due to the shear lag stress transfer from the matrix to the fibre via their interface. This paper presents an overview of the fibre–matrix interface and interfacial properties. First, the interface mechanisms (i.e., interdiffusion, chemical bonding and mechanical interlocking) of FRP composites are discussed. Next, the methodology for measuring interfacial properties, characterizing interface morphology and chemical composition, and numerical simulations on FRP interface are introduced. Lastly, the challenges for the characterization of interfacial properties are highlighted

Jute Fiber-Reinforced Polymer Tube-Confined Sisal Fiber-Reinforced Recycled Aggregate Concrete Waste

In this study, the compressive performance of sisal fiber-reinforced recycled aggregate concrete (SFRAC) composite, confined with jute fiber-reinforced polymer (JFRP) tube (the structure was termed as JFRP–SFRAC) was assessed. A total of 36 cylindrical specimens were tested under uniaxial compression. Three major experimental variables were investigated: (1) the compressive strength of concrete core (i.e., 25.0 MPa and 32.5 MPa), (2) jute fiber orientation angle with respect to the hoop direction of a JFRP tube (i.e., β = 0°, 30° and 45°), and (3) the reinforcement of sisal fiber (i.e., 0% and 0.3% by mass of cement). This study revealed that the prefabricated JFRP tube resulted in a significant enhancement of the compressive strength and deformation ability of RAC and SFRAC. The enhancements in strength and ultimate strain of the composite columns were more pronounced for concrete with a higher strength. The strength and ultimate strain of JFRP-confined specimens decreased with an increase in fiber orientation angle β from 0° to 45°. The sisal fiber reinforcement effectively improved the integrity of the RAC and reduced the propagation of cracks in RAC. The stress–strain behaviors of JFRP–RAC and JFRP–SFRAC were predicted by the Lam and Teng’s model with the revised ultimate condition equations