Steel cables and suspenders in bridges are at high risk of corrosion-fatigue and in some cases of fretting-fatigue in their anchorages. These factors greatly limit the service stresses of a specific cable system and involve expensive protection measures. In order to investigate the above limitations, the fretting fatigue behaviour of pin-loaded carbon fibre reinforced polymer (CFRP) straps was studied as models for corrosion-resistant bridge suspenders. Two types of straps were tested: small model straps with a sacrificial CFRP ply and large full-scale straps. In a first phase, five fully laminated and carbon pin-loaded CFRP model straps were subjected to an ultimate tensile strength test. Thereafter, and in order to assess their durability, 20 model straps were subjected to a fretting fatigue test, which was successfully passed by 4 straps. An S-N curve was generated for a load ratio of 0.1 and a frequency of 10 Hz. In a second phase, one full-scale strap was tested for its ultimate tensile strength and two full-scale straps were fatigue-tested. The influence of fretting fatigue loading on the residual mechanical properties of the straps was also assessed, and although fretting fatigue represented an important limitation for laminated CFRP straps, it could be shown that the investigated CFRP tension members can compete with the well-established steel suspenders.
This paper considers a novel, alternative application of fibre-reinforced epoxy-based intumescent coatings as potential materials for strengthening concrete columns. An experimental programme is presented examining the compressive behaviour of unreinforced concrete cylinders at ambient temperature that are confined with fibre-reinforced intumescent wraps. It is demonstrated that these advanced composite coatings can provide effective passive confinement to concrete, achieving ultimate axial strength and strain enhancements that are comparable to those of conventional FRP wraps. The enhancements are also shown to be reasonably predicted by existing confinement models for FRP-confined concrete. The results demonstrate the strong potential of these fire protection materials as alternative strengthening systems for reinforced concrete columns, potentially eliminating the need for additional passive fire protection that is common with conventional fire-rated FRP wrapping systems.
SUMMARYThe construction sector continues to adapt to the challenges posed by climate change. Architects and engineers aim to build sustainable, energy, resource, and cost‐efficient structures by increasingly using bio‐based building materials. However, fire safety has always been a significant concern for timber building construction internationally. The objective of the study presented in this article is to document fire hazards of compressed straw when used as thermal and acoustic insulation within wood‐framed building assemblies. Three densities of compressed straw (75, 125, and 175 kg/m3) were selected and their combustion and thermal responses were evaluated at various scales, in attempt to define the optimal density considering various factors. The performance of the straw was also compared with commercially available insulation materials and then tested under exposure to severe heating in medium‐scale wood‐framed assemblies to evaluate the impacts of the straw as compared with a noncombustible insulation. The compressed straw with a density of 75 kg/m3 was found to have the best behavior with respect to both reactions to fire and insulation properties. The results suggest that compressed may have similar or better behavior under the heating conditions investigated when compared to a commercially available combustible insulation material. The use of this material as a primary insulation in a buildings is considered manageable by thoughtful design, construction, and building use without unduly increasing risks associated with fire.
The fretting fatigue performance of laminated, unidirectional (UD), pin-loaded, carbon fibre-reinforced polymer (CFRP) straps that can be used as bridge hanger cables was investigated at a sustained service temperature of 60 °C. The aim of this paper is to elucidate the influence of the slightly elevated service temperature on the tensile fatigue performance of CFRP straps. First, steady state thermal tests at ambient temperature and at 60 °C are presented, in order to establish the behaviour of the straps at these temperatures. These results indicated that the static tensile performance of the straps is not affected by the increase in temperature. Subsequently, nine upper stress levels (USLs) between 650 and 1400 MPa were chosen in order to establish the S–N curve at 60 °C (frequency 10 Hz; R = 0.1) and a comparison with an existing S–N curve at ambient temperature was made. In general, the straps fatigue limit was slightly decreased by temperature, up to 750 MPa USL, while, for the higher USLs, the straps performed slightly better as compared with the S–N curve at ambient temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.