Snubbing and Bundling Effects on Multiple Crack Spacing of Discontinuous Random Fiber-Reinforced Brittle Matrix Composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65960/1/j.1151-2916.1992.tb04457.x.pd

Trade-off between strength and ductility of random discontinuous fiber reinforced cementitious composites

It is well known that fiber reinforcement is an effective way of improving toughness of brittle materials. However, it is less clear how fiber reinforcement (particularly for random discontinuous fibers) can contribute to strength and ductility enhancement of the composites. In this paper, we address this issue from a micromechanics point of view. The conditions for multiple cracking, which is the mechanism of pseudo ductility, are briefly reviewed in terms of micromechanical parameters such as fiber aspect ratio, matrix toughness, and interfacial bond strength. Special attention is given to examining competing effect of these microparameters on composite strength and ductility. Experimental results of direct tensile tests of several random discontinuous fiber-reinforced high strength concretes and OPC paste are presented and discussed in light of recent advancements in pseudo strain-hardening theory.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31854/1/0000804.pd

Long-term Durability of FRP Bond in the Midwest United States for Externally-Strengthened Bridge Components

In this study, the bond strength of a typical FRP system subjected to long-term natural weathering in the Midwest United States is experimentally investigated, and the rate of degradation is estimated. To do this, the bond strength of an FRP system exposed to over fifteen years of weathering is determined with pull-off testing, and a relationship between strength reduction and exposure time is developed using regression analysis. For unweathered specimens, it was found that the attachment strength of the FRP system was governed by the concrete substrate, while for weathered specimens, the FRP system could detach by either a failure of the substrate, at the FRP/concrete interface, or FRP failure. It was found that a logarithmic curve best matches bond deterioration

Buckling of bridging fibres in composites

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43024/1/10855_2004_Article_BF00776363.pd

Association Between Net Vertebral Artery Flow Volume and Non-AF Stroke: A Retrospective 2-Year Analysis

Objectives: Association between net vertebral artery flow volume (NVAFV) and stroke types remains unclear. We hypothesize NVAFV is low in patients with posterior circulation infarction (PCI) and an ideal cut-off value for discriminating PCI from anterior circulation infarction (ACI) and controls may be present.Materials and Methods: As study candidates, we retrospectively enrolled hospitalized patients with first-time non-AF stroke within 2-years period. Consecutive non-AF, non-stroke subjects were enrolled as the control group. We compared NVAFV values among the PCI, ACI, and control groups.Results: Overall, 866 candidates—213, 418, and 235 candidates in the PCI, ACI, and control groups, respectively—were enrolled. NVAFV (mean ± SD) values were 134.8 ± 52.7, 152.3 ± 59.2, and 172.0 ± 54.7 mL/min in the PCI, ACI, and control groups, respectively. Statistics revealed significant difference (p < 0.001) among three groups. To use NVAFV as a diagnostic parameter, the AUC of any two groups should be between 0.58 and 0.69. Most (93.6%) of the controls had NVAFV above 100 mL/min. The odds ratio of any non-AF stroke is 3.48 if the NVAFV is below 100 mL/min.Conclusions: NVAFV is lowest in non-AF PCI group. Low NVAFV is associated with both non-AF ACI and PCI. No ideal cut-off value is available to discriminate PCI from other two conditions. We agree that an NVAFV of 100 mL/min is the lower limit of a normal value. Any value below 100 mL/min indicates high stroke risk and implies diffuse cerebral atherosclerosis and impaired cerebral perfusion

Review: optical fiber sensors for civil engineering applications

Optical fiber sensor (OFS) technologies have developed rapidly over the last few decades, and various types of OFS have found practical applications in the field of civil engineering. In this paper, which is resulting from the work of the RILEM technical committee “Optical fiber sensors for civil engineering applications”, different kinds of sensing techniques, including change of light intensity, interferometry, fiber Bragg grating, adsorption measurement and distributed sensing, are briefly reviewed to introduce the basic sensing principles. Then, the applications of OFS in highway structures, building structures, geotechnical structures, pipelines as well as cables monitoring are described, with focus on sensor design, installation technique and sensor performance. It is believed that the State-of-the-Art review is helpful to engineers considering the use of OFS in their projects, and can facilitate the wider application of OFS technologies in construction industry

Application of recycled tyre cord in concrete for shrinkage crack control

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43027/1/10855_2004_Article_BF00275355.pd

Control of Cs leachability in cementitious binders

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43025/1/10855_2004_Article_BF00636211.pd