Screw connectors for thin topping,timber–concrete composites

Timber floors with insufficient strength and stiffness can be upgraded by applying a concrete topping to form a composite structure. Conventional upgrades have a topping thickness of 40 mm or greater but recent research has proposed an alternative thin topping solution (20 mm). The shear connectors which transfer the forces between the timber joists and concrete topping are critical to the success of the upgrade. This paper presents the results of pushout testing of thin topping timber–concrete composite joints. A factorial experimental design was employed to assess how the inclination, topping thickness and timber density affect the stiffness and strength of screw joints. The results were statistically assessed to differentiate between the effects of each factor and establish the presence of interactions between factors. The screw inclination and topping thickness were found to be important factors when considering the stiffness of the joints. Topping thickness was the most critical factor for the strength of the joints.     

Evaluation of the benefits of vehicle safety technology: The MUNDS study

Real-world retrospective evaluation of the safety benefits of new integrated safety technologies is hampered by the lack of sufficient data to assess early reliable benefits. This MUNDS study set out to examine if a “prospective” case-control meta-analysis had the potential to provide more rapid and rigorous analyses of vehicle and infrastructure safety improvements. To examine the validity of the approach, an analysis of the effectiveness of ESC using a consistent analytic strategy across 6 European and Australasian databases was undertaken. It was hypothesised that the approach would be valid if the results of the MUNDS analysis were consistent with those published earlier (this would confirm the suitability of the MUNDS approach). The findings confirm the hypothesis and also found stronger and more robust findings across the range of crash-types, road conditions, vehicle sizes and speed zones than previous. The study recommends that while a number of limitations were identified with the findings that need be addressed in future research, the MUNDS approach nevertheless should be adopted widely for the benefit of all vehicle occupants.     

Environmental change in Lake Champlain revealed by long-term monitoring

Long-term monitoring data on Lake Champlain spanning the past two to five decades were analyzed to document water quality and biological changes in the lake. August mean surface water temperatures increased during 1964–2009 in most Lake Champlain regions at rates (0.035–0.085 °C/year) similar to what has been observed in the Laurentian Great Lakes and elsewhere. Secchi disk transparency increased by over a meter during 1964–2009 in regions along the main stem of the lake, with much of the increase occurring after the 1993 zebra mussel invasion. Transparency declined in northeastern regions where zebra mussel densities were lower. No trends in hypolimnetic dissolved oxygen concentrations or depletion rates were found in any of the deep lake regions during 1990–2009. Sodium concentrations tripled in the Main Lake region since the 1960s. Chloride increased in the Main Lake by 30% since 1992, but declined in northeastern regions of the lake during recent years, coincident with reductions in road salt use in Vermont. Total phosphorus concentrations decreased during 1979–2009 in southern and northwestern lake regions, but increased by 72% in Missisquoi Bay where chlorophyll-a concentrations doubled over the period. There was a general lakewide trend of decreasing total nitrogen levels during 1992–2009 that may have been due in part to reductions in atmospheric nitrogen loading to the watershed. Cyanobacteria increased their dominance within the phytoplankton community in northeastern regions of the lake since the 1970s.