Assessment of web crippling design provisions for application to proprietary soldier beams

Structures used for temporary works are lightweight so that they are easy to transport, erect and dismantle. Particular care should be taken in their design as local instabilities could arise due to their thin-walled nature. This article presents 12 tests on proprietary soldier beams subjected to two concentrate opposing loads applied simultaneously. The geometry of the proprietary beams feature cold-formed C-shaped sections with web holes connected back to back with internal spacers. In the absence of design rules for application to such members, the experimental results are used in the present investigation to assess the suitability of the provisions for the web crippling design of coldformed steel members as well as existing design methods from the literature, which account for the effect of perforations in the web. Experimental and predicted resistances are compared and design recommendations are provided.Leada Acro

Particulate Matter in the Hospital Environment

Investigations of particle concentration levels and size distribution were conducted in the complex hospital system of the Royal Children’s and the Royal Brisbane Hospitals. The aim of the measurements was to provide an indication of particulate sources in the hospital environment and relate particle characteristics to the operating parameters of the hospitals. The measurements were performed using the most advanced instrumentation for size classification in the submicrometer and supermicrometer levels. The conclusions from the investigation were (i) that indoor concentration levels of particle numbers are closely related to outdoor concentration levels, indicating that outdoor particulates were the main contributor to the indoor particulates in the hospitals under investigations and (ii) that the performance of filtration/ventilation systems is the most critical parameter in reducing general particulate concentration levels in those hospital units where medical procedures can result in generation of potentially hazardous organic aerosols

Effect of Face Velocity and the Nature of Aerosol on the Collection of Submicrometer Particles by Electrostatic Precipitator

Despite the electrostatic collection of aerosol particles is one of the most widely used air cleaning methods, there have not been sufficient amount of effort devoted to investigate its performance in the full range of operating conditions. This paper reports results of the tests of a two-stage electrostatic precipitator (ESP) conducted in the particle size range of 0.018 - 1.2m over a range of flow rates using NaCl and Environmental Tobacco Smoke (ETS) test aerosols. The total collection efficiency of the precipitator was found to increase with an increase in the count median diameter (CMD) of the particles, to have polynomial dependence on flow rate and no significant dependence on the type of test aerosol. The fractional efficiency of the precipitator was found to be dependent on flow rate. However, the “critical” particle size of about 1.2 m was found to exist when the fractional collection efficiency becomes independent of flow rate. For submicrometer particles, the collection efficiency was found to be independent of particle size at flow rates below 560 L.s-1. A minimum in the efficiency was observed in the 0.1 to 0.45 m particle size range and for particles smaller than about 0.02 m