Study of seismic control systems on the behaviour of industrial storage racks

University of Technology Sydney. Faculty of Engineering and Information Technology.Steel storage racks are structures which are used in factories and warehouses to store goods and merchandises. They consist of uprights, beams and braces made of cold-formed steel, and although they are very light in comparison with conventional structures, they are designed to carry very heavy loads. Storage racks are designed to resist horizontal loads in orthogonal directions using two different frame systems: moment resisting frames in down aisle direction and braced frames in cross aisle direction. The design of racks is different from typical buildings because they are made of slender thin walled members, hence, making them sensitive to global, local, and distortional buckling if overloaded. Moreover; the connections demonstrate highly nonlinear behaviours under loading. Due to the aforementioned reasons, the design of racks poses major challenges for engineers especially in seismic regions where mitigating the vulnerability of racks is important. The objective of this numerical and experimental research was to investigate the seismic behaviour of storage racks and to establish the effectiveness of two alternative control systems to improve the performance of the racks under seismic loads. The control systems studied are new generation passive dampers: (i) a pounding tuned mass damper (PTMD) and (ii) a base isolation system. Full scaled shake table testing was performed at the University of Technology, Sydney (UTS) to study the dynamic behaviour of storage racks and to verify the numerical models. As part of the research, numerical models based on the Finite Element Method (FEM) were developed and applied to conduct parametric analyses of the racks in order to compare the seismic response of cross aisle braced frames of different heights with and without control devices. The FEM results showed that PTMD dampers enhance by up to 40% the seismic behaviour of racks under 5 meters height while the base isolation system was more effective for tall racks. Financial support for this research was provided by Dexion

Scour at partially blocked box-culverts under steady flow

© 2016, Thomas Telford Services Ltd. All rights reserved. Culverts are built at locations where a waterway crosses a road or railway and creates a limitation to flow passage. Furthermore, blockage commonly occurs during flood events with accumulation of debris at the culvert inlet. The inlet blockage changes the flow structure at the outlet and may result in culvert failure. Despite this, the impacts of blockage on culvert hydraulics and downstream waterways have not received consideration in the literature. The purpose of this paper is to mitigate this deficiency by reporting on an investigation into scouring at the outlet of partially blocked culverts. Experimental tests were conducted under steady flow to investigate a relationship between the maximum scour depth, blockage ratio of the culvert and the flow characteristics. Both non-blocked and partially blocked conditions were considered. Consideration of the results obtained showed that the scoured area and maximum scour depth increased with partially blocked culverts conditions compared with equivalent non-blocked culverts

Location of the maximum scouring depth at the outlet of partially-blocked and non-blocked box culvert

Among various hydraulic structures, culvert is the most likely one which usually blocks by the debris that are carrying by flow during large flood events. The size of the structure and its location where a waterway crosses a road or railway increases the possibility of clogging. The blockage of culvert accelerates bed scouring at the outlet hence affects bed scouring profile. This leads to increase the risk of culvert collapsed and produce different kinds of damages to the society. The present study concerns the effect of upstream blockage on the scouring profile at the outlet of a box culvert. Therefore, the experimental program was designed to investigate the relationship between the scouring geometry and blockage ratio. The experimental tests were carried out under non-blocked and partially blocked conditions. The sediment material used in this study was uniform non-cohesive sand material. Results showed that the scouring bed profile is different in partially blocked condition when compared to the non-blocked condition. Additionally it was found that the maximum scouring depth in a partially blocked culvert occurred at a distance very close to the outlet of the box culvert. © 2014 Taylor & Francis Group, London

Blockage effects on scouring downstream of box culverts under unsteady flow

This experimental study is concerning scouring at the outlet of partially blocked box culverts under unsteady flow condition. The blockage of culverts is considered as an important factor on the scouring pattern at the outlet of the blocked box culverts. To investigate the effect of blockage on scouring pattern downstream of a box culvert under unsteady flow, some experimental tests were carried out in a laboratory flume located in the Hydraulics Laboratory of the University of Technology Sydney. The experimental tests were carried on in both partially blocked and non-blocked conditions and consequentially the effect of blockage on scour pattern is investigated. It was found that 88% to 98% of maximum scour depth occurs in the rising limb of the hydrograph

An In vitro Analysis of the Effects of Iron Sulfate and Iron Acetate on Streptococcus mutans

Statement of problem: Dental caries is a common infectious disease induced by Streptococcus mutans (S. mutans). Objectives: Due to the high incidence rate of dental caries and iron deficiency in the Iranian population, we have conducted this study to analyze the effects of iron acetate and iron sulfate on controlling the growth of S. mutans. Materials and Methods: In this in vitro study, we evaluated the antibacterial effects of iron sulfate and iron acetate on S. mutans by the disk diffusion method, minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). The results were compared to those for 0.2% chlorhexidine and penicillin as the controls. Results: Iron sulfate had higher MIC and MBC values compared to penicillin and chlorhexidine (P<0.001). Iron acetate MIC and MBC values did not significantly differ with penicillin and chlorhexidine. The iron sulfate inhibition zones at the 25 and 50 µg/mL doses were more than those of iron acetate. Conclusions: Iron sulfate and iron acetate solutions can inhibit the growth of S. mutans. Hence, different compounds that contain iron salts such as toothpastes, mouth washes, and food supplements can be produced to prevent dental caries and iron deficiency

Study of blockage effect on scouring pattern downstream of a box culvert

This experimental study is concerning with the scouring at the outlet of a box culverts. The blockage of culverts has considered as an important factor on the scouring pattern at the outlet of the box culverts. To investigate the effect of blockage on scouring pattern at the downstream of box culvert, some experimental tests were carried out in a laboratory flume located in the Hydraulic Laboratory of University of Technology Sydney (UTS). The experimental tests were carried on in both blocked and non-blocked conditions and consequentially the effect of blockage on depth of scour hole is investigated. It was found that for flow with Froude number of 0.09 there is a 15% increase in the depth of scour hole for a box culvert with 40 precent blockage. Furthermore, the scour depth in blocked condition with the Froude number of 0.12 was 22% deeper than box culvert with non-blocked condition. © 2013 Taylor & Francis Group