Application of the wave finite element method to reinforced concrete structures with damage

Vibration based methods are commonly deployed to detect structural damage using sensors placed remotely from potential damage sites. Whilst many such techniques are modal based there are advantages to adopting a wave approach, in which case it is essential to characterise wave propagation in the structure. The Wave Finite Element method (WFE) is an efficient approach to predicting the response of a composite waveguide using a conventional FE model of a just a short segment. The method has previously been applied to different structures such as laminated plates, thinwalled structures and fluid-filled pipes. In this paper, the WFE method is applied to a steel reinforced concrete beam. Dispersion curves and wave mode shapes are first presented from free wave solutions, and these are found to be insensitive to loss of thickness in a single reinforcing bar. A reinforced beam with localised damage is then considered by coupling an FE model of a short damaged segment into the WFE model of the undamaged beam. The fundamental bending, torsion and axial waves are unaffected by the damage but some higher order waves of the cross section are significantly reflected close to their cut-on frequencies. The potential of this approach for detecting corrosion and delamination in reinforced concrete beams will be investigated in future work

Schiff Base Complexes of Copper(II)

The crystal structures of four Schiff base molecules are presented, one of which is a re-appraisal of a previously reported structure. Crystals of N,N\u27-1,2-phenylene-bis(salicylideneiminato)copper(II) have been grown from both chloroform and pyridine. The structure from chloroform shows two crystallographically distinct squareplanar molecules per asymmetric unit in an orthorhombic cell, a = 20.159(2), b = 14.918(1), c = 13.329(1) Å; space group Pna21. Two different stereochemistries are observed when pyridine is the solvent. One has square planar geometry and the other square pyramidal with a pyridine molecule bound in the fifth co-ordination site. The space group is P1 with a = 8.748(4), b = 14.499(4), c = 18.725(5) Å, α = 109.93(3), β = 91.99(2), γ = 101.64(3)°. Bis(N-phenyl pyridoxylideneiminato)copper(II) crystallises in a monoclinic cell, space group P21/c, a = 5.7037(6), b = 20.394(1), c = 10.6321(6) Å, β = 101.443(6)° with the trans square planar co-ordination geometry. In the re-appraised structure of aqua(5-phosphopyridoxylidene-DLphenylalanineato) copper(II) the complex is square pyramidal with two oxygen and one nitrogen donor from the ligand. The fourth site is occupied by a water molecule and the fifth, apical donor is a phosphate oxygen from an adjacent molecule. The space group is triclinic P1 with a = 8.697(2), b = 13.039(3), c = 12.418(3) Å, α = 110.49(2), β = 108.61(2), γ = 63.65(10)°

Wave propagation in reinforced and prestressed concrete structures with damage

Corrosion of the steel reinforcement bars in reinforced concrete is the most common cause of premature failure that must be pre-empted. In this respect, wave based techniques provide a potential detection approach. In this paper, wave propagation is modelled in a steel reinforced concrete beam with and without prestress. A short section of the beam is modelled in ANSYS. This model is then used in the wave finite element (WFE) framework, which assumes spatial periodicity along the waveguide, to model a beam of infinite extent. Corrosion of the reinforcement bars is represented by a local loss of thickness. Numerical case studies are presented to investigate the effects of various configurations and the severity of damage on the dispersion curves of the propagating waves. Scattering matrices are also calculated for the damage site, by coupling damaged and undamaged sections of the waveguide. Wave modes are subsequently identified for which the reflection coefficients are potentially sufficiently large to observe and use for damage identification

Blood donation in a multicultural Australia-complexities of cultural misunderstanding and intergenerational conflict for African communities

Australia is a multicultural country, with 44% of the population either born overseas or having one overseas born parent (Australian Bureau of Statistics 2007). While Australia purports to embrace and leverage these cultural differences, this does possibly raise issues in regards to marketing to a range of culturally different groups within the community (Nwankwo and Lindridge 1998). Many organisations will potentially be unable to develop strategies targeting multiple cultural groups (Wilkinson and Cheng 1999). However, Australian nonprofit marketers may have a more pressing need to target distinctive cultural segments, especially as they often have a mission designed to foster wider social inclusion or to address the needs of specific cultural groups (Centre for Culture, Ethnicity and Health 2004, Renzaho 2007). This requires that marketers develop culturally relevant marketing activities going beyond simply advertising in different languages (Noble and Camit 2005). This paper seeks to outline some of the cultural challenges related to donating blood using Sub-Saharan African migrants as an example

The Crystal Structure and Conformation of bis(N-methyl-5-chlorosalicylideneiminato)nickel(II) and bis(N-ethyl-5-chlorosalicy lideneiminato)nickel(II)

The crystal structures of bis(N-methyl-5-chlorosalicylideneiminato) nickel(II) (A) and bis(N-ethyl-5-chlorosalicylideneiminato) nickel(II) (B) have been determined by X-ray structure analysis using heavy atom method and refined by fuU matrix leastsquares procedure to R values of 0.044 and 0.040 for (A) and (B), respectively. Both structures have molecular centre of symmetry and the nickel atom in a planar coordination. Molecules of both complex compounds have »stepped« conformation with distinct difference in the step heights: 0.121 and 0.702 A in (A) and (B), respectively. The Ni-O and Ni-N bond lengths are 1.818 and 1.924 A in (A), and \u271.830 and 1.916 A in (B)

An overview of zeolites synthesised from coal fly ash and their potential for extracting heavy metals from industrial wastewater

Zeolites are aluminosilicate minerals widely used in industrial applications including as commercial adsorbents and catalysts. This overview focuses on zeolites synthesised from coal fly ash (CFA). Human activities and industrial developments generate large volumes of polluted water, which have a significant ecological impact. Industrial wastewater may consist of different pollutant types, but of specific interest to this work are heavy metals, which. Heavy metal ions are among the most dangerous pollutants due to their toxicity and carcinogenicity. This overview covers the recent scientific literature, focused on using CFA-derived zeolites to remove Ni, Hg, Mn, Cu, Zn, Cd, Pb, Cr, Co both from synthetic solutions replicating industrial wastewater and actual wastewater streams. The results described in many papers cited in this review look promising for industrial wastewater treatment operations. Furthermore, the large variety of possible synthetic zeolites provides a route for energy-efficient, pollutant-specific remediation of industrial heavy metals

Variscan sourcing of Westphalian (Pennsylvanian) sandstones in the Canobie Coalfield, UK

The zircon age spectrum in a sample from the Canonbie Bridge Sandstone Formation (Asturian) of southern Scotland contains two main peaks. One is Early Carboniferous in age (348– 318 Ma), and corresponds to the age of igneous activity during the Variscan Orogeny. The other is of late Neoproterozoic to early Cambrian age (693–523 Ma), corresponding to the Cadomian. Together, these two groups comprise 70 % of the zircon population. The presence of these two peaks shows unequivocally that a significant proportion of the sediment was derived from the Variscides of western or central Europe. The zircon population also contains a range of older Proterozoic zircons and a small Devonian component. These could have been derived from the Variscides, but it is possible that some were locally derived through recycling of northerly derived sandstones of Devonian–Carboniferous age. The zircon age data confirm previous suggestions of Variscide sourcing to the Canonbie area, made on the basis of petrographical, heavy mineral and palaeocurrent evidence, and extend the known northward distribution of Variscan-derived Westphalian sediment in the UK

Magnetic Zeolite:Synthesis and Copper Adsorption Followed by Magnetic Separation from Treated Water

Zeolites are widely used in diverse applications, including the removal of heavy metals from wastewater. However, separating fine-sized zeolite particles from treated water is often a challenge. In this work, a novel method utilizing a colloidal polyvinyl alcohol (PVA) solution to bind iron oxide nanoparticles to a Linde Type A (LTA) zeolite was used to synthesize magnetic zeolite. Different zeolite–iron oxide nanoparticle loadings (10:1, 10:0.5, and 10:0.1) were used in batch adsorption experiments to investigate adsorption capacities and kinetics for Cu removal from an aqueous solution. The results showed that the magnetic zeolite maintained much of its adsorbent properties while facilitating a simplified process design. Thus, the adsorption capacity of pure LTA zeolite was found to be 262 mg/g for magnetic zeolite, with a 10:1 ratio—151 mg/g; 10:0.5—154 mg/g; and 10:0.1—170 mg/g. Magnetic separation was subsequently employed to remove the magnetic zeolite from the treated solution