A constitutive model based on the combination of damage mechanics and plasticity is developed to analyse the failure of concrete structures. The aim is to obtain a model, which describes the important characteristics of the failure process of concrete subjected to multiaxial loading. This is achieved by combining an effective stress based plasticity model with a damage model based on plastic and elastic strain measures. The model response in tension, uni-, bi- and triaxial compression is compared to experimental results. The model describes well the increase in strength and displacement capacity for increasing confinement levels. Furthermore, the model is applied to the structural analyses of tensile and compressive failure.Comment: arXiv admin note: text overlap with arXiv:1103.128

The well-known synergetic effect of blast and fragment loading, observed in numerous experiments, is often pointed out in design manuals for protective structures. However, since this synergetic effect is not well understood it is often not taken into account, or is treated in a very simplified manner in the design process itself. A numerical-simulation tool has been used to further study the combined blast and fragment loading effects on a reinforced concrete wall. Simulations of the response of a wall strip subjected to blast loading, fragment loading, and combined blast and fragment loading were conducted and the results were compared. Most damage caused by the impact of fragments occurred within the first 0.2 ms after fragments' arrival, and in the case of fragment loading (both alone and combined with blast) the number of flexural cracks formed was larger than in the case of blast loading alone. The overall damage of the wall strip subjected to combined loading was more severe than if adding the damages caused by blast and fragment loading treated separately, which also indicates the synergetic effect of the combined loading.

The enhanced energy absorption characteristics of fibre-reinforced concrete, compared to plain concrete, has in experimentally studies been shown to improve the projectile resistance and motivate its increased usage in protective structures. However, the high cost of undertaking experiments and the high parameter variation and dependency of the experimental setups and results, respectively, make it difficult to draw generic conclusions of how the addition and increased amount of fibres affects the local damage caused by projectile impact, which motivates the use of numerical simulations to study this. The numerical hydrocode AUTODYN was used in a qualitative study of how the addition of different amounts of fibres, modelled as different post-crack relations, influence the depth of penetration and crater formation on the front and rear face of a concrete target. Fibres added to the concrete mix had a minor influence on the depth of penetration while the crater size on both front and rear faces of the target decreases. The crack propagation beyond the crater on the front face was also reduced when fibres were added to the concrete. An increased amount of fibres in the concrete showed no effect on the size of the front-face crater, but led to further decreased size of the crater on the rear face of the concrete cylinder. It is concluded that the scabbing crater can be reduced in size and prevented by usage of fibre-reinforced concrete even if the depth of penetration is only slightly less than to penetration depth in plain concrete.Keywords: Numerical simulation, Projectile impact, Steel-fibre reinforced concrete, Penetration 1.Introduction A projectile impact may cause local and global damage to a concrete structure. Global damage consists of flexural deformations, which, unlike local damage, may cause structural failure. Local damage may cause spalling and crushing of concrete on the front face and scabbing on the rear face of the target, together with projectile penetration into the target or even full penetration (i.e. perforation) of the target [1,2]. Different variables have been proposed to measure local damage, such as depth of penetration, perforation and scabbing thickness or ballistic limit (i.e. the minimum velocity at which the projectile penetrates the target) in plain or reinforced concrete [2].Researchers have experimentally studied the behaviour of fibre-reinforced concrete under impact loading and observed a significant increase in the overall resistance to local damage when compared to plain concrete [3][4][5][6][7][8][9][10][11]. However, the structural behaviours of targets subjected to impact are complicated, depending on material factors as well as test-condition factors [6], which vary between the reported experiments and therefore make it difficult to draw generic conclusions of the effect of fibres and how it changes with different amounts of fibres in the concrete.The local damage parameters in concrete are often estimated by using empirical, semi-empirical or purely analytical eq...

Free-living N2-fixing Frankia strains isolated from Casuarina sp. were investigated for genomic polymorphism. We used six 10-mer oligonucleotides as single arbitrary primers (AP) for the polymerase chain reaction (PCR) in order to amplify random DNA fragments in the genome of free-living Frankia strains. Agarose-gels of the amplified genomic DNA revealed that two of the six arbitrary primers showed polymorphism in the eight different Frankia genomes. Analysis of the AP-PCR products showed 9 polymorphic bands ranging from 4.1-0.60 kb. We conclude that single arbitrary primers can be used to amplify genomic DNA, and that polymorphism can be detected between the amplification products of the different Frankia genomes.

Background Diabetes is a growing threat to public health, and secondary diseases like foot complications are common. Foot ulcers affect the individual’s quality of life and are a great cost to society. Regular foot examinations prevent foot ulcers and are a recommended approach both in Sweden and worldwide. Despite existing guidelines, there are differences in the execution of the foot examination, which results in care inequality. A structured foot examination form based on current guidelines was developed in this study as the first step toward digitalized support in the daily routine, and was validated by diabetes health care professionals. Objective The study aimed to validate a structured foot examination form by assessing health care professionals’ experiences of working with it “foot side” when examining patients with diabetes. Methods Semistructured interviews were held in a focus group and individually with 8 informants from different diabetes professions, who were interviewed regarding their experiences of working with the form in clinical practice. The users’ data were analyzed inductively using qualitative content analysis. The study is part of a larger project entitled “Optimised care of persons with diabetes and foot complications,” with Västra Götaland Region as the responsible health care authority, where the results will be further developed. Results Experiences of working with the form were that it simplified the foot examination by giving it an overview and a clear structure. Using the form made differences in work routines between individuals apparent. It was believed that implementing the form routinely would contribute to a more uniform execution. When patients had foot ulcers, the risk categories (established in guidelines) were perceived as contradictory. For example, there was uncertainty about the definition of chronic ulcers and callosities. The expectations were that the future digital format would simplify documentation and elucidate the foot examination, as well as contribute to the accessibility of updated and relevant data for all individuals concerned. Conclusions The foot examination form works well as a support tool during preventive foot examination, creates a basis for decision-making, and could contribute to a uniform and safer foot examination with more care equality in agreement with current guidelines. Trial Registration ClinicalTrials.gov NCT05692778; https://clinicaltrials.gov/ct2/show/NCT05692778