bluuebunny/crossref_metadata_2025 huggingface dataset:
Anxiety and depression in pregnancy: prevalence and associated risk factors among pregnant women attending antenatal clinic in Aminu Kano Teaching Hospital Kano, Nigeria
Authors: Gadanya Muktar Ahmed , Abulfathi Aisha Aliyu , Ahmad Fatima Adam
Published: July 2018

Pregnancy is not considered as a pathological state, however pregnancy heightens the vulnerability to emotional and psychological condition such as anxiety and depression. Untreated depression and anxiety during pregnancy may have negative effects on both the mother and the fetus. The objective of this study was to estimate the prevalence and associated risk factors of anxiety and depression during pregnancy. Cross sectional descriptive study using systematic sampling technique was used to collect data among 297 pregnant women attending antenatal clinic in Aminu Kano Teaching Hospital, Kano. Data was collected using a structured questionnaire, Mini International Neuropsychiatric Interview (MINI 6.0). About one-third of the respondents were in the age group 20- 25 years. The prevalence of anxiety and depression during pregnancy were found to be 23.2% and 26.6% respectively. Risk factors that were significantly associated with anxiety during pregnancy were co-morbid depression during pregnancy (P=0.01), and partner abuse (P=0.04), with 37.5% anxious among those abused compared to 21.5% among those not abused. Risk factors associated with depression during pregnancy were co-existing medical condition (P=0.04) with 45.7% of respondents with coexisting medical condition found to be depressed compared to 24.0% without co-existing medical condition. Anxiety and depression in pregnancy were found to be prevalent among the study subjects. Measures to detect anxiety and depression during pregnancy especially in those with risk factors should be introduced during routine antenatal care.
Thyroid peroxidase antibody levels among human immunodeficiency virus infected patients in Kano, North-Western Nigeria
Authors: Yahaya Isah A. , Sherif Sherifah U. , Abdulsalam Kabiru
Published: July 2018

Autoimmunity plays a role in the development of thyroid dysfunction in human immunodeficiency virus (HIV) infected patients. This study assessed the serum levels of thyroid peroxidise antibody (TPO-Ab) in relation to the various forms of thyroid dysfunction in HIV patients in Kano. Free tri-iodothyronine (fT3), free thyroxine (fT4), thyroid stimulating hormone (TSH) and TPO-Ab were measured using Chemiluminescent immunoassay(CLIA) on the serum of 70 HIV sero-positive patients on Highly Active Antiretroviral Therapy (HAART, as Group I), 70 HAART naïve HIV sero-positive patients (Group II) and 70 apparently healthy HIV negative controls (Group III). The prevalence of thyroid dysfunctions were 55.7%, 42.9% and 2.8% among groups I, II and III respectively. TPO-Ab was elevated in 1 (1.43%) HIV positive patient on HAART, Group I, that also had subclinical hyperthyroidism. Four participants (5.7%) among group III were found to have elevated anti-TPO levels. Thyroid dysfunction was more common among HIV-positive than HIV-negative participants. Thyroid dysfunction among HIV patients was mainly non-autoimmune in origin. However, thyroid autoimmunity appears to play a little role in the development of hyperthyroidism in HIV patients.
Sero-prevalence of human immunodeficiency virus infection among patients with newly diagnosed pulmonary tuberculosis in a teaching hospital in Bauchi, North-Eastern Nigeria
Authors: Gwalabe Sabiu Abdu , Dunga Jacob , Bara Yusuf Jibrin , Muhammad Alkali , Umar Mustapha Sabo , Bathna Sule
Published: July 2018

About a third of the human immunodeficiency virus (HIV) positive population worldwide is co-infected with Mycobacterium tuberculosis. However, data are lacking about the prevalence of HIV among patients with pulmonary tuberculosis (PTB) in a teaching hospital in Bauchi, northeast Nigeria. The aim of this study is to determine the sero-prevalence of HIV among patients with sputum smear positive PTB at Abubakar Tafawa Balewa University Teaching Hospital (ATBUTH), Bauchi, Bauchi State, Nigeria. This is a retrospective study review of patients’ medical records diagnosed with sputum smear positive PTB that attended and received treatment at directly observed treatment short course (DOTS) clinic of Abubakar Tafawa Balewa University Teaching Hospital (ATBUTH), Bauchi, Bauchi State, North-Eastern Nigeria from January, 2015- December, 2017. All the patients were newly diagnosed with sputum smear positive PTB using ZN stain testing of their sputum and screened for HIV antibodies. There were 155 patients studied comprising of 95 (61.29%) males and 60 (38.71%) females. One hundred and twenty (77.42%) patients were seronegative and 35 (22.58%) sero-positive for HIV. Most of the patients were within the ages of 15-54 years with mean age of 34.63±15.55. The sero-prevalence of HIV infection among the patients is 22.58%. Sero-prevalence of HIV is observed to be high among young and married patients with secondary level of education. The sero-prevalence of HIV infection among the patients is relatively lower than those reported in most parts of Nigeria and the sub-Saharan Africa, hence there is still need for continued screening of HIV antibodies among patients with PTB so as to reduce the morbidity and mortality that may result from the coinfection.
Assessing physicians’ intention to prescribe antimicrobials for chronic HIV/AIDS associated diarrhea among adults in Nigeria, using the theory of planned behavior
Authors: Misau Yusuf Abdu , Faruk Muhammad Bashir , Gwalabe Sabiu Abdu , Sunusi Usman Usman , Mogere Dominic , Mbaruk Suleiman Abdallah
Published: July 2018

Chronic diarrhea remains one of the commonest manifestation of HIV and a leading cause of morbidity and mortality despites gains in greater access to antiretroviral drugs and treatments of opportunistic infections globally. Yet, there is lack of precise evidence about the place of antimicrobials in chronic HIV associated diarrhea among adults. Physicians have continued to prescribe antimicrobials empirically or otherwise for chronic HIV associated diarrhea among adults. The aim of this study is to assess Physicians’ intension to prescribe antimicrobials in chronic HIV associated diarrhea among adults in Nigeria using the constructs of theory of planned behavior: Attitudes, Subjective Norms and Perceived behavioral control. An exploratory cross sectional survey was carried out. A structured questionnaire was developed following a pilot study to elicit salient beliefs among Physicians and a review of the literature. The study was carried out in 3 Northern Nigerian states among Physicians in Primary/Secondary and Tertiary hospitals in 2014. Data was analyzed using SPSS and STATA. After descriptive statistics, multiple logistic regression analysis was used to determine the relationship between the key constructs of TPB and Physician’s intension to prescribe antimicrobials in chronic HIV associated diarrhea among adults. We found strong intention to prescribe antimicrobials among Physicians respondents. The constructs of the theory of planned behavior explained 40% of variance of the Physicians’ intention to prescribe antimicrobials for chronic AIDS associated diarrhea in adults. Perceived control behavior and knowledge were the most important components of the model associated with intention. This study has further added new knowledge to the pool of evidence that Perceived Control Beliefs and Knowledge significantly influence Physicians’ intention to prescribe antimicrobials in chronic AIDS associated diarrhea. This finding reinforces the utility of theory of planned behavior as a tool to study health care service provision and utilization. There is need for future studies to test if changes in perceived control behavior and knowledge will leads to changes in intention to prescribe antimicrobials for chronic AIDS associated diarrhea and ultimately leading to a change in the clinical practice of managing chronic AIDS associated diarrhea in adults.
A taxonomic evaluation of the Thesium confine species complex (Santalaceae)
Authors: Mashego Kagiso S. , le Roux M. Marianne
Published: July 2018

Background: Thesium L. is the largest genus in the family Santalaceae (sandalwood family). The last taxonomic revision of the southern African species dates back to 1925. An urgent revision of the genus is required as indicated in a recent national biosystematics research strategy for South Africa.Objectives: To revise the Thesium confine species complex (Thesium durum, T. confine and Thesium spartioides) and to update the typification, nomenclature, descriptions and distribution ranges.Method: Morphological characters were studied using own field collections as well as herbarium specimens from K, NU, PRE and PRU and images on Global Plants (JSTOR). Distribution ranges of the studied species were updated.Results: An examination of morphological characters revealed great similarity between T. spartioides and T. confine. Both species have an herbaceous habit, decumbent growth form, terminal (or less frequently axillary) inflorescences and a sympatric northern distribution in South Africa. Thesium durum differs from T. spartioides and T. confine in having a shrubby habit, erect growth form and axillary inflorescences and occurs in the southern part of South Africa.Conclusion: Thesium spartioides is synonymised under T. confine, and T. durum is retained as a separate species.
Vulnerability of vulture populations to elephant impacts in KwaZulu-Natal
Authors: Rushworth Ian A. , Druce Dave , Craigie John , Coverdale Brent
Published: July 2018

Elephant were previously widespread in savanna and coastal systems of KwaZulu-Natal (KZN), but were virtually extirpated by 1870. Over time, elephant have been reintroduced into their former range in KZN, but always onto small fenced systems (mean size 191.3 km2 ± 87.8 km2, median size 107.0 km2, range 14 km2 – 900 km2). These populations have increased rapidly (8.4% per annum), and although a number of populations are now being managed using contraception, the majority of the populations (66.7%, 14 out of 21) are stocked above the ‘preferred density’ as defined in their approved management plans, while others will soon exceed the preferred density. Vulture populations in KZN are small, declining and already at risk of extinction. In KZN, 94.2% of tree-nesting vulture nests occur in areas with elephant; this could increase to 99.5% in the near future if proposed land-use change takes place. Anthropogenic impacts in the broader landscape mean that there are limited opportunities for vultures to nest elsewhere, and we hypothesise that loss of suitable nesting habitat in existing areas, including through impact of elephant on large trees, could result in declines and even extirpation of these species as breeding residents. Given the demonstrated and potential impacts of elephants on large trees necessary for vulture nesting, it is essential that the role of protected areas and extensive wildlife systems for vultures be adequately taken into account when managing elephant populations. It is important that a precautionary and adaptive management approach is taken regarding management of elephant in areas important for vultures, at least until the ecological interactions between vultures, vegetation, elephant and other drivers are better understood, and until the willingness and ability to manage elephant numbers and impact according to the elephant management plans are demonstrated.
Music of the Roms in the Primorje-Gorski Kotar County and the Possibilities of Using Music of the Romani in the Pedagogical Process in Croatia
Authors: Kalanjoš Ines Cvitković
Published: July 2018

The Roms are the most numerous minority group in Europe, a people without a parent state, and potentially an important factor in determining cultural policies and in the implementation of the educational process in the context of national states. On the territory of today‘s Republic of Croatia, they have been present for more than seven centuries. For the time being, the Roms in the Primorje-Gorski Kotar County are not encompassed by systematic research and there is indeed a need for a well-established scholarly knowledge about this segment of the population.
Is planet Earth as a whole likely to be wage-led?
Authors: Razmi Arslan
Published: July 2018

Open-economy considerations that create the possibility of ‘beggar-thy-neighbor’ effects offer one explanation for why the relationship between distribution, demand, and growth may be complicated in the short run. Several authors have argued recently, however, that even if demand and growth are profit-led in many individual countries, the global economy is likely to be wage-led since the planet as a whole runs balanced trade. This paper shows that this argument, while intuitively appealing, does not hold up to careful examination. Although the world economy as a whole is a closed system, it is not isomorphic to a closed economy, thanks to repercussion effects, relative price movements, and cross-country heterogeneity. Using asymmetries in consumption as a simple illustrative device I show that, in a two-country world, the effects of global redistribution depend on the nature of the constituent economies. This conclusion holds in spite of balanced trade at a planetary level, and regardless of whether one or both economies have excess capacity or whether zero-sum effects are present or not.
The financial instability hypothesis and the paradox of debt: a microeconometric approach for Latin America*
Authors: González Alejandro , Pérez-Caldentey Esteban
Published: July 2018

Hyman Minsky's financial instability hypothesis (FIH) argues that as part of the normal functioning of capitalist economies robust financial structures tend to evolve into highly leveraged fragile financial structures. The paradox of debt challenges the very foundation of Minsky's FIH as it maintains that the upward and downward phases of business cycles need not be characterized by processes of respective leveraging and deleveraging. Using a panel of firm-level data and seemingly unrelated regressions we analyse the relationship between debt and investment for 12 Latin American countries for the years 2005 (expansion) and 2009 (contraction). We reject the paradox of debt in favor of the FIH, regardless of our model specification or the choice of external financing. The FIH seems to intensify in expansions with respect to recessions, and its intensification during expansions is explained by a larger fraction of firms acquiring debt and new investment projects, rather than from further leveraging for those firms already engaged in fixed investment.
Fire performance of concrete-encased CFST columns and beam-column joints
Authors: Han Lin-Han , Zhou Kan
Published: July 2018

Concrete-encased CFST (concrete filled steel tube) structure is a type of composite structure featuring an inner CFST component and an outer reinforced concrete (RC) component. They are gaining popularity in high-rise buildings and large-span buildings in China nowadays. To date, the behaviour of concrete-encased CFST structures at ambient temperature has been investigated, but their fire performance has seldom been addressed, including the performance in fire and after exposure to fire. This paper summarizes the fire test results of concrete-encased CFST columns and beam-column joints. The cruciform beam-column joint was composed of one continuous concrete-encased CFST column and two cantilevered reinforced concrete (RC) beams. These specimens were subjected to a combined effect of load and full-range fire. The test procedure included four phases, i.e. a loading phase at ambient temperature, a standard fire exposure phase with constant load applied, a sequential cooling phase and a postfire loading phase. The main findings are presented and analysed. Two types of failure were identified, i.e. the failure during fire exposure and the failure during postfire loading. Global buckling failure was observed for all the column specimens. The column specimens with common load ratios achieved high fire ratings without additional fire protection. The concrete-encased CFST columns also retained high postfire residual strength. As for the joint members, beam failure was observed in all cases. The measured temperature-time history and deformation-time history are also presented and discussed. For both the column and joint specimens, the deformation over the cooling phase was significantly greater than that in the standard fire exposure phase.
Axially loaded grouted connections in offshore conditions using ordinary portland cement
Authors: Henneberg Joshua , Schaumann Peter , Raba Alexander
Published: July 2018

A grouted connection (GC) is a hybrid connection which joins two telescoped steel tubes by filling the annulus between the steel tubes with grout. GCs are frequently used to enable a force fitted connection between piles and substructure of offshore wind turbines. At latticed substructures this connection is located at mudline level in wet ambient conditions (AC). Nowadays special grout materials are used to achieve not only best mechanical properties but also a good performance during grouting in offshore conditions.To reduce production costs the use of ordinary portland cement (OPC) is investigated as an alternative filling material within this paper. OPC has a much lower tendency to segregate, as there are no aggregates added. This leads to more simplified, stable and cheaper production processes offshore. Further focus is put on the failure mode of OPC filled GCs in submerged condtions.For an appropriate use of OPC offshore a feasible mechanical performance needs to be ensured. Investigating this, small and large-scale laboratory tests were performed at Leibniz Universität Hannover. Using the experimental test setup of previous investigations for special high performance grouts (HPG) [1, 2], enables a direct comparison of HPG and OPC. Documenting liquid and solid OPC properties, like slump flow and compressive strength confirms a stable material quality. Small-scale ULS-tests showed significantly lower ULS-capacities and a more brittle failing process compared to HPG. Lagre-scale tests confirmed the observed failure mechanisms of Schaumann and Raba for OPC filled GCs in submerged conditions [3]. Carried out tests showed significant influence of grout material and confirmed influence of grout annulus size on fatigue capacity.
Experimental investigations on the load bearing behaviour of an innovative prestressed composite floor system in fire
Authors: Meyer Patrick , Schaumann Peter , Mensinger Martin , Koh Suet Kwan
Published: July 2018

In Germany, regulations for hollow spaces in slab systems require 30 minutes standard fire resistance of the load-bearing steel construction. Within a current national research project a natural fire scenario for the hollow space was developed based on realistic fire loads and ventilation conditions in the hollow space. Assuming this realistic fire scenario in the hollow space, two large scale tests on an innovative composite floor system were performed to evaluate the influence on the load bearing behaviour of the floor system. The integrated and sustainable composite floor system consists of a prestressed concrete slab, an unprotected, bisected hot rolled I-profile with composite dowels either in puzzle or clothoidal shape, and removable floor panels on the top of the I-profile. This floor system ensures the opportunity to adjust the technical building installations in accordance with the use of the building. This integrated and sustainable composite floor system was developed in several research projects. The standard fire resistance R90 for the fire scenario below the slab system has already been proven successfully. In this paper, experimental investigations regarding the heating and load bearing behaviour of the innovative composite floor system under the newly developed natural fire scenario of hollow spaces are presented. In doing so, the special test set-up to realise the fire tests for the fire scenario hollow space will be described in detail. After the fire scenario for the hollow space, the specimen was subjected to the ISO standard fire curve to establish the failure temperature of the unprotected I-profile. In addition to the temperature development and the load bearing behaviour inside the innovative floor during the heating phase, the cooling phase and the influence of a web opening on the load bearing behaviour will be discussed.
Design of concrete-filled high strength steel tubular X-joints subjected to compression
Authors: Li Hai-Ting , Young Ben
Published: July 2018

The structural performance and design of concrete-filled high strength steel tubular X-joints subjected to compression are investigated. A numerical investigation on the behaviour of concrete-filled high strength steel tubular chord members under concentrated bearing load has been performed. The high strength steel tubes had nominal yield stresses of 700 and 900 MPa. The infilled concrete had nominal concrete cylinder strengths of 35 and 100 MPa. In order to avoid the failure of brace members and reveal the true capacity of the X-joints, steel bearing plates were used to simulate the brace members. A finite element model was developed and validated against test results. Furthermore, a parametric study comprised 156 finite element analyses was carried out. The strengths of the concrete-filled high strength steel square and rectangular hollow section X-joints obtained from the parametric study together with available data in the literature were compared with the nominal strengths calculated from the CIDECT Design Guide. It is shown that the CIDECT design predictions exhibit significant scatter and could be unconservative for the concrete-filled tubular joints with chord sidewall slenderness ratio beyond 40 in this study. Hence, new design rules are proposed for concrete-filled high strength steel tubular X-joints subjected to compression. It is shown that the proposed design rules are able to provide reasonably good predictions.
Design of composite columns based on Eurocode – comparison between general and simplified methods
Authors: Unterweger Harald , Kettler Markus
Published: July 2018

In this paper, the results of a comprehensive parametric study for the member capacity of columns subjected to axial forces on the one hand and axial forces plus bending moments on the other hand are presented, considering all relevant types of composite sections: a) concrete encased sections, b) partially encased sections, c) concrete filled rectangular and circular tubes. Different steel grades and concrete strength classes are also considered. Firstly, the different methods of design in the Eurocode are briefly summed up: a) simplified method, based on buckling curves, for axial forces only, b) simplified method, based on a section verification with 2nd order moments, including equivalent geometric imperfections, c) a general method, based on geometrical and material nonlinear calculations with 3D-FEM-models. In the main part of the paper, the buckling resistance of the columns, based on these 3 methods, are compared, over the whole range of relative slenderness, for different section types, material strengths and type of loading (N, N + Mz, N + My). Also in the case of columns subjected to bending moments about the strong axis and axial forces, buckling about both axis is studied in detail.
Comparison investigation on the load capacity of octagonal, circular and square concrete filled steel tubes
Authors: Chan Tak-Ming , Zhu Jiong-Yi
Published: July 2018

This paper presents a comparative investigation on the load capacity of octagonal concrete filled steel tubes (CFST) with that of the commonly used circular and square CFST. Existing experimental data of octagonal CFST were collected and based on the cross-sectional properties of the existing octagonal specimens, the corresponding circular and square cross-section were generated under three different control parameters: total cross-sectional area of column, confinement ratio and axial stiffness. Those circular and square cross-sections were used in the numerical analysis of CFST to obtain the load capacity for the comparative investigation. Validated finite element models were built for the modeling of the circular and square CFST. The outcome of comparison shows that the confinement ratio is the crucial parameter to the difference of axial behaviour between octagonal and circular CFST. Under the same confinement ratio, octagonal CFST has a very close axial bearing performance to that in circular CFST and are much better than the square CFST.
Square reinforced CFST column to RC beam joint subjected to lateral loading: An investigation using finite element analysis
Authors: Gan Dan , Zhou Zheng , Zhou Xuhong , Tan Kang Hai
Published: July 2018

Concrete-filled steel tube (CFST) columns have been applied popularly in recent years, where they were connected with reinforced concrete (RC) beams or steel beams in a building. This paper proposes a joint system which connects the square reinforced concrete-filled thin-walled steel tube (RCFTWST) column and RC beam. In the joint system, reinforced bars are located in the square CFTWST column, and stiffeners are welded at adjacent sides of the square steel tube. Besides, the panel zone is strengthened by internal diaphragms. A finite element model (FEM) based on software ABAQUS was developed to evaluate the behavior of the proposed joint system under lateral loading, and parametric analysis was carried out. Based on the analysis results obtained from FEM, some important parameters were chosen. And two specimens were tested under combined axial compression and low-cyclic lateral load to assess the seismic performance of the proposed joint system. The axial load level was chosen as the parameter. Test results showed that all tested specimens performed well up to 5% drift and can satisfy the seismic requirements of “strong-joint weak-component”. In addition, the finite element model (FEM) is verified by comparing with the experimental results. The results can be well predicted by the model.
BEHAVIOUR OF STEEL AND COMPOSITE BEAM-COLUMN JOINTS SUBJECTED TO QUASI-STATIC AND IMPACT LOADS
Authors: TAN Kang Hai , CHEN KANG
Published: July 2018

The behaviour of steel and composite beam-column joints was investigated in this paper. A test programme on typical beam-column joints subjected to quasi-static and impact loads was presented. A comparison of different connections was conducted and composite slab effect was investigated. Based on the test results, a component-based modelling approach was proposed and validated. Basic nonlinear springs of beam-column joint models were developed. Mechanical properties of the nonlinear springs were defined based on either current design codes or models proposed by previous researchers. Good agreement with test results was achieved by the component-based models.
Seismic performance assessment of conventional steel and steel-concrete composite moment frames using CFST columns
Authors: Silva Antonio , Jiang Yadong , Macedo Luis , Castro Jose Miguel , Monteiro Ricardo
Published: July 2018

The research reported in this paper focuses on the assessment of the seismic performance of conventional steel moment-resisting frames (MRFs) and steel-concrete composite moment-resisting frames employing circular Concrete-Filled Steel Tube (CFST) columns. Two comparable archetypes (i.e. one steel MRF, with steel columns and steel beams; and one composite MRF, with circular CFST columns and steel beams) are designed, and used as the basis for comparison between the seismic performance associated with each typology. Both structures are designed against earthquake loads following the recommendations of Eurocode 8. The comparison of the obtained design solutions allows concluding that the amount of steel associated with the main structural members is higher for the steel-only archetype, even though the composite MRF has the higher level of lateral stiffness. This aspect is particularly relevant when one considers that a minimum level of lateral stiffness (associated with the P-Δ inter-storey drift sensitivity coefficient, θ), is imposed by the European code, which may ultimately govern the design process. The two case-studies are then numerically modelled in OpenSees, and their seismic performance is assessed through fragility assessment for a number of relevant limit states, and, finally, earthquake-induced loss estimation. In general, the results obtained clearly indicate that the composite MRF with circular CFST columns exhibits better seismic performance than the equivalent steel-only archetype. This is noticeably shown in the comparison of the fragility curves associated with the collapse limit state, which tend to show substantially higher probabilities of exceedance, at similar levels of 1st-mode spectral acceleration, for the steel-only case. Furthermore, seismic losses at several seismic intensity levels of interest tend to be higher for the steel MRF.
Analysis of concrete-filled steel tubular columns after fire exposure
Authors: Ibáñez Carmen , Bisby Luke , Rush David , Romero Manuel L. , Hospitaler Antonio
Published: July 2018

Concrete filled steel tubular (CFST) columns have a high probability to resist high temperatures compared to steel structures, whose evaluation after a fire is limited by the resulting deformation. A better understanding of the behaviour of CFST columns after a fire, affected by the maximum temperature achieved by the concrete infill, is required to properly estimate their residual strength and stiffness in order to adopt a reasonable strategy with minimum post-fire repair. In this paper, a fiber beam model for the simulation of the post-fire response of slender concrete-filled steel tubular (CFST) columns is presented. First, the model is validated against experimental results and subsequently it is employed to analyse the post-fire response of circular CFST columns. The variation of the residual strength with the load level for realistic fire resistance times is numerically studied. Actually, in a building, the columns support load even while a fire is being extinguished, so it is important to take into account this loading condition when predicting the post-fire behaviour. Therefore, in this research, the complete analysis comprises three stages: heating, cooling and post-fire under sustained load conditions. The model considers realistic features typical from the fire response of CFST columns, such as the existence of a gap conductance at the steel-concrete interface or the sliding and separation between the steel tube and the concrete.
Post-fire mechanical properties of high strength steels
Authors: Young Ben , Li Hai-Ting
Published: July 2018

High strength steels are becoming increasingly attractive for structural and architectural applications due to their superior strength-to-weight ratio which could lead to lighter and elegant structures. The stiffness and strength of high strength steels may reduce after exposure to fire. The post-fire mechanical properties of high strength steels have a crucial role in evaluating the residual strengths of these materials. This paper presents an experimental investigation on post-fire mechanical properties of cold-formed high strength steels. A series of tensile coupon tests has been carried out. The coupon specimens were extracted from cold-formed square hollow sections with nominal yield stresses of 700 and 900 MPa at ambient temperature. The specimens were exposed to various elevated temperatures ranged from 200 to 1000 °C and then cooled down to ambient temperature before tested to failure. Stress-strain curves were obtained and the mechanical properties, namely, Young’s modulus, yield stress (0.2% proof stress) and ultimate strength, of the cold-formed high strength steel materials after exposure to elevated temperatures were derived. The post-fire retention factors that obtained from the experimental investigation were compared with existing predictive equations in the literature. New predictive equations are proposed to determine the residual mechanical properties of high strength steels after exposure to fire. It is shown that the proposed predictive equations are suitable for both cold-formed and hot-rolled high strength steel materials with nominal yield stresses ranged from 690 to 960 MPa.
Finite element analysis of the flexural behavior of square CFST beams at ambient and elevated temperature
Authors: Ramli Sulong Nor Hafizah , Javed Muhammad F , Khan Niaz B , Kashif Sardar
Published: July 2018

This paper presents the finite element (FE) analysis and modeling of square concrete-filled steel tube (CFST) members subjected to a flexural load at ambient and elevated temperature. The commercial FE tool ANSYS was used in the 3D modeling taking into consideration material and geometric non-linearities.  The developed FE model can accurately predict the ultimate moment capacity of the square CFST members subjected to flexural loads and fire resistance time. A parametric study is conducted using the verified FE model to study the effect of the compressive strength of infilled concrete  and the yield strength of the steel tube on the flexural behavior of the square CFST members. The ultimate bending capacity of the CFST members increases by up to 27% when the yield strength of the steel tube increases from 210 MPa to 400 MPa while its fire resistance time decreases. For a D/t ratio equal to 30, the flexural capacity increases by 20% when the compressive strength of the infilled concrete increases from 60 MPa to 100 MPa, while it shows increase in fire resistance time.
Fragility curves for special truss moment frame with single and multiple vierendeel special segment
Authors: Kumar Rajesh , Sahoo Dipti Ranjan , Gupta Ashok
Published: July 2018

Special Truss Moment frame (STMF) is an open web truss moment frame, which dissipates the input seismic energy through a well-defined ductile special segment located near the mid-span of truss while other members of truss outside the special segment and columns are designed to remain elastic. In this paper, the performance and the fragility curve of STMFs consisting single and multiple vierendeel panels in the special segment are investigated. The seismic response of nine-story having the length to depth ratio of special segment 2.5 is considered to develop the fragility curve. The seismic response of each building was recorded by performing nonlinear incremental dynamic analyses. Each archetype modelled in nonlinear analysis program PERFORM-3D to carry out IDA under a suit of forty-four real Far Field ground motion records. Fragility curves were developed for these structures and the probability of exceedance at immediate occupancy (IO) level, Life safety (LS) level and Collapse performance (CP) level was assessed for two level of hazards, DBE level (10% probability of exceedance in 50 years) and MCE level (2% probability of exceedance in 50 years). For DBE level earthquake intensity, the probability of exceedance for the CP performance level of STMF building for both structure is marginal while at MCE level the probability of exceedance at CP performance level is 71% and 45% for single and multiple panels respectively.
Hysteretic performance research on high strength circular concrete-filled thin-walled steel tubular columns
Authors: Wang Jiantao , Sun Qing
Published: July 2018

Under violent earthquake motions, the severe damage in critical regions of structures could be ascribed to cumulative damage caused by cyclic loading. Using the high strength (HS) materials in concrete-filled steel tubular (CFST) columns is the effective way and popular tendency to promote the seismic behavior in anti-seismic design. In this paper, an experimental study on the hysteretic performance of high strength circular concrete-filled thin-walled steel tubular columns (HCFTST) columns was carried out. A total of six specimens were tested under constant axial compression combining cyclic lateral loading. The tested parameters were the different combinations of diameter-to-thickness (D/t) ratio, axial compression ratio (n) and concrete cylinder compressive strength (fc).The failure modes, load-displacement hysteretic curves, skeleton curves, dissipated energy and stiffness degradation were examined in detail. Through the experiment analysis result, it indicates that the ultimate limit state is reached as the severe local buckling and rupture of the steel tubes accompanying the core concrete crushing occur. Using high strength materials could have a larger elastic deformation capacity and the higher axial compression ratio within test scopes could motivate the potential of HS materials. In brief, the HCFTST columns with ultra-large D/t ratios under reasonable design could perform excellent hysteretic performance, which can be applied in earthquake-prone regions widely.
Punching Shear Mechanism Based Design of Concrete-Filled CHS T-Joints under In-Plane Bending
Authors: Xu Fei , Chan Tak-Ming , Chen Ju
Published: July 2018

The in-plane bending behaviour of concrete-filled circular hollow section (CHS) T-joints was examined in this paper. The main failure mode, the punching shear of the chord-wall, was observed from the test of four large-scale joints with the diameter ratio of brace to chord (β) ranging from 0.44 to 0.85. The tube-wall deformation was measured to assess the governing failure mode of the composite joints. Complementary finite element (FE) methodology was verified against the experimental findings and the validated FE models were used to further investigate the mechanical behaviour and the design methodology. The feasibility to apply a fracture criterion in the material-level to a large-scale structural simulation was evaluated. The validated FE modes could successfully capture the tube-wall fracture initiation and propagation. Based on both experimental and numerical investigations, it was shown that the capacity of composite joints was governed by the ultimate strength limit, i.e. punching shear strength, due to the infill concrete that mitigated both inward and outward deformation on the compressive and tensile sides, respectively. The analytical model was established to reveal the composite actions between the tube and the inner concrete, and to elaborate the development of the flexural section-resistance. Finally, the design equation was proposed and could well predict the moment capacity.
Experimental study on the thermal behaviour of fire exposed slim-floor beams
Authors: Albero Vicente , Espinós Ana , Serra Enrique , Romero Manuel L. , Hospitaler Antonio
Published: July 2018

Steel-concrete composite beams embedded in floors (slim-floors) offer various advantages such as the floor thickness reduction or the ease of installation of under-floor technical equipment. However, this typology presents important differences in terms of thermal behaviour, as compared to other composite beams, when exposed to elevated temperatures. These differences are due to their special configuration, being totally contained within the concrete floor depth. Moreover, the current European fire design code for composite steel-concrete structures (EN 1994-1-2) does not provide any simplified thermal model to evaluate the temperature evolution of each slim-floor part during a fire. Additionally, only a few experimental studies can be found which may help understand the thermal behaviour of these composite beams. This paper presents an experimental investigation on the thermal behaviour of slim-floor beams. Electrical radiative panels were used in the test setup to produce the thermal heating. The thermal gap between the lower flange of the steel profile and the bottom steel plate was studied, being found to be one of the most influential elements over the cross-section temperature gradient. The experimental campaign was developed by varying the cross-section configuration in order to evaluate the influence of this parameter over the slim-floor thermal behavior. Finally, the experiments carried out were used to develop and calibrate a finite element thermal model which may help in further research on the thermal behaviour of slim-floor composite beams.
Measuring Retail Visual Cues Using Mobile Bio-metric Responses
Authors: Dishman Paul , Groves Joshua , Jolley Dale
Published: July 2018

This research provides the results of a comprehensive in-store study that utilized eye tracking to determine the initial eye attractiveness of signage and displays used in a Toyota retail dealership. Potential car buyers (n = 24) walked randomly through the showroom for the first time, and were asked to view the various signs, displays, video monitors, decorations, and vehicles on display. Research was conducted while the dealership was open in order to include distractions from human interaction. Subjects’ eye movements and the objects viewed were captured using Tobii II eye tracking glasses at 60Mhz. A typical showroom self-tour lasted approximately 4:31 minutes. Subjects were then shown their results and Retrospective Think Aloud interviews were conducted with the subjects to determine positive and negative reactions to the observed objects. Signage measured included those required by Toyota, as well as those created by the dealership. Types of signage measured included digital, video, posters, stand-up cards, and ads placed on the vehicle. Each potential eye attractive object was identified and classified by type (signage, décor, digital signage, vehicle information, etc.). Every subject’s results were analyzed by the number of fixations and the time spent viewing each object. The study revealed that video or digital messaging was not any more effective than static signage, but that placement of the signage was a determining factor in the effectiveness of message receptivity. Many of the non-signage objects received more attention than did certain types of advertising signage. The various attributes of the objects and signs that received positive attention were analyzed as to their eye attactiveness characteristics. Although signage in a retail showroom is believed to be critical in providing advertising and product messages, this study (in its particular environment) demonstrated that signage is not viewed by customers as often as previouly thought.
Algorithmic Trading Systems Based on Google Trends
Authors: Gómez Martínez Raúl , Prado Román Camilo , De la Orden de la Cruz María del Carmen
Published: July 2018

In this paper we analyze five big data algorithmic trading systems based on artificial intelligence models that uses as predictors stats from Google Trends of dozens of financial terms. The systems were trained using monthly data from 2004 to 2017 and have been tested in a prospective way from January 2017 to February 2018. The performance of this systems shows that Google Trends is a good metric for global Investors’ Mood. Systems for Ibex and Eurostoxx are not profitable but Dow Jones, S&P 500 and Nasdaq systems has been profitable using long and short positions during the period studied. This evidence opens a new field for the investigation of trading systems based on big data instead of Chartism.
Big Data and Data Driven Marketing in Brazil
Authors: Finger Vítor , Reichelt Valesca , Capelli João
Published: July 2018

The main purpose of this article is the understanding of which marketing strategies related to big data are being implemented by Brazilian companies in different sectors, in addition to assessing these actions within an already established construct. To reach the proposed objectives, an exploratory, qualitative research was conducted using the multiple case study method. Thus, data were collected through bibliographical, documentary and semi-structured interviews, with the intent of formulating the construct by which the companies are studied. The study unit interviewed consisted of market professionals and big data specialists. As the main result, it was widely noticed the application of strategies related to big data by the companies surveyed. The classification of these actions within an already established construct, however, was not possible, since it was understood the existence of distinct stages of adoption for this technology, and it was not possible to label these companies as users of big data.
The Exercise Science Toolkit: a web application for exercise and health science students
Authors: Norton Kevin , Norton Lynda
Published: July 2018

The Exercise Science Toolkit is a web-based educational software program for exercise and health science tertiary students and professionals. The software was developed to facilitate student engagement with essential knowledge, skills and protocols in these disciplines, provide opportunities to conduct analyses on empirical data or simulations on an unlimited supply of virtual clients including difficult or rare cases, encourage overlearning opportunities at their own pace and in their own time, and shift the emphasis from passive knowledge delivery to creative acquisition and application of knowledge. The toolkit is evidence-based with numerous databases on age- and sex-specific population norms built from systematic searches. It uses established internationally accepted protocols for the analytical tools and test procedures. The toolkit has over 40 screens or tools to engage users in a variety of pedagogical modes including pre-class preparation, laboratories in real time, individual and group problem-based learning, online and distance education.
Layering Learning for Work-Readiness in a Science Programme
Authors: McKay Marianne , Smith-Tolken Antoinette , Alessandri Anne
Published: July 2018

In order to prepare our students for a challenging workplace, the Department of Viticulture and Oenology at Stellenbosch University in South Africa have ‘layered’ Engaged Learning strategies throughout the four-year undergraduate degree in an approach that is innovative in a science-based programme. In this research project, we assessed the effects of service-learning (SL) and a six-month internship on student employability by analysing reflections that were collected over a number of years. We also asked industry members whether they felt students had improved in key areas after the final year internship. The student submissions for SL showed evidence of personal growth and transformation, and those for the internship reflected industry requirements for professional skills in a complex and technically demanding milieu. It was found that these engaged experiences provided sound preparation for working life, as well as  giving students opportunities for self-questioning and personal growth, which is unusual in the natural sciences learning environment.
Game of phones: Integrating mobile technology into science and engineering classrooms.
Authors: Crump Vanessa , Sparks Julie
Published: July 2018

Mobile technologies are ubiquitous in the lives of our students. Rather than seeing the presence of these devices in the classroom as a hindrance or a distraction, educators should embrace the opportunities for greater student engagement, collaboration and useful feedback. This paper reports some uses of mobile technologies in classrooms at UTS Insearch and the responses of science and engineering students. We hope that our reflections will be a useful guide to other educators and suggest simple ways to integrate flipped learning and gamification into undergraduate classrooms. UTS Insearch has a blended learning approach to learning and teaching where students learn through seamless integration of technology-enhanced strategies and face-to-face activities. We focus on our experiences using learning tools, such as Kahoot! and Mentimeter, to demonstrate practical applications of gamification in science and engineering classrooms. The teaching style used in Australian universities incorporating student-centred flipped learning is foreign to many students, especially those from Non-English Speaking Backgrounds, but data from surveys and reflections allow us to conclude that a majority of students value the use of emerging technologies in learning and that they assist with motivation, formative assessment, collaborative learning and student engagement.