Stress concentration factors of concrete-filled T-joints under in-plane bending : experiments, FE analysis and formulae

Experimental and numerical investigations on seven cold-formed steel square hollow section (SHS) T-joints with concrete-filled chords were conducted for the determination of stress concentration factors (SCFs). The SCFs were experimentally determined using strain gauges and then numerically determined using Abaqus finite element analysis (FEA) software under static in-plane brace bending. Good agreement was observed between the two investigations. After validating the FEA results, a parametric study was conducted on the SCFs of concrete-filled SHS-SHS T-joints using Abaqus FEA to evaluate the effects of the non-dimensional parameters on the SCFs. Subsequently, design formulae for predicting the SCF of concrete-filled SHS-SHS T-joints subjected to in-plane bending were proposed. Comparable results were obtained between the numerical SCFs with SCFs calculated from the proposed design equations. The maximum SCF of concrete-filled SHS T-joints under in-plane brace bending occurred at different locations. The overall mean of the experimental reduction percentage in peak SCF due to concrete infill is 22% and the overall mean of the numerical reduction percentage in peak SCF due to concrete infill is 19%. The determination of SCFs in concrete-filled SHS-SHS T-joints under in-plane bending has been the subject of little research, and more information regarding the behavior of concrete-filled T-joints with SHS under in-plane bending needs to be provided to practicing engineers

Experimental investigation of retrofitting techniques for steel bridge girders subject to fatigue failure

Fatigue failure is major concern for infrastructure due to the increasing number of steel structures reaching the end of their design life each year. Increased loadings, deterioration due to weathering, climate change and human error also negatively impact the design life. Rehabilitating steel bridge girders rather than replacing the existing structure can provide an option for an economical and sustainable future. This paper presents the results of an experimental study which implements a simple retrofitting technique to combat fatigue failure. The retrofitting technique is applied to girders which have incurred fatigue cracking within the bottom flange. Experimental tests are performed on a riveted tapered 120-year-old girder and a new prefabricated hot rolled girder. The results from the experimental tests showed that fatigue cracking within the bottom flange of girders can be easily rehabilitated to increase the girder’s capacity to that of their original design. By utilising this simple designed retrofitting technique, existing structures do not need to be replaced. The technique shown herein is a viable method for increasing the service life of steel girders providing for a sustainable future

Explicit simulation of circular CFST stub columns with external steel confinement under axial compression

Concrete-filled steel tube (CFST) structural members have been widely used in engineering projects for their superior strength and ductility. However, the different lateral dilation characteristics between concrete infill and steel tube have caused imperfect composite interaction during the early loading stage. To overcome this issue, external steel confinements in the form of rings and spiral were previously suggested to minimise the lateral expansion of the steel tube and enhance the concrete confinement effects. This study presented the analytical behaviour of circular CFST short columns with an external ring or spiral confinements which are subjected to axial loading. An explicit finite element (FE) model was developed and verified based on previous experimental findings. Besides that, this study analysed the failure modes, axial load–strain relationship, stress distributions, and bond strength of the composite column components. Parametric analysis was also undertaken to evaluate the impact of material strengths, total steel ratio, and diameter-to-thickness ratio. The results suggest that the use of external steel confinement can enhance the compressive behaviour of CFSTs better than increasing the thickness of the steel tube when using the same steel ratio. Finally, simplified design formulations were developed to accurately calculate the ultimate capacity of CFST columns with and without external steel confinement

The Unconventional Strength Towards STEM Cohort

Science, Technology, Engineering and Mathematics (STEM) play a critically important role in Australia’s ability to innovate, expand and remain a competitive force globally. Indeed, ensuring that the workforce has the relevant skills in sufficient quantities through a reliable educational pipeline is quite challenging and requires an understanding of how these skills are and will be used within the Australian economy. Moreover, successfully delivering these skills for a knowledge economy will depend not only on producing the correct number of graduates but also on the education system supplying graduates from under-utilised groups (i.e. women & indigenous people) and diverse backgrounds. Currently, millions of children and young people are not developing the required skills to participate effectively in STEM environments. Young indigenous and female groups, in particular, are deprived of the opportunities to build their skills, including STEM literacy that is valued towards career progression in traditionally male-dominated fields (i.e. engineering and construction). As this white paper outlines, the challenges are drawn from recent literature, and a comprehensive review of existing initiatives is presented based on the observations of key partners, including Western Sydney University, the Australian government, research sector, industry, policymakers and communities. However, to build the STEM capacity of graduates with the right knowledge, competencies and qualities, two-way collaboration between the communities, educational institutions (from an early age), Australian workplaces and the government is essential, as no single sector can entirely solve the current STEM skills shortage. Western Sydney University is well-positioned within the high-density indigenous areas to respond to these issues, particularly by monitoring, engaging and promoting all graduates with STEM qualifications to meet the demand from the economy. In fact, by supporting equity and diversity throughout the STEM cohorts, educational institutions not only drive innovation but also establish a thriving STEM-skilled workforce that is fit for the future

Recent research on fatigue of tubular joints

Some of the structural systems used in the agricultural, road and mining industries are subjected to cyclic loading and are therefore prone to fatigue failure under service loads. These structural systems range from trailers, road sign portals, towers, bridges and dragline structures. Recent development has resulted in the production of steel materials that are relatively higher in strength and thin-walled. There has also been an increased use of concrete-filled tubular members in structural systems especially in long span bridge structures and towers. The understanding of tubular joints with concrete-filled chords has therefore become important. This paper therefore outlines recent research that has been carried out to better understand the behaviour of various welded thin-walled tube-plate and tube-tube joints under cyclic loading. The research has also included tests on tubular joints with concrete-filled chords under cyclic loading. The research has focussed on high cycle fatigue loading which is typical of loads in the agricultural, road and mining industries. The cyclic loading reveal the typical failure modes in the empty tubular joints and tubular joints with concrete-filled chords under cyclic loading. Measurement of stress distribution is also important in understanding the behaviour of structures under cyclic loading. The measurement of stress distribution can be carried out using both experimental and numerical methods. The welded connection interface shows that the areas of high stress concentration are the hot spots where fatigue cracks initiate and propagate leading to failure

Towards achieving good assessment practice : a case study

The University of Tasmania (UTAS) is currently undertaking a major review of assessment as it moves towards implementation of standard-based criterion referenced assessment. A review was undertaken of the third year design unit taught by the School of Engineering. This review revealed that the existing unit outline did not adequately define the assessment tasks and that the assessment criteria in the existing unit outline were not comprehensive enough to provide a guideline as to what was expected at each performance standard. This paper describes a project undertaken to design and develop a study guide in which assessment in the design unit are more clearly defined. The foundational work for the study guide was the development of learning activities and assessment tasks that were aligned to the learning objectives

Communication in engineering studies : review and case study

This paper reviews existing literature relating to communication in engineering education. A case study is then considered. The case study looks at the course structure of an existing civil engineering degree. Analysis of the different communication skills that can be obtained in this course is analysed. Deficiencies in the types of communication competencies that can be obtained are identified. Methods of improving these deficiencies are discussed

Effect of thickness and joint type on fatigue performance of welded thin-walled tube-to-tube T-joints

This paper summarizes the proposed fatigue design curves for three different thin-walled T-joints following the testing of 99 specimens in the welded condition. The specimens are made up of cold-formed high-strength thin-walled (t<4mm) circular hollow sections (CHS) and square hollow sections (SHS). Fatigue tests were carried out under constant amplitude stress range on thin CHS-CHS, CHS-SHS and SHS-SHS T-joints, for the load "in-plane bending in the brace". Fatigue failure occurred in chord members of thicknesses 3mm, 3mm and 3.2mm for SHS-SHS, CHS-SHS and CHS-CHS T-joints respectively. Different options are recommended for the design of the T-joints based on the deterministic method and least-squares method of statistical analysis

Towards achieving good assessment practice : a case study

The University of Tasmania (UTAS) is currently undertaking a major review of assessment as it moves towards implementation of standard-based criterion referenced assessment. A review was undertaken of the third year design unit taught by the School of Engineering. This review revealed that the existing unit outline did not adequately define the assessment tasks and that the assessment criteria in the existing unit outline were not comprehensive enough to provide a guideline as to what was expected at each performance standard. This paper describes a project undertaken to design and develop a study guide in which assessment in the design unit are more clearly defined. The foundational work for the study guide was the development of learning activities and assessment tasks that were aligned to the learning objectives

Welded thin-walled RHS-to-RHS cross-beams under cyclic bending

Galvanized sections are suitable for use in the road transport industry, the agricultural industry and for recreational structure. The structural systems in which galvanized sections can be used include chassis boxes, roof frames, base frames and drawbars among others. These structural systems are subjected to cyclic loading in service. The structural systems are therefore prone to fatigue failure. In Australia, galvanized sections, commonly known as DuraGal, are thin-walled with wall thicknesses less than 4mm. There are currently no fatigue design rules for sections of thicknesses less than 4mm. The connections under investigation namely cross-beam connections, are not covered in current fatigue design guidelines. This paper reports on fatigue tests of cross-beam connections made up of galvanized rectangular hollow sections (RHS). The fatigue test data in the present investigation is compared to data from previously reported work on galvanized cross-beam connections. Stress concentration factors have been determined in a typical connection to verify the crack pattern observed in these connections