Applications, behaviour and construction of high performance steels in steel-concrete composite structures

[EN] This paper addresses the applications, behaviour and construction of high performance steels in steel-concrete composite structures. For the purposes of this paper, high performance steels will include high strength, stainless and weathering steels. Akin to many innovations in the construction industry, high performance steels have generally been adopted for the use in iconic projects well before design procedures have been developed in standards. This paper will provide a summary of many of the applications particularly as they pertain to iconic projects in Australasia and internationally. Recent research in these areas will also be summarised and important design parameters as they deviate from traditional mild structural steel will be highlighted. Australasian advances in the standardisation of both bridges and buildings incorporating high performance steels will also be summarised, with particular reference to the Australasian Design Codes in Bridge Structures, ASNZS 5100 Part 6; and Building Structures ASNZS 2327 which have both been published in 2017. The paper will conclude with suggestions for further research and will identify areas of significant gaps in Australasian and international standards which will also guide future research in this area.The author would like to acknowledge the support of the Australian Research Council which is supporting the ongoing work in this paper through the awarding of the following two Discovery Project Grants, DP170100001, “Coupled service and ultimate behaviour of high strength composite columns”, and DP180100418, “Behaviour & design of large fabricated stainless steel composite structures”. Ongoing experimental research is currently being funded through these two project grants.Uy, B. (2018). Applications, behaviour and construction of high performance steels in steel-concrete composite structures. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 91-97. https://doi.org/10.4995/ASCCS2018.2018.8375OCS919

Rotordynamic Forces from Discharge-to-Suction Leakage Flows in Centrifugal Pumps: Effects of Geometry

The rotordynamic forces generated by the fluid flow through the impeller leakage path of a centrifugal pump are now well established. The present paper examines the effects of modifying the leakage path geometry by changing the front shroud, from a conical shape to a more typical curved design, and the effects of low pressure seal design on these forces. It is found that only the cross-coupled stiffness is affected by the change of path geometry. Changing the low pressure seal from an axial to a radial clearance does, however, significantly affect the rotordynamic forces. A bulk flow numerical model is found to predict the same general result for the low pressure seal tests. The model agrees with the general trends with increasing leakage flow coefficient exhibited by the data, but appears to underpredict the magnitude of the normal force

Behaviour and design of composite beams subjected to negative bending and compression

This paper investigates the behaviour of steel–concrete composite beams subjected to the combined effects of negative bending and axial compression. Six full-scale tests were conducted on composite beams subjected to negative moment while compression was applied simultaneously. Following the tests, a nonlinear finite element model was developed and calibrated against the experimental results. The model was found to be capable of predicting the nonlinear response and the ultimate failure modes of the tested beams. The developed finite element model was further used to carry out a series of parametric analyses on a range of composite sections commonly used in practice. It was found that, when a compressive load acts in the composite section, the negative moment capacity of a composite beam is significantly reduced and local buckling in the steel beam is more pronounced, compromising the ductility of the section. Rigid plastic analysis based on sectional equilibrium can reasonably predict the combined strength of a composite section and, thus, can be used conservatively in the design practice. Based on the experimental outcomes and the finite element analyses a simplified design model is proposed for use in engineering practice

Numerical analysis of concrete-filled spiral welded stainless steel tubes subjected to compression

[EN] Spiral welded stainless tubes are produced by helical welding of a continuous strip of stainless steel. Recently, concrete-filled spiral welded stainless steel tubes have found increasing application in the construction industry due to their ease of fabrication and aesthetic appeal. However, an in-depth understanding of the behaviour of this type of structure is still needed due to the lack of proper design guidance and insufficient experimental verification. In this paper, the mechanical performance of concrete-filled spiral welded stainless steel tubes will be numerically investigated with a commercial finite element software package, through which an experimental program can be designed properly. Specifically, the proposed finite element models take into account the effects of material and geometric nonlinearities. Moreover, the initial imperfections of stainless steel tubes and the form of helical welding will be appropriately included. Enhancement of the understanding of the analysis results can be achieved by extending results through a series of parametric studies based on the developed finite element model. Thus, the effects of various design parameters will be further evaluated by using the developed finite element model. Furthermore, for the purposes of wide application of such types of structure, the accuracy of the behaviour prediction in terms of ultimate strength based on current design codes will be studied. The authors herein compared the load capacity between the finite element analysis results and the existing codes of practice.Li, D.; Uy, B.; Aslani, F.; Hou, C. (2018). Numerical analysis of concrete-filled spiral welded stainless steel tubes subjected to compression. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 365-371. https://doi.org/10.4995/ASCCS2018.2018.7200OCS36537

A Parametric Evaluation of the Effect of Inlet Swirl on the Rotordynamic Forces Generated by Discharge-to-Suction Leakage Flows in Shrouded Centrifugal Pumps

Unsteady forces generated by the fluid flow through the impeller leakage path of a centrifugal pump were investigated. The effect of leakage path inlet (pump discharge) swirl on the rotordynamic forces was examined for various ratios of fluid tangential velocity to impeller tip speed. It was observed that changing the inlet swirl velocity does not appear to significantly affect the measured forces for a given leakage flow coefficient. A bulk flow numerical model was found to predict the same general result. The model agreed with experimental data for small values of the leakage flow coefficient

Assessing the behavior of column-splice connections between CFSTS in axial tension

Increasing the sustainability of construction materials is a key goal in the construction industry. As the demand for high-rise residential structures grows, new more efficient methods of achieving sustainability are required. Rendering larger structures demountable to enable the re-use of steel structural members is one solution. The aim of this study was to investigate and assess the behavior of blind bolted column-column connections between concrete filled steel tubes in axial tension. The investigation aimed to address the need for accurate design guidelines for tensile members in the composite design standards such as Eurocode 4 and encourage the use of columncolumn connections in large-scale demountable structures. A numerical investigation of the blind bolted column-column connection has been performed using ABAQUS. The model consisted of two concrete filled square hollow steel sections connected using sleeve plates welded to the top tube only, as well as 16 M20 Lindapter Hollobolts connecting the tubes. The numerical investigation revealed that the sections tested conformed with AS1170.1 regarding columns in tension. Results of the numerical investigation have been compared against experimental results for a continuous CFST and it was found that the connections performed better in tension. The parametric analysis revealed no dependence of the shape of force-displacement relationships on diameter to thickness ratio, concrete compressive strength or yield stress

Strength of concrete-filled steel box columns with local buckling effects

The key aspects and features of a nonlinear fiber element analysis method for predicting the strength and behavior of concrete-filled steel box columns with local buckling effects are discussed. The methods is quite useful in predicting the ultimate strengths and behavior of concrete slabs and can also be employed in the advanced analysis of composite frames

Performance-Based Optimization for Strut-Tie Modeling of Structural Concrete

Conventional trial-and-error methods are not efficient in developing appropriate strut-and-tie models in complex structural concrete members. This paper describes a performance-based optimization (PBO) technique for automatically producing optimal strut-and-tie models for the design and detailing of structural concrete. The PBO algorithm utilizes the finite element method as a modeling and analytical tool. Developing strut-and-tie models in structural concrete is treated as an optimal topology design problem of continuum structures. The optimal strut-and-tie model that idealizes the load transfer mechanism in cracked structural concrete is generated by gradually removing regions that are ineffective in carrying loads from a structural concrete member based on overall stiffness performance criteria. A performance index is derived for evaluating the performance of strut-and-tie systems in an optimization process. Fundamental concepts underlying the development of strut-and-tie models are introduced. Design examples of a low-rise concrete shearwall with openings and a bridge pier are presented to demonstrate the validity and effectiveness of the PBO technique as a rational and reliable design tool for structural concrete