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5 PO1 3AH, UK, +44 (0) 7415725441, clifford.okeh@port.ac.uk 6 7 ABSTRACT. 8The use of steel fibre hybridisation with different aspect ratios have been seen to enhance the pre and 9 post cracking response of concrete, however the invention of new innovative macro hooked ends steel 10 fibres with multiple hooks and increase in its linear length have been recently investigated. The results 11show that the new innovative macro hooked ends steel fibre with multiple hooks performed better than 12 single hooked ends steel fibre with respect to material properties when used in self-compacting 13 concrete. Therefore, the need to further investigate the performance of this new innovative macro 14 (MAC) hooked ends steel fibre when combined with straight micro (MIC) steel fibre of the same aspect 15 ratio in self-compacting concrete would be useful in the study of the stress-strain curve relationship of 16 this composite material. 17A laboratory investigation on two different conditions of steel fibre hybridisation using straight MIC 18 steel fibre (Length 13mm and diameter 0.2mm) with two different types of hooked ends MAC steel 19 fibres, Single (S1) and Double (M2) hook(s) at 0.75% and 1% fibre content respectively. These are 20 optimised values from previous experiments (laboratory tests conducted using different macro steel 21 fibres at 0.25%, 0.5%, 0.75% and 1% fibre content). The Uniaxial direct tension test method is used. 22The results show that steel fibre hybridisation decreased workability due to the influence of the micro 23 steel fibre content irrespective of the hooked ends steel fibre type. The use of Single hook (S1) macro 24 hooked end steel fibre in steel fibre hybridisation further improved the material properties (compressive 25 strength, tensile strength and fracture energy) when compared to the use of only macro hooked end steel 26 fibre. However a decrease in the fracture energy is observed when Double hooks M2 macro hooked end 27 steel fibre is used. Although positive results are seen with respect to other properties.28 29 Keywords: Single and double hooked ends steel fibres, Micro-steel fibre, Fracture energy, Tensile30 Strength, Compressive strength, Uniaxial tension test, Stress-strain relationship.31 32 33 34 35 Notwithstanding the improvement in the performance of SFRC with the inclusion of micro steel fibres 58 which affects the fibre matrix bond characteristics, the influence of macro steel fibre geometry (straight, 59 hooked, twisted, crimped etc.) presents different bond characteristics when used in concrete, hence 60 alters the behaviour in both the pre and post cracking zone (Lok and Pei 1998). 61The enhanced concrete performance in tension when single hooked end steel fibre is used compared to 62 straight steel fibre geometrical characteristics cannot be over-emphasised as a result of the additional 63 frictional force generated due to straightening of the hooks leading to higher frictional pull-out force 64 (Breitenbucher et al 2014) in addition to the improvement in the matrix adhesion...

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Purpose The paper aims to leverage the importance of the integrated automatic structural design for tall buildings at the early stage. It proposes to use an automatic prototype to perform the structural design, analysis and optimisation in a building information modelling (BIM)-based platform. This process starts with extracting the required information from the architectural model in Revit Autodesk, such as boundary conditions and designs different options of the structural models in Robot Autodesk. In this process, Dynamo for Revit is used to define the mathematical functions to use different variables and generate various structural models. The paper aims to expand the domain of automation in the BIM platform to reduce the iterative process in different areas such as conceptual structural design and collaboration between architects and structural engineers to reduce the time and cost at the early stages. Design/methodology/approach The paper begins with an exploratory research by adopting a qualitative methodology and using open-ended questions to achieve more information about the phenomenon of automation and interoperability between structural engineers and architects and gain new insight into this area. Furthermore, correlation research is used by adopting quantitative and short questions to compare the proposed prototype with the traditional process of the structural design and optimisation and the interoperability between architects and engineers and consequently, validate the research. Findings As an outcome of the research, a structural design optimisation (SDO) prototype was developed to semi-automate the structural design process of tall buildings at the early stages. Moreover, the proposed prototype can be used during the early stage of structural design in different areas such as residential buildings, bridges, truss, reinforced concrete detailing, etc. Moreover, comprehensive literature regarding using automation in structural design, optimisation process and interoperability between architects and engineers is conducted that provides a new insight to contribute to future research and development. Research limitations/implications Due to the time limit, the paper results may lack in a comprehensive automatic structural design process. Therefore, the researchers are encouraged to expand the workability of the prototype for a comprehensive automatic design check such as automatic design for the minimum deflection, displacement of different types of buildings. Practical implications The prototype includes implications for the development of different automatic designs. Originality/value The focus of this paper is the optimisation of the structural design in the BIM platform by using automation. This combination is one of the novelties of this paper, and the existing literature has a very limited amount of information and similar work in this area, especially interoperability between architects and engineers.

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Integrated optimization of structural topology and control system is considered. The problem is formulated as mixed discrete‐continuous multi‐objective programming with a linear quadratic regulator cost index, and measures of robustness and controllability as objectives. The Genetic Algorithm (GA), a guided random search technique, is adopted for the problem‐solving. A member elimination strategy that allows deleted members to be recovered is suggested in the search procedure. As verification for the proposed method, optimum layout and actuator placement for a 45‐bar truss is illustrated. Numerical results indicate that the genetic algorithm can converge to optimum solutions by searching only a minor fraction of the solution space. Discussions on the algorithm are presented. © 1998 John Wiley & Sons, Ltd.

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