Ayman Y. Nassif

Proposal of design formulae for equivalent elasticity of masonry structures made with bricks of low modulus:English

Bricks of low elastic modulus are occasionally used in some developing countries, such as Indonesia and India. Most of the previous research efforts focused on masonry structures built with bricks of considerably high elastic modulus. The objective of this study is to quantify the equivalent elastic modulus of lower-stiffness masonry structures, when the mortar has a higher modulus of elasticity than the bricks, by employing finite element (FE) simulations and adopting the homogenization technique. The reported numerical simulations adopted the two-dimensional representative volume elements (RVEs) using quadrilateral elements with four nodes. The equivalent elastic moduli of composite elements with various bricks and mortar were quantified. The numerically estimated equivalent elastic moduli from the FE simulations were verified using previously established test data. Hence, a new simplified formula for the calculation of the equivalent modulus of elasticity of such masonry structures is proposed in the present study.

Effects of steel fibre-aggregate interaction on mechanical behaviour of steel fibre reinforced concrete

ABSTRACT This work investigated the effects of fibre type, dosage and maximum aggregate size on the mechanical behaviour of concrete reinforced with steel fibres. Hooked-end steel fibres with 50 and 60 mm length and aspect ratios (length/diameter) of 45, 65 and 80 were used with maximum sizes of coarse aggregate of 10 and 20 mm. The same mix proportions of concrete were used throughout the investigation. Flexural testing of 600 mm square panels was performed. Subsequently, cores were taken from these panels and X-ray computed tomography was used to analyse the positioning of fibres in hardened concrete. The experimental results show that the performance of steel fibre-reinforced concrete improved drastically when compared to plain concrete without fibres. Longer, thinner fibres and smaller aggregates were noted to give the best results.

Distribution and orientation of steel fibres in steel fibre reinforced concrete

The use of fibres to reinforce brittle materials for better performance has been employed since time immemorial. Therefore, inclusion of steel fibres in concrete has always improved the post-cracking strength and concrete ductility to a large extent while full potential of steel fibre reinforced concrete (SFRC) is still yet to be exploited in practice. This study investigated the effects of fibre type, dosage and maximum aggregate size on distribution and orientation and hence, the flexural performance of steel fibre reinforced concrete. Hooked-end steel fibres with 50 mm and 60 mm length, aspect ratio of 45, 65 and 80, and dosages of 0 kg/m³, 25 kg/m³, 40 kg/m³, 50 kg/m³ and 60 kg/m³ were used with maximum sizes of coarse aggregate of 10mm and 20mm. X-ray Computed Tomography was employed for imaging cores taken from the slab specimens after testing. The experimental results show a remarkable improvements in flexural strength up to 83% observed at larger dosage of steel fibre and when good interaction leading to better distribution and orientation of fibres within concrete matrix is sustained between right fibre geometry and appropriately sized aggregate.

Engineering design education and training with particular reference to design of bridges

This paper presents a case study of an undergraduate integrated civil engineering design project module. This module involved significant input from practicing structural and civil engineers as well as architects leading to a holistic course of study taking into consideration technical, social, economic and environmental issues. The teaching philosophy focused on engagement and motivation focusing on behavioral affective and cognitive dimensions and providing appropriate support at the right time for maximum impact on learning. Educational theories related to acquiring skills and construction of knowledge based on cognitive apprenticeship, knowledge-scaffolding and constructive alignment were explored and used in the design of the module. The assessment ensured engagement and motivation with clear support for just-in-time continuous formative assessment. Learning-diaries and minutes of design meetings were introduced as a tool contributing to knowledge-scaffolding. This paper presents a methodology of how the educational theories can be applied in a pragmatic manner for a more effective education and training of engineers.