No abstract

A case study using finite-element software for the dynamic analysis and structural design of a machine foundation on piles in homogeneous sandy soil is reported. A parametric study was carried out to investigate the effect of the foundation geometry, the amplitude and frequency of the dynamic load, and the damping ratio. It is concluded that as the pile cap thickness increases the oscillation of displacement decreases due to material damping inherent in the concrete of the pile cap. There is a limit of the pile cap size at which its stiffness governs its dynamic response. Above this size the weight of the pile cap overrides its stiffness effect, and the additional weight leads to an increase in pile displacement. When the pile group size increases, the frequency at which maximum displacement occurs increases, and hence the system becomes more stable against resonance. In the case of changing the pile spacing, the maximum moment factor I M is always at the pile cap centre, where the load is applied. This factor increases when the pile spacing increases. The dimensionless displacement factor I z decreases markedly as the pile cap length increases, reflecting the increase in displacement with pile cap length.

Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) is a superior type of concrete. It has ultra-high strength, ductility and durability. Despite the large number of researches that have been performed to study it, no perfect approach has been determined yet to identify the proportion of materials involved in its composition, nor ideal curing methods after casting with the possibility of performing effectively. Also, there is no uniform technique for pouring concrete to ensure that fibres are spread properly. This paper focuses on the review of techniques carried out to choose the quality and quantity of materials used for UHPFRC with the analysis and comparison of the researchers’ findings to identify optimal proportions, pouring and treatment regimens to attain the best results of mechanical properties of UHPFRC. The optimum packing density resulting from high cement content, using silica fume, fine aggregate, low w/cm ratio and high dosage of HRWRA are the key factors to reach ultra-high strength. Incorporation of short steel fibres leads to improving ductility, tensile strength and enhance strain hardening of UHPFRC. Heat treatment or steam curing stimulates the reaction between SiO2 in cementitious materials and Ca(OH)2 produced on cement hydration which results in rising strength.

No abstract

The performance of railway track under dynamic loading depends on many parameters such as type of sleepers, ballast, soilstructure interaction and the relation of contact forces between the track and railway. The rail track classified as low and high speeds, where speed is a very important factor in design. Many theoretical models were derived and some developed for dynamic analysis of railway track system with assumptions that simplified or matched actually the real behavior especially the support of sleepers as linear or nonlinear and the contact between railway and track. In the present paper, a Finite Elements Approach is one of the numerical analysis by ANSYS software that adopted here to study the performance of harmonic analysis of railway track system. Harmonic ranges were applied with constant applied loading based on the European code for the steel rail.