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Submarine pipelines are usually laid unburied. Free spanning may be caused in the line by seabed unevenness, topology changes, scouring, or sand waves. In seismically active areas, the free spannings are prone to severe ground excitations. This article deals with the seismic performance of the submarine pipeline free spanning, and the water/pipeline interaction during the event is its focal point. For this, a numerical finite-element model has been used. Results from a conventional added mass approach have been examined against those from a more elaborate coupled acoustic-structural model. With the coupled system the surrounding seawater, pipe body, seabed, and free spanning have all been incorporated into the model. Both random earthquake and harmonic excitations have been considered. A time domain incremental dynamic analysis (IDA) method has been used to evaluate the pipeline performance. Effects from type, frequency, intensity, and direction of excitation and the free-span length on the pipeline response have been investigated. In most cases, the added mass approach has been found to provide more conservative predictions (in some cases up to 60%) for the free-spanning seismic response in comparison to those obtained from the acoustic method. For the earthquake excitations, the predictions obtained from each of the two methods have been more consistent as compared to the results obtained for harmonic excitation

Abstract. Improved mechanical and physical properties of an Al-Si alloy as a well-known casting alloy is strongly dependent upon the morphology of silicon particles, Al grains and also type of intermetallics which are in turn a function of alloy composition, solidification rate and heat treatment. This study aims at investigating the influence of the different solidification conditions (high pressure die, gradient and sand cast) and heat treatment on the microstructure (dendrite parameters, silicon particle morphology, intermetallic compounds), mechanical properties and fracture surface appearance of Al-9Si-4Mn alloy. To identify the features of microstructure and fracture surface analysis, a combination of optical metallography, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) have been employed. The results show that the cooling rate has a strong effect on the evolution of intermetallics, morphology of the silicon and dendrite parameters.Introduction:

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