Numerical Simulation on Residual Responses of Adjacent Piles After Spudcan Penetration and Extraction

The effect of the mobile jack-up spudcan penetration and extraction on adjacent platform piles is an important issue in ocean engineering. Residual moments along piles will exist due to strata plastic deformation after spudcan extraction. If the residual response is large, the combination of the residual load and extreme environmental load may become the controlling load case for the piled structure. In order to understand the variation of the pile responses during spudcan penetration and after extraction, adjacent pile responses are calculated using the Coupled Eulerian Lagrangian (CEL) finite element method. Two kinds of typical seabed, clay and fine sand, are considered during calculation. The effects of the spudcan penetration depth, the spudcan-pile clearance, the shear strength of strata and the pile head constraint on adjacent pile responses are analyzed during spudcan penetration and after extraction. Calculated results show that residual responses of adjacent piles depend on the penetration depth, the clearance, the shear strength and the pile head constraint. The residual response of piles in soft clays is different from that in sands. For piles in soft clays, the residual response of adjacent piles will increase with decrease of the shear strength and the maximum residual pile shaft moment is larger than that during spudcan penetration. For piles in sands, the maximum residual pile shaft moment is about 70–80% of that during spudcan penetration. Therefore, the residual response of piles should be considered when the effect of spudcan penetration on adjacent platform piles is evaluated.

Preparation of Strontium Titanate Nanocube Particles Using Complex Titanium Raw Materials and their Accumulations

In this study, strontium titanate (SrTiO3, ST) nanocube particles were successfully prepared, with a size of 12 nm, normal size distribution with standard deviation of 10 %, and sharp edge corner, by solvothermal method using complex titanium raw materials of TiO2and titanium isoproxide. Moreover, the well-dispersed ST nanocube slurry was also prepared using electric double layer with hydrochloric acid. Finally, using the ST nanocube slurry, ST nanocube accumulation was prepared by two kinds of forces of capillary force and absorption force by plaster. The obtained ST nanocube accumulation was not 3-dimentional aliened ST nanocube structure, but randomly piled structure.

Wave Interaction With Piled Structures: Application With IH-FOAM

This paper presents a numerical analysis of the interaction of waves with piles. A model called IH-FOAM, based on OpenFOAM®, is used. IH-FOAM is able to simulate and to absorb waves in three-dimensional domains, reducing the computational cost and extending the range of applicability of the CFD modelling to the study of offshore and coastal structures. In this work, a detailed analysis of mono and multi-piled structures is carried out. Several piles layouts are studied Wave run-up and forces have been studied for the multi-piled structures. Those magnitudes have been compared with the single piled structure pointing out the difference in the wave induced hydrodynamics and the non-linear interaction between the waves and the structures. The work contained in this paper presents a first step which will be extended in the future to analyse more complex layouts and the effects of broken waves.

Dynamic Instability of Pile-Supported Structures in Liquefiable Soils during Earthquakes

Piles are long slender columns installed deep into the ground to support heavy structures such as oil platforms, bridges, and tall buildings where the ground is not strong enough to support the structure on its own. In seismic prone zones, in the areas of soft soils (loose to medium dense soil which liquefies like a quick sand) piles are routinely used to support structures (buildings/ bridges). The pile and the building vibrate, and often collapse, in liquefiable soils during major earthquakes. In this paper an experimental and analytical approach is taken to characterize this vibration. The emphasis has been given to the dynamic instability of piled foundations in liquefied soil. The first natural frequency of a piled-structure vibrating in liquefiable soil is obtained from centrifuge tests. The experimental system is modelled using a fixed-free Euler-Bernoulli beam resting against an elastic support with axial load and tip mass with rotary inertia. Natural frequencies obtained from the analytical method are compared with experimental results. It was observed that the effective natural frequency of the system can reduce significantly during an earthquake.

Microstructure and Biocompatibility of Gradient Bioceramic Composite Coating Fabricated by Wide-Band Laser Cladding

In this study, microstructure and biocompatibility of gradient bioceramic composite coating fabricated by Wide-Band Laser Cladding is investigated. The experimental results indicate that the coating consists of an alloyed transition layer and the bioceramic coating. The bioceramic coating is mainly comprised of HA, CaTiO3, CaO, α-TCP, β-TCP and TiO. The coral-shaped structure and short-rod piled structure existing on the surface of coating. After the implantation of the bioceramic coatings into dogs’ femur for 6, 12, and 24 weeks, hypersusceptibility, rejection and pathological changes are not found. No fiber cyst, necrosis of bone tissue and chronic inflammation obviously appear through slice observation of hard tissues. The bioceramic coating with different ratios of Ca : P have different abilities to induce osteogenesis. At Ca: P=1.4 and 0.6wt.% Y2O3 (No.3 sample), the bioceramic coating is of best bioactivity and biocompatibility.