Evaluation of the p-y method in the design of monopiles for offshore wind turbines

Monopile foundations, currently designed using the p-y method, are technically viable in supporting larger offshore wind turbines in waters to a depth of 30 m. The p-y method was developed to better understand the behavior of laterally loaded long slender piles required for the offshore oil and gas installations. The lateral load-deformation behavior of two monopiles, 5 and 7.5 m dia, installed in soft clays of varying undrained shear strength and stiffness, was studied. A combination of axial and lateral loads expected at an offshore wind farm location with a water depth of 30 m was used in the analysis. It was established that the Matlock (1970) p-y curves are too soft and under-estimate the ultimate soil reaction at all depths except at the monopile tip. At the pile tip, the base shear was not accounted for in the p-y curves, hence resulting in the over-estimation of the soil reaction. Consequently, the Matlock (1970) p-y formulation significantly underestimates the monopile ultimate lateral capacity. The use of the Matlock (1970) p-y method would result in over-conservative designs of monopiles for offshore wind turbines. This is an abstract of a paper presented at the Offshore Technology Conference (Houston, TX 5/6-9/2013).

Controlled amine functionality in self-assembled monolayers via the hidden amine route: chemical and electronic tunability.

A synthetic strategy for fabricating a dense amine functionalized self-assembled monolayer (SAM) on hydroxylated surfaces is presented. The assembly steps are monitored by X-ray photoelectron spectroscopy, Fourier transform infrared- attenuated total reflection, atomic force microscopy, variable angle spectroscopic ellipsometry, UV-vis surface spectroscopy, contact angle wettability, and contact potential difference measurements. The method applies alkylbromide-trichlorosilane for the fabrication of the SAM followed by surface transformation of the bromine moiety to amine by a two-step procedure: S(N)2 reaction that introduces the hidden amine, phthalimide, followed by the removal of the protecting group and exposing the free amine. The use of phthalimide moiety in the process enabled monitoring the substitution reaction rate on the surface (by absorption spectroscopy) and showed first-order kinetics. The simplicity of the process, nonharsh reagents, and short reaction time allow the use of such SAMs in molecular nanoelectronics applications, where complete control of the used SAM is needed. The different molecular dipole of each step of the process, which is verified by DFT calculations, supports the use of these SAMs as means to tune the electronic properties of semiconductors and for better synergism between SAMs and standard microelectronics processes and devices.