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Shell has developed a novel mono-diameter well concept for oil and gas wells as opposed to the traditional telescopic well design. A Mono- diameter well contains multiple casing sections with the same internal diameter. This is achieved by expansion of the casing sections concerned using an expansion cone. Since the well is drilled in stages and casings are inserted to support the open hole, an overlap section between two consecutive (expandable) casings exists which has to be expanded. When the cone enters the overlap section, the expansion force increases dramatically due to the expansion of two casings, cured cement and formation layers. When the cone finalizes the expansion of the overlap section it pops out, the expansion force vanishes and the cone accelerates upwards and it generates an empty volume to be filled by the well fluid (mud). As a result of this, fluid starts to flow through the drill pipe, around the cone and the fluid volume below the cone starts to decompress. This induces a surge pressure wave traveling upwards and a swab pressure wave in the expanded casing traveling downwards. If the pressure difference between outside and inside of the expanded casing exceeds the collapse rating of the casing, the casing will collapse which leads to the loss of the concerned well section. Repair of such a failure costs time and money, therefore this swab pressure must be well predicted to enable the installation process to be designed such that this collapse can be avoided. A model of fully coupled fluid-structure interaction between cone and the well fluid is built for calculating the swab pressure propagating downward and surge pressure propagating upward resulted from transient process occurring after cone pops out. This model has shown an effective tool for predicting the swabbing pressure in field deployments performed lately in Gulf of Mexico and according to its output the suitable cone is selected in order to avoid the casing collapse.

This paper describes a technique to magnify the scattering of a wave at a defect by using the natural behavior of a structure. The fundamental physical principle of the detection strategy as well as the way to exploit this principle for detecting defects are explained. The influence of the parameters defect location, defect size and natural frequency selected, is investigated in a numerical example considering a 1mm thick A3 Aluminum plate. The proposed defect detection strategy is based on the measurement of frequency response functions at a very limited number of response locations and is therefore very easy to apply. Furthermore, an experimental validation of the detectability of a square 4mm through thickness defect is performed. Due to its simplicity and the low number of sensors necessary, the strategy explained in this paper allows the detection of a defect very rapidly. ispartof: pages:2020-2025 ispartof: X International Conference on Structural Dynamics, EURODYN 2017 vol:199 pages:2020-2025 ispartof: International Conference on Structural Dynamics, EURODYN location:Rome date:11 Sep - 13 Sep 2017 status: published

Given the increasing demand for taller structures in wind energy applications and the accompanying need for a better understanding of their structural response, the present study performs aeroelastic analysis on a novel wind turbine structure and discusses the obtained results. The response of a hybrid onshore wind turbine tower consisting of a 60 m lattice structure and a 60 m tapered tubular structure, with a 5 MW class AII turbine, is investigated. From the Design Load Cases (DLC) established in IEC64100-1 standard, focus is set on DLC 1.1 and DLC 1.3 which correspond to power production conditions and embody the requirements for loads resulting from atmospheric turbulence during normal and extreme operating conditions respectively. DLC 6.1 which refers to standstill or idling conditions under extreme wind model is also studied. In order to account for the interaction between elastic, viscous and inertial forces of the structure and the external aerodynamic forces, ashes, an integrated analysis software, is used. After developing the wind turbine tower model and generating the turbulence models, 600 seconds simulations are performed. The wind flow is assumed to be parallel to the hub axis. For DLC 1.1 and DLC 1.3, parametric studies with the wind speed ranging from 3 to 25 m/s, with an incremental step of 1 m/s, are executed. In DLC 6.1, the blades are feathered and the wind speed is rapidly increased to 42.5 m/s. Time histories of the elemental forces and the nodal displacements are extracted in critical positions of both the lattice and the tubular part. The mean values of the output data are evaluated and plotted against the wind speed. Conclusions regarding the influence of the wind speed on the induced tower behaviour are drawn.

Wind and earthquake load have historically been conceived to act independently. However, if we reflect on the fact that major seismic events are usually followed by a number of aftershocks and that wind is constantly flowing at high intensities around wind farms, which induces additional demands of resistance to infrastructure, then the joint probability of middle-to strong earthquakes and low-to mild wind events becomes more relevant. In this paper a generalised approach is used to estimate the ratio between earthquake and wind forces and their effect on infrastructure. Following, a probabilistic analysis is carried out to show that under certain conditions the combination of these natural events can induce additional demands of strength and ductility to wind turbines which could lead to unforeseen damage.

Leaks have been detected and localized in water distribution in many countries for years, by using the cross-correlation of pipe vibration measured either side of a suspected leak and/or by using listening sticks. However, in modern plastic pipes this is problematic because of the strong coupling between the water and the pipe which results in significant attenuation of the coupled fluid-pipe wave, which in turn is responsible for the propagation of leak noise. Hence leak noise does not propagate as far as it did in older metallic pipes. This paper discusses how the vibro-acoustic behavior of the water-pipe-soil system influences leak noise propagation. To investigate this, a numerical model is developed, and the results are compared with those from an analytical model for two water pipe systems, one in the UK and one in Brazil. Experimental results are also presented. It is shown that the important difference between the two systems is the shear stiffness of the surrounding soil, which has a profound effect on both the speed of leak noise propagation and the attenuation of the noise along the pipe.

© 2017 The Authors. Published by Elsevier Ltd. For the design of slender footbridges, the vibration serviceability under pedestrian excitation is often the governing criterion. In design stage, vibration levels are predicted using simplified load models that are extrapolated from single-person force models to represent the effect of a crowd. However, these load models disregard Human-Human Interaction (HHI) and Human-Structure Interaction (HSI). This contribution investigates the effect of human-human interaction on the resulting structural response. A social force model is applied to simulate the realistic pedestrian traffic. The time-varying position and velocity of each pedestrian in the crowd are transferred into the necessary inputs for detailed step-by-step simulations of the pedestrian-induced forces and the resulting pedestrian-induced vibrations. The results show that accounting for HHI results into a reduced global walking speed. Also, the inter-person variability of the step frequencies is lower than when HHI is disregarded. As an alternative to the computationally expensive social force model, the effect of HHI is translated into an equivalent distribution of step frequencies of the pedestrians in the crowd. The results show that this simplified model allows for a very good approximation of the HHI effects on the resulting crowd-induced loading and structural response. ispartof: pages:2907-2912 ispartof: Procedia Engineering vol:199 pages:2907-2912 ispartof: X International Conference on Structural Dynamics location:Rome, Italy date:10 Sep - 13 Sep 2017 status: published