Offshore wind structures are subjected to cyclic loadings from wind, wave and current which must be accounted for when designing foundations. The effects of cyclic loadings can govern the dimension of the foundations. However, less standard and calculation procedure for designing foundations under cyclic loadings is generally accepted in practical design. A parametric study at the generic clay profiles were carried out by using the conventional beam column approach and the finite element analysis. In addition, a monopile foundation at the layered soil profiles in Korean West Sea were designed taking into cyclic loading effect account. Both design results show that the bending moments and shear forces along the pile by using beam column approach are larger than the results from the FE analysis. The FE analysis gives less pile displacement and rotation than the beam column approach. The reason for these differences can be partially explained by the soil reactions in the upper soil profiles. For the clay layers the lateral soil resistance is generally higher in the FE analyses compared to the cyclic p-y curves. However the lateral resistance in the silt sand layers is greater by using the standard cyclic p-y curves with a drained friction angle than using the constitutive models applying cyclic properties. Based on the results, a practical approach of monopile design for the specific offshore location can be recommended by calibrating and simplifying cyclic p-y curves from the results of FE analyses taking into account the cyclic stress-stain response of the soil.
CMTS has played the key role in HFC's cable-data system, and its port resources are the key factors that manage a operational group of subscribers. Usually a port is provisioned to manage a cell which covers the geographically grouped subscribers in HFC network. Since each upstream or downstream port has got a certain capacity. too many subscribers assigned on a CMTS port make all the subscribers suffer from bandwidth contention. That's why service providers put a limit on per-cell subscribers(ie. 200 subscribers per cell). However, putting equal limit on the number of subscribers among ports has been proved not useful any longer.In my previous researchll I , I have discussed the issue of upstream bandwidth contention. This time, the paper will discuss how to maximize the port utilization from the service provider's viewpoint, especially by traffic load balancing. The method suggested is highly dynamical, economical, and has been implemented, field-tested. The paper will show not only the traffic engineering mechanism, but also the result of the test applying the mechanism.
Offshore wind-turbine support structures are largely made of steel since steel monopiles have accounted for the majority of installations in the last decade. As turbines become bigger, steel structures have led to an exponential increase in material and installation costs. From this point of view, the use of concrete for future support structures has been initiated. In this study, concrete–steel composite piles have been investigated. A pre-tensioned high strength concrete pile was placed in the lower part, mainly to support the axial load, and a steel pile in the upper part to resist the lateral load. A mechanical joint was adapted to connect the two different types of piles. Static axial, dynamic axial, and lateral load tests were performed to evaluate the load-displacement response of the composite pile, verify the integrity of the mechanical joint, and investigate its potential application to offshore wind foundations. This paper focused on the load-displacement response and the connection integrity; in particular, it investigated the lateral load-displacement response by comparing it to the results of beam-spring analysis. Based on the results from the field tests, a site-specific lateral load-displacement curve was suggested, and the connection integrity was verified.
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